Narrow Band Gap Conjugated Polymers Employing Cross-Conjugated Donors Useful In Electronic Devices
20220332870 · 2022-10-20
Assignee
- THE UNIVERSITY OF SOUTHERN MISSISSIPPI (Hattiesburg, MS, US)
- The Regents Of The University Of California (Oakland, CA)
Inventors
- Jason D. Azoulay (Hattiesburg, MS, US)
- Benjamin A. Zhang (San Mateo, CA, US)
- Yi Liu (San Ramon, CA, US)
Cpc classification
C08L65/00
CHEMISTRY; METALLURGY
C08G61/126
CHEMISTRY; METALLURGY
C08G2261/3243
CHEMISTRY; METALLURGY
C08G2261/3246
CHEMISTRY; METALLURGY
C08G2261/1424
CHEMISTRY; METALLURGY
C09D165/00
CHEMISTRY; METALLURGY
C08G2261/3227
CHEMISTRY; METALLURGY
International classification
Abstract
The invention provides for new polymer compounds and methods for the preparation of modular narrow band gap conjugated compounds and polymers that incorporate exocyclic cross-conjugated donors or substituents, as well as novel monomer components of such polymers and the resulting products which comprise materials and useful electronic devices with novel functionality.
Claims
1. A narrow band gap conjugated polymer prepared by copolymerizing at least one first donor monomer or oligomer having the formula: ##STR00016## wherein G is a leaving group suitable for a cross-coupling polymerization reaction, FG is selected from the group consisting of unsubstituted C.sub.0-C.sub.36 hydrocarbyl, substituted C.sub.1-C.sub.36 hydrocarbyl, unsubstituted C.sub.6-C.sub.20 aryl, substituted C.sub.6-C.sub.20 aryl, unsubstituted C.sub.3-C.sub.20 heteroaryl, substituted C.sub.3-C.sub.20 heteroaryl, C.sub.6-C.sub.20 arylene substituted with a C.sub.1-C.sub.36 hydrocarbyl, F, Cl, Br, I, CN, —R.sup.2, SR.sup.2—OH, —OR.sup.2, —COOH, —COOR.sup.2, —NH.sub.2, —NHR.sup.2, or NR.sup.2R.sup.3, where R.sup.2 and R.sup.3 are independently selected from a C.sub.1-C.sub.24 hydrocarbyl group; FG′ is selected from the group consisting of unsubstituted C.sub.6-C.sub.20 aryl, substituted C.sub.6-C.sub.20 aryl, unsubstituted C.sub.3-C.sub.20 heteroaryl, and substituted C.sub.3-C.sub.20 heteroaryl; and when FG′ is unsubstituted hydrocarbyl or substituted hydrocarbyl, FG cannot be C.sub.0-hydrdoxarbyl; m is an integer of at least 1; Y is selected from the group consisting of S, BR.sup.3, PR.sup.3, Se, Te, NH, or Si, wherein R.sup.3 is a C.sub.1-C.sub.24 hydrocarbyl group; with at least one acceptor second monomer selected from a)-b) that provide a structural unit in the copolymer: a) substituted and unsubstituted monomers derived from the group consisting of thiadiazoloquinoxaline, quinoxaline, thienothiadiazole, thienopyridine, thienopyrazine, pyrazinoquinoxaline, benzothiadiazole, bis-benzothiadiazole, benzobisthiadiazole, thiazole, thiadiazolothienopyrazine, thiadiazoloquinoxaline and diketopyrrolopyrrole, and b) monomers selected from the group consisting of: ##STR00017##
2. The polymer of claim 1, wherein the second monomer is selected from the group consisting of a substituted benzothiadiazole, an unsubstituted benzothiadiazole, a substituted thiadiazolothienopyrazine, an unsubstituted thiadiazolothienopyrazine, and P8 ##STR00018##
3. The polymer of claim 2, wherein the substituted thiadiazolothienopyrazine is a structural unit selected from the group consisting of: ##STR00019##
4. The polymer of claim 1, wherein FG and FG′ are selected from the group consisting of unsubstituted hydrocarbyl and substituted hydrocarbyl.
5. The polymer of claim 1, wherein the first monomer is an electron-deficient heteroaromatic ring system.
6. The polymer of claim 1, wherein the second monomer is an interchain unit comprising an electron-deficient heteroaromatic ring system.
7. The polymer of claim 1, wherein G is selected from the group consisting of Br, Cl, I, triflate (trifluoromethanesulfonate), a trialkyl tin compound, boronic acid (—B(OH).sub.2), or a boronate ester (—B(OR.sup.5).sub.2, where each R.sub.5 is C.sub.1-C.sub.12 alkyl or the two R.sup.5 groups combine to form a cyclic boronic ester.
8. The polymer of claim 1, wherein G is selected from the group consisting of Br, H, or any group suitable for direct heteroarylation polycondensation.
9. The polymer of claim 1, wherein the donor is incorporated into a molecule or oligomer.
10. The polymer of claim 1, wherein the synthesized polymers have a band gap of between about 0.1 eV to about 1.2 eV.
11. The polymer of claim 1, further comprising a third monomer comprising double or triple bonds separated by a single bond.
12. The polymer of claim 1, wherein the polymers synthesized have the formula: ##STR00020## wherein G is a leaving group suitable for a cross-coupling polymerization reaction, a) FG is selected from the group consisting of unsubstituted C.sub.0-C.sub.36 hydrocarbyl, substituted C.sub.1-C.sub.36 hydrocarbyl, unsubstituted C.sub.6-C.sub.20 aryl, substituted C.sub.6-C.sub.20 aryl, unsubstituted C.sub.3-C.sub.20 heteroaryl, substituted C.sub.3-C.sub.20 heteroaryl, C.sub.6-C.sub.20 arylene substituted with a C.sub.1-C.sub.36 hydrocarbyl, F, Cl, Br, I, CN, —R.sup.2, SR.sup.2—OH, —OR.sup.2, —COOH, —COOR.sup.2, —NH.sub.2, —NHR.sup.2, or NR.sup.2R.sup.3, where R.sup.2 and R.sup.3 are independently selected from a C.sub.1-C.sub.24 hydrocarbyl group; FG′ is selected from the group consisting of unsubstituted C.sub.6-C.sub.20 aryl, substituted C.sub.6-C.sub.20 aryl, unsubstituted C.sub.3-C.sub.20 heteroaryl, and substituted C.sub.3-C.sub.20 heteroaryl; or b) FG and FG′ are selected from the group consisting of unsubstituted hydrocarbyl and substituted hydrocarbyl; m is an integer of at least 1; Y is selected from the group consisting of S, BR.sup.3, PR.sup.3, Se, Te, NH, or Si, wherein R.sup.3 is a C.sub.1-C.sub.24 hydrocarbyl group; with at least an acceptor second monomer selected from a)-b) that provide a structural unit in the copolymer: a) substituted and unsubstituted monomers derived from the group consisting of thiadiazoloquinoxaline, quinoxaline, thienothiadiazole, thienopyridine, thienopyrazine, pyrazinoquinoxaline, benzothiadiazole, bis-benzothiadiazole, benzobisthiadiazole, thiazole, thiadiazolothienopyrazine, thiadiazoloquinoxaline and diketopyrrolopyrrole, and b) monomers selected from the group consisting of: ##STR00021## π.sub.S represents a conjugated spacer comprising double or triple bonds in a molecule separated by a single bond, across which some sharing of electrons occurs; and n is an integer>1.
13. The polymer of claim 1, wherein the first monomer comprises at least one monomer or oligomer having the formula: ##STR00022## where G is a leaving group suitable for a cross-coupling polymerization reaction, FG is C.sub.0 hydrocarbyl; FG′ is selected from the group consisting of substituted C.sub.6-C.sub.20 aryl and substituted C.sub.3-C.sub.20 heteroaryl; and Y is selected from the group consisting of S, BR.sup.3, PR.sup.3, Se, Te, NH or Si, wherein R.sup.3 is a C.sub.1-C.sub.24 hydrocarbyl group.
14. The polymer of claim 1, wherein the polymer is configured to used to tune structural properties, electrical properties, or a combination thereof, of electronic devices and to form improved materials for electronic devices.
15. The polymer of claim 14, wherein the electrical devices are organic optoelectronic devices.
16. The polymer of claim 15, wherein the electrical devices are hybrid organic-inorganic optoelectronic devices.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These drawings accompany the detailed description of the invention and are intended to illustrate further the invention and its advantages. The drawings, which are incorporated in and form a portion of the specification, illustrate certain preferred embodiments of the invention and, together with the entire specification, are meant to explain preferred embodiments of the present invention to those skilled in the art. Relevant FIGURES are shown or described in the Detailed Description of the Invention as follows:
[0018]
[0019]
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
DETAILED DESCRIPTION OF THE INVENTION
[0028] The invention provides for the synthesis of novel polymer compounds and methods of preparing narrow band gap conjugated polymers utilizing exocyclic cross-conjugated donor substituents, as well as novel monomer components of such polymers, and the resulting products that comprise materials and useful electronic and optoelectronic devices having novel functionalities. The materials, methods, and compositions of the invention provide the ability to fine-tune structural and/or electronic properties to obtain modular, solution-processable donor-acceptor (DA) conjugated polymers. The invention provides new polymers suitable for use in electronic devices as well as novel monomer components of such polymers, and electronic devices incorporating such novel polymers.
1. In one embodiment, the invention provides polymers of the formula:
##STR00001## [0029] wherein FG and FG′ are selected from the group consisting of substituted C.sub.1-C.sub.36 hydrocarbyl, unsubstituted C.sub.6-C.sub.20 aryl, substituted C.sub.6-C.sub.20 aryl, unsubstituted C.sub.3-C.sub.20 heteroaryl, substituted C.sub.3-C.sub.20 heteroaryl, unsubstituted C.sub.6-C.sub.20 aryl-C.sub.0-C.sub.36 hydrocarbyl, C.sub.6-C.sub.20 aryl, C.sub.0-C.sub.36 hydrocarbyl, F, Cl, Br, I, CN, —R.sup.2, [0030] SR.sup.2—OH, —OR.sup.2, —COOH, —COOR.sup.2, —NH.sub.2, —NHR.sup.2, or NR.sup.2R.sup.3, where R.sup.2 and R.sup.3 are independently selected from a C.sub.1-C.sub.24 hydrocarbyl group, and [0031] when FG′ is unsubstituted hydrocarbyl or substituted hydrocarbyl, FG cannot be C.sub.0-hydrdoxarbyl;
π.sub.A is an electron-poor or electron-deficient aromatic moiety;
π.sub.S represents a conjugated spacer comprising double or triple bonds in a molecule that are separated by a single bond, across which some sharing of electrons occurs;
m is an integer of at least 1;
Y is selected from the group consisting of S, —CH═CH—, BR.sup.3, PR.sup.3, Se, Te, NH, NR.sup.4 or Si,
wherein R.sup.3 and R.sup.4 comprise suitable functionalities, and
n is an integer >1.
[0032] The “π.sub.A” components which are used as intrachain units in the polymers can be any electron-deficient heteroaromatic ring system. “Electron-deficient aromatic ring system” and “electron-poor aromatic ring system” are used synonymously, and are intended to embrace 1) heteroaromatic ring systems, where the electron density on the carbon atoms of the heteroaromatic system is reduced compared to the analogous non-heteroaromatic system, and 2) aromatic ring systems, where the electron density on the carbon atoms of the aromatic system is reduced due to electron-withdrawing substituents on the aromatic ring (e.g., replacement of a hydrogen of a phenyl group with fluorine). The copolymers of the invention utilize a structure which permits an internal charge transfer (ICT) from an electron-rich unit to an electron-deficient moiety within the polymer backbone.
[0033] In some embodiments, π.sub.A is selected from substituted and unsubstituted moieties selected from the group consisting of thiadiazoloquinoxaline; quinoxaline; thienothiadiazole; thienopyridine; thienopyrazine; pyrazinoquinoxaline; benzothiadiazole; bis-benzothiadiazole; benzobisthiadiazole; thiazole; thiadiazolothienopyrazine; diketopyrrolopyrrole, etc.
2. In additional embodiments, the invention provides synthesized polymers comprising at least one novel monomer and/or oligomer compound of the formula:
##STR00002##
where leaving group G can be a leaving group suitable for a cross-coupling reaction such as a Stille or Suzuki-type polymerization reactions. In some embodiments, G can be Br, Cl, I, triflate (trifluoromethanesulfonate), a trialkyl tin compound, boronic acid (—B(OH).sub.2), or a boronate ester (—B(OR.sup.5).sub.2, where each R.sub.5 is C.sub.1-C.sub.12 alkyl or the two R.sup.5 groups combine to form a cyclic boronic ester. In some embodiments, G can be a trialkyl tin compound, such as (CH.sub.3).sub.3—Sn—. In some embodiments, G can be H, Br or any group suitable for a direct heteroarylation polycondensation. Other embodiments include functionality relevant for Kumada, Sonogashira, Negishi, and Hiyama couplings.
3. In additional embodiments, the invention provides compounds wherein said donor is incorporated into a small molecule or oligomer.
4. The invention further provides for methods for producing organic, or hybrid organic-inorganic, optoelectronic devices, which incorporate the materials described in paragraphs 1-3 above.
[0034] Some embodiments described herein are recited as “comprising” or “comprises” with respect to their various elements. In alternative embodiments, those elements can be recited with the transitional phrase “consisting essentially of” or “consists essentially of” as applied to those elements. In further alternative embodiments, those elements can be recited with the transitional phrase “consisting of” or “consists of” as applied to those elements. Thus, for example, if a composition or method is disclosed herein as comprising A and B, the alternative embodiment for that composition or method of “consisting essentially of A and B” and the alternative embodiment for that composition or method of “consisting of A and B” are also considered to have been disclosed herein. Likewise, embodiments recited as “consisting essentially of” or “consisting of” with respect to their various elements can also be recited as “comprising” as applied to those elements. Finally, distances, sizes, amounts, percentages, quantities, temperatures, and similar features and data provided herein are approximations, and can vary with the possible embodiments described and those not necessarily described but encompassed by the invention.
EXAMPLES
Example 1. Synthesis of 2,6-dibromo-(3,5-didodecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (1)
[0035] This example involved the synthesis of monomer 1. The inventors' synthetic approach is depicted in Scheme 1 and begins with the preparation of 3,5-didodecylbenzyl alcohol (1a). Linear (R=n-C.sub.12H.sub.25) solubilizing groups were chosen on the basis of minimizing steric and electronic contributions and for promoting sufficient solubility of the polymer products. The coupling of dodecylzinc bromide with 3,5-dibromobenzyl alcohol was accomplished using a sterically bulky Pd-PEPPSI-IPent pre-catalyst. Heating of the reaction mixture ensured high conversion without a loss in specificity providing 1a in good overall yield (>70%). Conversion of the alcohol to the bromide was accomplished using PBr.sub.3 in CH.sub.2Cl.sub.2. Subsequent reaction with PPh.sub.3 provided the phosphonium salt (1c). The olefin can be accessed through the reaction of 1c (as illustrated in Scheme 1) and Wittig olefination from the ketone. Alternative routes also exist. This strategy should provide facile access to a wide variety of functionalized derivatives for subsequent examination. The reaction of 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-4-one with 1c proceeds using NaOEt in EtOH, affording the desired aryl olefin functionalized CPDT building block (1) in 73% yield.
##STR00003##
Monomer Synthesis
[0036] 3,5-Didodecylbenzyl alcohol (1a). Pd-PEPPSI-IPent (84 mg, 1.5 mol %) and 3,5-dibromobenzyl alcohol (2.0 g, 7.58 mmol) were added to an oven-dried flask equipped with a stir bar. The flask was sealed and purged with argon. Toluene (15 mL) was added to dissolve the contents and the resulting solution was cooled to 0° C. in an ice bath. A THF solution of dodecylzinc bromide (25 mL, 19 mmol) was added dropwise over a period of 5 minutes. The ice bath was then removed, and the reaction was allowed to warm to room temperature and stirred for 16 hours. After this time, the reaction was heated to reflux for 2 hours. After cooling, the reaction mixture was quenched by the addition of hydrochloric acid (1 N) and subsequently neutralized with KOH (1 N). The mixture was poured into a separatory funnel and extracted with 3×50 mL ethyl acetate. The combined organic layer was washed with brine (50 mL) and dried over anhydrous MgSO.sub.4. Solvents were removed in vacuo and purification by flash chromatography using (10:1 hexanes:ethyl acetate) as the eluent gave 2.4 g of a colorless oil (5.82 mmol, 71%). .sup.1H NMR (500 MHz, CDCl.sub.3, 298 K): δ 7.02 (s, 2H), 6.95 (s, 1H), 4.67 (d, J=5.8 Hz, 2H), 2.60 (t, J=7.5 Hz, 4H), 1.60 (m, 4H), 1.36-1.20 (m, 36H), 0.90 (t, J=7.0 Hz, 6H). MALDI/TOF m/z: 443.18, calculated: 444.43.
[0037] 3,5-Didodecylbenzyl bromide (1b). 1a (2.0 g, 4.5 mmol) was dissolved in 20 ml anhydrous CH.sub.2Cl.sub.2 and the solution was cooled to 0° C. in an ice bath. While stirring, PBr.sub.3 (1.2 g, 4.5 mmol) was added dropwise. The ice bath was then removed and the reaction was allowed to warm to room temperature and stirred overnight. The reaction mixture was quenched by the addition of DI water. The mixture was poured into a separatory funnel and extracted with 3×30 mL CH.sub.2Cl.sub.2. The combined organic layer was washed with brine (50 mL) and dried over anhydrous MgSO.sub.4. Solvents were removed in vacuo and yielded 2.24 g of a white solid (4.4 mmol, 99%). .sup.1H NMR (500 MHz, CDCl.sub.3, 298 K): δ 7.04 (s, 2H), 6.95 (s, 1H), 4.5 (s, 2H), 2.58 (t, J=7.8 Hz, 4H), 1.62 (m, 4H), 1.36-1.20 (m, 36H), 0.90 (t, J=6.8 Hz, 6H). MALDI/TOF m/z: 505.82, calculated: 506.35.
[0038] 2,6-dibromo-(3,5-didodecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (1). 1b was dissolved in 20 ml anhydrous toluene with triphenylphosphine (1.16 g, 4.4 mmol). The solution was heated at reflux overnight. Solvents were removed in vacuo and 3.34 g of a waxy white solid (4.4 mmol) was obtained and used without further purification. 1c (2 g, 2.60 mmol) was combined with 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-4-one (0.90 g, 2.60 mmol) and dissolved in 20 ml of ethanol. The solution was heated to 60° C. and a solution of 15% NaOEt (1.50 ml, 2.60 mmol) in EtOH (10 mL) was added dropwise. The solution was stirred at 60° C. overnight. The reaction was then allowed to cool to room temperature, quenched with DI water (10 ml) and extracted with dichloromethane. The organic layer was washed with water, brine and solvents were removed in vacuo. The residue was purified by flash chromatography using hexanes as the eluent, affording 1.44 g of a red solid (1.89 mmol, 73%). .sup.1H NMR (500 MHz, C.sub.6D.sub.6, 298 K): δ 7.25 (s, 1H), 7.00 (s, 2H), 6.82 (s, 1H), 2.57 (t, J=7.8 Hz, 4H), 1.66 (m, 4H), 1.49-1.29 (m, 36H), 0.91 (t, J=7.1 Hz, 4H). MALDI/TOF m/z: 759.79 calculated: 758.22.
Example 2. Synthesis of the Reactive Monomers 2 and 3
[0039] The copolymerization of monomers, such as those shown in Scheme 1, is limited as a result of lithiation-based approaches used to install reactive functionalities necessary for polymerization reactions. Subsequent reaction of the brominated monomers with 3.5 equiv. of hexamethylditin (SnMe.sub.3).sub.2 using Pd(PPh.sub.3).sub.4 in toluene affords the corresponding bis-trimethylstannyl species in yields ˜75%. Importantly, the same reaction conditions, purification procedures, and approach can be applied in the presence of a wide variety of functionality and monomer combinations. This approach provides access to a substantially more diverse array of materials than traditional lithiation-based strategies and can be used for the generation of more diverse building blocks and the installation of a variety of functionality where necessary. Due to the statistical nature of the reaction, higher analogs of (2) are formed. Under these reaction conditions, the dimeric species (3) constitutes ˜10% of the product and can be isolated from the monomeric species through standard chromatographic methods. Adjustment of the reaction conditions can be used to tailor the product distribution. Scheme 2 shows the synthesis of 2 and 3.
##STR00004##
(4-(3,5-didodecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethylstannane) (2). In an nitrogen filled glove box, 1 (1.00 g, 1.31 mmol), 3.5 equivalents Me.sub.3SnSnMe.sub.3 (1.50 g, 4.58 mmol) and Pd(PPh.sub.3).sub.4 (151 mg, 0.13 mmol) were combined in a schlenk flask and 20 mL of toluene was added. The flask was sealed, removed from the glove box and heated to 80° C. for 12 hours. The reaction mixture was allowed to cool and volatiles were removed in vacuo. The residue was extracted with diethyl ether, filtered and poured into a separatory funnel containing 50 mL DI water. The organic layer was washed with 3×50 mL DI water, dried over anhydrous MgSO.sub.4, and all volatiles were removed in vacuo. Purification was accomplished by column chromatography on reverse phase silica using ethanol (containing 1% triethylamine) as the eluent affording 864 mg of a viscous red oil (0.93 mmol, 71%). .sup.1H NMR (500 MHz, C.sub.6D.sub.6, 298 K): δ 7.56 (s, 1H), 7.44 (m, 2H), 7.38 (s, 1H), 7.31 (s, 1H), 7.07 (s, 1H), 2.64 (t, J=7.8 Hz, 4H), 1.70 (m, 4H), 1.47-1.25 (m, 36H), 0.92 (t, J=6.7 Hz, 6H), 0.30 (s, 9H, Sn—CH.sub.3), 0.23 (s, 9H, Sn—CH.sub.3).
Example 3. Copolymerization Reactions
[0040] Copolymerization of 2 with 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (P1), 4,9-dibromo-6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (P2), 4,9-dibromo-6,7-dithienyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (P3) was carried out via microwave heating using Pd(PPh.sub.3).sub.4 (3-4 mol %) as the catalyst in xylenes. The copolymers were obtained in >80% yields following purification via soxhlet extraction. Scheme 3 shows microwave mediated copolymerization of 2.
##STR00005##
General Procedure for Copolymerization Reactions of P1-P3.
[0041] A microwave tube was charged with 2 (100 mg, 0.161 mmol) and quinoxaline derivative (0.161 mmol). The tube was brought inside a glove box and approximately 500 μl of xylenes containing 4.1 mg of Pd(PPh.sub.3).sub.4 from a stock solution was added. The tube was sealed, removed from the glove box and subjected to the following reaction conditions in a microwave reactor: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 40 min. After this time, the reaction was allowed to cool leaving a solid gelled material. The mixture was dissolved in chlorobenzene, then precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively with methanol (4 h), acetone (4 h), hexanes (12 h), and again with acetone (2 h). The polymer was dried in vacuo.
P1: Yield: 76.4 mg (0.093 mmol, 87%) of a black solid. The .sup.1H NMR spectra was very broad as the polymer showed a very strong tendency toward aggregation at 315 K. .sup.1H NMR (500 MHz, CHCl.sub.3, 315 K): δ 9.60-6.50 (br, 6H), 3.51-2.87 (br m, 10H), 1.99-0.54 (br, 46H).
P2: Yield: 70.4 mg (0.086 mmol, 80%) of a black solid. The .sup.1H NMR spectra was very broad as the polymer showed a very strong tendency toward aggregation at 315 K. .sup.1H NMR (500 MHz, CHCl.sub.3, 315 K): δ 9.70-6.50 (br, 16H), 3.72-2.73 (br m, 4H), 2.07-0.89 (br, 46H).
P3: Yield: 90.3 mg (0.094 mmol, 88%) of a black solid. The .sup.1H NMR spectra was very broad as the polymer showed a very strong tendency toward aggregation at 393 K. .sup.1H NMR (500 MHz, 398 K CHCl.sub.3, 315 K): δ 9.70-6.50 (br, 12H), 3.74-2.81 (br m, 4H), 1.99-0.64 (br, 46H).
Example 4. Solid-State Optical and Electrochemical Properties of P1-P3
[0042] The UV-Vis-IR absorption spectra of thin films of P1-P3 are compared in
Example 5. Fabrication of Electrically Conductive and Photoconductive Devices
[0043] More detailed electrical characterization of very narrow band gap DA copolymers has revealed that these semiconducting materials resemble inhomogeneous, phase separated conducting polymers. In these systems, it is likely that the transport properties are limited by poor control over sterics, electronics, film structure, and through the use of spacers (such as bridging thiophenes) to achieve planarity. A progression in the transport properties is evident when progressing to narrower band gaps in the novel materials of the invention. The electrical properties are also highly dependent on interchain arrangements and the solubilizing groups employed. Linear current-voltage (IV) characteristics obtained on thin-film devices of P1-P3 demonstrate intrinsic electrical conductivity in the absence of “dopants”. A large difference in the conductivity is evident when comparing P2 (σ˜10.sup.−3 S/cm) and P3 (σ˜10.sup.−1 S/cm), which may reflect different levels of electronic coupling arising from the presence of bulky aryl substituents on the TQ acceptor. The intrinsic electrical conductivity of these materials further highlights how structural and electronic control gives rise to the unique properties.
[0044] Silicon substrates with a 300 nm SiO.sub.2 gate dielectric were cleaned using detergent, DI water, acetone, and IPA. The substrates were treated with UV-Ozone for 20 minutes. Gold contacts (50 nm) were thermally evaporated at 1×10.sup.−7 torr using a shadow mask. Substrates were then treated with OTS solution in toluene to deposit a self-assembled monolayer. Following rinsing with toluene, acetone, and IPA, the active layer (10 mg/ml polymer in CHCl.sub.3) was spun onto the substrate at 3000 rpm. Conductivity tests were conducted using a two point probe method under nitrogen. Scans were conducted from −10 to 10 V. Standard FET measurements with gate voltages did not result in a field effect.
[0045]
ADDITIONAL EXAMPLES
Donor-Acceptor Polymers with an Infrared Photoresponse
[0046] Donor-acceptor (DA) conjugated polymers provide an important platform for the development of solution-processed optoelectronic devices. The complex interrelation between electronic properties and conformational disorder in these materials complicates the identification of design guidelines to control the bandgap at low energies, limiting the design of new optoelectronic and device functionalities. The present invention demonstrates that DA polymers comprised of exocyclic olefin substituted cyclopentadithiophene donors, in combination with conventional electron acceptors, display very narrow optical band gaps (1.2>E.sub.g.sup.opt>0.7 eV) and primary photoexcitations extending into the shortwave infrared. The invention includes use of any electron-deficient heteroaromatic ring system as the acceptor. Theoretical calculations reveal fundamental structure-property relationships toward band gap and energy level control in these spectral regions. Bulk heterojunction photodiodes fabricated using these new materials demonstrate a detectivity (D*) of >10.sup.11 Jones within a spectral range of 0.6-1.43 μm and measurable D* to 1.8 μm, the longest reported to date for conjugated polymer-based systems. The present invention systematically controls the structural and electronic properties and the band gap (E.sub.g.sup.opt=optical band gap) of conjugated copolymers within the 1.2 eV>E.sub.g.sup.opt>0.1 eV range across multiple systems.
Introduction
[0047] The inherent flexibility afforded by molecular design has accelerated the development of a wide variety of (opto)electronic technologies based on solution-processable organic semiconductors (OSCs). Donor-acceptor (DA) polymers comprised of alternating electron-rich (donor) and electron-poor (acceptor) moieties have emerged as the dominant class of high performance materials to date in organic photovoltaic (OPV) and photodetector (OPD) applications. State-of-the-art OPDs, based on a bulk heterojunction (BHJ) architecture, have demonstrated a broad spectral response (0.3-1.45 μm), detectivities (D*)>10.sup.12 Jones (1 Jones=1 cm Hz.sup.0.5 W.sup.−1), and a linear dynamic range over 100 dB in the visible sub-band (0.5 and 0.8 μm). There is significant interest in expanding the scope of these materials to improve functionality in the near-infrared (NIR: 0.9-1.4 μm) and extend utility into the shortwave IR (SWIR: 1.4-3 μm) to serve as alternatives to conventional inorganic semiconductor materials.
[0048] Unlike inorganic semiconductors, photoexcitation of OSCs does not lead to substantial instantaneous free carrier generation. Organic photoresponsive devices necessitate a lower ionization potential species (donor polymer) that manifests a singlet manifold transition (S.sub.0.fwdarw.S.sub.1) and possess a large intensity in the spectral region of interest. Photoexcitation results in bound electron-hole pairs (excitons), which require a suitable energy offset, facilitated by a higher electron affinity acceptor (typically a fullerene derivative, (
[0049] These complexities motivated an investigation of molecular design strategies that yield a reduction in bandgap and promote the appropriate properties suitable for long wavelength (λ) light detection in a conventional BHJ architecture. The prototypical narrow bandgap polymer PCPDTBT (P4a) is shown in
Example A
[0050] Materials and Methods. All manipulations of air and/or moisture sensitive compounds were performed under an inert atmosphere using standard glove box and Schlenk techniques. Reagents, unless otherwise specified, were purchased from Sigma-Aldrich and used without further purification. Solvents (xylenes, THF, toluene, and ethanol) were degassed and dried over 4 Å molecular sieves. Deuterated solvents (C.sub.6D.sub.6, CDCl.sub.3, and C.sub.2D.sub.2Cl.sub.4) were purchased from Cambridge Isotope Labs and used as received. 3,5-dibromobenzaldehyde and 4,7-dibromobenzo[c][1,2,5]thiadiazole were purchased from Oakwood Chemical and Sigma-Aldrich respectively, and purified by column chromatography prior to use. Tetrakis(triphenylphosphine)palladium(0) was purchased from Strem Chemicals and used as received. Alkylzinc halides were prepared according to a previously reported procedure. 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophene, 4,7-dibromobenzo[c][1,2,5]selenadiazole, 4,7-dibromo[1,2,5]-selenadiazolo[3,4-c]pyridine, 4,9-bis(5-bromothiophen-2-yl)-6,7-dioctyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline, and 4,6-Bis(5-bromo-2-thienyl)thieno[3,4-c][1,2,5]thiadiazole were prepared according to previously reported procedures. .sup.1H and .sup.13C NMR spectra were collected on a Bruker Ascend 600 MHz spectrometer and chemical shifts, δ (ppm) were referenced to the residual solvent impurity peak of the given solvent. Data reported as: s=singlet, d=doublet, t=triplet, m=multiplet, br=broad; coupling constant(s), J are given in Hz. Flash chromatography was performed on a Teledyne Isco CombiFlash Purification System using RediSep Rf prepacked columns. Microwave assisted reactions were performed in a CEM Discover microwave reactor. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra were measured on a Bruker Microflex LT system. The number average molecular weight (M.sub.n) and dispersity (Ð) were determined by gel permeation chromatography (GPC) relative to polystyrene standards at 160° C. in 1,2,4-trichlorobenzene (stabilized with 125 ppm of BHT) in an Agilent PL-GPC 220 high temperature GPC/SEC system using a set of four PLgel 10 μm MIXED-B columns. Polymer samples were pre-dissolved at a concentration of 1.00-2.00 mg mL.sup.−1 in 1,2,4-trichlorobenzene with stirring for 4 h at 150° C. Overlap of aromatic protons with solvent occurred in both CDCl.sub.3 and C.sub.6D.sub.6 for compounds 1a, 1b, 2a, and 2b. The structures were confirmed using .sup.13C NMR and MALDI-TOF mass spectrometry.
[0051] UV-Vis-NIR Spectroscopy. UV-Vis-NIR spectra were recorded using a Cary 5000 UV-Vis-NIR spectrophotometer. Thin films were prepared by spin coating a 10 mg mL.sup.−1 chlorobenzene (C.sub.6H.sub.5Cl) solution onto quartz substrates at 2000 rpm.
[0052] Electrochemistry. Electrochemical characteristics were determined by cyclic voltammetry (50 mV s.sup.−1) carried out on drop-cast polymer films at room temperature in degassed anhydrous acetonitrile with tetrabutylammonium hexafluorophosphate (0.1 M) as the supporting electrolyte. The working electrode was a platinum wire, the counter electrode was a platinum wire and the reference electrode was Ag/AgCl. After each measurement the reference electrode was calibrated with ferrocene and the potential axis was corrected to the normal hydrogen electrode (NHE) using −4.75 eV for NHE.
[0053] Device Fabrication. Pre-patterned indium tin oxide (ITO) substrates were ultrasonically cleaned in detergent, deionized water and 2-propanol for 15 min sequentially. Polyethylenimine (PEIE) (35-40 wt %, 7000 g mol.sup.−1, Sigma Aldrich) was diluted with 2-methoxyethanol to achieve a concentration of 0.4 wt %. The diluted PEIE solution was spin coated onto the cleaned ITO substrate at 3500 rpm to form a film of ˜10 nm, which was then annealed at 120° C. for 10 min in ambient conditions. For P5, the polymer and [70]PCBM (Osilla Ltd.) in a 1:2 ratio were dissolved in anhydrous chlorobenzene:chloroform (3:1) at a polymer concentration of 14 mg mL.sup.−1. For P6, the polymer and [70]PCBM (1:2) were dissolved in chlorobenzene:chloroform (2:1) at a polymer concentration of 15 mg mL.sup.−1. The solutions were stirred at 45° C. overnight in a nitrogen atmosphere. Four percent (4%) 1,8-diiodooctane (DIO) was added prior to spin coating P6. For P7 and P8, the polymers (8.5 mg mL.sup.−1 and 7.5 mg mL.sup.−1) were dissolved in chlorobenzene at 80° C. overnight in a nitrogen atmosphere then filtered. [70]PCBM was added to give a solution with a 1:2 polymer:fullerene ratio and stirred at 80° C. for an additional 1 h. After this time, 3% DIO was added to the solution. The blend solutions were spin coated on the PEIE/ITO substrate at a spin speed of 1800, 1800, 700, and 300 rpm to form films with thicknesses of 175, 184, 385, and 255 nm for P5, P6, P7, and P8 based devices, respectively. To complete the fabrication of the OPD, 15 nm MoO.sub.3, followed by 100 nm Ag, was deposited on top of the blend film through thermal evaporation in a vacuum chamber at a pressure of 3×10.sup.−6 mbar. The effective areas of these photodetectors was 8.5 mm.sup.2 (P5) and 9 mm.sup.2 (P6-P8) measured with the help of an optical microscope. The devices were encapsulated between glass slides bonded with epoxy and subsequently characterized in air. The photodiode spectral response was amplified through a low-noise amplifier with an internal load resistor of 100 kΩ (for high gain) or 100Ω (for low gain) and measured with a lock-in amplifier, using a monochromatic light source modulated by a mechanical chopper at a frequency of 390 Hz. Cutoff filters at 455 nm, 645 nm, and 1025 nm were used to reduce the scattered light due to higher order diffraction. The lock-in amplifier can accurately measure a modulated photocurrent down to a magnitude of 2×10.sup.−11 A.
Synthesis and Characterization
[0054] 3,5-didodecylbenzaldehyde (1a). In a nitrogen filled glove box, Pd-PEPPSI-IPr (0.274 g, 3.5 mol %) and 3,5-dibromobenzaldehyde (3.04 g, 11.5 mmol) were added to an oven-dried flask equipped with a stir bar. Toluene (30 mL) was added and the reaction mixture was stirred at room temperature to dissolve the contents. A THF solution (˜0.50 M) of n-dodecylzinc bromide (81.0 mL, 40.3 mmol) was then added dropwise over a period of 30 min using a dropping funnel. After stirring for 16 h at room temperature, the reaction was heated to 60° C. and stirred at that temperature for 2 h. Upon cooling, the reaction mixture was quenched with saturated NH.sub.4Cl (150 mL) and filtered through a Buchner funnel. The biphasic mixture was then poured into a separatory funnel, the water layer removed, and the organic phase washed with 3×100 mL 1 M Na.sub.3EDTA (3 equiv. NaOH with EDTA), water (1×100 mL), and brine (1×100 mL). The organic solution was then dried with MgSO.sub.4 and filtered through Celite. Volatiles were removed in vacuo and purification by flash chromatography on silica gel (hexanes to hexanes:ethyl acetate=95:5 as the eluent) afforded a pale white solid (3.47 g, 68%). .sup.1H NMR (600 MHz, CDCl.sub.3) δ 9.98 (1H, s), 7.51 (2H, s), 2.66 (4H, t, J=7.8 Hz), 1.64 (4H, m), 1.40-1.20 (36H, m), 0.89 (6H, t, J=6.7 Hz). .sup.13C NMR (151 MHz, CDCl.sub.3) δ 192.95, 143.98, 136.82, 135.15, 127.29, 35.78, 32.07, 31.46, 29.82, 29.80, 29.72, 29.62, 29.57, 29.51, 29.42, 22.84, 14.25. MS (MALDI-TOF) m/z calculated for C.sub.31H.sub.54O: 442.42, found 442.61.
[0055] 3,5-ditetradecylbenzaldehyde (1b). In a nitrogen filled glove box, Pd-PEPPSI-IPr (0.277 g, 3.5 mol %) and 3,5-dibromobenzaldehyde (3.07 g, 11.6 mmol) were added to an oven-dried flask equipped with a stir bar. Toluene (30 mL) was added and the reaction mixture was stirred at room temperature to dissolve the contents. A THF solution (˜0.50 M) of n-tetradecylzinc bromide (82.0 mL, 40.7 mmol) was then added dropwise over a period of 30 min using a dropping funnel. After stirring for 16 h at room temperature, the reaction was heated to 60° C. and stirred at that temperature for 2 h. Upon cooling, the reaction mixture was quenched with saturated NH.sub.4Cl (150 mL) and filtered through a Buchner funnel. The biphasic mixture was then poured into a separatory funnel, the water layer removed, and the organic phase washed with 3×100 mL 1 M Na.sub.3EDTA (3 equiv. NaOH with EDTA), water (1×100 mL), and brine (1×100 mL). The organic solution was then dried with MgSO.sub.4 and filtered through Celite. Volatiles were removed in vacuo and purification by flash chromatography on silica gel (hexanes to hexanes:ethyl acetate=95:5 as the eluent) afforded a colorless oil (4.06 g, 70%). .sup.1H NMR (600 MHz, CDCl.sub.3) δ 9.97 (1H, s), 7.51 (2H, s), 2.66 (4H, t, J=7.8 Hz), 1.64 (4H, m), 1.40-1.20 (44H, m), 0.89 (6H, t, J=6.7 Hz). .sup.13C NMR (151 MHz, CDCl.sub.3) δ 192.96, 143.97, 136.83, 135.13, 127.28, 35.78, 32.08, 31.46, 29.86, 29.84, 29.83, 29.81, 29.73, 29.62, 29.52, 29.42, 29.42, 22.84, 14.25. MS (MALDI-TOF) m/z calculated for C.sub.35H.sub.62O: 498.48, found 498.83.
[0056] 2,6-dibromo-4-(3,5-didodecylbenzylidene)-4H-cyclopenta-[2,1-b:3,4-b′]dithiophene (2a). Under nitrogen, sodium ethoxide (0.463 g, 6.80 mmol) was added to a suspension of 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (1.04 g, 3.09 mmol) in ethanol (10 mL) at 50° C. After 30 min of stirring, a 50° C. solution of 1a (1.37 g, 3.09 mmol) in ethanol (20 mL) was added dropwise. The reaction mixture was slowly heated and refluxed under nitrogen for 3 h. The reaction was then allowed to cool to room temperature, quenched with DI water (100 mL) and extracted with dichloromethane. The organic layer was washed with water (1×100 mL), brine (1×100 mL), and then dried with MgSO.sub.4. After filtration through a Buchner funnel, volatiles were removed in vacuo and purification by flash chromatography (pentane as the eluent) yielded a red oil that solidified upon standing (1.67 g, 71%). .sup.1H NMR (600 MHz, C.sub.6D.sub.6) δ 7.23 (1H, s), 7.01 (2H, s), 6.83 (1H, s), 2.57 (4H, t, J=7.8 Hz), 1.66 (4H, m), 1.47-1.21 (36H, m), 0.91 (6H, t, J=6.7 Hz). .sup.13C NMR (151 MHz, C.sub.6D.sub.6) δ 145.18, 143.55, 140.58, 140.48, 136.69, 136.22, 132.04, 130.38, 130.05, 127.74, 126.48, 123.29, 111.46, 110.40, 36.31, 32.38, 32.06, 30.21, 30.16, 30.13, 30.12, 30.08, 29.87, 29.87, 23.16, 14.40. MS (MALDI-TOF) m/z calculated for C.sub.40H.sub.56Br.sub.2S.sub.2: 760.81, found 760.22.
[0057] 2,6-dibromo-4-(3,5-ditetradecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (2b). Under nitrogen, sodium ethoxide (0.453 g, 6.67 mmol) was added to a suspension of 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (1.02 g, 3.03 mmol) in ethanol (10 mL) at 50° C. After 30 min of stirring, a 50° C. solution of 1b (1.51 g, 3.03 mmol) in ethanol (20 mL) was added dropwise. The reaction mixture was slowly heated and refluxed under nitrogen for 3 h. The reaction was then allowed to cool to room temperature, quenched with DI water (100 mL) and extracted with dichloromethane. The organic layer was washed with water (1×100 mL), brine (1×100 mL), and then dried with MgSO.sub.4. After filtration through a Buchner funnel, volatiles were removed in vacuo and purification by flash chromatography (pentane as the eluent) yielded a red oil that solidified upon standing (1.51 g, 61%). .sup.1H NMR (600 MHz, C.sub.6D.sub.6) δ 7.24 (1H, s), 7.01 (2H, s), 6.83 (1H, s), 2.57 (4H, t, J=7.8 Hz), 1.67 (4H, m), 1.47-1.21 (44H, m), 0.92 (6H, t, J=6.7 Hz). .sup.13C NMR (151 MHz, C.sub.6D.sub.6) δ 145.18, 143.56, 140.59, 140.50, 136.71, 136.23, 132.04, 130.40, 130.05, 128.22, 128.06, 127.90, 127.74, 126.48, 123.29, 111.46, 110.41, 36.30, 32.37, 32.05, 30.22, 30.21, 30.21, 30.21, 30.16, 30.12, 30.06, 29.86, 29.85, 23.15, 14.39. MS (MALDI-TOF) m/z calculated for C.sub.44H.sub.64Br.sub.2S.sub.2: 816.47, found 816.28.
[0058] (4-(3,5-didodecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethylstannane) (3a). In a nitrogen filled glove box, 2a (0.995 g, 1.31 mmol), 5 equiv. Me.sub.3SnSnMe.sub.3 (2.14 g, 6.54 mmol), and Pd(PPh.sub.3).sub.4 (0.0982 g, 8.50×10.sup.−2 mmol) were combined in a 35 mL microwave tube. The mixture was dissolved in approximately 25 mL of toluene. The tube was sealed, removed from the glove box and heated at 80° C. for 12 h. The reaction was allowed to cool and volatiles were removed in vacuo. The residue was extracted with hexanes, filtered, and poured into a separatory funnel containing 50 mL DI water. The organic layer was washed with DI water (3×50 mL), dried over anhydrous MgSO.sub.4, and all volatiles removed in vacuo. Purification was accomplished by flash chromatography on reverse phase silica (ethanol containing 1% triethylamine as the eluent) affording a viscous red oil (0.862 g, 71%). .sup.1H NMR (600 MHz, C.sub.6D.sub.6, 298 K) δ 7.52 (1H, s), 7.42 (2H, s), 7.36 (1H, s), 7.30 (1H, s), 7.06 (1H, s), 2.64 (4H, t, J=7.8 Hz), 1.70 (4H, m), 1.47-1.21 (36H, m), 0.92 (6H, t, J=6.7 Hz), 0.31 (9H, s), 0.23 (9H, s). .sup.13C NMR (151 MHz, C.sub.6D.sub.6) δ 150.78, 147.29, 145.74, 143.29, 143.28, 137.52, 137.50, 136.41, 131.59, 131.14, 129.14, 129.13, 128.22, 128.06, 127.90, 36.43, 32.38, 32.15, 30.21, 30.21, 30.18, 30.16, 30.06, 30.02, 29.87, 23.16, 14.42, −8.30, −8.37. MS (MALDI-TOF) m/z calculated for C.sub.46H.sub.74S.sub.2Sn.sub.2: 928.33, found 928.12.
[0059] (4-(3,5-ditetradecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethylstannane) (3b). In a nitrogen filled glove box, 2b (0.940 g, 1.15 mmol), 5 equiv. Me.sub.3SnSnMe.sub.3 (1.88 g, 5.75 mmol), and Pd(PPh.sub.3).sub.4 (0.0864 g, 7.48×10.sup.−2 mmol) were combined in a 35 mL microwave tube. The mixture was dissolved in approximately 25 mL of toluene. The tube was sealed, removed from the glove box and heated at 80° C. for 12 h. The reaction mixture was allowed to cool and volatiles were removed in vacuo. The residue was extracted with hexanes, filtered, and poured into a separatory funnel containing 50 mL DI water. The organic layer was washed with water (3×50 mL), dried over anhydrous MgSO.sub.4, and all volatiles were removed in vacuo. Purification was accomplished by flash chromatography on reverse phase silica (ethanol containing 1% triethylamine as the eluent) affording a viscous red oil (0.839 g, 74%). .sup.1H NMR (600 MHz, C.sub.6D.sub.6, 298 K) δ 7.53 (1H, s), 7.43 (2H, s), 7.37 (1H, s), 7.31 (1H, s), 7.07 (1H, s), 2.64 (4H, t, J=7.8 Hz), 1.70 (4H, m), 1.47-1.21 (44H, m), 0.92 (6H, t, J=6.7 Hz), 0.31 (9H, s), 0.23 (9H, s). .sup.13C NMR (151 MHz, C.sub.6D.sub.6) δ 150.79, 147.30, 145.75, 143.30, 143.28, 137.53, 137.51, 136.44, 131.59, 131.15, 129.19, 129.14, 128.22, 128.06, 127.90, 36.43, 32.38, 32.15, 30.22, 30.19, 30.17, 30.13, 30.06, 30.01, 29.87, 23.16, 14.40, −8.32, −8.39. MS (MALDI-TOF) m/z calculated for C.sub.50H.sub.82S.sub.2Sn.sub.2: 984.39, found 984.12.
[0060] Synthesis of P4. A microwave tube was loaded with 3a (150 mg, 0.162 mmol) and 4,7-dibromobenzo[c][1,2,5]-thiadiazole (45.4 mg, 0.154 mmol). The tube was brought inside a glove box and approximately 6.5 mg of Pd(PPh.sub.3).sub.4 and 750 μL of xylenes were added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 40 min. After this time, the reaction was allowed to cool leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively with methanol (4 h), acetone (4 h), hexanes (12 h), hexanes:THF (3:1) (12 h), and again with acetone (2 h). The polymer was dried in vacuo to give 81 mg (67%) of a blue solid. GPC (160° C., 1,2,4-trichlorobenzene) Mn=8.0 kg mol.sup.−1, Ð=1.21. λ.sub.max (solution, CHCl.sub.3, 25° C.)/nm 812 (ε/L mol.sup.−1 cm.sup.−1 18,161); λ.sub.max (thin film)/nm 893. .sup.1H NMR (600 MHz, C.sub.2D.sub.2Cl.sub.4, 398 K) δ 8.55-6.35 (8H, br m), 3.35-2.51 (4H, br), 2.30-0.85 (46H, br).
[0061] Synthesis of P5. A microwave tube was loaded with 3a (150 mg, 0.162 mmol) and 4,7-dibromobenzo[c][1,2,5]-selenadiazole (52.6 mg, 0.154 mmol). The tube was brought inside a glove box and approximately 6.5 mg of Pd(PPh.sub.3).sub.4 and 750 μL of xylenes were added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 40 min. After this time, the reaction was allowed to cool leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively with methanol (4 h), acetone (4 h), hexanes (12 h), hexanes:THF (3:1) (12 h), and again with acetone (2 h). The polymer was dried in vacuo to give 89 mg (71%) of a green solid. GPC (160° C., 1,2,4-trichlorobenzene) Mn=10.1 kg mol-1, Ð=2.90. λ.sub.max (solution, CHCl.sub.3, 25° C.)/nm 878 (ε/L mol.sup.−1 cm.sup.−1 19,073); λ.sub.max (thin film)/nm 927. .sup.1H NMR (600 MHz, C.sub.2D.sub.2Cl.sub.4, 398 K) δ 8.55-6.25 (8H, br m), 3.43-2.43 (4H, br m), 2.27-0.81 (46H, br).
[0062] Synthesis of P6. A microwave tube was loaded with 3a (150 mg, 0.162 mmol) and 4,7-dibromo[1,2,5]selenadiazolo-[3,4-c]pyridine (52.7 mg, 0.154 mmol). The tube was brought inside a glove box and approximately 6.5 mg of Pd(PPh.sub.3).sub.4 and 750 μL of xylenes were added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 40 min. After this time, the reaction was allowed to cool leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively with methanol (4 h), acetone (4 h), hexanes (12 h), hexanes:THF (3:1) (12 h), and again with acetone (2 h). The polymer was dried in vacuo to give 83 mg (66%) of a green solid. GPC (160° C., 1,2,4-trichlorobenzene) Mn=13.2 kg mol.sup.−1, Ð=1.64. λ.sub.max (solution, CHCl.sub.3, 25° C.)/nm 883 (ε/L mol.sup.−1 cm.sup.−1 14,260); λ.sub.max (thin film)/nm 911. .sup.1H NMR (600 MHz, C.sub.2D.sub.2Cl.sub.4, 398 K) δ 8.75-6.20 (7H, br m), 3.40-2.53 (4H, br m), 2.52-0.79 (46H, br).
[0063] Synthesis of P7. A microwave tube was loaded with 3a (150 mg, 0.162 mmol) and 4,9-bis(5-bromothiophen-2-yl)-6,7-dioctyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (113 mg, 0.154 mmol). The tube was brought inside a glove box and approximately 6.5 mg of Pd(PPh.sub.3).sub.4 and 750 μL of xylenes were added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 50 min. After this time, the reaction was allowed to cool leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively with methanol (4 h), acetone (4 h), hexanes (12 h), THF (12 h), and again with acetone (2 h). The polymer was dried in vacuo to give 153 mg (80%) of a black solid. GPC (160° C., 1,2,4-trichlorobenzene) Mn=18.8 kg mol.sup.−1, Ð=1.91. λ.sub.max(solution, CHCl.sub.3, 25° C.)/nm 1073 (ε/L mol.sup.−1 cm.sup.−1 34,009); λ.sub.max (thin film)/nm 1079. .sup.1H NMR (600 MHz, C.sub.2D.sub.2Cl.sub.4, 398 K) δ 9.31-6.25 (10H, br m), 3.30-2.45 (8H, br m), 2.46-0.75 (76H, br).
[0064] Synthesis of P8. A microwave tube was loaded with 3b (150 mg, 0.152 mmol) and 4,6-Bis(5-bromo-2-thienyl)thieno[3,4-c][1,2,5]thiadiazole (67.2 mg, 0.145 mmol). The tube was brought inside a glove box and approximately 6.5 mg of Pd(PPh.sub.3).sub.4 and 750 μL of xylenes were added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 30 min. After this time, the reaction was allowed to cool leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively with methanol (4 h), acetone (4 h), hexanes (12 h), THF (12 h), and again with acetone (2 h). The polymer was dried in vacuo to give 109 mg (74%) of a purple solid. GPC (160° C., 1,2,4-trichlorobenzene) Mn=14.4 kg mol.sup.−1, Ð=1.64. λ.sub.max (solution, CHCl.sub.3, 25° C.)/nm 963 (ε/L mol.sup.−1 cm.sup.−1 22,843); λ.sub.max (thin film)/nm 967. .sup.1H NMR (600 MHz, C.sub.2D.sub.2Cl.sub.4, 398 K) δ 8.55-6.25 (10H, br m), 3.25-2.43 (4H, br m), 2.50-0.51 (54H, br).
Results and Discussion
[0065]
[0066] The comparatively lower bandgap of P4 (E.sub.g.sup.DFT=1.34 eV) relative to P4a and P4b (E.sub.g.sup.DFT=1.56 eV and 1.47 eV, respectively) can be ascribed to planarization of the CPDT core (in contrast to the modest curvature of C, Si, and C═NPh substituted analogs), and a reduction in the overall bond length alternation. P4 is highly planar with negligible rotational disorder (donor/acceptor dihedral angle=179.36°), which contributes to extended electron delocalization. Solubilizing substituents are oriented nearly orthogonal and situated at a site remote to the polymer backbone in P4. Collectively, these structural features are likely to permit improved n-interactions, further mitigate backbone torsion, and increase resilience toward conjugation saturation behavior. The lowest vertical excitation energy (E.sub.g.sup.vert), which more appropriately approximates the onset of optical absorption, was obtained through extrapolation of a series of oligomers (n=1-6) to n.fwdarw.∞ and fitting the data to the Kuhn equation. In moving across the series we note a progressive narrowing of E.sub.g.sup.vert: P4=1.04 eV; P5=0.94 eV; P6=0.88 eV; P7=0.68 eV; P8=0.63 eV, illustrating iterative control throughout the NIR and extension into the SWIR. Structural and electronic characteristics associated with C═CPh substitution manifest in other donor/heterocyclic acceptor configurations (P7 and P8). As in several other similar materials, the HOMO is delocalized over the whole n-system and the LUMO is more localized on the acceptor. The spectra of the (P4-P8).sub.6 oligomers exhibit one dominant S.sub.0.fwdarw.S.sub.1 transition of HOMO.fwdarw.LUMO character with large oscillator strengths, consistent with DA polymers commonly utilized in photoresponsive devices.
[0067] Band gap engineering at low energies will require careful chemical, electronic, and structural control. Modular side-chain engineering approaches are also necessary owing to the immense difficulty in achieving the appropriate phase characteristics associated with polymers and heterojunction blends. To address these challenges, the inventors developed a synthetic route amenable to systematic structural and electronic variation as depicted in Scheme 4, which shows the synthesis of P4-P8. Linear (R=C.sub.12H.sub.25 and C.sub.14H.sub.29) solubilizing groups were introduced into the 3,5-positions of the Ph ring to minimize backbone torsion and promote solubility. The coupling of dodecylzinc bromide and tetradecylzinc bromide with 3,5-dibromobenzaldehyde was accomplished using a Pd-PEPPSI-IPr pre-catalyst. Optimization of the solvent system (toluene/THF=1:3), catalyst loading (3.5%), and heating of the reaction mixture ensured high conversions, providing the coupled products (1a and 1b) in overall yields>60% in the presence of the aldehyde functionality. The reaction of 1a and 1b with 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophene using sodium ethoxide (NaOEt) in ethanol (EtOH) affords the desired C═CPh substituted CPDT donors (2a and 2b) in 71% and 61% yield. Reaction with 5 equiv. of hexamethylditin (Me.sub.3SnSnMe.sub.3) using Pd(PPh.sub.3).sub.4 in toluene affords the bis-trimethylstannyl donors (3a and 3b) in >70% yields.
##STR00006## ##STR00007##
[0068] Copolymerization of 3a with 4,7-dibromobenzo[c]-[1,2,5]thiadiazole (P4), 4,7-dibromobenzo[c][1,2,5]-selenadiazole (P5), 4,7-dibromo-[1,2,5]selenadiazolo[3,4-c]pyridine (P6) 4,9-bis(5-bromothiophen-2-yl)-6,7-dioctyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (P7), and 3b with 4,6-bis(5-bromo-2-thienyl)thieno[3,4-c][1,2,5]thiadiazole (P8) was carried out via microwave heating using Pd(PPh.sub.3).sub.4 (3.5 mol %) as the catalyst in xylenes. This resulted in the rapid formation of polymers in reaction times <60 minutes and isolated yields of 65-80% after purification by soxhlet extraction. P7 (R=C.sub.12H.sub.25, R′=C.sub.8H.sub.17) and P8 (R=C.sub.14H.sub.29) required additional solubilizing units to promote solubility of the extended π-systems in common organic solvents used for solution processing. Gel permeation chromatography (GPC) at 160° C. in 1,2,4-trichlorobenzene showed number average molecular weights (M.sub.n)˜8-19 kg mol.sup.−1 ensuring >10 repeat units to allow a comparison between experiment and theory, albeit well below typical high performance materials.
[0069] Absorption spectra of P4-P8 at 25° C. in chloroform (CHCl.sub.3) and as thin-films are shown in
[0070] Substitution of BT for BSe (P5), wherein a single atom in the benzochalcogenodiazole unit is varied from sulfur (S) to selenium (Se), results in red-shifted absorption profile (λ.sub.max=0.93 μm) with measurable absorbance extending to λ>1.4 μm in the solid state. The electrochemical characteristics reflect a modest reduction in the LUMO energy (E.sub.HOMO=−5.01 eV; E.sub.LUMO=−3.75 eV; E.sub.g.sup.elec of 1.26 eV). A further reduction is obtained by incorporating a PSe analog (P6), resulting in higher electron affinity in the backbone and a narrower band gap (E.sub.g.sup.opt=0.94 eV). A pronounced bathochromic shift is evident in transitioning to the solid state in P6, leading to measurable absorbance extending to λ>1.6 μm. It should be noted that the PSe for BSe substitution also reduces the symmetry of the repeat unit, which may account for the broad spectral features. Electrochemical measurements are consistent with a reduction in both the HOMO-LUMO energies (E.sub.HOMO=−5.10 eV; E.sub.LUMO=−3.95 eV; E.sub.g.sup.elec of 1.15 eV).
[0071] Heteroannulated variants of BT, such as thiadiazoloquinoxaline (TQ), result in a significant reduction in the LUMO, which can be mitigated by the presence of thiophene spacers. A further narrowing of the bandgap was obtained in P7 (λ.sub.max=1.08 μm) with measurable absorbance extending to λ>1.6 μm in the solid state. A plot of absorbance squared is consistent with low energy excitations at these wavelengths and E.sub.g.sup.opt˜0.85 eV (1.46 μm). The pronounced absorption shoulder and similar spectral profiles in solution and the solid state are consistent with strong intermolecular interactions in P7. Substitution of the TQ-based acceptor with a thiophene flanked thieno[3,4-c][1,2,5]thiadiazole heterocycle results in a further redshift consistent with theoretical predictions (P8: E.sub.HOMO=−4.85 eV; E.sub.LUMO=−3.95 eV; E.sub.g.sup.elec of 0.90 eV; E.sub.g.sup.opt˜0.74 eV). The utility of bridgehead C═CPh substitution in mitigating conjugation saturation behavior is evident in view of values for E.sub.g.sup.elec and E.sub.g.sup.opt that are similar with those from theory (E.sub.g.sup.DFT and E.sub.g.sup.vert), compared in Table 1. P4-P8 retain the appropriate difference in electrochemical potential relative to common fullerene acceptors, such as [60]PCBM and [70]PCBM (LUMO˜−4.2 and −4.3 eV, respectively), providing the necessary driving force needed for efficient charge separation.
TABLE-US-00001 TABLE 1 Optical, electrochemical, and calculated properties of P4-P8. λ.sub.max E.sub.g.sup.opt E.sub.g.sup.vert E.sub.HOMO/E.sub.LUMO E.sub.g.sup.elec E.sub.g.sup.DFT (μm).sup.a [eV].sup.b [eV] [eV].sup.c [eV].sup.d [eV].sup.e P4 0.89 1.11 1.04 −5.01/−3.65 1.36 1.34 P5 0.93 1.08 0.94 −5.01/−3.75 1.26 1.24 P6 0.91 0.94 0.88 −5.10/−3.95 1.15 1.12 P7 1.08 0.85 0.68 −4.80/−3.66 1.14 0.91 P8 0.97 0.74 0.63 −4.85/−3.95 0.90 0.88 .sup.aFilms spin coated from a C.sub.6H.sub.5Cl solution (10 mg mL.sup.−1). .sup.bEstimated from the absorption onset of the film. .sup.cE.sub.Homo calculated from the onset of oxidation, E.sub.LUMO calculated from the onset of reduction. .sup.dE.sub.g.sup.elec calculated from the difference between E.sub.HOMO and E.sub.LUMO. .sup.eHOMO/LUMO orbital energy gap (E.sub.g.sup.DFT).
[0072] To demonstrate the ultimate utility of copolymers based on C═CPh substitution, BHJ photodetectors were fabricated using P5-P8 in combination with [70]PCBM.
[0073] The specific detectivity (D*) is the main figure of merit that takes both dark current (
CONCLUSIONS
[0074] These results demonstrate detection of longer λ light than was previously possible using OSCs and highlight the potential of tunable NIR-SWIR photoresponsive DA polymers that can be applied in a variety of photodetection applications traditionally limited to inorganic semiconductors, colloidal quantum dots, and carbon nanotubes. From a broader perspective, more precise narrow bandgap DA polymers of the present invention will enable targeted engineering of the bandgap at low energies, the generation of materials for fundamental studies, and enable new functionality in the IR spectral regions.
Donor-Acceptor Conjugated Polymers with Tunable Open Shell Configurations and High Spin Ground States
[0075] Organic semiconductors with tunable electronic structures, cooperative electronic properties based on n-electrons, and controlled spin pairing underlie the development of next generation (opto)electronic technologies. In particular, n-conjugated molecules with intramolecular high spin ground states are of fundamental interest for revealing emergent phenomena and are anticipated to play a role in future magnetic, spintronic, and quantum information technologies. While significant achievements have been made in the fundamental chemistry of organic high spin molecules, nearly all are unstable or highly localized. The present invention demonstrates the coalescence of molecular design features that gives rise to a charge neutral, very narrow bandgap donor-acceptor conjugated polymer with a high spin (S=1) ground state. The material is synthesized using conventional/scalable synthetic approaches, is solution-processable, adopts an amorphous solid-state morphology, demonstrates intrinsic electrical conductivity, and exhibits stability under ambient conditions. Quantum chemical calculations demonstrate that very narrow bandgaps afforded through extended conjugation are related to the coexistence of nearly degenerate states, and that building blocks bearing non-disjoint (cross-conjugated) functionalities along the polymer backbone can modulate the electronic topology and promote intramolecular ferromagnetic coupling in the extended π-system. Electron paramagnetic resonance and superconducting quantum interference device magnetometry studies are consistent with antiferromagnetically interacting triplet (S=1) polymer chains exhibiting a high-to-low spin energy gap of 9.30×10.sup.−3 kcal mol (J=1.62 cm.sup.−1, 2 J/k.sub.B=4.67 K). The results provide new molecular design guidelines to access, stabilize, and tune the properties of high spin diradicals with novel spin-spin interactions and magnetic functionalities.
Results and Discussion.
[0076] The complexities associated with the synthesis and application of high spin organic systems motivated the investigation of design strategies which may favor and stabilize this electronic configuration. A high spin (S=1), very narrow bandgap DA copolymer was produced and synthesized as follows. The inventors first identified a narrow bandgap copolymer structure (E.sub.g.sup.DFT<0.2 eV) comprised of an exocyclic olefin (C═CPh) substituted 4H-cyclopenta[2,1-b:3,4-b]dithiophene (CPDT) donor and a strong thiadiazoloquinoxaline (TQ) acceptor (C═CPhCPDT-alt-TQ, P1 in
Nature of the Ground State Electronic Structure.
[0077] The properties of P1 were studied by Electron paramagnetic resonance (EPR) spectroscopy (frozen matrix) and superconducting quantum interference device (SQUID) magnetometry of solid powder samples. The EPR Intensity from 4 to 50 K reveals a continuous decrease of the spin susceptibility. The data can be fitted to the Bleaney-Bowers equation from 4 to 25 K and yields a high-to-low spin energy gap, ΔE(T.sub.1.fwdarw.S.sub.0), of 9.3×10.sup.−3 kcal mol.sup.−1 (J=1.62 cm.sup.−1, 2 J/k.sub.B=4.67 K). The temperature dependence of the magnetic susceptibility indicated a paramagnetic ground state after subtraction of the diamagnetic component (
Examples B
[0078] Example 6. This example involved the detailed material synthesis procedure for P1B.
A microwave tube was loaded with (4-(3,5-didodecylbenzylidene)4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethylstannane) (150 mg, 0.162 mmol) and 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (57.8 mg, 0.155 mmol). This tube was brought inside the glovebox, and 750 μL of a Pd(PPh.sub.3).sub.4/xylenes stock solution (3.5 mol %) was added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor with stirring: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 30 min. After this time, the reaction was allowed to cool, leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively (under a N.sub.2 atmosphere and in the absence of light) with methanol (2 h), acetone (2 h), hexanes (2 h), a 1:1 mixture of hexanes and tetrahydrofuran (12 h), and then acetone (2 h). The polymer was dried in vacuo to give 85 mg (68%) of a black solid. Data are as follows: Mn=15.0 kgmol.sup.−1 and Ð=1.50; .sup.1HNMR (600 MHz, 1,1,2,2-tetrachloroethane-d.sub.2, 398 K); δ 8.00 to 6.50 (6H, br m), 3.60 to 2.50 (4H, br m), 2.30 to 1.15 (40H, br m), 1.10 to 0.80 (6H, br in), and 0.72 (6H, s); absorption; λ.sub.max (solution, 1,2-dichlorobenzene, 25° C.)=1.25 μm, λ.sub.max (thin film)=1.30 μm, and ε=16,057 L mol.sup.−1 cm.sup.−1.
##STR00008##
Example 7. This example involved the detailed material synthesis procedure for P2B.
A microwave tube was loaded with (4-(3,5-ditetradecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethylstannane) (88 mg, 0.089 mmol) and 4,9-dibromo-6,7-dimethyl-[1,2,5)thiadiazolo[3,4-g)quinoxaline (31.8 mg, 0.085 mmol). The tube was brought inside the glovebox, and 410 μL of a Pd(PPh3)4/xylenes stock solution (3.5 mol %) was added. The tube was sealed and subjected to the following reaction conditions in a microwave reactor with stirring: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 30 min. After this time, the reaction was allowed to cool, leaving a solid gelled material. The mixture was precipitated into methanol and collected via filtration. The residual solid was loaded into an extraction thimble and washed successively (under a N.sub.2 atmosphere and in the absence of light) with methanol (2 h), acetone (2 h), hexanes (2 h), a 1:1 mixture of hexanes and tetrahydrofuran (12 h), and then acetone (2 h). The polymer was dried in vacuo to give 62 mg (77%) of a black solid. Absorption: λ.sub.max (solution, CHCl.sub.3, 25° C.)=1.21 μm, λ.sub.max (thin film)=1.32 μm.
##STR00009##
Example 8. This example involved the material synthesis procedure for P3B, P4B, and P5B.
General procedure for the polymer synthesis: (4,4-dialkyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethyl-stannane) (0.107 mmol, 1.05 equiv), 4,9-dibromo-6,7-dialkyl-[1,2,5]thiadiazolo[3,4-g] quinoxaline (0.101 mmol, 1.0 equiv) were weighed into a microwave tube with a stir bar and 3.5 mol % of Pd(PPh.sub.3).sub.4 in 250 μL xylene was added inside the glove box. The tube was sealed and subjected to the reaction conditions in a microwave reactor. The reaction mixture was cooled to room temperature, and the polymer was precipitated into methanol. The polymer was then filtered and purified by Soxhlet extraction (under N.sub.2 atmosphere and protected from light) using methanol (2 h), acetone (2 h), hexanes (12 h) and followed by acetone (2 h) in the end. The residual solvent under reduced pressure was removed to afford the black solid product.
P3B: Conditions: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 20 min. Yield: 80%. .sup.1H NMR (600 MHz, 1,1,2,2-Tetrachloroethane-d.sub.2, 398 K): δ 9.41-9.04 (br, 2H), 3.23-2.85 (br, 4H, CDT-CH.sub.2), 2.36-2.15 (br, 4H, CH.sub.2), 1.44-0.93 (br, 88H, CH.sub.2, CH.sub.3). Absorption: λ.sub.max (solution, CHCl.sub.3, ambient temperature)=1.15 μm; λ.sub.max (thin film)=1.23 μm; ε=23413 L mol.sup.−1 cm.sup.−1. ICP-OES: Pd=0.15 wt % (0.014 mmol g−1) and no Fe and Sn were detected.
P4B: Conditions: 120° C. for 5 min, 140° C. for 5 min, 170° C. for 60 min, and 190° C. for 10 min. Yield: 72%. .sup.1H NMR (600 MHz, chloroform-d, 333 K): δ 9.38-9.16 (br, 1H), 7.99-7.84 (br, 2H), 7.69-7.24 (br, 4H), 2.26-2.11 (br, 2H, CH.sub.2), 1.44-0.80 (br, 64H, CH.sub.2, CH.sub.3). Absorption: λ.sub.max(solution, CHCl.sub.3, ambient temperature)=1.38 μm; λ.sub.max (thin film)=1.46 μm; F: =33841 L mol.sup.−1 cm.sup.−1.
P5B: Conditions: 120° C. for 5 min, 140° C. for 5 min, 170° C. for 60 min, and 190° C. for 10 min. Yield: 79%. .sup.1H NMR (600 MHz, chloroform-d, 333 K): δ 9.31-8.88 (br, 1H), 7.95-7.40 (br, 3H), 7.24-6.93 (br, 2H), 2.34-1.85 (br, 4H, CH.sub.2), 1.44-0.97 (br, 60H), 0.96-0.76 (br, 6H). Absorption: λ.sub.max (solution, CHCl.sub.3, ambient temperature)=1.46 μm; λ.sub.max (thin film)=1.66 μm; ε=33087 L mol.sup.−1 cm.sup.−1.
##STR00010##
Example 9. This example involved the detailed material synthesis procedure for P6B.
4-(3,5-bis(hexadecyloxy)benzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)bis(trimethylstannane) (100 mg, 0.093 mmol, 1.05 equiv), 4,7-bis(5-bromothiophen-2-yl)-2λ.sup.4δ.sup.2-benzo[1,2-c;4,5-c′]bis[1,2,5]thiadiazole (46 mg, 0.08 mmol, 1.0 equiv) were weighed into a microwave tube with a stir bar and 3.5 mol % of Pd(PPh.sub.3).sub.4 in 430 μL xylene was added inside the glove box. The tube was sealed and subjected to the following reaction conditions in a microwave reactor with stirring: 120° C. for 5 min, 140° C. for 5 min, and 170° C. for 5 min. The reaction mixture was cooled to room temperature, and the polymer was precipitated into methanol. The polymer was then filtered and purified by Soxhlet extraction (under N.sub.2 atmosphere and protected from light) using methanol (2 h), acetone (2 h), hexanes (2 h), 2:1 mixture of hexanes and THF (12 h) and followed by acetone (2 h) in the end. The polymer was dried in vacuo to afford 83 mg (80%) black solid product. Absorption: λ.sub.max (solution, CHCl.sub.3, ambient temperature)=1.18 μm; λ.sub.max (thin film)=1.29 μm.
##STR00011##
Example 10. This Example Involved the Detailed Material Synthesis Procedure for P7B:
[0079] P7B: 4-(3,5-bis(hexadecyloxy)benzylidene)-4H-cyclopenta[2,1-b: 3,4-b 1dithiophene-2,6-diyl)bis(trimethylstannane) (80 mg, 0.075 mmol, 1.05 equiv), 4,7-bis(5-bromo selenophen-2-yl)-2λ.sup.4δ.sup.2-benzo[1,2-c;4,5-c′]bis[1,2,5]thiadiazole (43 mg, 0.071 mmol, 1.0 equiv) were weighed into a microwave tube with a stir bar and 3.5 mol % of Pd(PPh.sub.3).sub.4 in 340 μL xylene was added inside the glove box. The tube was sealed and subjected to the following reaction conditions in a microwave reactor with stirring: 120° C. for 5 min, 140° C. for 5 min, and 150° C. for 5 min. The reaction mixture was cooled to room temperature, and the polymer was precipitated into methanol. The polymer was then filtered and purified by Soxhlet extraction (under N.sub.2 atmosphere and protected from light) using methanol (2 h), acetone (2 h), hexanes (2 h), 1:1 mixture of hexanes and THF (12 h) and followed by acetone (2 h) in the end. The polymer was dried in vacuo to afford 63 mg (70%) black solid product. Absorption: λ.sub.max (solution, CHCl.sub.3 ambient temperature)=1.40 μm; λ.sub.max (thin film)=1.49 μm.
##STR00012##
TABLE-US-00002 TABLE 1 Solu- tion Film λ.sub.ma .sup.a λ.sub.max .sup.b E.sub.g.sup.opt c E.sub.HOMO .sup.d E.sub.LUMO .sup.e E.sub.g.sup.elec f Polymer (μm) (μm) [eV] [eV] [eV] [eV] P1B 1.25 1.30 0-0.5 −4.79 −4.23 0.56 P2B 1.21 1.32 0-0.5 −4.65 −3.95 0.70 P3B 1.15 1.23 0.66 −5.15 −4.00 1.15 P4B 1.38 1.46 0.59 −5.52 −4.35 0.9 P5B 1.46 1.66 0.54 −5.07 −4.27 0.8 P6B 1.18 1.29 0.50 −4.85 −4.00 0.85 P7B 1.40 1.49 0.44 −4.5 −3.65 0.85 .sup.a Dilute solution was made from CHCl.sub.3. .sup.b Films spin coated from a C.sub.6H.sub.5Cl solution (10 mg mL.sup.−1). .sup.c Estimated from the absorption onset of the film. .sup.d E.sub.HOMO calculated from the onset of oxidation, .sup.e E.sub.LUMO calculated from the onset of reduction, .sup.f E.sub.g.sup.elec calculated from the difference between E.sub.HOMO and E.sub.LUMO.
indicates data missing or illegible when filed
Examples C
Example 11
[0080] A series of donor acceptor polymers comprised of exocyclic olefin substituted 4-benzylidene-4H-cyclopenta[2,1-b:3,4-b′]bithiophene (C═CPhCDT) donors were prepared to form P1C-P11C.
##STR00013##
Example 12
[0081] Narrow bandgap polymer, P12C was prepared, (poly (4-(5-(4-(3,5-bis(dodecyloxy)benzylidene)-4H-cyclopenta [2,1-b:3,4-b]dithiophen-2-yl)thiophen-2-yl)-6,7-dioctyl-9-(thiophen-2-yl)-[1,2,5]thiadiazole [3,4-g]quinoxaline). The extended conjugation in this material promotes a narrow bandgap of approximately, E.sub.g˜1.1 eV, with an absorption maximum (λ.sub.max) of 1050 nm.
##STR00014##
Examples D
Example 13
[0082] Narrow bandgap polymers were prepared to form P1D-P8D:
##STR00015##
All parameters presented herein including, but not limited to, sizes, dimensions, times, temperatures, pressures, amounts, quantities, ratios, weights, volumes, and/or percentages, and the like, for example, represent approximate values. Further, references to ‘a’ or ‘an’ concerning any particular item, component, material, or product is defined as at least one and could be more than one.
[0083] The above detailed description is presented to enable any person skilled in the art to make and use the invention. Specific details have been revealed to provide a comprehensive understanding of the present invention and are used for explanation of the information provided. These specific details, however, are not required to practice the invention, as is apparent to one skilled in the art. Descriptions of specific applications, analyses, materials, components, dimensions, and calculations are meant to serve only as representative examples. Various modifications to the preferred embodiments may be readily apparent to one skilled in the art, and the general principles defined herein may be applicable to other embodiments and applications while still remaining within the scope of the invention. There is no intention for the present invention to be limited to the embodiments shown and the invention is to be accorded the widest possible scope consistent with the principles and features disclosed herein.
[0084] While various embodiments of the present invention have been described above and in the attached documents, it should be understood that they have been presented by way of example and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope of the present invention. In fact, after reading the above description, it will be apparent to one skilled in the relevant art(s) how to implement the invention in alternative embodiments. The applicants have described the preferred embodiments of the invention, but it should be understood that the broadest scope of the invention includes such modifications as additional or different methods and materials. Many other advantages of the invention will be apparent to those skilled in the art from the above descriptions, reference documents, and the subsequent claims. Thus, the present invention should not be limited by any of the above-described exemplary embodiments.
[0085] The process, apparatus, system, methods, products, and compounds of the present invention are often best practiced by empirically determining the appropriate values of the operating parameters, or by conducting simulations to arrive at best design for a given application. Accordingly, all suitable modifications, combinations, and equivalents should be considered as falling within the spirit and scope of the invention.
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