Vitamin B_(12) Model Complexes: Synthesis and Characterization of Thiocyanato Cobaloximes and Thiocyanato Bridged Dicobaloximes of O-donor Ligands: DNA Binding and Antimicrobial Activity

摘要

Complexes of thiocyanato(L)cobaloximes where L is urea, acetamide, semicrabazide and formamide were synthesized and characterized. The reaction of thiocyanato (L) cobaloximes (SCNCo(DH)2(L)) with benzyl (aquo) cobaloxime PhCH2Co (DH)2(OH2) was found to produce a series of thiocyanato bridged dicobaloximes of a general formula of PhCH2Co(DH)2SCNCo (DH2)(L). Evidence for formulation as dicobaloximes containing thiocyanato ligand bridges was obtained from infrared data which show 20 - 45 cm~(-1) increase in vCN upon formation of the dicobaloxime from the corresponding terminal thiocyano-cobaloxime (SCNCo(DH)2(L)). Further characterization of these two series was done on the basis of ( ~1H, ~(13)C)NMR, LCMS and elemental analysis. Anti-microbial activity of thiocyanato(L)cobaloximes and thiocyanato bridged dicobaloximes were screened against E. Coli. The DNA-binding behaviors of both monomers and dimers were investigated by spectroscopic methods and viscosity measurements. The results indicated that the dimer complexes bind with calf-thymus DNA in an intercalative mode via the terminal benzyl ring into the base pairs of DNA. It was observed that the monomer complexes did not interact with DNA. Fluorescence spectra for the interaction between thiocyanato bridged dicobaloximes and DNA were also studied.