Synthesis, structure, Hirshfeld analysis and fluorescence properties of a new asymmetric salamo-based ligand and its Cu(II) complex involving oxime oxygen coordination

Abstract

A new asymmetric salamo-based ligand (H₂L) was synthesized and upon reaction with Cu(ClO₄)₂ an extremely rare dinuclear Cu(II) complex [Cu₂(L)₂] was formed and characterized by elemental analyses, infrared spectroscopy, UV–vis absorption spectroscopy, X-ray single crystal diffraction and Hirshfeld surface analyses. The Cu(II) complex consists of two Cu(II) ions and two fully deprotonated ligand (L)^2– units. The Cu(II) is coordinated with the N₂O₂ cavity (N1, N2, O1 and O4) of L^2– and the oxime oxygen (O3) of another L^2– unit to form a uncommon dinuclear structure. The Cu(II) is five-coordinated, τ = 0.02, and has a configuration of slightly twisted tetragonal pyramidal geometry. The comparison between H₂L and its Cu(II) complex through Hirshfeld surface analyses shows that the interaction of O-H/H-O is reduced, indicating that deprotonation of phenolic hydroxyl group and the coordination of Cu(II) forms a stable complex. In addition, fluorescence quenching of the Cu(II) complex compared to H₂L further confirms the above experimental results.

GRAPHICAL ABSTRACT

Keywords:

• Salamo-based ligand
• Cu(II) complex
• synthesis
• crystal structure
• Hirshfeld surface analysis

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (21968032) and the Program for Excellent Team of Scientific Research in Lanzhou Jiaotong University (201706), which are gratefully acknowledged.