134184-02-4Relevant articles and documents
Synthesis and properties of new derivatives of 4,5-dicyanoimidazole and 4,4′,5,5′-tetracyano-2,2′-biimidazole
Apen, Paul G.,Rasmussen, Paul G.
, p. 6178 - 6187 (1991)
The synthesis and properties of new derivatives of 4,5-dicyanoimidazole (1, HDcim) and 4,4′,5,5′-tetracyano-2,2′-biimidazole (2, H2Tcbiim) are reported. Conditions for selective metalation at the 2-position of N-protected 4,5-dicyanoimidazoles are described. Various protecting groups were used. Oxidative coupling of N-protected 2-lithio-4,5-dicyanoimidazoles with cupric chloride gives new 1,1′-disubstituted derivatives of 4,4′,5,5′-tetracyano-2,2′-biimidazole (13-15, R2Tcbiim where R = CH3, CH2OCH3, CH2Ph). Ullmann coupling of 1-methyl-2-bromo-4,5-dicyanoimidazole (6) gives (CH3)2Tcbiim (13). Deprotection of R2Tcbiim (when R = CH3 or CH2OCH3) gives H2Tcbiim (2). Several new routes to H2Tcbiim are now available. Reaction of H2Tcbiim with 1 ,n-dihaloalkanes (n = 2, 3, and 4) gives the corresponding 1,1′-alkyl-bridged derivatives 16-18 or (CH2)nTcbiim (n = 2, 3, and 4). (CH2)2Tcbiim (16) has also been synthesized via an intramolecular Ullmann coupling reaction of 19. The physical, structural, and electronic properties of these new cyanoimidazoles have been investigated by using UV-visible spectroscopy and cyclic voltammetry. Dicyanoimidazoles and tetracyanobiimidazoles are moderate to weak electron acceptors. (CH2)2Tcbiim (16) forms a 1:1 complex with tetrathiafulvalene (TTF). The donor (D)-acceptor (A) complex, [TTF][(CH2)2Tcbiim], forms as red needles from acetonitrile solution. X-ray crystallography of [TTF] [(CH2)2Tcbiim] shows extended alternate or "mixed" stacking (...DADADA...). The photoluminescence spectrum of the complex shows an emission band centered at 660 nm with onset of emission at 530 nm.
