Oximato bridged copper(II) dimers: Synthesis, crystal structure, magnetic, thermal and electrochemical properties

The reactions of the Schiff-base ligands 3-(4-methylimidazol-5-yl)methylenehydrazonobutan-2-one oxime (LH) and 3-(1-methylimidazol-2-yl)methylenehydrazonobutan-2-one oxime (L′H) with copper(II) perchlorate hexahydrate and copper(II) nitrate trihydrate in a 1:1 molar proportion in methanol gave rise to [Cu2L2(H2O)2](ClO4)2 (1a), [Cu2L2(H2O)2](NO3)2·1.5H2O (1b), [Cu2L2′(H2O)2](ClO4)2 (2a) and [Cu2L2′(NO3)(H2O)](NO3)·0.5H2O (2b) in substantial yields. The complexes have been characterized by C, H, N microanalyses, ESI-MS, FTIR, UV–Vis spectra, conductivity measurements and room temperature magnetic susceptibility and EPR measurements. The X-ray crystal structures of two (1a and 2b) of the complexes have been determined. 1a and 2b are oximato bridged Cu(II) dimers. Variable temperature magnetic studies on 1a, 2a and 2b manifest that the Cu(II) centers are antiferromagnetically spin coupled. The electrochemical studies show a Cu(II) to Cu(I) reduction in methanol. The thermal behaviors of 1b and 2b have also been studied.

Graphical abstractThree dinuclear copper(II) compounds [Cu2L2(H2O)2](ClO4)2 (1a), [Cu2L2(H2O)2](NO3)2·1.5H2O (1b) and [Cu2L2′(NO3)(H2O)](NO3)·0.5H2O (2b) with LH = 3-(4-methylimidazol-5-yl)methylenehydrazonobutan-2-one oxime and L′H = 3-(1-methylimidazol-2-yl)methylenehydrazonobutan-2-one oxime have been synthesized and characterized. These oximato bridged copper complexes have a ‘N3O2’ coordination chromophore. Each copper center is in a square pyramidal coordination environment. All these compounds are antiferromagnetically spin-coupled. Electrochemical and thermal behaviors of the complexes have also been studied.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Syntheses of oximato bridged binuclear Cu(II) complexes. ► X-ray crystallography. ► Magnetic studies. ► Thermal and electrochemical behavior.