Magnetic interactions in dicopper(II) complexes of a new endogenous alkoxo bridging ligand with exogenous pyrazolate, azide and acetate bridges. X-ray structure of [Cu₂L(μ-C₃H₃N₂)(OClO₃)(H₂O)](ClO₄)·H₂O (HL=1,3-bis[N-methyl-N-(2-pyridylethyl)amino]propan-2-ol)

Abstract

Using a new dinucleating ligand, 1,3-bis[N-methyl-N-(2-pyridylethyl)amino]propan-2-ol (HL), in its deprotonated form, three new binuclear copper(II) complexes [Cu₂(L)(μ-X)(ClO₄)(H₂O)](ClO₄)·H₂O (X=C₃H₃N₂^- (prz), N₃^- and MeCO₂^-) have been synthesized. The crystal structure of pyrazolate (prz) compound was determined and revealed that the complex contains an endogenous bridging alkoxide ligand and an exogenous bridging prz ligand. A water molecule is coordinated to a copper(II) center and is hydrogen-bonded to the alkoxide O atom. A perchlorate ion is 'semi-coordinated' to another copper(II) center as a monodentate ligand and is hydrogen-bonded to a second water molecule. The coordination geometry around both copper centers resembles a distorted square pyramid. The magnetochemical characteristics of these compounds were determined by temperature-dependent magnetic studies, revealing their antiferromagnetic behavior [-2J (in cm^-1) values: 550±25 for prz, 360±10 for azide and 100±10 for acetate]. The ground state magnetic orbital involved in spin coupling is similar (d_x2_-y2) in these complexes. Differences in the magnetic behavior have been rationalized in terms of the bridging ligand orbital complementary/countercomplementary concept. Spectroscopic properties of these complexes are also reported.