Synthesis and Structural Characterization of a Double Helical Dinuclear Copper(II) Complex With Tetradentate Biacetyl Bis(benzoylhydrazone)

Rasoul Vafazadeh,Anthony C Willis,Najmeh Abdollahi

doi:10.17344/acsi.2017.3263

Rasoul Vafazadeh, Anthony C Willis + Show 1 more

Open Access

https://doi.org/10.17344/acsi.2017.3263

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Abstract

The reaction of tetradentate hydrazone ligand H2babh with Cu(CH3COO)2 in methanol solvent leads to the formation of the mono-nuclear complex [Cu(babh)]. However, on being dissolved in dichloromethane solvent and on addition of ethanol solvent, a dinuclear complex of [Cu2(μ1,3-babh)2(C2H5OH)2] is obtained. The X-ray crystallography indicates that the dinuclear helical complex formation is caused due to the unsymmetrical twisting of the H2babh ligand. One oxygen and two nitrogen atoms from the ligand and one oxygen atom from the other ligand coordinate to each copper(II) center. Both the copper(II) centers in a dinuclear unit are penta-coordinate with a slightly distorted square pyramidal geometry. The IR spectra of mono- and dinuclear copper(II) complexes have different bands. The absorption spectra of mono- and di-nuclear complexes are quite similar in methanol solvent. However, the electronic absorption spectra of the two complexes are basically different in the solid state.

Highlights

A comparison of the IR spectra of the free ligand and mononuclear, Cu(babh), and dinuclear, [Cu2(μ1,3babh)2(C2H5OH)2], complexes indicates that the ligand is coordinated to the copper(II) center
The electronic absorption spectra were recorded for copper(II) complexes in various solvents, methanol, ethanol, dichloromethane and N,N’-dimethylformamide (DMF) in the visible and UV regions
The dinuclear helical complex formation is caused by the unsymmetrical twisting along the –C=N–N=C– single bond and two nitrogen atoms and one oxygen from each ligand are coordinated to each copper(II) center

Summary

Introduction

The design and construction of multinuclear transition metal complexes have attracted great interest in recent years because of the role that these metal systems play in a large number of biological processes, molecular magnetic materials, and their variety of structures and interesting properties.[1,2,3,4,5,6,7,8] Among them, the synthesis and study of multinuclear copper(II) complexes has attracted considerable interest due to exploration of their structures, and because the function of copper(II) centers in many important biological process.[8,9,10,11,12]. There are a variety of strategies for synthesizing homo- and hetero-multinuclear complexes. The bridging ligands such as halides, pseudo-halides, oxalate, sulfate, etc. Have been widely used in the synthesis of multinuclear complexes.[13,14,15,16] In the self-assembly process, the constituent ligands play important roles in the synthesis of polynuclear copper(II) compounds. Structure of dinuclear copper(II) complex bridging phenoxo or hydroxo oxygen donor atoms.[11,17,18] The other strategy for the formation of these complexes. We have described the synthesis and crystal structures of a dinuclear copper(II) complex double helicates with the tetradentate N2O2-donor ligand biacetyl bis(benzoylhydrazone), H2babh (Scheme 1). The structure of the complex is compared with mono- and dinuclear copper(II) complexes that have been previously reported with the H2babh ligand.[21,22]

Experimental

Results and Discussion

Conclusion