Investigating two structurally different penta-coordinated trigonal bipyramidal Co(II) non-symmetric salamo-type complexes

A new non-symmetric salamo-type multidentate chelating ligand H2L (4-Formyl-6'-methoxyl-2,2'-[ethyl-enedioxybis(nitrilomethylidyne)]diphenol) was designed and prepared. Two Co(II) complexes with different structures, [Co(L)(H2O)] (1) and [Co2(L)2]2 & sdot;3CH3CN & sdot;2CH3OH (2) were prepared by the reactions of H2L with two different Co(II) salts (Co(OAc)2 & sdot;4H2O/CoCl2 & sdot;6H2O) in various organic solvents at an ambient temperature, respectively. Due to varying degrees of distortion of the ligand during the coordination reactions, the bonding modes of the ligand in complexes 1 and 2 are different. Complex 1 forms a penta-coordinated mononuclear, and complex 2 forms a penta-coordinated binuclear structure. By comparing UV-Vis and infrared spectroscopy of H2L with those of the corresponding complexes further characterize coordination between the ligand H2L and Co(II) ions. Theoretical calculations of DFT, BVS (Valence Bonding and Calculation), and IRI (Interaction Region In-dicator) were used to show the different forces present in complexes 1 and 2, and BVS calculations confirmed that Co is '+2 ' valence in the complexes. Fluorescence property studies indicated that the possible mechanism for the decrease in fluorescence intensity upon binding of H2L to Co(II) ions is chelation fluorescence quenching.