Crystal structures, spectra and magnetic properties of di-2-pyridylamine (dpa) Cu II complexes [Cu(dpa) 2(N 3) 2]·(H 2O) 2 and [Cu 2(μ-ox)(dpa) 2(CH 3CN) 2](ClO 4) 2

Abstract

Two Cu II complexes with di-2-pyridylamine (dpa) and combined bridging ligands (azide or oxalato anions), [Cu(dpa) 2(N 3) 2]·2H 2O ( 1) and [Cu 2(μ-ox)(dpa) 2(CH 3CN) 2](ClO 4) 2 ( 2), have been synthesized and characterized by IR spectra, elemental analyses, TGA, UV–Vis spectra and ESR technique. The crystal structures of both complexes have been determined by single crystal X-ray diffraction analyses. In the mononuclear complex 1, the Cu II center is coordinated to four N atoms of dpa and two N donors of azide (CuN 6), taking an elongated octahedral geometry. The solvent water molecules interlink the neutral [Cu(dpa) 2(N 3) 2] units through hydrogen bonds to form a two-dimensional (2D) layered structure with strong π–π stacking interactions between the adjacent pyridine rings. Complex 2 is made up of centro-symmetric dinuclear [Cu 2(μ-ox)(dpa) 2(CH 3CN) 2] 2+ cation and non-coordinated perchlorate anions, assembling into a one-dimensional (1D) ladder structure through hydrogen bonding with π–π stacking co-effect. The magnetic properties of 2 have been investigated by variable-temperature magnetic susceptibility and magnetization measurements, indicating a very strong anti-ferromagnetic coupling between the intra-molecular Cu II centers (having the perfect square-pyramidal geometry) with J=−382 cm −1. The strength of the exchange interaction is discussed in detail on the basis of the structural feature.