Exploring two helical centrosymmetric homotetranuclear Cu (II) bis (salamo)-based complexes

Two helical centrosymmetric homotetranuclear Cu (II) complexes, [Cu-4(L)(2)(EtOH)(2)](ClO4)(2)-2EtOH-2CHCl(3) (1) and [{Cu-4(L)(2)(EtOH)(2)}{Cu-4(L)(2)(HNO3)(2)}](NO3)(4)-3EtOH-3MeOH (2), were synthesized by the reactions of a symmetric bis (salamo)-based ligand H3L with Cu (ClO)(2)-6H(2)O and Cu (NO)(3)-3H(2)O, respectively, and certified by elemental analyses, UV-Visible absorption spectra, infrared spectra and single-crystal X-ray analysis techniques. X-ray crystal structure analyses reveal that four Cu (II) atoms of complex 1 are attached to two deprotonated ligand (L)(3-) units with the help of two coordinated ethanol molecules, and then forming a helical centrosymmetric complex by H-bonding and pi(sic)pi interactions. While complex 2 unit cell contains two crystallographically independent but chemically identical homotetranuclear complexes (molecules A and B), eight Cu (II) atoms are coordinated by four deprotonated ligand (L)(3-) units. The coordination mode of four Cu (II) atoms from molecule A is the same as complex 1; at the same time, oxygen atoms on nitrates are involved in the coordination of another four Cu (II) atoms from molecule B. The short-range interactions in complexes 1 and 2 were calculated by Hirshfeld surfaces analyses. The molecular orbital energy levels, molecular stabilities of complexes 1 and 2 were analyzed by DFT calculations. In addition, antibacterial assays were also investigated in detail.

Automated summary

Two helical centrosymmetric homotetranuclear Cu (II) complexes were synthesized and characterized in this study. The coordination modes and molecular stabilities were analyzed through structural analysis and calculations, and the antibacterial activities were also investigated.