Study on solvent effect and coordination characteristics of two different types of Cu(II) salamo-salen-salamo-hybrid complexes

Based on the condensation reaction of a containg-formyl asymmetric salamo-based ligand with ethylenediamine, a salamo-salen-salamo-hybrid multi-compartment ligand possessing both salen and salamo structural moieties was prepared, and its different types (Cu(II): H2L)2−) of copper(II) complexes, confirmed as [Cu(H2L)]2·4EtOH (1) and [Cu2(H2L)2]·2MeOH·(Me)2CO (2), have been synthesized and elucidated structurally. In the complexes, Cu(II) ion is sited at the salen's N2O2 cavity, while the salamo structural moieties do not participate in coordination. This coordination characteristic indicates that the coordination ability of salen and salamo structural moieties in salamo-salen-salamo-hybrid ligand varies, with salen having relatively stronger coordination ability, which may be due to the incorporation of more electronegative multiple O atoms on C=N bonds, resulting in a decrease in the electron cloud density on the N atoms of the multi-oxime groups and a decrease in the coordination ability. Thus, Salen structural moiety on the hybrid ligand has stronger coordination ability than salamo structural moieties. In addition, due to the solvent effect, the extension direction of the single salamo long chain is different, and the configurations of the complexes are also different. Through X-ray diffraction analysis and DFT theoretical computations of the ligand and the complexes, the weak intramolecular and intermolecular interactions of the complexes, as well as the intermolecular C-H···π & π···π interactions of the complexes, were discussed. The ligand and the copper(II) complexes were analyzed for their MESP, as well as to show the mobile regions of the molecules in the complex molecules. Due to the solvent effect, the spatial orientation of the long chain of salamo has undergone significant changes, changing the region where the complex molecules move in a specific space.