Experimental and theoretical magneto-structural studies on the dicarboxylato-bridged nature of the dicopper(II)-based metal-organic frameworks

Two unprecedented metal-organic frameworks (MOFs) based on binuclear copper(II) second building units (SBUs), [Cu(INAIP)(dib)]center dot 3.5H(2)O (1) and [Cu(INAIP)(4,4'-bpy)]center dot 3H(2)O (2), [H(2)INAIP = 5-(isonicotinamido)isophthalic acid, dib = 1,4-di(1-imidazolyl) benzene and 4,4'-bpy = 4,4'-bipyridine] have been synthesized by mixed H(2)INAIP and rigid N-donor ligands with Cu(II) salt under hydrothermal conditions. Single crystal X-ray diffraction analysis revealed that the binuclear Cu(II) SBUs have similar coordination environments in complexes 1 and 2, however, 1 shows ferromagnetic interactions with J = 2.34 cm (1) while 2 exhibits antiferromagnetic interactions with J = -2.52 cm (1) within the Cu(II) dimer fitted by the spin Hamiltonian H = -JS(1)S(2). Density functional theory (DFT) calculations were carried out using two simplified models based on their structures and the results revealed that the coupling constant with different basis sets matches well with the experimental J values of 1 and 2. This is an unusual example using theoretical calculations that evaluate the magnetic coupling interactions for the coordination polymers with binuclear subunits. (C) 2012 Elsevier B. V. All rights reserved.