Solvent‐assisted formation of ruthenium(II)/copper(I) complexes containing thiourea derivatives: Synthesis,crystal structure,density functional theory,enzyme mimetics and in vitro biological perspectives

N ,N ‐(diethylamino)(thiocarbonyl)]‐substituted benzamidine ligands have been synthesized from the reaction of N ,N ‐(diethylamino)(thiocarbonyl)]benzimidoyl chloride with functionalized amines such as 2‐aminophenol and 2‐picolylamine. The reaction of N ,N ‐(diethylamino)(thiocarbonyl)]‐2‐hydroxyphenylbenzamidine ( H ₂ L ₁ ) with ruthenium(II) precursor RuHCl(CO)(PPh₃)₃] afforded complex 1 of the type Ru(L₁)(CO)(PPh₃)₂] in which the ligand coordinated in tridentate ONS mode. The reaction of H ₂ L ₁ with copper precursor Cu(CH₃COO)(PPh₃)₂] induced C═N bond cleavage of the ligand and afforded complex 3 of the type Cu(1,1‐DT)(Cl)(PPh₃)₂] (1,1‐DT = 1,1‐diethylthiourea) in which the ligand coordinated in a monodentate fashion. The ligand N ,N ‐(diethylamino)(thiocarbonyl)]‐2‐picolylbenzamidine ( HL ₂ ) reacted with ruthenium(II) and copper(I) precursors to form complex 2 of the type Ru(1,1‐DT)(Cl₂)(CO)(PPh₃)₂] and complex 3 , respectively, in which the ligand underwent C═N cleavage and coordinated in a monodentate fashion via C═S group. In complexes 1 and 2 , the two triphenylphosphine co‐ligands coordinated in trans position whereas, in complex 3 , the two triphenylphosphine co‐ligands coordinated in cis position. All the compounds were characterized using infrared, UV–visible, (¹H, ¹³C, ³¹P) NMR, ESI‐MS and elemental analyses. The molecular structures of ligand H ₂ L ₁ and complexes 1 – 3 were determined using X‐ray crystallography, which confirmed the coordination mode of the ligands with metals. The crystal structure of complexes 1 and 2 revealed a distorted octahedral geometry around the ruthenium ion and the structure of complex 3 indicated a tetrahedral geometry around the copper ion. With the X‐ray structures, density functional theory computations were carried out to determine the electronic structure of the compounds. The interactions of complexes 1 – 3 with calf thymus DNA and bovine serum albumin protein were investigated using UV–visible and fluorescence spectroscopic and viscometric methods. Catecholase‐ and phosphatase‐like activities promoted by complexes 1 – 3 under physiological conditions have been studied. In vitro anticancer activities have been demonstrated by MTT assay, acridine orange/ethidium bromide and diamidino‐2‐phenylindole staining against various cancerous cell lines.