Insight into two unusual stable homomultinuclear copper (II)-based bis (salamo)-type complexes

Using symmetrical bis (salamo)-type tetraoxime ligand H3L and Cu (ClO4)(2)center dot 6H(2)O in different solvent systems, two unusual homomultinuclear Cu (II) complexes, [Cu-4(L)(2)(CH3CH2OH)(2)](ClO4)(2)center dot 2H(2)O (1) and [Cu-2(L)](n) (ClO4)(n)center dot nCH(3)CN (2), were synthesized and characterized by single-crystal X-ray diffraction analyses, elemental analyses, infrared (IR), ultraviolet-visible (UV-Vis) spectroscopy, Hirshfeld surfaces analyses, and density functional theory (DFT) calculations. Complex 1 includes [Cu-4(L)(2)(CH3CH2OH)(2)](2+) ion, two ClO4- counter anions, two coordinated ethanol molecules and two aquatic dissociative molecules, the two deprotonated ligand (L)(3-) units package around four Cu (II) ions yield a centrosymmetric helical molecules with a charged linear folding center, while complex 2 forms a 1-D linear topology structure and is only the substitution of chloroform in the solvent system of complex 1 with acetonitrile. Coordination mode of complex 2 is widely different from that of complex 1. In the Cu (II) ions of complex 1, there are two coordination modes of Cu (II) ions, the hexa-coordinated distorted octahedral structure and the penta-coordinated distorted tetragonal pyramid structure, but complex 2 only has almost perfect tetragonal pyramid geometry. Fluorescence properties of H3L and its complexes 1 and 2 have also been explored.

Automated summary

Two unusual homomultinuclear Cu(II) complexes were synthesized and characterized, showing significant differences in coordination mode and geometry.