Synthesis and chemical properties of π-conjugated poly(imidazole-2,5-diyl)s

Poly(N,N'-dihexyl-2,2'-biimidazole-5,5'-diyl), PBIm(NHex), poly(N,N'-dimethoxymethyl-2,2'-biimidazole-5,5'-diyl), PBIm(NMOM), and poly(N-methylimidazole), PIm(NMe), were prepared by dehalogenative polycondensation using a zerovalent nickel complex. PBIm(NHex), PBIm(NMOM), and PIm(NMe) showed number-average molecular weights, M-n's, of 15000, 12000, and 8200 (GPC; poly(methyl methacrylate) standards), respectively, and PBIm(NHex) gave an [eta] value of 0.24 dL g(-1) in formic acid. PBIm(NHex) showed a UV-vis absorption peak at 308 nm in CHCl3, which was shifted by 97 nm to a longer wavelength from that of N-hexylimidazole. Powder XRD data of PBIm(NHex) and PIm(NMe) supported formation of a stacked structure in the solid. Films of polymers received electrochemical oxidation at about 1.0 V vs Ag+/Ag. Deprotection of PBIm(NMOM) afforded poly(2,2'-imidazole-5,5'-diyl) which showed UV-vis peaks at 320 nm in film and at 350 nm in formic acid, respectively. PBim(N-Hex) formed a copper(II) complex in reaction with CuCl2, which was followed by UV-vis spectroscopy.