Spectroscopic and biological studies of mono- or binuclear complexes derived from thio-Schiff bases of some transition metals

Abstract

Two novel Schiff base ligands, 4,6-bis((E)-1-(2-mercaptophenylimino)ethyl)benzene-1,3-diol, H 4 L a , and 1,2-((E)-1-(6-((E)-1-(2-mercaptophenylimino)ethyl)pyridine-2-yl)ethylideneamino)benzenthiol, H 2 L b , have been synthesized by the condensation of 4,6-diacetyl resorcinol (DAR) or 2,6-diacetyl pyridine (DAP) with 2-aminobenzenthiol (ABT), in the molar ratio 1:2 [1 (DAR or DAP):2 ABT]. The structures of ligands were elucidated by elemental analysis, infrared (IR), UV-VIS as well as 1 H-NMR. Reaction of the Schiff base ligands with the transition metals Co(II), Ni(II), Cu(II), Zn(II), VO(IV) and Ru(III) afforded two series of the corresponding transition metal complexes in the molar ratio 1:2 or 1:1. The ligand, H 4 L a , behaves as tetrabasic hexadentate, which hosts the two metal ions at the centers of two SNO sites, while H 2 L b acts as a compartmental dibasic pentadentate ligand forming mono-or binuclear complexes through the coordinate sites N 3 S 2 . The structures of the newly prepared complexes were characterized on the basis of the elemental analysis, spectroscopic data (IR, UV-VIS, 1 H-NMR and ESR spectra along with magnetic susceptibility measurements) besides the molar conductance measurements and thermal gravimetric analyses. The bonding sites are the azomethane, sulfur atoms and phenolic oxygen for H 4 L a or pyridine nitrogen for H 2 L b . The complexes exhibit mono-or binuclear structures, distorted octahedral, tetrahedral, square planar or square pyramid structure. Synthesized compounds have also been screened for their biological activity against species of pathogenic fungi and bacteria and were found to possess appreciable fungicidal and bactericidal properties.

Synthesis, spectroscopic, coordination and biological activities of some organometallic complexes derived from thio-Schiff base ligands

“…The proton resonance of the thiol groups (3.51 ppm) for HLa-Maf ligands and the signals of the thiol groups for H 2 Lb-Daf (3.48 ppm) disappeared on adding D 2 O, which indicate that these protons are acidic. This observation has been further supported by the absence of resonances for SH protons in the spectra of [UO 2 (La-Maf)(H 2 O) 2 ]·NO 3 , 3 and [UO 2 (Lb-Daf)]·2H 2 O, 9 complexes, indicates deprotonation of the —SH group of the Schiff bases and coordination of the sulfur atoms through the coordination to the metal atom [62] . Moreover, in the spectra of diamagnetic UO 2 (IV) complexes 4 and 10 the protons of methyl group bonded to the azomethine groups are shifted downfield compared to that of the free ligand as a result of chelation of azomethine group to metal ion, indicate that, the chelation of the ligand with the metal ions involves the nitrogen atom of the ligands.…”

Catechol‐ and Phenol‐Containing Thio‐Schiff Bases: Synthesis, Electrochemical Properties and Biological Evaluation

“…It is known that imino‐phenols, imino‐thiophenols, as well as their catechol containing analogs exhibit antibacterial and cytotoxic properties [11c,34] . The antimicrobial activity of target compounds was determined against the bacterial species of Staphylococcus aureus ( ATCC 43300, ATCC 6538p), Escherichia coli ATCC 25922.…”

Complexes of Schiff base of benzopyran-4-one derivative

“…3. The electronic absorption spectrum of Schiff base L as discussed before [18] exhibits band at 340 nm (29,412 cm -1 ) due to intraligand p -p* transition [29]. The bathochromic shift in Table 4, which may be due to a LMCT transition.…”