Estimation of conventional C–H⋯π (arene), unconventional C–H⋯π (chelate) and C–H⋯π (thiocyanate) interactions in hetero-nuclear nickel(ii)–cadmium(ii) complexes with a compartmental Schiff base

Abstract

Three new heteronuclear nickel(II)/cadmium(II) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)₂] (1), [(SCN)(CH₃CO₂)Cd(L)Ni(CH₃OH)₂] (2) and [(SCN)(Cl)Cd(L)Ni(NH₂CH₂CH₂CH₂NH₂)]_n (3) {where H₂L = N,N′-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N₂O₄ compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(II) is placed in the inner N₂O₂ environment and cadmium(II) is placed in the outer O₄ compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C–H⋯π (chelate) interactions in the solid state of both complexes and C–H⋯π (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2–6 ns.