Dicopper(II) complexes with sulphur bridge: Syntheses, spectral and electrochemical properties

A family of dithiocarbonate sulphur bridged dinuclear copper(II) complexes containing [Cu2II(μ-Rx)μ-OPh)]2+ (R=Me, Et,nPr,iPr,nBu, Bz; x=OCS2) core with supporting weak imidazolidine bridge has been synthesized for the first time using aμ-bis(tetradentate) amine phenol ligand (H3L). The ligand reacts with CuCl2·2H2O and different KRx in aqueous acetone in air affording crystalline [Cu2(μ-Rx)(μ-L)]·2H2O in excellent yields. Both the Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes have MN2O2 S coordination spheres. Taking the help of one exogenous bridging ligand (Rx−) the triply bridged CuII-CuII intimate complex is formed in a Schiff-base ligating environment. The ligand provides one imine and one inbuilt imidazolidine nitrogen and two phenolic bridging and terminal oxygen donors forming five- and six- membered chelate rings around each metal centre. In the pentacoordinated complexes [Cu2(μ-Rx)(μ-L)]·2H2O, dithiocarbonate ligands are present as exogenous bridging ligands. The presence of large polarizable sulphur atoms around each copper(II) centre significantly modify the nature of the complexes to be electroactive as detected by cyclic voltammetry, compared to the analogous exogenous acetate bridging complexes. The copper-copper magnetic interaction is dependent on the nature of different R groups and presence of S donors. Both electron transfer behaviours and magnetic properties of copper(II)-copper(II) complexes are assessed with respect to a heterodinuclear copper(II)-zinc(II) complex in identical ligating environment.