FUNCTIONAL ZINC-COMPLEXES OF TRIS(IMIDAZOLYLMETHYL)AMINE LIGANDS

The three N-R-substituted tris(benzimidazolylmethyl)amine ligands L (1a: R = H, 1b: R = Me, 1c: R = Bz) from zinc complexes with biologically active ligands on the fifth coordination site, starting from L, Zn(ClO4)2, and the coligand. The N-protected amino acids glycine, histidine, and cysteine yield [L . Zn-OCO-CHR-NHAc]ClO4 (2a, 3a, 4a). Aspirin, salicylic acid, and orotic acid are incorporated as [L . Zn-X]ClO4 (5a-c: X = O-acetylsalicylate, 6a: X = salicylate, 7a-c: X = orotate). Similarly the sulfonamide furosemide is bound by its carboxylate function in [L . Zn-Fur]ClO4 (8a-c). The aqua complex resulting from ligand 1a and Zn(ClO4)2 forms hydrogen bonds to nitriles and aldehydes, which has allowed the isolation of [L . Zn-OH2...RCN](ClO4)2 (9a: RCN = MeCN, 10a: RCN = PrCN) and of [L . Zn-OH2...RCHO](ClO4)2 (11a: RCHO = anisaldehyde, 12a: RCHO = p-tolualdehyde). The structure determination of the salicylate complex 6a has confirmed the monodentate O-coordination of the carboxylate substrates to zinc.