Novel dirhenium(III,III) complexes with bridging diphenylphosphinomethane and dithiocarbamato ligands: A combined experimental and theoretical study

Sodium salts of dimethyldithiocarbamate (L-Me), diethyldithiocarbamate (L-Et) and pyrrolidinedithiocarbamate (L-Pyr) react with the double-bonded diamagnetic dirhenium(III,III) complex Re-2(mu-dppm)(2)(mu-Cl)(2)Cl-4 (1) (dppm = Ph2PCH2PPh2) in refluxing ethanol to afford the diamagnetic substitution products of the type [Re-2(mu-dppm) (eta(2)-LR)(2)(mu-eta(2)-LR)(2)](PF6)(2), where LR represents the dithiocarbamato ligands [LR = S2CNMe2, 2(L-Me); S2CNEt2, 2 (L-Et) and S2CN(CH2)(4), 2(L-Pyr)]. The complexes were isolated as hexafluoridophosphate salts. These are the first examples of dirhenium(III,III) complexes that contain bridging dithiocarbamato ligand along with the dppm ligand. The spectral and electrochemical properties of the complexes are reported. The identity of 2(L-Me) and 2 (L-Et) was established by single crystal X-ray structure determination (Re -Re distance similar to 2.55 angstrom) and is shown to have edge-shared bioctahedral structure. The electronic structure and the absorption spectra of the complexes are scrutinized by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses. DFT analysis shows that the highest occupied molecular orbitals are mainly metal d* based orbitals. The complex 2(L-Et) was tested for its ability to exhibit DNA-binding activity. The antifungal activity of the complex 2 (L-Et) was also determined against the fungal pathogen Colletotrichum gloeosporioides (CG).