中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | 5,5'-Diethoxy-4,6,4',6'-tetrakis-{4-[(triisopropylsilanyl)-ethynyl]-phenyl}-5,6,5',6'-tetrahydro-4H,4'H-[2,2']bi[imidazo[4,5-d]imidazolylidene] | 501947-51-9 | C80H112N8O2Si4 | 1330.16 |
In order to obtain sulfur-containing tetraazafulvalenes the derivatives 1 - 3 were cross-coupled with different types of acetylenes via palladium-catalyzed reactions. Starting from the tetrabromoaryl derivative 3a, four bromine atoms could be replaced by 2-ethynylthiophene. Under analogous conditions, the methylsulfanyl esters 7 -11 could be obtained by employing 4-ethynylbenzoic acid 4-(methylsulfanyl)butylester 6. Lipoic acid could be integrated into tetraazafulvalenes successfully in a two step reaction. First, the Sonogashira coupling method yielded the compound 12 possessing two (4-anilino)ethynyl residues which were then condensed with lipoic acid to give derivative 13.
Whereas the NMR data suggest the predominance of prototropic form A, UV/vis spectra of the deeply colored tetraazafulvalenes are in favor with structure B rather than with structure A. DFT calculations at the B3LYP/6-31G(d) level showed that tautomeric form B is about 60 kJ/mol more stable than A. In addition, time-dependent density functional theory calculations support the substructure of two crossed diazaheptamethinemerocyanines.