A combined experimental and computational study on supramolecular assemblies in hetero-tetranuclear nickel(ii)–cadmium(ii) complexes with N2O4-donor compartmental Schiff bases†
Abstract
Two new hetero-tetranuclear nickel(II)/cadmium(II) complexes, a cubane [(CH3CO2)2Ni2(L1)2Cd2(NCS)2] (1) and a linear tetramer [(DMSO)2NiL2Cd(NCS)(μ1,3-SCN)Ni(DMSO)L2Cd(NCS)2] (2) {where H2L1 = N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine and H2L2 = N,N′-bis(3-ethoxysalicylidene)propane-1,3-diamine are potential octadentate compartmental Schiff bases}, were synthesized and characterized. The structures of both complexes were confirmed by single crystal X-ray diffraction studies. Complex 1 contained a Ni2Cd2O4 cubane core, whereas complex 2 featured an end-to-end thiocyanate-bridged tetranuclear moiety. Furthermore, complex 1 showed C–H⋯H–C interactions, whereas a unique S⋯π interaction was observed in complex 2. Theoretical studies were performed using several computational tools such as NBO and AIM analyses. Both complexes showed photoluminescence in DMSO medium at room temperature upon irradiation with ultraviolet light. The lifetimes of the excited states were ∼27 ns.