SYNTHESIS AND CHARACTERIZATION OF FUNCTIONALIZED ANALOGS OF 1,3,6,8-TETRAKIS(METHYLSULFANYL)PYRENE AND THEIR ELECTRON-CONDUCTING RADICAL-CATION SALTS

Radical-cation salts of sulfur-substituted aromatic compounds, formed upon chemical and electrochemical oxidation of the neutral parent comp ounds, represent an important class of stable electron-conducting mate rials with many potential uses in molecular-electronics. Many electron ic devices require, however, macromolecular materials bound to an elec trode surface. While a large number of sulfur-substituted aromatic com pounds capable of forming electron-conducting radical-cations salts ha ve been thus far reported, none of them bears functional groups that c ould be used to bind these compounds to a polymer backbone or an elect rode surface. In this paper, we report the synthesis of functionalized analogs of 1,3,6,8-tetrakis(methylsulfanyl)pyrene, where one of the m ethylsulfanyl groups has been replaced by an amide group. Substitution of the methylsulfanyl group by the amide group does not inhibit the f ormation of highly electron-conducting radical-cation salts. N-(3,6,8- Tris(methylsulfanyl)pyren-1-yl)acetamide (3a) forms, upon oxidation wi th iodine, a radical-cation salt (4a) similar to those formed by the p arent 1,3,6,8-tetrakis(methylsulfanyl)pyrene 2. The electron-conductiv ity of radical-cation salt 4a was found to be 1 S cm(-1) at room tempe rature. The amide group was also used as a handle to introduce additio nal functionality on the molecule. Coupling of 3,6,8-tris(methylsulfan yl)pyren-1-ylamine (10) with the gamma-carboxyl group of N-(tert-butox ycarbonyl)-L-glutamic acid alpha-tert-butyl ester was achieved via the formation of a mixed anhydride with isobutylchloroformate. This funct ionalized 3,6,8-(trismethylsulfanyl)pyrene derivative will be used in polymerization reactions onto electrode surfaces, providing a new surf ace-bound electroactive polymer with potential applications in molecul ar devices.