SYMMETRIC TETRAALKYNYLATED ANTHRACENES AND THE PROCESS FOR PREPARING THE SAME FOR SENSING AND OPTOELECTRONIC APPLICATIONS

Abstract

The present invention relates to symmetric tetraalkynylated anthracene and more particularly tetraethynylated compounds with Formula III. The invention also provides a tetrafold sonogashira route towards these of symmetric tetraethynylated anthracene compounds with Formula III. The compounds of the present invention show good to excellent synthetic yield and find application in sensors and optoelectronic devices and show positive solvatochrism and halochromism. The sensor uses symmetric tetraalkynylated anthracene as channel material and the sensor has high sensitivity of 19.95 percent to 900 ppm and 0.86 percent to 50 ppm.

Claims

1. A symmetric tetraalkynylated anthracene derivative having general Formula III: ##STR00013## wherein: R is selected from but not limited to hydrogen, alkyl, halo, aryl, substituted aryl, hetroaryl; an alkyl is selected from but not limited to methyl, ethyl, isopropyl, cyclopentyl, cyclohexyl, amino, NN dimethyl, trimethyl silyl, trifluoromethyl; an aryl is selected from but not limited to phenyl, chloro phenyl, bromo phenyl, methyl benzene, ethyl benzene, methoxy benzene, NN dimethyl aniline, toluly, 1-Napthyl, anthracenyl, biphenyl, benzophenone, triphenyl amine; a heteroaryl group is selected from but not limited to thiophene, furan, pyrole, pyridine, imidiazole, benzimidazole, quinolone, isoquinoline; a halo is selected from but not limited to chloro, Bromo, fluoro; said anthracene derivative of Formula III is a channel material for sensors and optoelectronic devices; and wherein said symmetric tetraethynylated anthracenes show positive solvatochrism and halochromism.

2. The symmetric tetraalkynylated anthracene derivatives as claimed in claim 1, wherein the derivatives with Formula III are selected from but not limited to ##STR00014## ##STR00015##

3. The sensor comprising symmetric tetraalkynylated anthracene derivatives as claimed in claim 1 as channel material.

4. The sensor as claimed in claim 3, wherein the sensor has a high sensitivity of 19.95 percent to 900 ppm and 0.86 percent to 50 ppm.

5. The sensor as claimed in claim 3, wherein the sensor has an excellent response time ranging from 0 to 15 s with a good recovery time of 40 to 60 s.

6. A process for synthesizing symmetric tetraalkynylated anthracene derivatives having Formula III according to Scheme-2: ##STR00016## wherein the process comprising the steps of: a) degassing a 1:1 mixture of base and solvent under argon environment by freeze-pump-thaw process; b) adding compound of Formula I, compound of Formula II, ligand, CuI and catalyst to the degassed reaction mixture obtained in step I and further degassing the mixture for another 10-12 minutes; c) refluxing the degassed reaction mixture obtained in step II for 12-15 hours; d) passing the reaction mixture obtained in step III through celite after completion of the reaction to obtain a crude extract; and e) evaporating the crude extract under reduced pressure to dryness and purifying the crude product by chromatography to obtain compound of Formula III.

7. The process as claimed in claim 6, wherein a combination of palladium catalyst, Bis(acetonitrile)dichloropalladium(II) (Pd(CH3CN)2Cl2) and ligand (cataCXium A) is used in a ratio of 1:2.

8. The process as claimed in claim 6, wherein the base and solvent are present in a ratio of 1:1 and the compound of Formula I and compound of Formula II are present in a ratio of 1:6.

9. The process as claimed in claim 6, wherein the base is selected from but not limited to trimethylamine, potassium carbonate, potassium bicarbonate, sodium bicarbonate, cesium carbonate, potassium hydroxide, piperidine, sodium tert-butoxide, potassium tert-butoxide.

10. The process as claimed in claim 6, wherein the solvent is selected from but not limited to tetrhydrofuran (THF), toluene, N-alkylpyrrolidones, dimethylformamide (DMF), dioxane or mixture thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] An understanding of the novel process of the present invention may be obtained by reference to the following drawings:

[0031] FIG. 1 depicts Interactions present in the solid-state structures of (a) 6 and (b) 6a according to an embodiment of the present invention.

[0032] FIG. 2 depicts Solvatochromism demonstrated by the compounds 6e and 6f according to an embodiment of the present invention.

[0033] FIG. 3 depicts Halochromism demonstrated by the compounds 6e and 6f;

[0034] FIG. 4 depicts the schematics of the fabricated sensing device using compound of Formula III as the channel material.

[0035] FIG. 5 depicts the I-V characteristic of the sensing device using compound of Formula III as the channel material.

[0036] FIG. 6 depicts the sensors' AER and sensitivity vs H.sub.2 concentration plots.

[0037] FIG. 7 depicts the sensor's sensitivity to various VOCs at 900 ppm concentration.

[0038] FIG. 8 depicts the temperature response of the sensor.

[0039] FIG. 9 depicts the sensor's transient response.

DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention now will be described hereinafter with reference to the detailed description, in which some, but not all embodiments of the invention are indicated. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. The present invention is described fully herein with non-limiting embodiments and exemplary experimentation.

[0041] The present invention provides a single step one pot route for synthesis of compound of Formula III via tetrafold sonogashira coupling.

##STR00007##

[0042] where R is hydrogen, alkyl, halo, aryl, substituted aryl, hetroaryl; [0043] alkyl is selected from methyl, ethyl, isopropyl, cyclopentyl, cyclohexyl, amino, NN dimethyl, trimethyl silyl, trifluoromethyl; [0044] Aryl is selected from phenyl, Chloro phenyl, bromo phenyl, methyl benzene, ethyl benzene, methoxy benzene, NN dimethyl aniline, toluly, 1-Napthyl, anthracenyl, biphenyl, benzophenone, triphenyl amine. [0045] Heteroaryl group is selected from thiophene, furan, pyrole, pyridine, imidiazole, benzimidazole, quinolone, isoquinoline. [0046] Halo is selected from chloro, Bromo, fluoro.

[0047] In an embodiment of the present invention is provided a tetra fold sonogashira coupling process for synthesis of compound of Formula III

##STR00008##

[0048] generally comprising the step of: [0049] I. Degassing a 1:1 mixture of base and solvent under argon environment by freeze-pump-thaw process; [0050] I. adding compound of Formula I, compound of Formula II, ligand, CuI and catalyst to the degassed reaction mixture obtained in step I; degassing the mixture for another 10-12 minutes; [0051] III. refluxing the reaction mixture obtained in step II for 12-15 hours; [0052] IV. passing the reaction through celite after completion of the reaction; and [0053] V. evaporating the crude extract under reduced pressure to dryness and purifying the crude product by chromatography. [0054] In an embodiment of the invention is described a process for synthesis of compounds with Formula III,

##STR00009##

[0055] In an embodiment of the present invention, Scheme-2 utilizes a combination of palladium catalyst, Bis(acetonitrile)dichloropalladium(II) (Pd(CH.sub.3CN).sub.2Cl.sub.2) and ligand cataCXium?A in a ratio of 1:2.

##STR00010##

[0056] In a preferred embodiment of the invention, the solvent used in the Scheme-2 is selected from tetrahydrofuran (THF), toluene, N-alkylpyrrolidones, dimethylformamide (DMF), Dioxane or mixture thereof.

[0057] In a preferred embodiment of the invention base is selected from trimethylamine, potassium carbonate, potassium bicarbonate, sodium bicarbonate, cesium carbonate, potassium hydroxide, piperidine. Sodium tert-butoxide, potassium tert-butoxide.

[0058] In a preferred embodiment of the invention the base and solvent are present in a ratio of 1:1 and the compound of Formula I and compound of Formula II are present in a ratio of 1:6.

[0059] In an embodiment of the invention are provided compounds with general Formula III prepared by the scheme III;

##STR00011## ##STR00012##

[0060] Referring to FIG. 1 of the present invention, there is illustrated interactions present in the solid-state structures of compound (a) 6 and (b) 6a. Compound 6 and 6a exhibit several p-p interactions apart from various C Phenyl-H . . . ? interactions in the solid-state. The compound 6 shows two effective p-p interactions with an average distance of 3.393 ? (FIG. 1). Compound 6 demonstrates a total of seven C Phenyl-H . . . p(C?C) interactions including two symmetrical bifurcated18 C-phenyl-H . . . ?(C?C) interactions with an average bond distance of 2.762 ? and five other unsymmetrical T-shaped C-phenyl-H . . . ?(C?C).

[0061] Referring to FIG. 2 of the present invention, there is illustrated the Solvatochromism demonstrated by the compounds 6e and 6f. Color in various solvents under 365 nm UV light is demonstrated by (a) 6e and (b) 6f. (c) Normalized absorption spectra of 6e according to Reichardt polarity scale by increasing the solvent polarity from hexane to DMSO. (d) Normalized emission spectra of 6e according to Reichardt polarity scale by increasing solvent polarity from hexane to DMSO. (c) Normalized absorption spectra of 6f according to Reichardt polarity scale by increasing the solvent polarity from hexane to DMSO. (d) Normalized emission spectra of 6f according to Reichardt polarity scale by increasing solvent polarity from hexane to DMSO.

[0062] Referring to FIG. 3 of the present invention, there is illustrated Halochromism demonstrated by the compounds 6e and 6f, Color after sequential addition of acid and base under 365 nm UV light is demonstrated by (a) 6e and (b) 6f. (c) Hypsochromic shift in emission spectra of 6e upon gradual addition of CF3CO2H. (d) Major recovery of the emission spectra of 6e upon neutralization with Et3N. (c) Disappearance of emission maxima of 6f upon gradual addition of CF3CO2H. (d) Complete recovery of the emission spectra of 6f upon neutralization with Et3N.

[0063] Referring to FIG. 4 of the present invention, there is illustrated the schematic of the fabricated sensor having compound of Formula III as the channel material. The sensor was fabricated on a clean undoped silicon/silicon oxide (Si/SiO2) substrate that was exposed to UV light for 10 minutes before fabrication. A printing system (Make, Model: K-FAB TECH PRIVATE LIMITED, K-FT1PS) was used to control and optimise the metal contact pads' fabrication. The printing head of the system contains a stainless steel micro girder patterning tool through which ink flows down to the substrate. The printing was done at room temperature with a relative humidity of around 45 percent. On the SiO2 substrate, two distinct AgNP ink spots were drop-cast with a 1 mm spacing. The tip of the micro girder is positioned to lightly tap AgNP ink on the upper surface of a spot. AgNP ink is then dragged closer to the other spot to reduce the gap. The second AgNP spot is then treated similarly, with the ink dragged closer to the previously printed electrode to reduce the channel gap to about 20 ?m. The printed electrodes were gently heated at 160? C. for 20 minutes. With 2 ?l of AgNP ink, the entire electrode fabrication process is completed in 30 minutes. Further, the channel material i.e the compound of Formula III was dropped cast over the printed AgNP electrodes; the drop cast has a diameter of about 2 mm. The sensor was then annealed for five minutes at 120? C.

[0064] Referring to FIG. 5 of the present invention, there is illustrated the I-V characteristic of the sensing device using compound of Formula III as the channel material. The electrical characteristics of the sensing device were investigated using a Keithly 2600 source metre. A low-noise triaxial cable connects the device to the analyzer. For performing the sensing experiment, an in-house designed gas sensing system (Fabricator: Genrenew India) was integrated with the above analyzer via low-noise triaxial cables. The gas sensing chamber was outfitted with an Mass Flow Controller (MFC) panel that consists of three Mass Flow Controllers (MFCs) with varying flow rates to obtain the desired gas concentration. One MFC controls the carrier gas flow, while the other MFCs control the analyte gas flow. The sensing experiment was carried out in two circumstances: (a) in nitrogen ambient and (b) in different concentrations of hydrogen (H.sub.2).

[0065] The gas sensing chamber was purged with nitrogen before being vacuumed three times to avoid cross-contamination. The sensors' baseline readings were taken in a nitrogen ambient, at less than 1% humidity and close to atmospheric pressure. Sweeping voltage from 0 to 5 V was used to analyse the I-V characteristic of sensing devices. The device shows a ohmic characteristic. A series of experiments were carried out to evaluate the response of the devices by varying the concentration of hydrogen gas from 100 to 9000 ppm. The electrical properties confirm an increase in current with increasing hydrogen concentration. The interaction with H.sub.2 gas reduces the device's resistance. Because H.sub.2 is a reducing gas, interacting with it raises the concentration of surface electrons on n type semiconductors. The following equation was used to determine the response of the gas sensors.

[00001]$S=\frac{.Math.R_g-R_o.Math.}{R_o}?100\%$

[0066] where Rg is the average electrical resistance obtained by sweeping the voltage from 0 to 5V toward varying H.sub.2 concentrations, and Ro is the average electrical resistance of the sensors in the nitrogen atmosphere.

[0067] Referring to FIG. 6 of the present invention, there is illustrated the sensors' AER and sensitivity vs H.sub.2 concentration plots. The AER response confirms that a significant shift in the fabricated device. According to the results, the sensor has a high sensitivity of 19.95 percent to 900 ppm and 0.86 percent to 50 ppm.

[0068] Referring to FIG. 7 of the present invention, there is illustrated the sensor's sensitivity to various VOCs at 900 ppm concentration. The desired VOC concentrations were achieved by combining it with DI water and injecting it into the chamber. VOCs exhibit significantly lower responses than H.sub.2 gas at the same concentration. When the sensor's limit of detection (LOD) is calculated using the formula below [4], it shows a value of 49 ppm.

[00002]$LOD=3?\frac{.Math.?.Math.}{\mathrm{slope}}$

[0069] where slope denotes the average electrical resistance for the various analyte gas concentrations and ? is the standard deviation of the base reading.

[0070] Referring to FIG. 8 of the present invention, there is illustrated the temperature response of the sensor. For the sensor's response to temperature variation, a tightly sealed chamber was used. Initially, the chamber was kept at 20? C. and then heated to 160? ? C. to analyze the sensor characteristics related to resistance variation. FIG. 8 depicts the variation of resistance with temperature. The resistance decreases significantly in the temperature range of 20 to 160 degrees Celsius. As a result, it is possible to conclude that the device's resistance decreases as the temperature rises. Temperature is an external factor that can affect the sensor.

[0071] Referring to FIG. 9 of the present invention, there is illustrated the sensor's transient response. The sensor was continuously flashed to seven pulses of H.sub.2 gas at various concentrations of 100, 250, 400, 550, 700, and 900 ppm, accompanied by a mild evacuation of the gas in the sensing chamber at a constant voltage of 5 V. For different H.sub.2 concentrations, the transient response provides an excellent response time ranging from 0 to 15 s with a good recovery time of 40 to 60 s. The gas in-conditioning process begins when the gas sensing chamber is pressurised to atmospheric pressure, and the gas out-conditioning process begins when the flow of the analyte gas is stopped and evacuated. A mild baseline shift was observed when the sensor shifted back and forth between mild vacuum and test gas environment.

TABLE-US-00001 TABLE 2 Photo physical properties of Tetraethynylated anthracenes synthesized via tetra-fold Sonogashira coupling ?.sub.ems (nm) ?.sub.max.sup.a Log(?).sup.b Thin E.sub.g(eV).sup.g E.sub.HOMO.sup.h Entry Compound (nm) (LM.sup.?1cm.sup.?1) Solution.sup.a Film.sup.c Powder.sup.d ?(%).sup.e ?.sub.av(ns).sup.f Solution Solid (eV) 1 6 345 4.17 500 543 601 61 4.54 2.47 2.04 ?5.78 2 6a 348 3.92 507 595 584 61 4.36 2.44 2.00 ?5.58 3 6b 359 4.03 514 633 653 60 4.83 2.39 1.95 ?5.33 4 6d 368 3.74 517 610 636 47 2.96 2.36 1.92 ?2.84.sup.i 5 6e 322 3.54 575 642 402 31 4.18 2.16 1.79 ?5.11 6 6f 344 4.07 572 635 639 31 3.56 2.21 1.99 ?5.27 7 6g 310 4.05 464 556 567 60 6.70 2.62 1.92 ?5.39 8 6i 342 3.95 503 547 567 56 4.79 2.47 2.04 ?5.71

[00003]${?}_{av}=\frac{?B_t{?}_i^2}{?B_t{?}_i},$

[0072] Referring to Table 2 of the present invention is illustrated, the photophysical properties of tetraethynylated anthracenes synthesized via tetra-fold Sonogashira coupling. .sup.aThe absorption (10.sup.?5 M) as well as emission (10.sup.?6 M) spectra recorded in CHCl.sub.3. .sup.b Log (?) was calculated from the plot of absorbance vs concentration. .sup.cEmission spectra were recorded on glass on which a thin film was prepared by drop-cast method. .sup.dEmission spectra were recorded in powder form of the compounds. .sup.eQuantum yield were calculated with respect to quinine sulfate in 0.1 M H.sub.2SO.sub.4 as standard (?=54%). .sup.fThe average lifetime of the compounds calculated by using the equationwhere ?.sub.av=average lifetime in excited state of the luminescence compound, B=pre-exponential factor, ?.sub.i=decay lifetime of photoluminescence in excited state for the i.sup.th component. .sup.gThe band-gaps were calculated from the Tauc plot. determined from cyclic voltammetry. .sup.iE.sub.LUMO from cyclic voltammetry.

[0073] The quantum yield is the ratio between the emitted number of photons and the absorbed number of photons by the fluorophores. Relative fluorescence quantum yield was calculated by the following equation (1),

[00004]$\begin{array}{cc}\mathrm{?\_F}=\mathrm{?\_R}?I/\mathrm{I\_R}?\mathrm{A\_R}/A?\left(?/\mathrm{?\_R}\right)2& \left(1\right)\end{array}$

[0074] Where ?F and ?R are relative quantum yields of analyte and reference respectively; I, IR are the area of emission of the analyte and reference; A, AR are the maximum absorbance of analyte and reference; ?, ?R are the refractive index of analyte and reference solutions, respectively.

General Procedure for Synthesis of Compounds with Formula III:

[0075] A two-neck round bottom flask was taken, evacuated and charged with argon three times. anhydrous triethylamine (7 mL) and anhydrous THF (7 mL) were added into the round bottom flask and the solvent was degassed by freeze-pump-thaw process. This was followed by addition of 2, 6, 9, 10-tetrabromoanthracene (0.404 mmol), Pd(CH3CN)2Cl2 (0.0404 mmol), CataCXium? A (0.0810 mmol), CuI (0.0810 mmol), and alkyl/aryl acetylene (2.43 mmol) which were then stirred under reflux condition overnight. After the completion of the reaction, the reaction mixture was passed through celite by using DCM (200 mL?3) as eluent and filtrate was evaporated under reduced pressure. NMR yield of crude product was determined by .sup.1H NMR 1, 4-dioxane as external standard. The crude product was purified by column chromatography (eluent: Hexane and DCM).

Example 1

Synthesis of 2, 6, 9, 10-tetrakis(phenylethynyl)anthracene (6)

[0076] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: 35% DCM in hexane). The product obtained was an orange solid with yield 58%. 1H NMR (400 MHZ, CDCl3) ? 8.79 (d, J=0.8 Hz, 2H), 8.60 (d, J=8.9 Hz, 2H), 7.69 (dd, J=6.2, 4.9 Hz, 5H), 7.66 (d, J=1.5 Hz, 1H), 7.53 (d, J=8.0 Hz, 4H), 7.28 (d, J=7.9 Hz, 4H), 7.20 (d, J=7.9 Hz, 4H). 2.45 (s, 6H), 2.40 (s, 6H). 13C{1H} NMR (151 MHz, CDCl3) ? 139.32, 138.88, 132.01, 131.87, 131.85, 131.67, 130.76, 129.51, 129.34, 127.63, 122.11, 120.26, 120.19, 118.45, 103.35, 91.88, 89.67, 85.52, 21.83, 21.75. MALDI-TOF calculated exact mass for C50H34 (M+): 634.26, found: 634.91.

Example 2

Synthesis of 2, 6, 9, 10-tetrakis((2-methoxyphenyl)ethynyl)anthracene (6b)

[0077] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: 40% DCM in hexane) The product obtained was a red solid with yield 61%. 1H NMR (400 MHZ, CDCl3) ? 9.10 (s, 2H), 8.74 (d, J=8.9 Hz, 2H), 7.82-7.69 (m, 4H), 7.60 (dd, J=7.5, 1.6 Hz, 2H), 7.38 (ddd, J=15.6, 8.7, 1.6 Hz, 4H), 7.01 (ddd, J=26.0, 17.0, 8.0 Hz, 8H), 4.12 (s, 6H), 3.97 (s, 6H). 13C{1H} NMR (151 MHz, CDCl3) ? 160.73, 160.20, 133.81, 133.01, 132.19, 131.50, 131.39, 130.37, 130.11, 129.58, 127.67, 122.16, 120.71, 118.79, 112.85, 112.61, 110.87, 110.75, 99.87, 94.67, 91.01, 87.65, 56.00, 55.98. MALDI-TOF calculated exact mass for C50H34O4 (M+): 698.24, found: 698.65.

Example 3

Synthesis of ((anthracene-2, 6, 9, 10-tetrayltetrakis(ethyne-2, 1-diyl))tetrakis(benzene-4, 1-diyl))tetrakis(phenylmethanone) (6d)

[0078] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: 90% DCM in hexane). The product obtained was a maroon solid with yield 88%. 1H NMR (400 MHZ, CDCl3) ? 8.87 (s, 2H), 8.67 (d, J=8.9 Hz, 2H), 7.94 (s, 8H), 7.84 (dd, J=14.4, 7.7 Hz, 12H), 7.77 (t, J=9.2 Hz, 6H), 7.63 (q, J=7.2 Hz, 4H), 7.53 (q, J=7.4 Hz, 8H). 13C{1H} NMR (151 MHz, CDCl3) ? 196.06, 195.99, 137.71, 137.50, 137.45, 137.34, 132.90, 132.80, 132.21, 132.04, 131.83, 131.81, 131.19, 130.50, 130.33, 130.19, 130.15, 129.88, 128.62, 128.57, 127.78, 127.30, 127.15, 122.10, 118.67, 102.82, 92.87, 91.44, 88.66. MALDI-TOF calculated exact mass for C74H.sub.4204 (M+): 994.30, found: 994.86.

Example 4

Synthesis 4, 4, 4,4-(anthracene-2, 6, 9,10-tetrayltetrakis(ethyne-2, 1-diyl))tetrakis(N, N-dimethylaniline) (6e)

[0079] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: 60% DCM in hexane). The product obtained was a brown solid with yield 64%. 1H NMR (400 MHZ, CDCl3) ? 8.78 (s, 2H), 8.60 (d, J=8.8 Hz, 2H), 7.68 (d, J=8.7 Hz, 4H), 7.64 (d, J=8.1 Hz, 2H), 7.52 (d, J=8.7 Hz, 4H), 6.78 (d, J=8.9 Hz, 4H), 6.70 (d, J=8.8 Hz, 4H), 3.06 (s, 12H), 3.02 (s, 12H). 13C{1H} NMR (151 MHZ, CDCl3) ? 150.55, 150.34, 133.13, 133.11, 131.85, 131.34, 130.25, 129.25, 127.59, 122.19, 118.19, 112.12, 112.01, 110.37, 110.25, 104.33, 92.70, 88.78, 84.84, 40.42, 40.39. MALDI-TOF calculated exact mass for C54H46N4 (M+): 750.37, found: 750.90.

Example 5

Synthesis of 4, 4, 4, 4-(anthracene-2, 6, 9, 10-tetrayltetrakis(ethyne-2, 1-diyl))tetrakis(N, N-diphenylaniline) (6f)

[0080] The compound was prepared following the general procedure for synthesis of compound of Formula III. The product obtained was a maroon solid with yield 31%. 1H NMR (400 MHZ, CDCl3) ? 8.76 (d, J=0.8 Hz, 2H), 8.58 (d, J=8.9 Hz, 2H), 7.67-7.61 (m, 6H), 7.46 (d, J=8.7 Hz, 4H), 7.29 (dt, J=9.7, 4.9 Hz, 15H), 7.15 (dd, J=14.7, 8.0 Hz, 18H), 7.07 (ddd, J=21.2, 9.4, 5.3 Hz, 15H). 13C{1H} NMR (151 MHZ, CDCl3) ? 148.61, 148.27, 147.30, 147.23, 132.91, 132.88, 131.96, 131.56, 130.58, 129.62, 129.56, 129.42, 127.61, 125.31, 125.21, 123.91, 123.77, 122.35, 122.11, 118.28, 116.00, 115.97, 103.60, 92.03, 89.70, 85.64. MALDI-TOF calculated exact mass for C94H62N4 (M+): 1247.50, found: 1247.97.

Example 6

Synthesis of (anthracene-2, 6, 9, 10-tetrayltetrakis(ethyne-2, 1-diyl))tetrakis(trimethylsilane) (6g)

[0081] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: hexane). The product obtained was a yellow solid with yield 83%. 1H NMR (600 MHz, CDCl3) ? 8.66 (s, 2H), 8.44 (d, J=8.9 Hz, 2H), 7.57 (dd, J=8.9, 1.3 Hz, 2H), 0.43 (s, 18H), 0.31 (s, 18H). 13C{1H} NMR (151 MHz, CDCl3) ? 132.16, 131.82, 131.77, 129.55, 127.48, 121.92, 118.47, 109.46, 105.59, 100.92, 96.83, 0.22, 0.10. MALDI-TOF calculated exact mass for C34H.sub.42Si4 (M+): 562.23, found: 562.62.

Example 7

Synthesis of 2, 2, 2, 2-(anthracene-2, 6, 9, 10-tetrayltetrakis(ethyne-2, 1-diyl)) tetrathiophene (6h)

[0082] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: 40% DCM in hexane). The product obtained was a yellow powder with yield 59%. 1H NMR (600 MHZ, CDCl3) ? 8.73 (s, 2H), 8.55 (d, J=8.9 Hz, 2H), 7.68 (d, J=8.9 Hz, 2H), 7.56 (d, J=3.5 Hz, 2H), 7.45 (d, J=5.1 Hz, 2H), 7.40 (d, J=3.4 Hz, 2H), 7.36 (d, J=5.1 Hz, 2H), 7.17-7.13 (m, 2H), 7.08-7.05 (m, 2H). 13C{1H} NMR (151 MHz, CDCl3) ? 132.94, 132.65, 131.88, 131.65, 130.61, 129.43, 128.53, 127.98, 127.67, 127.64 127.40, 123.27, 123.09, 121.93 118.33, 96.50, 93.82, 89.80, 85.26. MALDI-TOF calculated exact mass for C38H.sub.18S4 (M+): 602.02, found: 602.36.

Example 8

Synthesis of 3, 3, 3, 3-(anthracene-2, 6, 9, 10-tetrayltetrakis(ethyne-3, 1-diyl)) tetrathiophene (6i)

[0083] The compound was prepared following the general procedure for synthesis of compound of Formula III. The crude product was purified by column chromatography (eluent: 40% DCM in hexane). The product obtained was a brown powder with yield 20%. 1H NMR (400 MHZ, CDCl3) ? 8.78 (s, 2H), 8.60 (d, J=8.9 Hz, 2H), 7.81 (dd, J=2.7, 1.3 Hz, 2H), 7.69 (d, J=1.6 Hz, 1H), 7.66 (d, J=1.5 Hz, 1H), 7.65-7.63 (m, 1H), 7.46-7.44 (m, 4H), 7.35 (dd, J=5.0, 3.0 Hz, 2H), 7.30 (dd, J=5.1, 0.9 Hz, 3H). 13C{1H} NMR (151 MHz, CDCl3) ? 132.00, 131.70, 130.74, 130.16, 130.08, 129.65, 129.50, 129.39, 127.65, 126.00, 125.71, 122.25, 122.21, 121.96, 118.37, 98.16, 89.64, 86.90, 85.47. MALDI-TOF calculated exact mass for C46H.sub.26 (M+): MALDI-TOF calculated exact mass for C38H18S4 (M+): 602.02, found: 602.41

TABLE-US-00002 TABLE 1 Physical appearance and yield of synthesized symmetric tetraethynylated anthracenes Compound Yield in %(.sup.1H-NMR Physical Code conversion) appearance 6 98 Orange solid 6a 92 Orange solid 6b 84 Orange solid 6c NA 6d 93 Red solid 6e 76 Brown solid 6f 65 Maroon solid 6g 64 Yellow solid 6h 69 Yellow solid 6i 88 Brown solid

[0084] Referring to Table 1 of the present invention, there is illustrated the yields and physical appearance of the compounds synthesized via tetra-fold Sonogashira coupling.

[0085] Therefore, the present invention provides a robust, efficient and a single step one pot process for synthesis of symmetric tetraethynylated compounds which show exciting photophysical properties where these symmetric tetraethynylated anthracenes exhibit solvatochromism and halochromism. The former also exhibits a low band-gap of 1.79 eV in the solid-state. The present invention synthesizes the symmetric tetraethynylated compounds in good to excellent yield.

[0086] Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.