Supramolecular motifs and solvatomorphism within the compounds [M(bpy)(3)](2)[NbO(C2O4)(3)]Cl center dot nH(2)O (M= Fe2+, Co2+, Ni2+, Cu2+ and Zn2+; n=11, 12). Syntheses, structures and magnetic properties

摘要

Solvatomorphism has been found between two series of complexes of the composition [M(bpy)(3)](2)[NbO(C2O4)(3)]Cl center dot nH(2)O[M = Fe2+ (1, 2), Co2+ (3, 4), Ni2+ (5, 6), Cu2+ (7) and Zn2+ (8, 9); bpy = 2,2'-bipyridine)], crystallizing in the monoclinic space group P2(1)/c [3, 5, 8 (n = 11)]or in the orthorhombic space group P2(1)2(1)2(1) [2, 4, 6, 7 (n = 12)]. All the structures contain two symmetry independent [M(bpy)(3)](2+) cations, one [NbO(C2O4)(3)](3-) anion, one Cl- anion, and crystal water molecules. The cations possess a trigonally distorted octahedral geometry, with an additional tetragonal distortion in 7. Analysis of crystal packing reveals a specific type of supramolecular contact comprising four bipyridine ligands from two neighbouring [M(bpy)(3)](2+) cations-quadruple aryl embrace (QAE) contact. The contact is realized by the alignment of two molecular two-fold rotation axes, preserving the parallel orientation of the molecular three-fold rotation axes. The resulting two-dimensional honeycomb lattices of [M(bpy)(3)](2+) cations are placed between the hydrogen bonding layers made of [NbO(C2O4)(3)](3-) and Cl- anions and the majority of the crystal water molecules. The temperature-dependent magnetic susceptibility measurements (1.8-300 K) show a significant orbital angular momentum contribution for 3 and 4 (high-spin Co2+), the influence of zero field splitting for 5 and 6 (Ni2+) and a substantially paramagnetic Curie behaviour for the Cu2+ compound (7).