Differential study on the transition from a new polyhalogen-substituted unsymmetric salamo-based ligand to its Cu(II) and Co(II) complexes

Abstract

Two structurally different Cu(II) and Co(II) complexes, [Cu(L)] (1) and [Co₂(L)₂]⋅2CH₃OH (2), constructed from a new polyhalogen-substituted unsymmetric salamo-based ligand (H₂L, 4-chloro-4′-bromo-6-bromo-6′-tert-butyl-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) were synthesized by wet-chemical methods. Complexes 1 and 2 were characterized through elemental analyses, IR and UV-vis spectroscopies and single crystal X-ray crystallography. In addition, the differences of the structures, electronic absorption characteristics and fluorescence property transitions from the ligand to complexes 1 and 2 were studied. The largest difference is that the ligand H₂L can react with M(OAc)₂ (M = Cu(II) and Co(II)) to give two complexes with distinct structures and behaviors. There are two chemically identical but crystallographically independent structural units (molecules A and B) in 1. Moreover, each Cu(II) ion (Cu1 or Cu2) is four-coordinate and possesses a square planar geometry, but both Co(II) ions of 2 are bridged by phenoxide ions and possess five-coordinate trigonal bipyramidal configurations. At the same time, Hirshfeld surface analyses showed there are short-range interaction features from the ligand to complexes 1 and 2, the O···H/H···O interactions of the ligand are significantly stronger than those of 1 and 2.

Graphical abstract

Keywords:

• Unsymmetric salamo-based ligand
• complex
• synthesis
• crystal structure
• fluorescence

Acknowledgements

This work was supported by the Science and Technology Program of Gansu Province (21YF5GA057), which is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.