Insight into Crystal Structures, Hirshfeld Surfaces and Fluorescent Properties of Multinuclear Co(II) and Ni(II) Salamo-Based Complexes Involving Lone Pair π-Interactions

Two multi-nuclear Co(II) and Ni(II) complexes, [{Co3(L)2(EtOH)2(μ-OAc)2}2]·2CH3CH2OH· CH2Cl2·CHCl3·CH3CN (1) and [{Ni3(L)2(EtOH)2(μ-OAc)2}2]·3CH2Cl2 (2) have been synthesized from asymmetric salamo-based polydentate chelating ligand (H2L) and Co(OAc)2·4H2O or Ni(OAc)2·4H2O, respectively, and characterized by elemental analyses, IR and UV-Vis spectra, and X-ray crystallography. Complexes 1 and 2 crystallize in monoclinic space groups as centrosymmetric structures. Also, complexes 1 and 2 can form two crystallographically independent but chemically identical molecular structures (molecules I and II) with M(II) (M = Co and Ni) atoms characterized by six-coordinated distorted octahedral geometries. The central M(II) atoms are located in the O6 coordination cavities, as well as the terminal M(II) atoms are located in N2O4 coordination environments. Lone pair π-interactions are involved in complexes 1 and 2 formation, and the intermolecular interactions have been quantitatively approached by Hirshfeld surfaces analysis. Fluorescence properties of the complexes have been studied.