A Combined Experimental and Theoretical Study to Explore the Importance of σ-Hole Carbon Bonding Interactions in Stabilizing Molecular Assemblies

Two new hetero-dinuclear nickel(II)/cadmium(II) complexes, [(DMF)(1.78)(DMSO)(0.22)(NiLCd)-Cd-1(Cl)(NCS)] (1) and [(DMF)(H2O)(NiLCdCl2)-Cd-2]DMF (2) with compartmental Schiff bases, H2L1=N,N'-bis(3-ethoxysalicylidene)-2,2-dimethylpropane-1,3-diamine and H2L2 = N,N'-bis(5-bromo-3-methoxysalicylidene)-2,2-dimethylpropane-1,3-diamine, have been prepared and characterized by single crystal X-ray diffraction analysis. In each complex, nickel(II) and cadmium(II) are placed in the N2O2 and O2O2' compartments of the Schiff base respectively. Both complexes form interesting supramolecular assemblies in the solid state. Energy associated with conventional C-H center dot center dot center dot pi interaction in complex 1 and unconventional sigma-hole carbon bonding interaction in complex 2 in the solid state of these complexes are estimated by DFT calculation and characterized by Natural Bond Orbital analysis and molecular electrostatic potential surface analysis as well.