Experimental and computational studies of two binuclear Co(II) and Ni(II) bis(salamo)-like complexes

Acetate-bridged binuclear Co(II) and Ni(II) complexes, [Co-2(L)(mu-OAc) (EtOH)] (1) and [Ni-2(L)(mu-OAc)(EtOH)] (2) were synthesized via the reaction of a new bis(salamo)-like ligand with two different metal(II) acetates. X-ray single crystal diffraction analyses showed that two metal(II) ions (Co or Ni) occupy two sets of N2O2 cavities, respectively. The acetate group bridges the two metals, and the ethanol oxygen atom participates in the coordination. Furthermore, UV-vis titration experiments clearly indicated that the complexation between H3L and M(II) ions leads to the 1:2 complexes [(L)M-2](+) through a highly synergistic process. Bond valence sum (BVS) calculations exhibited that the Co(II) and Ni(II) ions are divalent. Secondly, the ligand H3L highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap analysis and surface electrostatic potential were theoretically analyzed by theoretical calculation (density functional theory), and the reactivity of M(II) ions and the ligand in the complex formation process was demonstrated. Finally, the microscopic properties of the complexes were deeply understood through the calculation of the weak intramolecular interactions and the unstressed regions outside the complexes.