Synthesis, crystal structures and magnetic properties of new oxalato- and phenolato-bridged binuclear copper(II) complexes with Schiff-base ligands
Résumé
Two binuclear complexes of copper(II), [(Hfsaaep)Cu(μ-C2O4)Cu(Hfsaaep)] (1) and [Cu2(Hfsadmpn)2(H2O)2](ClO4)2 (2), have been synthesized by using Schiff-base ligands derived from 3-formyl-salicylic acid: 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid (H2fsaaep) and 3-N-[N′,N′-dimethylaminopropyl)formimidoyl]salicylic acid (H2fsadmpn). The crystal structures of compounds 1 and 2 have been solved. That of compound 1 consists of neutral binuclear entities with copper atoms bridged by one oxalato group, which connect axial–equatorial positions of the two coordination polyhedra. The copper atoms are related by an inversion center and exhibit a distorted square-pyramidal stereochemistry. The Cucdots, three dots, centeredCu distance within the binuclear unit is 5.482(1) Å. The structure of 2 consists of cationic centrosymmetric binuclear entities and perchlorate anions. The tertiary amino groups from the ligands are protonated. The copper(II) ions are bridged by phenolic oxygen atoms, assuming a square-pyramidal geometry bridge the copper(II) ions. The apical positions are occupied by the aqua ligands (Cu---O=2.335(4) Å). The distance between the copper atoms is 3.008(2) Å. Cryomagnetic investigations of the two compounds reveal antiferromagnetic interactions between the copper ions in both compounds (1: J=−9 cm−1; 2: J=−646 cm−1).