Multinuclear Co(II) and Zn(II) salamo-based complexes with unique τ5 parameters: Structure characterizations, Hirshfeld surfaces and fluorescence properties

Abstract

The multinuclear Co(II) and Zn(II) salamo-based complexes [{Co2(L)(μ-OMe)}8]·11CH3OH·2H2O (1) and [Zn2(L)(μ-OEt)]·CHCl3 (2) have been successfully isolated by the solvent evaporation method and characterized structurally by elemental analyses, IR spectra and UV–Vis spectra. Complex 1 consists of four closely related neutral dinuclear units, 1A, 1B, 1C and 1D, while complex 2 consists of three closely related neutral dinuclear units 2A, 2B and 2C. Complexes 1 and 2 are unique examples of crystallographically independent but chemically identical molecules with unique τ5 parameters. For complex 1, all the Co(II) atoms possess extremely distorted trigonal bipyramidal geometries, except the for Co4 atom, with the Co(II) atoms lying out of the plane of the equatorial donor atoms. For complex 2, except for the Zn5 atom, the Zn(II) atoms possess extremely distorted trigonal bipyramidal geometries and square-based pyramidal geometries. Significantly, the geometries about the Co4 and Zn5 atoms show τ5 values very close to 0.500 and there are few such examples like those. Complex 2 has an obvious fluorescence enhancement, which may be caused by intramolecular charge transfer (ICT) and blocks the ligand to the metal charge transfer transition (LMCT) process. The intermolecular interactions were quantitatively analyzed by Hirshfeld surface analyses.