New ferromagnetic dinuclear triply-bridged copper(II) compounds containing carboxylato bridges: Synthesis, X-ray structure and magnetic properties

The new triply-bridged dinuclear copper(II) complexes, [Cu2(μ-O2CH)(μ-OH)2(dpyam)2](ClO4) · H2O (1), [Cu2(μ-O2CCH3)(μ-OH)(μ-OH2)(dpyam)2](S2O8) (2), [Cu2(μ-O2CCH3)(μ-OH)(μ-OH2)(bpy)2](NO3)2 (3), [Cu2(μ-O2CCH3)(μ-OH)(μ-OH2)(phen)2](BF4)2 · 0.5H2O (4), [Cu2(μ-O2CCH2CH3)(μ-OH)(μ-OH2)(phen)2](NO3)2 (5) and [Cu2(μ-O2CCH3)(μ-OH)(μ-Cl)(bpy)2]Cl · 8.5H2O (6) (dpyam = di-2-pyridylamine, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized crystallographically and also their spectroscopic and magnetic properties have been studied. A structural classification of this type of dimers, based on the data obtained from X-ray diffraction analysis in the present work and those reported in the literature has been performed. In these complexes, the local geometry around the copper centre is generally a distorted square pyramid and distorted trigonal bipyramid with different degrees of distortion. The global geometry of the dinuclear complexes can be described in terms of the relative arrangement of the two five-coordinate environments, giving rise to different classes (A–F) of complexes. The most logical explanations have been provided for each class describing different magnetic interactions. Practically, there is a clear correlation between structural data and J values of the class B complexes. Extended Hückel calculations were performed for the present complexes 1–6, as well as for some other class B complexes, showing the different molecular orbitals involved in their corresponding frontier orbitals, together with their energy. The results are found to be useful for the proper interpretation and correlation of the magnetic data and the dinuclear structure of the present complexes.

Graphical abstractSix new triply-bridged dinuclear copper(II) complexes containing carboxylato bridges have been reported and their magnetic properties studied. A structural classification of this type of dimers has been performed, based on the local five-coordinate geometry with different degrees of distortion and the relative arrangement of the two basal planes, giving rise to different classes (A–F) of complexes. The most logical explanations have been made for each class describing different magnetic interactions. Practically, the correlations between structural data and J values are found for some classes of complexes. Extended Hückel calculations were preformed for class B complexes, the results are found to be useful for the proper interpretation and correlation of the magnetic data and dimer structure of the present complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide