Synthesis of aza-acenes as novel n-type materials for organic electronics

Abstract

Acenes, such as aza-acenes are attractive materials for organic semiconductors, specifically for n-type materials. There are disclosed new derivatives of acenes that are fabricated using novel synthesis. For example, the disclosed fabrication strategies have allowed for the first time new aza-tetracene and aza-pentacene derivatives. The HOMO and LUMO energy levels of these materials are tunable through appropriate substitution and as predicted, deepened. There are also disclosed organic photosensitive devices comprising at least one aza-acene such as aza-tetracene and aza-pentacene.

Claims

1. An organic photosensitive optoelectronic device comprising at least one heterojunction at the interface of at least one donor material and at least one acceptor material, wherein the acceptor material comprises at least one aza-acene; wherein the aza-acene is a diaza-tetracene selected from 4,10-diphenyl-3,9-diaza-tetracene (DPDAT), 4,8,10,14-tetraphenyl-3,9-diaza-tetracene (TPDAT), 4,10-dichloro-3,9-diaza-tetracene (DCDAT), 8,14-diphenyl-4,10-dichloro-3,9-diaza-tetracene (DPDCDAT), 8,14-diphenyl-4,10-dicyano-3,9-diaza-tetracene (DPDCNDAT), and 4,10-dicyano-3,9-diaza-tetracene (DCNDAT).

2. The device of claim 1, wherein the diaza-tetracene is DPDCNDAT and the at least one donor material is boron subphthalocyanonine chloride(SubPc).

3. The device of claim 2 having a structure Indium Tin Oxide (ITO)/SubPc/DPDCNDAT/Bathocuproine (BCP)/Al.

Description

(1) FIG. 1 depicts the systematic lowering of HOMO and LUMO energy levels calculated at B3LYP/6-31G* for aza-tetracenes and aza-pentacenes.

(2) FIG. 2 shows an exemplary synthetic scheme for the synthesis of a 3,9-diaza-tetracene.

(3) FIG. 3 shows an exemplary synthetic scheme for the synthesis of a 5,12-diaza-pentacene.

(4) FIG. 4 shows the absorption spectrum of a 4,10-dichloro-3,9-diaza-tetracene and a 4,10-diphenyl-3,9-diaza-tetracene.

(5) FIG. 5 shows the absorption spectrum of a 4,10-dicyano-3,9-diaza-tetracene and a 2,8-diphenyl-4,10-dicyano-3,9-diaza-tetracene.

(6) FIG. 6 shows cyclic voltammetry (CV) measurements for 4,10-dichloro-3,9-diaza-tetracene.

(7) FIG. 7 shows CV measurements for 4,10-diphenyl-3,9-diaza-tetracene.

(8) FIG. 8 shows CV measurements for 4,10-dicyano-3,9-diaza-tetracene.

(9) FIG. 9 shows CV measurements for 2,8-diphenyl-4,10-dicyano-3,9-diaza-tetracene.

(10) FIG. 10 shows CV measurements for additional aza-acene compounds.

(11) FIG. 11 shows absorption/emission spectra for particular diaza-tetracenes

(12) FIG. 12 provides additional absorption and electrochemical properties of particular diaza-tetracenes.

(13) FIG. 13 shows current density-vs.-voltage characteristics for OPV devices employing a particular diaza-tetracene as an acceptor material.

(14) As described herein, aza-acenes may be synthesized by aromatizing a compound selected from I through XIX. In some embodiments, the compound selected from I through XIX is aromatized with a treatment comprising an oxyphilic reagent. The oxyphilic reagent may be, for example, phosphoryl trichloride (POCl.sub.3), phosphoryl tribromide (POBr.sub.3), phosphorous tribromide (PBr.sub.3), pentachloro-phosphorane (PCl.sub.5), phosphorous trichloride (PCl.sub.3), tetrabenzyl pyrophosphate, 1-dibenzyl phosphite, phenyldichlorophosphate, and thionyl chloride (SOCl.sub.2). In certain embodiments, the oxyphilic reagent is POCl.sub.3. In this embodiment, the compound selected from I through XIX undergoes a deoxygenation-chlorination reaction to yield the corresponding dichloro-aza-acene, which can be subjected to further transformation to yield desired substituents.

(15) In other embodiments, the compound selected from I through XIX is aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents. In some embodiments, the protective group is MEM, although persons of ordinary skill in the art would recognize that other protective groups may be used. The protective group on the quinolone nitrogen allows treatment with alkyl or aryl organolithium reagents or alkyl or aryl Grignard reagents to yield the desired aza-acenes. The synthesis of compounds I through XIX may rely on the use of anilines or derivatives thereof as primary starting materials. Anilines are much simpler starting materials compared to o-diaminoarenes, and as a result they provide a greater number of potential derivatives that can be accessed. Another advantage of the present invention is the use of POCl.sub.3 to aromatize compounds I through XIX to aza-acenes. This avoids any problems in oxidation chemistry, as quinolone residues have previously been shown to aromatize with POCl.sub.3. A compound selected from I though XIX may also be synthesized using aminopyridines or derivatives thereof. The significance of these materials is found in the ability to incorporate nitrogen into every ring of acenes, such as tetracene and pentacene.

(16) There are a variety of approaches to form the carbon-nitrogen bond between an aromatic amine and an aryl-halide. The most common methods are those involving Cu and Pd catalyst, specifically Ullmann or Buchwald-Hartwig conditions. Another approach may use the acid catalyzed condensation chemistry using aromatic-amines which is the traditional route in forming the bond in the synthesis of both epindolidione and quinacridone. The carbon-nitrogen bond formation is not limited to these approaches. For example, Conrad-Limpach cyclization has been demonstrated from a variety of carbonyl functionalities mostly from carboxylic acids, amides and thio-esters; however, other functionalities may also be suitable. The cyclization conditions are typically carried out in hot polyphosphoric acid (PPA) but are not limited to this reagent as the reaction can occur through a pure thermal process or through the aid of other strong acids.

(17) In one embodiment of the present invention, a method of synthesizing a compound selected from aza-tetracenes comprises the step of aromatizing a compound selected from I through VI.

(18) In one embodiment, the compound to be synthesized is selected from

(19) ##STR00005## ##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010## ##STR00011## ##STR00012## ##STR00013##
wherein X.sub.1 and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor, and Y.sub.1 is selected from CH and N.

(20) In some embodiments, the compound selected from I through VI is aromatized with a treatment comprising an oxyphilic reagent as described herein. In other embodiments, the compound selected from I through VI is aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(21) In some embodiments, the compound to be synthesized is selected from aza-tetracenes, wherein the method of synthesizing further comprises the step of synthesizing a compound selected from I through VI, wherein Y.sub.n is C. In some embodiments, the compound selected from I through VI, wherein Y.sub.n is C, is synthesized using an aniline or a derivative thereof having a general formula

(22) ##STR00014##
wherein R.sub.1-4 are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor, and W is selected from H, —CO.sub.2H, —CO.sub.2R, —COSR, and —CONR.sub.2. As one of ordinary skill in the art would appreciate, desired substituents on the aza-acenes may be achieved by using particular anilines or derivatives thereof as starting materials.

(23) A diaza-tetracene aromatized from an exemplary compound of compound I may be synthesized, for example, based on the following reaction scheme:

(24) ##STR00015##
A diaza-tetracene aromatized from an exemplary compound of compound II may be synthesized, for example, based on the following reaction scheme:

(25) ##STR00016##
A diaza-tetracene aromatized from an exemplary compound of compound II may also be synthesized, for example, based on the following reaction scheme:

(26) ##STR00017##

(27) Alternatively, aromatization to the aza-acene may be accomplished by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein. The following reaction scheme provides an example of using MEM-CI to protect the quinolone nitrogens followed by treatment with an aryl Grignard reagent:

(28) ##STR00018##

(29) A diaza-tetracene aromatized from an exemplary compound of compound III may be synthesized, for example, based on the following reaction scheme:

(30) ##STR00019##
wherein the resulting compound j may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(31) A diaza-tetracene aromatized from an exemplary compound of compound VI may be synthesized, for example, based on the following reaction scheme:

(32) ##STR00020##
wherein the resulting compound k may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(33) One of ordinary skill in the art would understand that after aromatizing with an oxyphilic reagent, such as POCl.sub.3, the resulting dichloro-aza-acenes described herein can be subject to further transformations to yield desired substituents.

(34) In one embodiment, the aza-tetracene to be synthesized is a diaza-tetracene selected from

(35) ##STR00021## ##STR00022##
wherein X.sub.1 and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor.

(36) Aza-tetracenes having 3 or more nitrogens in their cores, such as triaaza-tetracene and tetraaza-tetracene may be obtained by using an aminopyridine or a derivative thereof in place of aniline or a derivative thereof. Aminopyridines or derivatives thereof may also be used in conjunction with anilines or derivatives thereof on a step-by-step basis to obtain aza-acenes having 3 or more nitrogens in their cores. Thus, in some embodiments, the compound to be synthesized is selected from aza-tetracenes, wherein the method of synthesizing further comprises the step of synthesizing a compound selected from I through VI. In some embodiments, the compound selected from I through VI is synthesized using an aminopyridine or a derivative thereof having a general formula selected from

(37) ##STR00023##
wherein X.sub.1-3 are independently selected from N and C, R.sub.1-3 are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor, with the proviso that any of R.sub.1-3 is H when the X to which it is bonded is N, and W is selected from H, —CO.sub.2H, —CO.sub.2R, —COSR, and —CONR.sub.2. As one of ordinary skill in the art would appreciate, the particular aminopyridine or derivative thereof that is used will affect the positions of the nitrogens in the aza-acenes, as well as the substituents on the aza-acenes.

(38) A tetraaza-tetracene aromatized from an exemplary compound of compound I, may be synthesized based on, for example, the following reaction scheme:

(39) ##STR00024##
wherein the resulting compound a may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(40) Triaza-tetracenes aromatized from exemplary compounds of compounds I and II may be synthesized by unsymmetrical syntheses based on, for example, the following schemes:

(41) ##STR00025## ##STR00026##
wherein the resulting compounds b and c may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(42) In one embodiment, the aza-tetracene to be synthesized is a triaza-tetracene or tetraaza-tetracene selected from

(43) ##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031## ##STR00032## ##STR00033##
wherein X.sub.1 and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a psuedohalide, an alkyl, and an electron acceptor, and Y.sub.1 is selected from CH and N.

(44) In another embodiment of the present invention, a method of synthesizing a compound selected from aza-pentacenes, comprises the step of aromatizing a compound selected from compounds VII through XIX.

(45) In one embodiment, the compound is selected from

(46) ##STR00034## ##STR00035## ##STR00036## ##STR00037## ##STR00038## ##STR00039## ##STR00040## ##STR00041## ##STR00042## ##STR00043## ##STR00044## ##STR00045## ##STR00046## ##STR00047## ##STR00048##
wherein X.sub.1 and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor.

(47) In some embodiments, the compound selected from VII through XIX is aromatized with a treatment comprising an oxyphilic reagent as described herein. In other embodiments, the compound selected from VII through XIX is aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(48) In some embodiments, the compound to be synthesized is selected from aza-pentacenes, wherein the method of synthesizing further comprises the step of synthesizing a compound selected from VII through XIX, wherein Y.sub.n is C. In some embodiments, the compound selected from VII through XIX, wherein Y.sub.n is C, is synthesized using an aniline or a derivative thereof having a general formula

(49) ##STR00049##
wherein R.sub.1-4 are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor, and W is selected from H, —CO.sub.2H, —CO.sub.2R, —COSR, and —CONR.sub.2.

(50) A diaza-pentacene aromatized from exemplary compounds of compound VII, may be synthesized, for example, based on the following schemes:

(51) ##STR00050##
wherein the resulting compounds d and e may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein. The following reaction scheme provides an example of using MEM-Cl to protect the quinolone nitrogen followed by treatment with an aryl Grignard reagent:

(52) ##STR00051##

(53) A diaza-pentacene aromatized from an exemplary compound of compound VIII may be synthesized, for example, based on the following reaction scheme:

(54) ##STR00052##
wherein the resulting compound h may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(55) A diaza-pentacene aromatized from an exemplary compound of compound XII, may be synthesized, for example, based on the following reaction scheme:

(56) ##STR00053##
wherein the resulting compound m may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(57) In one embodiment, the aza-pentacene to be synthesized is a diaza-pentacene selected from

(58) ##STR00054##
wherein X.sub.1 and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a psuedohalide, an alkyl, and an electron acceptor.

(59) Aza-pentacenes having 3 or more nitrogens in their cores, such as triaza-pentacenes, tetraaza-pentacenes, and pentaaza-pentacenes, may be obtained in some instances by using aminopyridines or derivatives thereof in place of anilines or derivatives thereof. Aminopyridine or a derivative thereof may also be used in conjunction with aniline or a derivative thereof on a step-by-step basis to obtain aza-pentacenes having 3 or more nitrogens in their cores. Aniline or a derivative thereof, aminopyridine or a derivative thereof, and pyridine derivatives, or combinations thereof may also be used as starting materials to obtain aza-pentacenes having 3 or more nitrogens in their cores. Thus, in some embodiments, the compound to be synthesized is selected from aza-pentacenes, wherein the method of synthesizing further comprises the step of synthesizing a compound selected from compounds VII through XIX. In some embodiments, the compound selected from VII through XIX is synthesized using an aminopyridine or a derivative thereof having a general formula selected from

(60) ##STR00055##
wherein X.sub.1-3 are independently selected from N and C, R.sub.1-3 are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor, with the proviso that any of R.sub.1-3 is H when the X to which it is bonded is N, and W is selected from H, —CO.sub.2H, —CO.sub.2R, —COSR, and —CONR.sub.2. As one of ordinary skill in the art would appreciate, the particular aminopyridine or derivative thereof that is used will affect the number and position of the nitrogens in the aza-acenes, as well as the substituents on the aza-acenes.

(61) A triaza-pentacene aromatized from an exemplary compound of compound VII, may be synthesized based on, for example, the following reaction scheme:

(62) ##STR00056##
wherein the resulting compound f may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(63) A tetraaza-pentacene aromatized from an exemplary compound of compound VIII, may be synthesized based on, for example, the following reaction scheme:

(64) ##STR00057##
wherein the resulting compound g may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(65) A pentaaza-pentacene aromatized from an exemplary compound of compound X, may be synthesized based on, for example, the following reaction scheme:

(66) ##STR00058##
wherein the resulting compound i may be aromatized by an oxyphilic reagent as described herein, or aromatized by bonding a protective group to the quinolone nitrogens followed by treatment with a reagent selected from alkyl or aryl organolithium reagents and alkyl or aryl Grignard reagents as described herein.

(67) In one embodiment, the aza-pentacene to be synthesized is a triaza-pentacene, tetraaza-pentacene, or pentaaza-pentacene selected from

(68) ##STR00059## ##STR00060## ##STR00061## ##STR00062## ##STR00063## ##STR00064## ##STR00065## ##STR00066## ##STR00067## ##STR00068## ##STR00069## ##STR00070## ##STR00071##
wherein X.sub.1 and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor.

(69) The reaction schemes provided herein serve as examples only and are not meant to limit the invention in any way. One of ordinary skill in the art would understand that the chemistry disclosed herein allows for a variety of aza-acenes, such as aza-tetracenes and aza-pentacenes, to be envisioned. For example, reaction materials may be modified to vary the degree and position of aza-substitution, as well as to obtain desired substituents on the aza-acenes. The aza-acene compounds may be symmetric or asymmetric with a varying number of quinolone residues present in the precursor compound for later aromatization. This would allow one of ordinary skill in the art to place nitrogen at virtually any position 1-12 in tetracene or 1-14 in pentacene.

(70) The aza-acene compounds contemplated by the present invention may be used as n-type materials in organic electronics. In one embodiment, there is disclosed an organic photosensitive optoelectronic device comprising at least one aza-acene. In some embodiments, the at least one aza-acene is selected from aza-tetracenes and aza-pentacenes.

(71) In some embodiments, the at least one aza-acene compound is an aza-tetracene selected from diaza-tetracenes, triaza-tetracenes, and tetraaza-tetracenes.

(72) In some embodiments, the at least one aza-acene compound is an aza-tetracene having a general formula selected from

(73) ##STR00072##
wherein Y.sub.n are independently selected from C and N, and R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor with the proviso that any of R.sub.n is H when the Y to which it is bonded is N.

(74) In some embodiments, the at least one aza-acene compound is an aza-pentacene selected from diaza-pentacenes, triaza-pentacenes, tetraaza-pentances, and pentaaza-pentacenes.

(75) In some embodiments, the at least one aza-acene compound is an aza-pentacene having a general formula selected from

(76) ##STR00073## ##STR00074## ##STR00075##
wherein Y.sub.n are independently selected from C and N, R.sub.n are independently selected from saturated carbocyclic, saturated heterocyclic, unsaturated carbocyclic, and unsaturated heterocyclic rings with adjacent R.sub.n, a H, an aryl, a halide, a pseudohalide, an alkyl, and an electron acceptor with the proviso that any of R.sub.n is H when the Y to which it is bonded is N, and Z is selected from CH and CH.sub.2

(77) In some embodiments, the organic photosensitive optoelectronic device comprises at least one donor-acceptor heterojunction. The donor-acceptor heterojunction may be formed at an interface of at least one donor material and at least one acceptor material. In some embodiments, the at least one acceptor material comprises the at least one aza-acene compound. In some embodiments, the aza-acene compound is selected from aza-tetracenes and aza-pentacenes. In some embodiments, the aza-tetracene is selected from diaza-tetracenes, triaza-tetracenes, and tetraaza-tetracenes. In some embodiments, the aza-pentacene is selected from diaza-pentacene, triaza-pentacene, tetraaza-pentacene, and pentaaza-pentacene.

(78) In some embodiments, the diaza-tetracene is selected from 4,10-diphenyl-3,9-diaza-tetracene (DPDAT), 4,8,10,14-tetraphenyl-3,9-diaza-tetracene (TPDAT), 4,10-dichloro-3,9-diaza-tetracene (DCDAT), 8,14-diphenyl-4,10-dichloro-3,9-diaza-tetracene (DPDCDAT), 8,14-diphenyl-4,10-dicyano-3,9-diaza-tetracene (DPDCNDAT), and 4,10-dicyano-3,9-diaza-tetracene (DCNDAT).

(79) In some embodiments, the at least one donor material is chosen from squarine (SQ), boron subphthalocyanonine chloride (SubPc), copper phthalocyanine (CuPc), chloro-aluminum phthalocyanine (CIAlPc), poly(3-hexylthiophene) (P3HT), tin phthalocyanine (SnPc), diindenoperylene (DIP), and combinations thereof.

(80) In some embodiments, the diaza-tetracene is DPDCNDAT and the at least one donor material is SubPc.

(81) In one embodiment, the organic photosensitive optoelectronic device has the structure ITO/SubPc/DPDCNDAT/BCP/Al.

(82) The organic photosensitive devices of the present invention may be structured in various configurations with varying material combinations. U.S. Patent Publication No. 2012/0235125 is hereby incorporated by reference for its disclosure of organic photovoltaic device structures and materials.

(83) In some embodiments, the organic photosensitive optoelectronic device is a solar cell.

(84) In some embodiments, the organic photosensitive optoelectronic device is a photodetector.

(85) As used herein, the term “alkyl” means a straight-chain or branched saturated hydrocarbyl group. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl and n-hexyl.

(86) As used herein, the term “aryl” means an aromatic hydrocarbyl group. The aryl group may be monocyclic or multicyclic. Examples of aryl groups include phenyl and naphthyl groups.

(87) As used herein, the term “electron acceptor” means functional groups that have vacant pi-symmetry molecular orbitals, which are within 1-2 eV of the HOMO of the molecule they are appended to. These materials interact with the molecule by accepting electron density and thus lowering the energy of the molecule's HOMO. Common electron acceptors include, for example, nitro, cyano, formyl, phenyl, vinyl immine, tricyano-vinyl, fluoroalkyl, pyridinium, carboxyl, and ester groups.

EXAMPLES

(88) FIG. 2 provides an example of a synthesis for 3,9-diaza-tetracenes in accordance with the present invention. Epindolidiones (5a-b) were prepared starting from commercially available dihydroxy fumaric acid. Compound 1 was treated with thionyl chloride in dry methanol to afford the methyl ester 2 in 74% yield. The dimethyl bis(arylamino)maleates (3a-b) were obtained in good yield by refluxing 2 in methanol with a catalytic amount of HCl in the presence of an aryl aniline. Maleates (3a-b) were then subjected to refluxing Dowtherm A to afford the 2-methoxycarbonyl-3-arylamino-4-quinolones (4a-b). Heating 4a-b in polyphosphoric acid for 2 hours afforded epindolidiones (5a-b) in excellent yield. Treatment of epindolidione (5a-b) in neat phosphorous oxychloride in the presence of K.sub.2CO.sub.3 gave the 4,10-dichloro-3,9-diaza-tetracenes (6a-b) in modest yields. Compound 6a was subjected to a variety of Suzuki coupling conditions all of which failed or gave yields <10% of compound 7a. Under Kumada conditions using PEPPSI-IPr as the palladium source, compounds 7a-b were prepared in excellent yields. Cyanation of 6a-b with a catalytic amount of sodium p-SO.sub.2Ph with KCN in hot DMF afforded 8a-b in low yields.

(89) As an additional example of the synthetic scheme shown in FIG. 2, the individual reactions are further explained as follows:

(90) ##STR00076##

(91) Dimethyl dihydroxyfumarate (2) was prepared by stirring a solution of 1 (25.00 g, 16.9 mmol) with 50 g of MgSO.sub.4 in 200 mL of dry MeOH and cooling to 0° C. The mixture was purged with dry HCl for 4 hours. The ice bath was removed and the reaction stirred for 2 hours at room temperature. The mixture was left at room temperature overnight undisturbed. A white precipitate formed and was collected by vacuum filtration and washed with cold MeOH. The white solid was suspended in ice cold H.sub.20 (400 mL) and vigorously stirred then immediately collected by filtration, washed with cold H.sub.2O and MeOH. The material was air dried overnight to give 24.6 g (83%) of dimethyl dihydroxyfumarate (2). Dimethyl 2,3-bis(phenylamino)fumarate (3a) was prepared by stirring a solution of 2 (14.3 g, 81.2 mmol) and aniline (22.7 g, 243.7 mmol) in 200 mL of dry MeOH under a N.sub.2 atmosphere. The reaction mixture was heated to reflux overnight after the addition of 3 mL of Concentrated HCl. A yellow precipitate formed and was filtered off after cooling the reaction to 0° C. The precipitate was washed thoroughly with cold MeOH and hexanes and was allowed to air dry to give 18.72 g (71%) of dimethyl 2,3-bis(phenylamino)fumarate (3a). Dimethyl 2,3-bis([1,1′-biphenyl]-2-ylamino)fumarate (3b) was prepared by stirring a solution of 2 (9.4 g, 53.4 mmol) and 2-aminobiphenyl (20.0 g, 118.2 mmol) in 100 mL of dry MeOH under a N.sub.2 atmosphere. The reaction mixture was heated to reflux overnight after the addition of 1.5 mL of Concentrated HCl. A bright yellow precipitate was collected by filtration, washed with MeOH and hexanes to give 19.03 g (75%) of dimethyl 2,3-bis([1,1′-biphenyl]-2-ylamino)fumarate (3b).

(92) ##STR00077##
2-Methoxycarbonyl-3-arylamino-4-quinolone (4a) was prepared by heating a solution of 3a (12.91 g, 39.5 mmol) in Dowtherm A (80 mL) to 120° C. and adding the solution dropwise to 100 mL of refluxing Dowtherm A under N.sub.2 atmosphere. The reaction was further refluxed for 1 hour after the addition, cooled to room temperature, and left overnight. A yellow precipitate was collected by filtration and washed repeatedly with hexanes. The material was air dried to yield 5.03 g (43%) of 2-methoxycarbonyl-3-arylamino-4-quinolone (4a). 2-Methoxycarbonyl-3-arylamino quinolone (4b) was prepared by heating a solution of 3b (14.3 g, 29.8 mmol) in Dowtherm A (80 mL) to 120° C. and adding the solution dropwise to 100 mL of refluxing Dowtherm A under N.sub.2 atmosphere. The reaction was further refluxed for 1 hour after the addition, cooled to room temperature, and left overnight. A red precipitate was collected by filtration and washed repeatedly with hexanes. The material was air dried to yield 8.25 g (62%) of 2-methoxycarbonyl-3-arylamino-4-quinolone (4b). Epindolidione (5a) was prepared by charging a 250 mL round bottom flask with ˜100 mL of PPA followed by 9.5 g of 4a under a N.sub.2 atmosphere. The mixture was heated to 150° C. for 2 hours. The reaction was cooled to ˜90° C., slowly adding water to the reaction mixture until the vigorous hydrolysis reaction ceased. The mixture was then poured into 300 mL of water and vigorously stirred. The yellow precipitate was collected by filtration and then suspended in 400 mL of THF and vigorously stirred. The bright yellow precipitate was collected by filtration and washed with MeOH to yield 7.55 g (89%) of epindolidione (5a). 4,10-Diphenyl epindolidione (5b) was prepared by charging a 100 mL schlenk flask with ˜60 mL of PPA with 4.7 g of 4b under a N.sub.2 atmosphere. The mixture was heated to 150° C. for 2 hours. The reaction was cooled to ˜90° C., slowly adding water to the reaction mixture until the vigorous hydrolysis reaction ceased. The mixture was then poured into 300 mL of water and vigorously stirred. The precipitate was collected and suspended in 300 mL of THF and vigorously stirred. A bright yellow precipitate was collected by filtration and washed with hexanes to yield 3.93 g (90%) of 4,10-diphenyl epindolidione (5b).

(93) ##STR00078##
4,10-Dichloro-3,9-diazatetracene (6a) was prepared by stirring a solution of 5a (2.35 g, 8.96 mmol) in POCl.sub.3 (130 mL) with K.sub.2CO.sub.3 (7.00 g, 50.6 mmol) and purging with N.sub.2 for 20 minutes. The reaction was heated to 90° C. overnight. The reaction was cooled to room temperature and POCl.sub.3 was removed by vacuum distillation. The crude material was then added to 500 mL of aqueous 10% K.sub.2CO.sub.3 and vigorously stirred. The precipitate was collected and loaded on silica gel and eluted with CHCl.sub.3 to yield 1.44 g (54%) of 4,10-dichloro-3,9-diazatetracene (6a). 2,8-Diphenyl-4,10-dichloro-3,9-diazatetracene (6b) was prepared by stirring a solution of 5b (5 g, 12.1 mmol) in POCl.sub.3 (250 mL) with K.sub.2CO.sub.3 (15.0 g, 108.5 mmol) and purging with N.sub.2 for 20 minutes. The reaction was heated to 90° C. overnight. The reaction was cooled to room temperature and POCl.sub.3 was removed by vacuum distillation. The crude material was then added to 500 mL of aqueous 10% K.sub.2CO.sub.3 and vigorously stirred. The precipitate was collected and loaded on silica gel and eluted with CHCl.sub.3 to yield 2.39 g (44%) of 2,8-diphenyl-4,10-dichloro-3,9-diazatetracene (6b).

(94) ##STR00079##
4,10-Diphenyl-3,9-diazatetracene (7a) was prepared by charging an oven dried 100 mL schlenk flask with 6a (400 mg, 1.34 mmol) and 10 mol % of PEPPSI-IPr (91 mg) in dry dioxane (60 mL) and purging with N.sub.2 for 20 minutes. 3.0 M phenyl magnesium bromide (2.67 mL, 8.02 mmol) was then added dropwise to the reaction mixture. After the addition, the reaction was heated to 70° C. The reaction was cooled to room temperature and diluted with ethyl acetate (30 mL) and stirred. The solvent was removed and the crude material was purified by column chromatography and then recrystallized from toluene to yield 448 mg (88%) of 4,10-diphenyl-3,9-diazatetracene (7a). 2,4,8,10-tetraphenyl-3,9-diazatetracene (7b) was prepared by charging an oven dried 100 mL schlenk flask with 6b (603 mg, 1.34 mmol) and 10 mol % of PEPPSI-IPr (91 mg) in dry dioxane (60 mL) and purging with N.sub.2 for 20 minutes. 3.0 M phenyl magnesium bromide (2.67 mL, 8.02 mmol) was then added dropwise to the reaction mixture. After the addition, the reaction was heated to 70° C. The reaction was cooled to room temperature and diluted with ethyl acetate (30 mL) and stirred. The solvent was removed and the crude material was purified by column chromatography and then recrystallized from ethyl acetate and hexanes to yield 394 mg (55%) of 2,4,8,10-tetraphenyl-3,9-diazatetracene (7b). 4,10-Dicyano-3,9-diazatetracene (8a) was prepared by stirring in an oven dried 250 mL schlenk flask 6a (500 mg, 1.67 mmol), 18-crown-6 (133 mg), potassium cyanide (655 mg, 10.06 mmol) and PEPPSI-IPr (170 mg, 15 mol %) in dry DMF (150 mL) and purging with N.sub.2 for 20 minutes. The reaction was then heated to 90° C. overnight in an oil bath. The reaction was cooled to room temperature and then DMF was removed by vacuum distillation. The crude material was loaded on silica and purified by column chromatography eluting with DCM:Hexane (80:20) to yield 90 mg (20%) of 4,10-dicyano-3,9-diazatetracene (8a). 2,8-Diphenyl-4,10-dicyano-3,9-diazatetracene (8b) was prepared by stirring in an oven dried 250 mL schlenk flask 6b (200 mg, 0.44 mmol), 18-crown-6 (20 mg), potassium cyanide (165 mg, 2.53 mmol) and PEPPSI-IPr (45 mg, 15 mol %) in dry DMF (60 mL) and purging with N.sub.2 for 20 minutes. The reaction was then heated to 90° C. overnight in an oil bath. The reaction was cooled to room temperature and then DMF was removed by vacuum distillation. The crude material was loaded on silica and purified by column chromatography eluting with DCM:Hexane (80:20) to yield 84 mg (44%) of 2,8-diphenyl-4,10-dicyano-3,9-diazatetracene (8b).

(95) FIG. 3 provides an example of a synthesis for 5,12-diaza-pentacenes in accordance with the present invention. Quinacridones (11a-b) were prepared starting from commercially available dimethyl succinylosuccinate (9). Compound 9 was refluxed in acetic acid open to atmosphere overnight in the presence of an aniline to give 10a-b in good yield. Cyclization of 10a-b in polyphosphoric acid gave quinacridones 11a-b in excellent yield. Treatment of 11a-b or the sodium salt of 11a-b in neat phosphorous oxychloride in the presence of K.sub.2CO.sub.3 afforded 7,14-dichloro-5,12-diazapentacenes (12a-b). Compounds 13(a-b) and compounds 14(a-b) were prepared following the same technique used to prepare 7(a-b) and 8(a-b) from 6(a-b).

(96) FIGS. 6-10 show CV measurements for particular aza-acene compounds. All CV measurements were performed using a EG&G Potentiostat/Galvanostat model 283. All scans were recorded at a scan rate of 50 mV/s in dry and degassed DCM with 0.1 M tetra(n-butyl)ammonium hexafluorophosphate (Aldrich) as the supporting electrolyte. Ferocene/ferrocenium (Fc/Fc.sup.+) redox couple was used as an internal standard. A glassy carbon rod, a platinum wire, and a silver wire were used as the working electrode, the counter electrode, and the pseudo reference electrode, respectively.

(97) FIG. 11 shows additional absorption/emission spectra for particular diaza-tetracenes.containing phenyl, chloro, or nitrile substituents and combinations thereof. Additionally, phenyl substituents were added at the 1 and 7 positions for select diaza-tetracenes. These substituents affect the frontier molecular orbital (FMO, i.e., HOMO, LUMO) energies, band gap, and crystal packing of the molecule. These material substitution patterns were chosen to minimize or eliminate their dipolar character, thereby preventing carrier trapping expected for disordered polar materials. The absorption of the diaza-tetracenes are red-shifted to tetracene with compound gg absorbing to 750 nm. With the exception of compound ee, the emission of the diaza-tetracenes are red-shifted relative to tetracene. Additionally, the structure seen in the emission diminishes with the addition of phenyl substituents at the 1 and 7 positions as evidenced in cc, dd, and gg.

(98) FIG. 12 provides additional absorption and electrochemical properties of particular diaza-tetracenes. Electrochemical properties of the diaza-tetracenes were examined using cyclic voltammetry (CV). The primary reduction potentials of the diaza-tetracenes varied by 1V, from −1.77 V for cc to −0.78 V for hh. The LUMO energies of the diaza-tetracenes were calculated from the reduction potentials obtained through CV using previously published correlations. The optical energy gap, E.sub.g, was taken as the intersection of the lowest energy transition and the fluorescence spectrum for the acenes, i.e. aa-hh, and the absorption edge for a thin film of C.sub.60. The LUMO levels of gg and hh, are similar to that of C.sub.60. The LUMO energies of ee, ff, gg, and hh suggest that they may be useful as acceptors in OPVs. The range of LUMO levels achieved here exhibit the wide FMO tunability that is available via this synthetic pathway.

(99) X-Ray diffraction data were obtained for aza-tetracene thin films to determine their crystalline morphology. At both low (0.2 Å/s) and high (>20 Å/s) deposition rates in vacuum, the aza-tetracenes showed no diffraction peaks, suggesting an amorphous structure.

(100) OPV devices were fabricated using copper phthalocyanine (CuPc), N,N′-Bis-(1-naphthalenyl)-N,N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPD) and boron subphthalocyanine-chloride (SubPc) as donors with each of the acceptors aa-hh. Devices using ee and ff produced no photoresponse, although the absorption and atomic force microscopy (AFM) data suggest that ee and ff are continuous thin films. The likely reason for the poor performance is a poor match of the donor exciton energy to the LUMOs of ee and ff. Adding cyano groups shifts the LUMO levels to below that of C60, making suitable acceptors when matched with a SubPc donor. The device with a SubPc donor and cyano-aza-acene acceptor gg exhibited diode character in the dark along with photoresponse. The device current density-vs.-voltage characteristics for devices with gg are shown in FIG. 13. Compared to C60, gg exhibited significantly reduced short circuit current density (JSC), but comparable VOC: 1.78 mA/cm2 vs 4.15 mA/cm2 and 0.85 V vs 1.0 V, respectively. Additionally, the fill factor (FF) of the diazatetracene devices were lower compared to those made with C60: 0.40 vs 0.54, respectively, consistent with a higher resistivity for gg and hh relative to C60. While gg lacks a molecular dipole moment, the cyano groups can result in significant changes in the local electric field surrounding, the molecule leading to disorder-induced charge traps. Such enhanced resistivity is expected to lower FF, as observed. The aza substitution is not expected to give large fluctuations in the local electrical field around the molecules, and hence it is expected that the cyano-based deficiencies observed in the OPVs will be reduced or eliminated in aza-substituted materials.