US007125989B2

(12) United States Patent (10) Patent No.: US 7,125,989 B2 Afzali-Ardakani et al. (45) Date of Patent: Oct. 24, 2006

(54) HETERO DIELS-ALDER ADDUCTS OF Bao et al., “Organic Field-Effect Transistors with High Mobility PENTACENE AS SOLUBLE PRECURSORS Based on Phthalocyanine'. American Institute of Physic, p. OF PENTACENE 3066-3068, 1996. Herwig et al., “A Soluble Pentacene Precursor. Synthesis, Solid (75) Inventors: Ali Afzali-Ardakani, Yorktown State Conversion into Pentacene and Application in a Field-Effect Heights, NY (US); Tricia L. Breen, Transistor”. Advanced Matter, 1999, vol. 11, No. 6, p. 480-483. Hopewell Junction, NY (US); Christos Dimitrakopoulos et al., “Molecular Beam Deposited Thin Films of D Dimitrakopoulos, Ossining, NY Pentacene for Organic Field Effect Transistor Applications”, American Institute of Physics, p. 2501-2508, Aug. 15, 1996. (US) Freer et al., “Generation of a Thioaldehyde S- (Sulphine) by Retro-Diels-Alder Reactions'. J. Chem. Soc., Chem. Commun. (73) Assignee: International Business Machines 1987. Corporation, Armonk, NY (US) Bladon et al., “Ethyl and Methyl Thioxoacetates, Dienophilic Thioaldehydes Formed from sulphenyl Chlorides by 1.2-Elimina (*) Notice: Subject to any disclaimer, the term of this tion”. J. Chem. Soc. Perkin Trans. I, 1985, p. 1541-1545. patent is extended or adjusted under 35 Kirby et al., “The Transient Dienophile Diethyl Thioxomalonate and U.S.C. 154(b) by 473 days. its S-Oxide (sulphine Formed by Retro-Diels-Alder Cleavage Reac tions”, J. Chem. Soc. Perkin Trans. I, 1990, p. 3176-3181. (21) Appl. No.: 10/300,645 Garnier et al., “Structural Basis for High Carrier Mobility in Conjugated Oligomers'. Elservier Sequoia, Lausanne, 1991, p. (22) Filed: Nov. 20, 2002 163-171 Klauk et al., “Pentacene Organic Thin-Film Transistors and ICs”. (65) Prior Publication Data Deposition, p. 6367. US 2003/O144562 A1 Jul. 31, 2003 * cited by examiner Related U.S. Application Data Primary Examiner Kahsay Habte (60) Provisional application No. 60/333,312, filed on Nov. (74) Attorney, Agent, or Firm Ohlandt, Greeley, Ruggiero 26, 2001. & Perle, L.L.P.; Daniel P. Morris, Esq. (51) Int. Cl. (57) ABSTRACT CO7D 417/04 (2006.01) CO7D 413/04 (2006.01) CO7D 403/04 (2006.01) The present invention describes organic solvent-soluble Diels-Alder adducts of polycyclic aromatic compounds, (52) U.S. Cl...... 544/14: 544/63; 544/233; Such as, oligothiophene, perylene, benzoghilperylene, coro 549/24 nene and polyacenes, with variety of dienophiles containing (58) Field of Classification Search ...... 544/63, at least one heteroatom and in Some cases two heteroatoms 544/14, 233; 549/24 bonded to aromatic moiety, such as, thioXomalonates, aZodi See application file for complete search history. carboxylates, thialdehyde, acylnitroso and N-sulfinyla (56) References Cited mides. The Diels-Alder adducts are prepared by a simple, one step cycloaddition reaction of the polycyclic aromatic OTHER PUBLICATIONS compounds, such as, pentacene, or other fused aromatic Prabhakaran et al. Synlett (2000), (5), 658-662.* compounds, with heterodienophiles. The Diels-Alder Paul F. Vogt and Marvin J. Miller, “Development and Applications adducts according to the present invention all form soluble of Amino Acid Derived Chiral Acylnitroso Hetero Diels-Alder adducts with pentacene and can be converted back to Reactions”, Tetrahedron report No. 439, p. 1317-1348. Apr. 18, pentacene by retro-Diels-Alder reaction at moderate 1997. (60–250° C.) temperatures both in bulk, in solution or as Bao et al., “Soluble and Processable Regioregular Poly(3- thin-films. Hexylthiophene) for Thin Film Field-Effect Transistor Applications with High Mobility”, American Institute of Physics, p. 4108-41 10, 1996. 25 Claims, 3 Drawing Sheets U.S. Patent Oct. 24, 2006 Sheet 1 of 3 US 7,125,989 B2

& w i i t . . . . . PRECURSOR PENTACENE

20 30 40 50 60 70 80 WAVELENGTH

Fig. 1 U.S. Patent Oct. 24, 2006 Sheet 2 of 3 US 7,125,989 B2

100

6 O

4 O

O 1 OO 2OO 300 400 T (C) Fig. 2 U.S. Patent Oct. 24, 2006 Sheet 3 of 3 US 7,125,989 B2 23456 OOOOO 1 O

3OOO 2500 2OOO 1500 1OOO WAVENUMBER, cm

Fig. 3 US 7,125,989 B2 1. 2 HETERO DELS-ALDER ADDUCTS OF not stable in air and its field-effect characteristics deterio PENTACENE AS SOLUBLE PRECURSORS rates on exposure to air, its application as semiconductor OF PENTACENE becomes less desirable. The best performance as semiconductor among organic BACKGROUND OF THE INVENTION materials to date has been achieved by thin films of penta cene deposited under high vacuum and temperature as This application claims priority from Provisional Appli reported by Dimitrakopoulos et al., in U.S. Pat. Nos. 5,946, cation Ser. No. 60/333,312 filed on Nov. 26, 2001. 511; 5,981,970 and 6,207472 and other publications by This application is related to U.S. application Ser. No. Brown et al., J. Appl. Phys. 80(4), 1996, pages 2136-2139 10/300,630, filed on Nov. 20, 2002, entitled “Thin Film 10 and Dimitrakopoulos et al., J. Appl. Phys. 80 (4), pages Transistors. Using Solution Processed Pentacene Precursor as Organic Semiconductor, filed herewith on the same day, 2501 2507. cross-referenced and incorporated herein by reference. Recently, thin-film transistors on plastic Substrates using evaporated films of pentacene as the p-channel carrier with FIELD OF INVENTION 15 mobility of 1.7 cm.V.Sec.' and an on/off ratio of 10 has been reported by Jakson et al., in Solid State Technology, This invention relates to the synthesis of various Diels Vol. 43 (3), 2000, pages 63-77. Alder adducts of polycyclic aromatic compounds, such as, Thin films of pentacene are very stable in air and even pentacene, with heterodienophiles having at least one hetero moderate temperatures and as far as performance is con atom from N, O, or . The adducts are highly soluble in cerned, pentacene is the most attractive organic material to common organic solvents and can be easily converted back replace amorphous . to pentacene in Solid state by heating at moderate tempera The drawback for pentacene is that it is insoluble in tures. common organic solvents and it can only be deposited as thin film by expensive high vacuum and temperature tech BACKGROUND OF THE INVENTION 25 niques. Thin-film transistors and other electronic devices using There has been very little effort for the synthesis of organic semiconductors are emerging as alternatives to soluble pentacene derivatives and the only example of established methods using amorphous silicon (C-Si:H) as soluble pentacene is by Muellen, K. et al., “A soluble 30 pentacene precursor: Synthesis, Solid-state conversion into the semiconductor. pentacene and application in a field-effect transistor.” Adv. A variety of organic compounds have been proposed and Mat. 11 (6), p. 480 (1999), in which a precursor of pentacene tested as semiconducting materials for TFT devices. For is synthesized by a tedious multi-step synthetic approach. example, among the p-channel (hole transport) materials The derivative, which is soluble in organic compounds and that have been characterized are thiophene oligomers pro 35 can be processed from Solution, is converted back to pen posed as organic semiconductor material for TFT in Garnier, tacene by heating at moderate to high temperature F., et al., “Structural basis for high carrier mobility in conjugated oligomers' Synth. Meth., Vol. 45, p. 163 (1991), (140 200° C.). and phthalocyanines described in Bao, Z. et al., “Organic The drawback for using this compound as a pentacene Filed-effect transistors with high mobility based on copper precursor is that due to multi-step synthesis (more than 9 phthalocyanine' Appl. Phys. Lett., Vol. 69, p. 3066 (1996). 40 steps), its preparation, especially in large scale is almost Pentacene, which is a member of poly(acene) compounds impractical. In addition, its conversion to pentacene occurs has been proposed as an organic semiconductor material in at a relatively high temperature, which prevents the use of Lin et al. IEEE 54th Annual Device Research Conference, most plastics as Substrates. 1996, pages 2136-2139, and Dimitrakopoulos et al., J. Appl. Thioaldehydes, RCHS, and the more stable thioxoacetate Phys., 80 (4), 1996, pages 2501-2507. 45 ROCO CHS have been used in Diels-Alder reactions with Some soluble organic compounds have also been charac variety of dienes as reported by G. Kirby et al., in “Ethyl and terized as organic semiconducting materials. For example methyl thioxoacetates, dienophilic thioaldehydes formed poly(3-alkylthiophene) described in Bao, Z. et al., “Soluble from sulphenyl chlorides by 1.2-elemination.” J. Chem. Soc., Perkin Trans, 1, 1541 (1985). and Processable regioregular poly(3-hexylthiophene) for 50 thin film field-effect transistors application with high mobil The adduct of anthracene which is the second member of ity”. Appl. Phys. Lett., Vol. 69, page 4108 (1996). polyacene with thioxoacetate and its oxidation to less stable An attractive material would have a high carrier mobility S-oxide was reported by G. Kirby et al. in “Generation of a which is close to that of amorphous silicon (0.1-1 cm.V. thioaldeyde S-oxide by retro-Diels-Alder reaction, Chem. 1...Sec.), with a very high on/off ratio (>10). For an organic 55 Commun., 718, 1987. This reaction, shown below, is an material to replace amorphous silicon, not only would it example of a Diels-Alder adduct as a precursor of fused have the electrical properties cited above but also it should aromatic compounds. be processable from solution so that it could become com mercially attractive. CH Among the organic compounds which have been studied 60 as semiconductors, only regioregular poly(3-hexylth iophene) is readily soluble in organic solvents and thin films CHOCO-CH=S of this compound has been processed from solution for --- construction of TFTs. The drawback for this compound is that it has relatively low (5x10° cm.V.Sec.) carrier 65 mobility and even much less satisfactory on/off ratio of less CH3 than 100. In addition, because thin films of this polymer are US 7,125,989 B2 3

-continued H COCH3

10 COCH N

15 O CH

Another example of hetero dienophile with one hetero Other hetero dienophiles with two heteroatoms which atom are oxomalonates and thioxomalonates (RR'C=O and have been used in Diels-Alder reactions are those with RR'C=S respectively) as shown by J. Barluenga et al., in - N=N- and R N=S=O functionalities. Examples of “Diels-Alder reaction of unactivated 2-AZa-1,3-dienes with dienophiles with -nitrogen double bonds are various diethyl ketomalonate: A dioxide equivalent Tetra aZodicarboxylates (ROCO-N=N COOR) and those hedron Lett., Vol. 30, pages 2685–2688, 1989 and G. Kirby with nitrogen-sulfur double bonds are N-sulfinyl amines or et al., in “The transient dienophile and its S-oxide (sulphine) 25 N-sulfinyl amides (R-N=S=O) or (RCO N=S=O). None of the above references describes precursors of formed by retro Diels-Alder reaction”. J. Chem. Soc., Perkin polycyclic aromatic compounds that are: (1) Diels-Alder Trans., 3175, 1990 for oxo- and thioxomalonate respec adducts of a polycyclic aromatic compound, such as, pen tively. Again, one of the dienes shown to react with this tacene, with a dienophile and (2) highly soluble in common hetero dienophile, is anthracene in which a labile anthracene 30 organic solvents. adduct having carbon-sulfur bond is formed as shown in the Accordingly, it is an object of this invention to synthesize following scheme: precursors of polycyclic aromatic compounds, Such as, pentacene, which are highly soluble in common organic Solvents. 35 Another object of this invention is to provide a precursor

---(EtOCO)-C=O of a polycyclic aromatic compound. Such as, pentacene, that P2S5 is convertible in bulk or as thin films back to pentacene in a retro-Diels-Alder reaction at relatively low temperatures. EtOC COEt Still another object of the invention is to devise a simple 40 synthetic approach to the preparation of these compounds, He which produces high yields of the compounds and is easily ( ) S o scalable. Still another object of this invention is to cast thin films of these materials from solution and regenerate thin films of 45 pentacene upon heating the former at low or moderate EtOC COEt temperatures. Os The present invention provides highly soluble precursors of polycyclic aromatic compounds. Such as, pentacene, which are synthesized in one step via the Diels-Alder 50 reaction of polycyclic aromatic compound with a variety of dienophiles having at least one heteroatom in the dienophile moiety. Hetero Diels-Alder reactions with dienolphiles having SUMMARY OF THE INVENTION two active heteroatoms have also been used successfully for 55 the preparation of a variety of nitrogen and/or Sulfur con The present invention provides a Diels-Alder adduct of a taining compounds. An example of Such dienophiles are polycyclic aromatic compound with a dienophile, wherein acylnitroso (RCO N=O) compounds which are generated the polycyclic aromatic compound is selected from: olig in situ from corresponding hydroxamic acids. An extensive othiophene, perylene, benzoghilperylene, coronene and review of Diels-Alder reactions of various dienes with 60 polyacene; and wherein the dienophile is represented by the acylnitroso dienophiles has been published by M. Miller et formula: al., in “Development and applications of amino acid derived chiral acylnitroso hetero Diels-Alder reaction'. Tetrahedron, wherein each X and Y can independently be N or CR": Vol. 54, pages 1317-1348, 1998. Again, the use of 65 wherein R-X= can be O, S, SO and SO; and anthracene or its derivatives has been a prime example in wherein each R', R and R' can independently be hydro this report as shown in the following scheme: gen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, US 7,125,989 B2 5 aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group R, wherein R can be , alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub stituted aryl having a substituent selected from: —F. —Cl, Br, —NO. —COR, —POH, -SOH, trialkylsilyl and 5 acyl: wherein the acyl is represented by the formula: R5 O O R4 RCO - wherein R can be hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl; wherein each R. R. RandR is independently selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi with the proviso that at least one of X and Y is a hetero 10 tuted aryl, a group wherein R and R together form one or atom selected from: N, O and S. more fused benzo rings and a group wherein R and R' The present invention further provides a process for together form one or more fused benzo rings, wherein n is preparing a Diels-Alder adduct of a polycyclic aromatic at least 1; and compound with a dienophile, the process comprising the 15 wherein the dienophile is represented by the formula: step of contacting: R X=Y R2 wherein each X and Y is independently selected from: N (a) a polycyclic aromatic compound selected from: olig and CR"; wherein R' X= can be O, S, SO and SO; and othiophene, perylene, benZoghilperylene, coronene and a wherein each R', RandR is independently selected from: compound represented by the formula: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, R6 R3 alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub 25 stituted aryl having a substituent selected from: —F. —Cl, Br, —NO, COR, —POH, -SOH, trialkylsilyl and R5 O O R4 acyl: wherein the acyl is represented by the formula: RCO - wherein Rican be hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl, with wherein each R. R. RandR is independently selected 30 the proviso that at least one of X and Y is a hetero atom from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi selected from: N, O and S; and tuted aryl, a group wherein R and R together form one or (b) evaporating the solvent to produce the thin film of the more fused benzo rings and a group wherein R and R' Diels-Alder adduct of the polycyclic aromatic compound together form one or more fused benzo rings, wherein n is with the dienophile. at least 1; and 35 The present invention also provides a method of forming (b) dienophile represented by the formula: a thin film of polycyclic aromatic compound, comprising the steps of R X=Y R2 (a) applying onto a Substrate a solution of a Diels-Alder adduct of a polycyclic aromatic compound with a dienophile wherein each X and Y is independently selected from: N 40 in a Suitable solvent, wherein the polycyclic aromatic com and CR': wherein R-X= can be O, S, SO and SO: pound is selected from: oligothiophene, perylene, benzo wherein each R', Rand R7 is independently selected from: Ighilperylene, coronene and a compound represented by the hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, formula: aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, 45 alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub R6 R3 stituted aryl having a substituent selected from: —F. —Cl, Br, —NO. —COR, —POH, -SOH, trialkylsilyl and acyl: wherein the acyl is represented by the formula: R5 O O R4 RCO - wherein Rican be hydrogen, alkyl of 1-12 carbon 50 atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl, with wherein each R. R. RandR is independently selected the proviso that at least one of X and Y is a hetero atom from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi selected from: N, O and S: tuted aryl, a group wherein R and R together form one or wherein the contacting is carried out under reaction 55 more fused benzo rings and a group wherein R and R' conditions sufficient to produce the Diels-Alder adduct. together form one or more fused benzo rings, wherein n is The present invention further still provides a method at least 1; and wherein the dienophile is represented by the forming a thin film of a Diels-Alder adduct of a polycyclic formula: aromatic compound with a dienophile, the method compris 60 ing the steps of wherein each X and Y is independently selected from: N (a) applying onto a Substrate a solution of a Diels-Alder and CR": wherein R-X= can be O, S, SO and SO; and adduct of a polycyclic aromatic compound with a dienophile wherein each R', RandR is independently selected from: in a suitable solvent, wherein the polycyclic aromatic com hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, pound is selected from: oligothiophene, perylene, benzo 65 aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group Ighilperylene, coronene and a compound represented by the R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, formula: alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub US 7,125,989 B2 7 8 stituted aryl having a substituent selected from: —F. —Cl, two heteroatoms bonded to aromatic moiety, Such as, thioX Br, NO. —COR, POH, -SOH, trialkylsilyl and omalonates, aZodicarboxylates, thialdehyde, acylnitroso and acyl: wherein the acyl is represented by the formula: N-sulfinylamides. RCO - wherein R can be hydrogen, alkyl of 1-12 carbon The Diels-Alder adducts are prepared by a simple, one atoms, aryl, substituted aryl, aralkyl and fluoroalkyl; with 5 step cycloaddition reaction of the polycyclic aromatic com the proviso that at least one of X and Y is a hetero atom pounds, such as, pentacene, or other fused aromatic com selected from: N, O and S: pounds, with heterodienophiles. The Diels-Alder adducts (b) evaporating the solvent to produce the thin film of the according to the present invention all form soluble adducts Diels-Alder adduct of the polycyclic aromatic compound with pentacene and can be converted back to pentacene by with the dienophile; and 10 retro-Diels-Alder reaction at moderate (60-250° C.) tem (c) heating the thin film of the Diels-Alder adduct at a peratures both in bulk, in solution or as thin-films. temperature and for a period of time sufficient to convert the Applicants have discovered that Diels-Alder adducts Diels-Alder adduct back to the polycyclic aromatic com according to the present invention having one to two het pound. eroatoms bonded to aromatic moiety makes Such adducts More particularly, the present invention provides a Diels 15 undergo a retro- Diels-Alder reactions at low to moderate Alder adduct of a polycyclic aromatic compound with a temperatures. dienophile represented by the formula: Applicants have also discovered that the Diels-Alder reactions with heterodienophiles are catalyzed by variety of Lewis acid catalysts and are carried out at low to moderate R2 2O temperatures. M Y Although there has been great body of work on Diels R6 RNYx / Alder reactions and adducts of anthracene (structure I, n=1) which is the second member of polyacenes, very little or no work has been reported on Diels-Alder reactions or adducts R5 O ( ) R3 25 for higher members of these class of compound like tet racene (n=2) and particularly for pentacene (n-3). This might be due to the fact that higher members of R4 polyacenes are not soluble in most organic solvents. 30 The present invention also describes a simple approach in wherein each X and Y is independently selected from: N which pentacene (or other polyacenes of I) are treated with and CR": a dienophile (formula II) to form a Diels-Alder adduct wherein R-X= can be O, S, SO and SO; and represented by formula III. wherein each R', R and R is independently selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi- 35 tuted aryl, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group R, wherein R can be hydrogen, alkyl of 1-12 II carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluo roalkyl and Substituted aryl having a Substituent selected from: – F – Cl, Br, NO, COR. --POH, -SOH, 40 trialkylsilyl and acyl; wherein the acyl is represented by the i formula: RCO - wherein R can be hydrogen, alkyl of III 1-12 carbon atoms, aryl. Substituted aryl, aralkyl and fluo roalkyl: with the proviso that at least one of X and Y is a hetero atom is selected from: N, O and S. BRIEF DESCRIPTION OF DRAWINGS CC FIG. 1 shows the UV/VIS spectra of Diels-Alder adduct 50 of pentacene and N-sulfinyl acetamide, (a) before and (b) wherein each X and Y is independently selected from: N after heating to 130° C., which converts the Diels-Alder and CR": adduct back to pentacene. wherein R-X= can be O, S, SO and SO; and FIG. 2 shows thermogravimetric analysis (TGA) diagram is wherein each R', R and R7 is independently selected of pentacene-N-sulfinyl acetamide adduct. from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi FIG. 3 shows the IR spectrum of pentacene-N-sulfinyl tuted aryl, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl acetamide adduct. and a group R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluo DETAILED DESCRIPTION OF THE 60 roalkyl and Substituted aryl having a Substituent selected INVENTION from: —F. —Cl, —Br. —NO. —COR, —POH, -SOH, trialkylsilyl and acyl: wherein the acyl is represented by the The present invention describes organic solvent-soluble formula: RCO - wherein R can be hydrogen, alkyl of Diels-Alder adducts of polycyclic aromatic compounds, 1-12 carbon atoms, aryl, Substituted aryl, aralkyl and fluo Such as, oligothiophene, perylene, benzoghilperylene, coro- 65 roalkyl: nene, oligothiophene and polyacenes with variety of dieno with the proviso that at least one of X and Y is a hetero philes containing at least one heteroatom and in some cases atom selected from: N, O and S. US 7,125,989 B2 10 Polyacenes are compounds, which can be represented by the formula: -continued

R2 W \ / y ( ) is R6 R3 S S S i R5 O O R4 Oligothiophene

10 wherein n is equal or greater than 1, and preferably from wherein each R. R. RandR is independently selected 1 to 5; and wherein R' and R are independently selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi from the group consisting of hydrogen, alkyl of 1-12 carbon tuted aryl, a group wherein R and R together form one or atoms, acyl, alkylphosphonate, hydroxyalkyl, mercap more fused benzo rings and a group wherein R and R' toalkyl, thiol, carboxylic acid, carboxylic acid ester, tri together form one or more fused benzo rings, wherein n is 15 alkoxysilane, amino, alkylamino, dialkylamino and ami at least 1, and preferably, n is at least 2. noalkane. The polyacene can be represented by the formula: The dienophile is represented by the formula: R X=Y R2 wherein each X and Y is independently selected from: N and CR 7: wherein R-X= can be O, S, SO and SO; and wherein each R', R and R is independently selected i from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi 25 tuted aryl, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl where n is from 2 to 6. In a preferred embodiment, n is equal and a group R, wherein R can be hydrogen, alkyl of 1-12 to 3 Such that the polycyclic aromatic compound represented carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluo by the above formula represents pentacene. A notable roalkyl and Substituted aryl having a Substituent selected example of the polyacenes is pentacene. from: —F. —Cl, —Br. —NO. —COR, —POH, -SOH, The Diels-Alder reactions can easily be carried out with 30 trialkylsilyl and acyl: wherein the acyl is represented by the other members of polyacenes like tetracene and hexacene. formula: RCO - wherein R can be hydrogen, alkyl of Other fused aromatic compounds like oligothiophene, 1–12 carbon atoms, aryl, substituted aryl, aralkyl and fluo perylene (III), benzog.hperylene (IV), coronene (V) and roalkyl: other fused aromatic compounds capable of forming Diels with the proviso that at least one of X and Y is a hetero Alder adducts can also be used to prepared soluble precur 35 atom selected from: N, O and S. sors of these sparingly soluble compounds. In a preferred embodiment where the polycyclic aromatic compound is a polyacene, the Diels-Alder adduct can be represented by the formula: III 40 R2 M Y R6 RNYx / 45 R5 ( ) R3 IV

50 wherein each X and Y is independently selected from: N and CR": wherein R-X= can be O, S, SO and SO; and 55 wherein each R', R and R is independently selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi tuted aryl, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluo 60 roalkyl and Substituted aryl having a Substituent selected from: —F. —Cl, —Br. —NO. —COR, —POH, -SOH, trialkylsilyl and acyl: wherein the acyl is represented by the formula: RCO - wherein R can be hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, aralkyl and fluo 65 roalkyl: with the proviso that at least one of X and Y is a hetero atom selected from: N, O and S. US 7,125,989 B2 11 12 The dienophiles described in this invention are chosen formula: RCO - wherein R is selected from: hydrogen, from known compounds and all have at least one heteroa alkyl of 1-12 carbon atoms, aryl, Substituted aryl, aralkyl tom, such as, N, O or S. connected by a double bond to a and fluoroalkyl: second heteroatom or carbon. Another example is the Diels-Alder reaction of thioxoma Examples of the dienophiles which are used in this lonate with pentacene to form an adduct with one carbon invention include dialkylaZodicarboxylate, thiooxoma sulfur bond as depicted in the following scheme. Diethyl lonates, N-sulfinylamides, acylnitroso compounds and other thioXomalonate is prepared in situ from the reaction of diethyl oXomalonate and phosphorous pentasulfide and compounds that fulfill the above requirements. reacted with pentacene in the presence of a catalyst or by Diels-Alder reaction of conjugated dienes with ethylenic heating in pyridine. or acetylenic dienophiles remain one of the most useful 10 transformations in organic synthesis. Heterodienophiles of the type RR'C=X have been employed less frequently but have considerable potential when only one carbon-carbon bond is required in the product. Because of the high reactivity of these hetero dienophiles 15 and the solubility of dienes used in these examples, the COEt Diels-Alder reactions are mostly carried out at low to room temperatures without the use of any catalyst. In cases where dienes are less reactive and have marginal Solubility, like anthracene and its derivatives, the Diels-Alder reaction is carried out at moderate temperatures, usually refluxing in C low boiling solvents. But because anthracene and its deriva tives are soluble in hot solvents, the reaction can be carried RO2C COR out without the presence of a catalyst. Higher homologous of polyacene like tetracene and pen 25 S tacene have little or no solubility in most common organic solvents in which a Diels-Alder reactions is carried out. Because of lack of solubility there has been no report of C Diels-Alder reaction of pentacene or tetracene with any dienophiles, and particularly with hetero dienophiles. 30 In this invention, Diels-Alder reactions and adducts of wherein each R is independently selected from: hydrogen, pentacene with various hetero dienophiles are described. alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, aralkyl, The common feature of all these reactions will be the use of chloroalkyl, fluoroalkyl and substituted aryl having a sub a Lewis acid to promote the reaction at moderate tempera stituent selected from: —F. —Cl, Br, NO. —COR, ture so that the thermally labile adducts can be isolated. —POH, -SOH, trialkylsilyl and acyl; wherein said acyl An example of Such an adduct wherein the polycyclic is represented by the formula: RCO - wherein R is aromatic compound is pentacene and the dienophile is a selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, thioxocarboxylate is represented by the formula: substituted aryl, aralkyl and fluoroalkyl: At temperatures higher than 150° C., the thioxomalonate 40 adduct, which is isolated by column chromatography as a H COR white crystalline compound, undergoes a retro Diels-Alder reaction to pentacene. However, if the sulfide is oxidized to corresponding S-oxide, then the adduct can be converted back to pentacene at temperature as low as 150° C. 45 Both the sulfide and S-oxide adduct are highly soluble in common organic solvents and can be processed from solu CXC tion to form thin films on substrates. Another class of adducts of pentacene is Diels-Alder reaction products of pentacene and dialkyl or diaralkyla The above Diels-Alder adduct in which the sulfur atom is 50 oxidized to the corresponding sulfoxide is represented by the Zodicarboxylates. These compounds are by themselves ther formula: mally labile and decompose above 100° C. Therefore, any Diels-Alder reaction of these compounds with pentacene has to be carried out low to moderate temperature. H COR The Diels-Alder adduct where the dienophile is an azodi 55 carboxylate of the formula RO CO. N=N COOR is shown below:

CC 60 wherein R is selected from: hydrogen, alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluo roalkyl and Substituted aryl having a Substituent selected 65 from: —F. —Cl, —Br. —NO. —COR, —POH, -SOH, trialkylsilyl and acyl: wherein said acyl is represented by the US 7,125,989 B2 13 14 R can be alkyl of 1-12 carbon atoms, aryl, aralkyl, (R=CHCHOCO ) were prepared and reacted with pen chloroalkyl, fluoroalkyl and substituted aryl having a sub tacene in the presence of methyl trioxide as Lewis stituent selected from: —F. —Cl, —Br. —NO. —COR, acid catalyst. In both cases, high yields of the adduct were trialkylsilyl and acyl; wherein the acyl is represented by the obtained and the compounds found to be highly soluble in formula: RCO - wherein R can be hydrogen, alkyl of 5 many organic solvents. 1-12 carbon atoms, aryl, Substituted aryl, aralkyl, chloro Thin films of these compounds were cast from solution alkyl and fluoroalkyl. and then heated at 120–140° C. to transform the compounds Preferably, R is benzyl, alkyl of one to five carbon atoms, back to pentacene is confirmed by its UV/VIS spectra (FIG. partially or fully chlorinated alkyl of one to four carbon 1) and thermogravimetric analysis TGA (FIG. 2) and IR atoms and partially or fully fluorinated alkyl of one to four 10 spectrum (FIG. 3). Although the onset of the retro Diels carbon atoms. Alder reaction temperature for bulk, as evident from TGA, The above Diels-Alder can be hydrolyzed to form a cyclic is about 140° C., thin films of these compounds can be diamine compound represented by the formula: converted back to pentacene at even lower temperatures of 110 120° C. 15 In still another example of Diels-Alder reaction of pen tacene with hetero dienophiles, a Diels-Alder adduct wherein the dienophile is an N-sulfinyl amide compound is represented by the formula:

and the adduct is represented by the formula:

and the diamine can be oxidized to give an azo compound 25 represented by the formula:

30

wherein R can be hydrogen, alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub COO stituted aryl having a substituent selected from: —F. —Cl, 35 Br, NO. —COR, POH, -SOH, trialkylsilyl and Employing a Lewis acid catalyst, Such as, tetra acyl: wherein the acyl is represented by the formula: chloride facilitates the Diels Alder reaction so it can be RCO - wherein Rican be hydrogen, alkyl of 1-12 carbon carried out at temperature below -40°C. Alternatively, less atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl. Referring to FIG. 1, the UV/VIS spectra of Diels-Alder active catalysts like tetrafluoroborate or methyl rhe 40 nium trioxide can be used to run the reaction above room adduct of pentacene and N-sulfinyl acetamide, (a) before and temperature by refluxing the mixture of pentacene, diaZodi (b) after heating to 130°C., which converts the Diels-Alder carboxylate and the catalyst in a low boiling solvent like adduct back to pentacene is shown. THF or chloroform. FIG. 2 shows thermogravimetric analysis (TGA) diagram These diaza adducts of pentacene are stable to high 45 of pentacene-N-sulfinyl acetamide adduct. temperatures and as such are not good candidates as penta FIG. 3 shows the IR spectrum of pentacene-N-sulfinyl cene precursors because thin films of these compounds have acetamide adduct. to be heated above 280° C. to convert to pentacene. For The above Diels-Alder adduct can be hydrolyzed to form example, the adduct of diethyl diazodicarboxylate (Rethyl) a compound represented by the formula: has a of 257°C. and is stable up to 300° C. But 50 when the carboxylate groups are hydrolyzed to the corre sponding acid, which automatically undergo decarboxyla tion to form the cyclic diamine, or oxidized form of the latter to diazo derivative, then the adduct becomes highly unstable and can be converted back to pentacene at moderate tem 55 peratures (50–100° C.). Thus, an important step in this process is the removal of the carboxylate protecting group at low temperatures so as to be able to isolate the amine or diazo compounds. The adducts of pentacene with a variety of dialkyl azodi 60 Although only two examples of N-sulfinyl amides are carboxylate were prepared. It was found that bis-trichloro shown here, N-sulfinyl derivatives are equally attractive ethyl carboxylates (R=CC1, CH, ) can easily be candidates for the preparation of soluble pentacene adducts. removed at room temperature in THF by treatment with For example, N-sulfinyl derivative of fluoroalkylamide powder to give the corresponding diamine. like trifluoracetamide (R=CF CO—) or higher alkyl In yet another example of Diels-Alder reaction of penta 65 amides (R=CH-CO , where n=1-10) can be used cene with hetero dienophiles, N-Sulfinyl acetamide instead of sulfinyl acetamide. N-Sulfinyl derivatives of (R=CHCO ) and N-sulfinyl benzyl carbamate aromatic amines (Raryl) where R is simply a phenyl US 7,125,989 B2 15 16 group or Substituted (nitro, keto, halo, alkyl, fluoroalkyl etc) alkyl groups like CF (CF)— where n is from Zero to 10. are known to undergo Diels-Alder reactions and can be used R could be also an aryl group like phenyl or substituted to prepare soluble adducts with pentacene. phenyl with substituents like one or more halogens (C1, F and Br), nitro group, carboxylic acid or esters, amines or amides, phosphonic acid or ester, trialkyl or trialkoxysilane. The adducts in which nitrogen is connected to an acyl R-NESEO (RCO) group could further be hydrolyzed to corresponding CHRhC) —NH group by treatment with base as shown in the fol R lowing reaction. 10

Nfor A. 15 O

R = CHCO CHSCHOCO C CO . H N In another example of the Diels-Alder reaction of penta f cene with a hetero dienophile, a Diels-Alder adduct wherein O the dienophile is a nitroso compound is represented by the formula:

25 -R Thin films of these adducts are prepared from solution by different techniques, e.g., spin-coating, casting, doctor blad 30 ing, etc. Once thin films of these adducts on Substrates are Coyo formed, they can easily be converted back to pentacene by heating the substrate on a hot plate or in an oven at modest temperatures. Any residual compounds other than pentacene formed during retro Diels-Alder reaction can be removed by wherein R can be hydrogen, alkyl of 1-12 carbon atoms, 35 dipping the Substrate solvents like alcohols, ethers, ketones alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl, Substi and the like, to get pure pentacene films. tuted aryl having a Substituent selected from: —F. —Cl, In the examples listed above the diene which was Br, —NO. —COR, —POH, -SOH, trialkylsilyl and employed in Diels-Alder reactions has been pentacene, but acyl: wherein the acyl is represented by the formula: other members of polyacenes like tetracene, hexacene and RCO - wherein R can be hydrogen, alkyl of 1-12 carbon 40 heptacene (structure I, n=2, 4 and 5 respectively) can also be atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl. used to make soluble derivatives with hetero dienophiles. Other acylnitroso compounds of general formula Although in all the structures depicted so far, the dieno R—CO N=O are very attractive and judged by its adduct phile has attached to the middle ring of pentacene (or with anthracene derivative can be converted back to penta polyacene in general) it is possible to have the dienophile cene at moderate temperatures. An example would be the 45 reaction of pentacene with N-oxyacetamide (R=CH ) react with other ring in polycyclic aromatic compounds like which can be generated from acetylhydroxamic acid and pentacene, as depicted in the following structure with reacted with pentacene in the presence of methyl rhenium R X=Y R representing hetero dienophiles of this trioxide to give desired adduct as shown bellow. invention: 50

RCO-NEO CHRhC)

COR 55

wherein each X and Y is independently selected from: N 60 and CR": wherein R-X= can be O, S, SO and SO; and wherein each R', R and R is independently selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi tuted aryl, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl 65 and a group R, wherein R can be hydrogen, alkyl of 1-12 In the above reaction R— can be chosen from alkyl carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluo groups of having one to twelve carbon atoms, halogenated roalkyl and Substituted aryl having a Substituent selected US 7,125,989 B2 17 18 from: —F. —Cl, —Br. —NO. —COR, —POH, -SOH, peratures (-70° C. to -40° C.) or room temperature or in trialkylsilyl and acyl; wherein the acyl is represented by the refluxing low boiling solvents like THF, acetonitrile or formula: RCO - wherein R can be hydrogen, alkyl of chloroform. Diels-Alder reactions of this invention proceeds 1-12 carbon atoms, aryl. Substituted aryl, aralkyl and fluo to give adducts in high yield and the isolation and purifica roalkyl: tion steps are simple. For this reason, the reaction can easily with the proviso that at least one of X and Y is a hetero be scaled up for large-scale preparation of the adducts. The atom selected from: N, O and S. products, which are formed in more than 90% yield, can be The Diels-Alder adducts can be prepared by a process separated by evaporation of the solvents at reduced pressure comprising the step of: and purified by flash chromatography. contacting: 10 (a) a polycyclic aromatic compound selected from: olig The adducts according to the present invention are soluble othiophene, perylene, benZoghilperylene, coronene and a in variety of common organic solvents including hydrocar compound represented by the formula: bons, chlorinated hydrocarbons, ethers, esters and ketones. This property of the adducts affords the preparation of thin 15 films of the adduct. Accordingly, the present invention R6 R3 includes a method of forming a thin film of a Diels-Alder adduct of a polycyclic aromatic compound with a dieno phile, the method comprising the steps of: R5 O O R4 (a) applying onto a Substrate a solution of a Diels-Alder adduct of a polycyclic aromatic compound with a dienophile wherein each R. R. RandR is independently selected in a Suitable solvent, wherein the polycyclic aromatic com from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi pound is selected from: oligothiophene, perylene, benzo tuted aryl, a group wherein R and R together form one or Ighilperylene, coronene and a compound represented by the formula: more fused benzo rings and a group wherein R and R' 25 together form one or more fused benzo rings, wherein n is at least 1; and (b) dienophile represented by the formula: R6 R3

30 wherein each X and Y is independently selected from: N R5 O O R4 and CR': wherein R' X= can be O, S, SO and SO; wherein each R', R and R is independently selected from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, wherein each R. R. RandR is independently selected aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group 35 from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, tuted aryl, a group wherein R and R together form one or alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub more fused benzo rings and a group wherein R and R' stituted aryl having a substituent selected from: —F. —Cl, together form one or more fused benzo rings, wherein n is Br, NO. —COR, POH, -SOH, trialkylsilyl and at least 1; and acyl: wherein the acyl is represented by the formula: 40 wherein the dienophile is represented by the formula: RCO - wherein R can be hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl, with R X=Y R2 the proviso that at least one of X and Y is a hetero atom wherein each X and Y is independently selected from: N selected from: N, O and S: and CR": wherein R-X= can be O, S, SO and SO; and wherein the contacting is carried out under reaction 45 wherein each R', RandR is independently selected from: conditions sufficient to produce the Diels-Alder adduct. hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, The Diels-Alder reaction of hetero dienophiles with poly aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group acenes and other fused aromatic compounds according to the R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, present invention are Lewis acid-catalyzed. The Diels-Alder alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub reaction is carried out at low to moderate temperatures, as 50 stituted aryl having a substituent selected from: —F. —Cl, the case may be, resulting in the formation of the adducts. Br, NO. —COR, POH, -SOH, trialkylsilyl and Preferably, the Diels-Alder reaction is carried out in the acyl: wherein the acyl is represented by the formula: presence of a Lewis acids and protic acids, including com RCO - wherein Rican be hydrogen, alkyl of 1-12 carbon pounds, such as, titanium(IV)tetrachloride, (IV)tetrachlo atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl, with ride, silver tetrafluoroborate, methyl rhenium trioxide, alu 55 minum chloride, diethyl aluminum chloride, silver the proviso that at least one of X and Y is a hetero atom trifluoroacetate, compounds, Sulfuric acid, trifluo selected from: N, O and S; and roacetic acid, methanesulfonic acid, trifluoromethane (b) evaporating the solvent to produce the thin film of the Sulfonic acid, and many others Lewis and protic acids Diels-Alder adduct of the polycyclic aromatic compound known in the art. 60 with the dienophile. The reactions are carried out in the presence of a Lewis The present invention further includes a method of form acid catalyst to lower the transition state energy of the ing a thin film of a polycyclic aromatic compound itself. The reaction and to be able to run the reaction at temperatures method comprises the steps of from below zero to moderate temperatures where the (a) applying onto a Substrate a solution of a Diels-Alder adducts are stable. 65 adduct of a polycyclic aromatic compound with a dienophile Depending on the nature of the dienophile and Lewis acid, in a Suitable solvent, wherein the polycyclic aromatic com Diels-Alder reactions can be carried out at very low tem pound is selected from: oligothiophene, perylene, benzo US 7,125,989 B2 19 20 Ighilperylene, coronene and a compound represented by the hours. By this time all the pentacene was dissolved and a formula: yellow clear solution was formed. The solvent was evapo rated on rotary evaporator and the residue was flash chro matographed on a column of silica gel first eluting with 9:1 R R3 hexane ethyl acetate to remove excess dimethylazodicar boxylate and then elution with 50:50 hexane ethyl acetate gave, after removal of the solvent, the adduct as white R5 O O R4 powder (1.65 gram, 90% yield), m.p.-273-275°C., onset of decomposition (conversion back to pentacene) at 285°C. IR, 10 KBr: 1754 and 1701 cm (carbonyl groups). Exact proce wherein each R. R. RandR is independently selected dure was followed and adducts of pentacene with diethyl from: hydrogen, alkyl of 1-12 carbon atoms, aryl, Substi aZodicarboxylate (m.p=292–294° C.), dibenzylazodicar tuted aryl, a group wherein R and R together form one or boxylate (m.p=295-297 C.) and bis-trichloroethylazodica more fused benzo rings and a group wherein R and R' boxylate were also synthesized in more than 90% yield. together form one or more fused benzo rings, wherein n is 15 at least 1; and wherein the dienophile is represented by the Example 2 formula: Diels-Alder adduct of N-Sulfinyl acetamide and penta cene: Pentacene (556 mg, 2 mmole) was added to a solution wherein each X and Y is independently selected from: N of N-sulfinyl acetamide (prepared according to procedure and CR"; wherein R' X= can be O, S, SO and SO; and reported by Kin et al., in “New facile synthesis of N-sulfi wherein each R', R and R is independently selected from: nylamine derivatives using N,N'-sulfinylbisimidazole and hydrogen, alkyl of 1-12 carbon atoms, aryl, Substituted aryl, N-(chlorosulfinyl)imidazole'. Tetrahedron Lett., Vol. 26, aralkyl, alkoxycarbonyl, aryloxycarbonyl, acyl and a group 1985, pages 3821–3824) (420 mg, 4 mmole) containing 30 R, wherein R can be hydrogen, alkyl of 1-12 carbon atoms, 25 mg. of methyl rhenium trioxide. The mixture was refluxed alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and Sub for 4 hours. The solution was cooled to room temperatures stituted aryl having a substituent selected from: —F. —Cl, and the solvent was evaporated on rotary evaporator. Excess Br, —NO. —COR, —POH, -SOH, trialkylsilyl and N-sulfinyl acetamide was removed in high vacuum and the acyl: wherein the acyl is represented by the formula: brown Solid residue was flash chromatographed on a column RCO - wherein R can be hydrogen, alkyl of 1-12 carbon 30 of silica gel eluting with 1% methanol in chloroform to give atoms, aryl, Substituted aryl, aralkyl and fluoroalkyl, with the adduct (690 mg, 91%) as white powder which was the proviso that at least one of X and Y is a hetero atom crystallized from 2:1 toluene-ethanol. m.p=140–142 (dec.). selected from: N, O and S: IR (KBr), 1675, 1376, 1282, 1124 and 893 cm. Thermo (b) evaporating the solvent to produce the thin film of the gravimetric analysis (FIG. 2), weight loss of 27% starting at Diels-Alder adduct of the polycyclic aromatic compound 35 140° C. with the dienophile; and Alternative work-up and isolation procedures are also (c) heating the thin film of the Diels-Alder adduct at a possible, and will be evident to those skilled in the art. temperature and for a period of time sufficient to convert the The present invention has been described with particular Diels-Alder adduct back to the polycyclic aromatic com reference to the preferred embodiments. It should be under pound. 40 stood that the foregoing descriptions and examples are only Thin films of these adducts are cast from solution and they illustrative of the invention. Various alternatives and modi can be converted back to pentacene films by simply heating fications thereof can be devised by those skilled in the art the substrate on which it is coated. without departing from the spirit and scope of the present Any suitable substrate can be used to prepare the thin invention. Accordingly, the present invention is intended to films of the polycyclic aromatic compounds of the present 45 embrace all such alternatives, modifications, and variations invention as well as the thin films of the Diels-Alder adducts that fall within the scope of the appended claims. thereof. Preferably, the substrate used to prepare the above thin films is a , silicon, plastic, glass or coated glass. We claim: The temperature of the retro-Diels-Alder reaction (con 1. A Diels-Alder adduct of a polycyclic aromatic com version of the adducts to pentacene) is dependent on the 50 pound with a dienophile, wherein said polycyclic aromatic nature of the dienophile used to prepare the adduct. The compound is a polyacene represented by the formula: conversion can be carried out at temperatures as low as 60° C. in the case of the pentacene diaZodicarboxylate adduct after hydrolysis, to more than 180° C. in the case of adduct R. R3 with thioxomalonate. However, typically, the temperature of 55 heating the thin-film of the Diels-Alder adduct is from about 80° C. to about 250° C. R5 O O R4 EXPERIMENTAL 60 wherein each R. R. RandR is independently selected Example 1 from the group consisting of hydrogen, alkyl of 1-12 carbon atoms, aryl, a group wherein Rand R together Diels-Alder adduct of pentacene and dimethylazodicar form one or more fused benzo rings and a group boxylate. Pentacene (834 mg., 3 mmole) and methyl rhe wherein R and R together form one or more fused nium trioxide (50 mg) were added to a solution of dim 65 benzo rings; and wherein n is 2–6; and wherein said ethylazodicarboxylate (1.05 g, 6 mmole) in 40 mL of dienophile is represented by the formula: anhydrous chloroform and the solution was refluxed for 18 US 7,125,989 B2 21 22 wherein each X and Y is independently selected from the group consisting of: N and CR": wherein R' X= together form a group selected from the A R2 group consisting of O, S, SO and SO; and Y wherein each R', R and R is independently selected 5 R6 R-X from the group consisting of hydrogen, alkyl of 1-12 R3 carbon atoms, aryl, aralkyl, alkoxycarbonyl, aryloxy- O carbonyl, acyl and a group R, wherein R is selected R5 4 from the group consisting of hydrogen, alkyl of 1-12 10 R carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoroalkyl and substituted aryl having a substituent wherein X, Y. R. R. R. R. Rand Rare as previously Selected from the group consisting of —F. —Cl. —Br. defined s uw s - we su-Y s - we s —NO, -CO.R. POH, —SOH, trialkylsilyl and 3. The Diels-Alder adduct of claim 1, wherein n is 2–3. acyl: wherein said acyl is represented by the formula: 15 RCO - wherein R is selected from the group con 4. The Dials-Alder adduct of claim 1 , wherein said sisting of hydrogen, alkyl of 1-12 carbon atoms, aryl, polyacene is represented by the formula: aralkyl and fluoroalkyl; with the proviso that at least one of X and Y is a hetero 2O atom selected from the group consisting of N, O and S. 2. A Diels-Alder adduct of a polycyclic aromatic com pound with a dienophile, wherein said polycyclic aromatic i compound is a polyacene rapresented by the formula: 25 where n is 2–6. 5. The Dials-Alder adduct of claim 4, wherein n is equal R R3 to 3 and said polycyclic aromatic compound is pentacene. 6. The Diels-Alder adduct of claim 1, wherein said dienophile is a thioxocarboxylate compound and said adduct R5 i R4 is represented by the formula:

wherein each R. R. RandR is independently selected H COR from the group consisting of hydrogen, alkyl of 1-12 35 carbon atoms, aryl, a group wherein RandR together S form one or more fused benzo rings and a group wherein R and R together form one or more fused benzo rings; and wherein n is 2–6; and wherein said dienophile is presented by the formula: 40 R X=Y R2 wherein R is selected from the group consisting of: wherein each X and Y is independently selected from the hydrogen, alkyl of 1-12 carbon atoms, alkoxy, acyl, group consisting of N and CR": aryl, aralkyl, chloroalkyl, fluoroalkyl and substituted wherein R' X= together form a group selected from the 45 aryl having a Substituent selected from the group con group consisting of O, S, SO and SO; and sisting of: —F. —Cl, Br, NO. —COR, POH, —SOH, trialkylsilyl and acyl: wherein said acyl is wherein each R', R and R7 is independently selected represented by the formula: RCO - wherein R is from the group consisting of hydrogen, alkyl of 1-12 Selected from the group consisting of hydrogen, alkyl carton atoms, aryl, aralkyl, alkoxycarbonyl, aryloxy- 50 of 1-12 carbon atoms, aryl, aralkyl and fluoroalkyl. carbonyl, acyl and a group R, wherein R is selected 7. The Dials-Alder adduct of claim 6, wherein the sulfur from the group consisting of hydrogen, alkyl of 1-12 atom is oxidized to corresponding Sulfoxide and wherein carbon atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, said adduct is represented by the formula: fluoroalkyl and substituted aryl having substituent Selected from the group consisting of —F. —Cl. —Br. - NO. —COR, POH, -SOH, trialkylsilyl and H COR acyl: wherein said acyl is represented by the formula: O RCO - wherein R is selected from the group con- Ns aralkylsisting ofand hydrogen, fluoroalkyl; alkyl of 1-12 carbon atoms, aryl, 60 C C with the proviso that at least one of X and Y is a hetero O atom selected from the group consisting of N, O and S; wherein said Diels-Alder adduct of said polycyclic aro- 65 8. The Diels-Alder adduct of claim 1, wherein said matic compound with said dienophile is represented by dienophile is thioXomalonate and said adduct is represented the formula: by the formula: US 7,125,989 B2 24

wherein R is selected from the group consisting at hydro gen, alkyl of 1-12 carbon atoms, alkoxy, acyl, aryl, 10 aralkyl, chloroalkyl, fluoroalkyl and substituted aryl 12. The Diels-Alder adduct of claim 1, wherein said having a Substituent selected from the group consisting dienophile is an aZodicarboxylate compound represented by of —F. —Cl. —Br. —NO. —COR, POH, the formula: —SOH, trialkylsilyl and acyl; wherein said acyl is represented by the formula: RCO - wherein R is 15 RO CO. N=N COOR Selected from the group consisting of hydrogen, alkyl of 1-12 carbon atoms, aryl, aralkyl and fluoroalkyl. and wherein said adduct is represented by the formula: 9. The Diels-Alder adduot of claim 1, wherein said dienophile is a nitroso compound and said adduct is repre sented by the formula:

-R

25

and Coco wherein R is selected from the group consisting of alkyl 30 of 1-12 carbon atoms, aryl, aralkyl, chloroalkyl, fluo wherein R is selected from the group consisting of: roalkyl and Substituted aryl having a substituent hydrogen, alkyl of 1-12 carton atoms, alkoxy, acyl, selected from the group consisting of —F. —Cl, —Br. aryl, aralkyl, chloroalkyl, fluoroalkyl, substituted aryl —NO. —COR, trialkylsilyl and acyl; wherein said having a Substituent selected from the group consisting acyl is represented by the formula: RCO - wherein R of: - F. —Cl, —Br. —NO, COR, POH, is selected from the group consisting of hydrogen, —SOH, trialkylsilyl and acyl: wherein said acyl is 35 alkyl of 1-12 carbon atoms, aryl, aralkyl, chloroalkyl represented by the formula: RCO - wherein R is and fluoroalkyl. Selected from the group consisting at hydrogen, alkyl of 13. The Diels-Alder adduct of claim 12, wherein R is 1-12 carbon atoms, aryl, aralkyl and fluoroalkyl. selected from the group consisting ot benzyl, alkyl of one to 10. The Diels-Alder adduct of claim 1, wherein said five carbon atoms, partially or fully chlorinated alkyl of one dienophile is an N-sulfinyl amide compound represented by 40 to four carbon atoms and partially or fully fluorinated alkyl the formula: of one to four carbon atoms. 14. The Diels-Alder adduct of claim 12, wherein said adduct is hydrolyzed to form a cyclic diamine compound wherein said adduct is represented by the formula: represented by the formula: 45

H 50 CSCC and 55 15. The Diels-Alder adduct of claim 14, wherein said wherein R is selected from the group consisting of: adduct is oxidized to give an azo compound represented by hydrogen, alkyl of 1-12 carbon atoms, alkoxy, acyl, the formula: aryl, aralkyl, chloroalkyl, fluoroalkyl and substituted aryl having a substituent selected from the group con sisting of —F. —Cl. —Br. —NO. —COR, POH, 60 —SOH, trialkylsilyl and acyl: wherein said acyl is represented by the formula: RCO - wherein R is Selected from the group consisting at hydrogen, alkyl of 1-12 carbon atoms, aryl, aralkyl and fluoroalkyl. 11. The Diels-Alder adduct of claim 10, wherein said 65 adduct is hydrolyzed to form a compound represented by the Coco formula: US 7,125,989 B2 25 26 16. A process for preparing a Diels-Alder adduct of a substituted aryl having a substituent selected from the polycyclic aromatic compound with a dienophile, said pro group consisting of —F. —Cl. —Br. —COR, trialkyl cess comprising the step of silyl and acyl represented by the formula: RCO - contacting: wherein R is selected from the group consisting of: (a) polyacene compound represented by the formula: 5 hydrogen, alkyl of 1-12 carbon atoms, aryl, aralkyl and fluoroalkyl; and R6 R3 wherein each R. R. RandR is independently selected from the group consisting of hydrogen, alkyl of 1-12 carbon atoms and aryl. R5 O O R4 22. The Diels-Alder adduct according to claim 1, wherein 10 said polycyclic aromatic compound is a polycyclic aromatic wherein each R. R. RandR is independently selected compound represented by the formula: from the group consisting of hydrogen, alkyl of 1-12 carbon atoms, aryl, a group wherein RandR together form one or more fused benzo rings and a group R6 R3 wherein R and R together form one or more fused 15 benzo rings, wherein n is 2–6; and (b) dienophile represented by the formula: R5 O O R4

wherein each X and Y is independently selected from the wherein n is 2–6; group consisting of N and CR"; wherein wherein each R. R. RandR is independently selected R'—X=together form a group selected from the group from the group consisting of hydrogen, alkyl of 1-12 consisting of O, S, SO and SO, wherein each R', R carbon atoms, aryl, a group wherein Rand R together and R is independently selected from the group con form one or more fused benzo rings and a group sisting of hydrogen, alkyl of 1-12 carbon atoms, aryl, 25 wherein R and R together form one or more fused Substituted aryl, aralkyl, alkoxycarbonyl, aryloxycar benzo rings; and bonyl, acyl and a group R, wherein R is selected from the group consisting of hydrogen, alkyl of 1-12 carbon wherein said dienophile is selected from the group con atoms, alkoxy, acyl, aryl, aralkyl, chloroalkyl, fluoro sisting of compounds represented by the formula: alkyl and Substituted aryl having a substituent selected 30 R N=O, RCO N=S=O, and RO CO from the group consisting of —F. —Cl. —Br. —NO, N=N COOR, —CO.R. POH, -SOH, trialkylsilyl and acyl: wherein said acyl is represented by the formula: wherein R is selected from the group consisting of alkyl RCO - wherein R is selected from the group con of 1-12 carbon atoms, aryl, aralkyl, chloroalkyl, fluo sisting of hydrogen, alkyl of 1-12 carbon atoms, aryl, roalkyl and Substituted aryl having a substituent 35 Selected from the group consisting of —F. —Cl. —Br. aralkyl and fluoroalkyl; with the proviso that at least —NO. —COR, and trialkylsilyl. one of X and Y is a hetero atom selected from the group 23. A process for preparing a Diels-Alder adduct com consisting of N, O and S; prising the step of wherein said contacting is carried out under reaction conditions sufficient to produce said Diels-Alder contacting: adduct. 40 (a) a polycyclic aromatic compound represented by the 17. The process of claim 16, wherein said contacting is formula: carried out in the presence of a catalyst selected from the group consisting of a protic acid and a Lewis Acid. 18. The process of claim 17, wherein said protic acid R6 R3 catalyst is selected from the group consisting of Sulfuric 45 acid, trifluoroacetic acid, trifluoromethanesulfonic acid and methanesulfonic acid. R5 O O R4 19. The process of claim 17, wherein said Lewis Acid catalyst is selected from the group consisting of titanium tetrachloride, tin tetrachloride, aluminum chloride, diethyl 50 wherein each R. R. RandR is independently selected aluminum chloride, silver trifluoroacetate, silver tetrafluo from the group consisting of hydrogen, alkyl of 1-12 roborate, methyl rhenium trioxide and a palladium com carbon atoms, aryl, a group wherein Rand R together pound. form one or more fused benzo rings and a group 20. A Diels-Alder adduct prepared by the process of claim wherein R and R together form one or more fused 17. benzo rings, wherein n is 2–6; and 21. A Diels-Alder adduct according to claim 1, repre 55 (b) dienophile selected from the group consisting of sented by the formula: compounds represented by the formula: R N=O, RCO N=S=O, and RO CO N=N COOR, 60 wherein R is selected from the group consisting of alkyl of 1-12 carbon atoms, aryl, aralkyl, chloroalkyl, fluo roalkyl and Substituted aryl having a substituent Selected from the group consisting of —F. —Cl. —Br. R4 —NO, —COR, and trialkylsilyl; 65 wherein said contacting is carried out under reaction wherein R is selected from the group consisting of alkyl conditions sufficient to produce said Diels-Alder of 1-12 carbon atoms, alkoxy, acyl, aralkyl, aryl, and adduct. US 7,125,989 B2 27 28 24. The process of claim 23, wherein said contacting is is selected from the group consisting of titanium tetrachlo carried out in the presence of a catalyst selected from the ride, tin tetrachloride, aluminum chloride, diethyl aluminum group consisting of a protic acid and a Lewis Acid. chloride, silver trifluoroacetate, silver tetrafluoroborate, 25. The process of claim 24, wherein said protic acid methyl rhenium trioxide and a palladium compound. catalyst is selected from the group consisting of Sulfuric 5 acid, trifluoroacetic acid, trifluoromethanesulfonic acid and methanesulfonic acid and wherein said Lewis Acid catalyst