Supramolecular motifs and solvatomorphism within the compounds[M(bpy)3]2[NbO(C2O4)3]Cl·nH2O(M=Fe~(2+),Co~(2+),Ni~(2+),Cu~(2+)and Zn~(2+);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·nH2O[M=Fe~(2+)(1,2),Co~(2+)(3,4),Ni~(2+)(5,6),Cu~(2+)(7)and Zn~(2+)(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_12_12_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 Co~(2+)),the influence of zero-field splitting for 5 and 6(Ni~(2+))and a substantially paramagnetic Curie behaviour for the Cu~(2+)compound(7).