Fluorescence properties of heterotrinuclear Zn(ii)–M(ii) (M = Ca, Sr and Ba) bis(salamo)-type complexes?

RSC Advances Pub Date: 2017-10-17 DOI: 10.1039/C7RA08789F

Abstract

A series of hetero-trinuclear Zn(II) complexes, [Zn2Ca(L)(OAc)2]·CHCl3 (1), [Zn2Sr(L)(OAc)2] (2) and [Zn2Ba(L)(OAc)2] (3) with a bis(salamo)-type tetraoxime ligand H4L were synthesized and characterized by elemental analyses, IR, UV-vis spectra etc. Spectral titrations and X-ray crystallography clearly show that the stoichiometry of the heterotrinuclear complexes are all 1?:?2:?1 (ligand/Zn(II)/M(II)). The different natures of the N2O2 and O6 sites of the ligand H4L lead to the site-selective introduction of two different kinds of metal(II) atoms. All the Zn(II) atoms are penta-coordinated with distorted square pyramidal geometries. The coordination numbers of Ca(II), Sr(II) and Ba(II) atoms in the O6 environment are all 8, and they have slightly distorted square antiprism geometries. Furthermore, ion competitive experiments show that the coordinating capability in the central O6 site is in the order of Ca(II) > Sr(II) > Ba(II).

Graphical abstract: Fluorescence properties of heterotrinuclear Zn(ii)–M(ii) (M = Ca, Sr and Ba) bis(salamo)-type complexes
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