The mono-, di-, and trinuclear copper(II) complexes containing pyrazole and glycylglycine or diethylenetriamine. Comparisons with imidazole containing copper(II) complexes

Abstract

The mixed ligand copper( II) complexes with pyrazole or 3-methylpyrazole and glycylglycine (Gly·Gly) or diethylenetriamine (dien) were prepared in neutral and basic solutions. The compounds obtained in neutral solutions were mononuclear complexes, while those in basic solutions were polynuclear complexes bridged by pyrazolate (pz) or 3-methylpyrazolate (3-Mepz). The Gly·Gly- and pz-containing compounds, Ca [Cu 2(Gly·Gly) 2(pz)] 2 ·8H 2O and K 2 [Cu 3- (Gly·Gly) 3(pz) 2]·5H 2O were proved to be a dinuclear complex and a linear-chain trinuclear one, respectively, from their magnetic properties. In both complexes copper( II) ions are antiferromagnetically coupled ( J =−12.3 cm −1 for the calcium salt complex and J = −9.4 cm −1 for the potassium salt complex). The dien-containing complexes, [Cu 2(dien) 2- (pz)] Br 3·H 2O and [Cu 2(dien) 2(pz)] (ClO 4) 3·4H 2O were also isolated and the existence of an antiferromagnetic exchange interaction ( J =−21.5 cm −1) between the two copper(II) ions was observed for the bromide salt complex. The magnetic properties of the perchlorate salt complex were considerably different from the corresponding bromide. Namely, the strong antiferromagnetic interaction (Weiss constant θ h =−154 K) was observed in the high- temperature range ( T > 130 K), but was not observed apparently (θ 1 = ∼0 K) in the low-temperature range (T < 130 K). Spectroscopic properties of these compounds were also investigated.