Penta- and Hexacoordinated Copper(II) Complexes with Azido and 4-amino-3,5-di-2-pyridyl-4H-1,2,4-triazole Ligands with Field-Induced Slow Magnetic Relaxation.

Abstract

Two new Cu(II) complexes with abpt (4-amino-3,5-di-2-pyridyl-4H-1,2,4-triazole) and azido ligands, [Cu(abpt)₂(N₃)]NO₃ (1) and [Cu(abpt)₂(N₃)₂]⋅2H₂O (2), have been prepared and characterized by crystal structure analysis, spectral and magnetic measurements. The presence of neutral abpt, as well as azido ligands was proved by IR spectroscopy and the composition of the complexes confirmed an elemental analysis. Monocrystal X-ray structure analysis revealed that 1 is an ionic pentacoordinated Cu(II) complex, exhibiting a distorted tetragonal pyramidal geometry of the coordination polyhedron, while 2 is a neutral molecular complex with a distorted octahedral environment of the Cu(II) atom. The structures are stabilized by π-π stacking interactions between the aromatic rings of abpt, as well as various intra- and intermolecular hydrogen bonds involving nitrate ions and molecules of solvated water in 1 and 2, respectively. A field-induced slow magnetic relaxation was observed at low temperatures in 1, described by the direct and Raman process involving low-energy intramolecular vibrational modes, which were predicted by the DFT calculations.