Copper(II) halide complexes of aminopyridines: Synthesis, structure, and magnetic behavior of neutral compounds of 5-IAP: (5-IAP)2CuCl2·H2O, [(5-IAP)2CuBr2]2, (5-IAP)2CuBr2 and (5-IAP)3CuCl2·nH2O (5IAP = 2-amino-5-iodopyridine)

Abstract

Reaction of 2-amino-5-iodopyridine (5IAP) with copper(II) bromide or chloride in alcoholic solution led to four coordination complexes: [(5-IAP)2CuCl2](H2O) (1), (5-IAP)2CuBr2 (2), [(5-IAP)2CuBr2]2 (3) and [(5-IAP)3CuCl2](H2O)n (4). The compounds were characterized by single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements. 1 crystallizes as monomeric units with the 5IAP ligands in the syn-conformation and one lattice water molecule. 2 also exhibits syn-conformation 5IAP ligands, but forms a common bromide bibridged dimer structure. 3 is a conformational polymorph of 2 with anti-oriented 5IAP ligands. Long Cu⋯Br contacts link the molecules into chains. 4 crystallizes with 1.67 lattice water molecules, disordered over three positions. All four compounds exhibit strong halogen bonding. Variable field and temperature magnetic data were obtained on 1–3. 1 is paramagnetic, with no indication of magnetic exchange down to 1.8 K. 2 is well modeled as an antiferromagnetic dimer (J/kB = −22 K) with significant antiferromagnetic interactions between the dimers. 3 is well modeled as a uniform antiferromagnetic chain (J/kB = −6 K) with weak interchain interactions.