The first examples of triply bonded dirhenium(II,II) complexes that contain bis(diphenylphosphino)methane and dithiocarbamato ligands: spectroscopic, structural, cytotoxicity and computational studies

Abstract

Sodium salts of dimethyldithiocarbamate, diethyldithiocarbamate and pyrrolidinedithiocarbamate react with the triply bonded dirhenium (II,II) complex Re₂(μ-Ph₂PCH₂PPh₂)₂Cl₄ (1) in refluxing ethanol to afford the products of the type Re₂(μ-Ph₂PCH₂PPh₂)(L_R)₄ (2(L_R)) where L_R represents the dithiocarbamato ligands [L_R = S₂CNMe₂, 2(L_Me); S₂CNEt₂, 2(L_Et) and S₂CN(CH₂)₄, 2(L_Pyr)]. These are the first examples of dithiocarbamato chelated dirhenium complexes with a Re₂⁴⁺ core containing Ph₂PCH₂PPh₂ (dppm) ligand. The spectral (IR, UV-vis, NMR, ESI-MS) and electrochemical properties of the complexes are reported. The identity of 2(L_Et) has been established by single-crystal X-ray structure determination (Re–Re distance 2.3196(8) Å). The electronic structure and the absorption spectra of the complexes are scrutinized by density functional theory (DFT) and time-dependent DFT (TD-DFT) analyses. DFT analysis shows that the highest occupied molecular orbitals are mainly metal δ* based orbitals. The complex 2(L_Et) was also screened in vitro for its antiproliferative properties against human non-small cell lung carcinoma cells (A549), the cervical cancer cell line (HeLa) and peripheral blood mononuclear cells (PBMCs) by MTT assay which indicates its preferential cytotoxicity against the cancer cells (A549, HeLa).