Copper(i) and silver(i) complexes of anthraldehyde thiosemicarbazone: synthesis, structure elucidation, in vitro anti-tuberculosis/cytotoxic activity and interactions with DNA/HSA

Abstract

A reaction of copper(I) halides (X = I, Br, Cl) and silver(I) halides with 9-anthraldehyde thiosemicarbazone (9-Hanttsc, H¹L) and triphenylphosphine produced halogen-bridged dinuclear complexes, [M₂(μ₂-X)₂(η¹-S-9-Hanttsc)₂(Ph₃P)₂] (M = Cu, X = Cl, 1; Br, 2; I, 3; M = Ag, X = Cl, 4; Br, 5). A similar reaction of 9-anthraldehyde-N¹-methyl thiosemicarbazone (9-Hanttsc-N¹-Me, H²L) with Ph₃P and silver(I) halides yielded sulfur-bridged dimers, [Ag₂X₂(μ₂-S-9-Hanttsc-N¹-Me)₂(Ph₃P)₂] (X = Cl, 9; Br, 10), however with copper(I) halides insoluble compounds were formed, which upon the addition of one extra mole of Ph₃P gave mononuclear complexes of the formula [CuX(η¹-S-9-Hanttsc-N¹-Me)(Ph₃P)₂] (X = Cl, 6; Br, 7; I, 8). All of the complexes have been characterized by elemental analysis, NMR (¹H, ¹³C) spectroscopy and single crystal X-ray crystallography (2, 5, 6, and 9). Both the ligands (H¹L and H²L) and their complexes (1–10) were tested for their anti-tubercular and anticancer activities. The interactions of the ligands and their complexes (copper and silver) with calf thymus DNA (ct-DNA) and human serum albumin (HSA) were examined through UV-visible and fluorescence spectroscopy. Results showed that copper complex 2 displayed strong interactions with ct-DNA and HSA having binding constant values of 6.66 × 10⁴ M⁻¹ and 3.28 × 10⁴ M⁻¹, respectively, followed by silver complex 10 which gave binding constant values of 4.60 × 10⁴ M⁻¹ and 3.06 × 10⁴ M⁻¹, respectively. All of the complexes also showed good interactions with DNA in docking studies.