Mononuclear and binuclear Cu(II) complexes of some tridentate aroyl hydrazones. X-ray crystal structures of a mononuclear and a binuclear complex

Cu(II) complexes of eight N,N,O-donor hydrazone ligands, obtained by condensation of pyridine-2-carbaldehyde and 2-acetylpyridine with four aroyl hydrazides, are reported. Reactions of Cu(ClO4)2·6H2O with the pyridine-2-carbaldehyde hydrazones (L1H, L2H, L3H, L4H) in presence of Et3N, in 1:2:2 molar ratio, lead to isolation of mononuclear octahedral Cu(II) complexes of formula [Cu(L)2] (L = L1−, L2−, L3−, L4−). However, for the 2-acetylpyridine hydrazones (L5H, L6H, L7H, L8H) reactions under similar conditions yield dichloro bridged complexes of the type [Cu2(μ-Cl)2(L′)2] (L′ = L5−, L6−, L7−, L8−), where each Cu(II) ion is in a square-pyramidal geometry, the chloride ions coming from the in situ reduction of perchlorate by the 2-acetylpyridine hydrazones. The X-ray crystal structures of [Cu(L1)2] and [Cu2(μ-Cl)2(L5)2] are reported. The spectroscopic and electrochemical behaviors of the complexes are also reported.

Graphical abstractCu(II) complexes of eight N,N,O-donor hydrazone ligands, obtained by condensation of pyridine-2-carbaldehyde and 2-acetylpyridine with four aroyl hydrazides are reported. Mononuclear [Cu(L)2] and binuclear [Cu2Cl2(L′)2] types of complexes were obtained. The spectroscopic and redox properties of the complexes are discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cu(II) complexes of eight N,N,O-donor hydrazone ligands are reported. ► Mononuclear [Cu(L)2] and binuclear [Cu2Cl2(L′)2] types of complexes were obtained. ► ZINDO/1 calculations show binuclear complexes are thermodynamically more stable. ► In situ reduction of perchlorate by the 2-acetylpyridine hydrazones (L′H) results in chloride.