Structural and magnetic properties of vanadyl dichloride solvates: from molecular units to extended hydrogen-bonded solids

Abstract

The preparation, structural characterization and magnetic properties of three solvent adducts of VOCl₂, trans-VOCl₂(THF)₂(H₂O) (1), trans-VOCl₂(H₂O)₂·2Et₂O (2) and cis-VOCl₂(MeOH)₃ (3) are described. In these solids, hydrogen bonding among the inorganic complexes is the critical determinant of the formation of extended magnetic networks. Compound 1 forms one-dimensional double chains where alternating monomers from the two branches of the chain are hydrogen bonded via the V–Cl⋯H–O–V network (with an axial water molecule and equatorial chloride ions). Magnetic studies indicate no interaction among the vanadyl centers. The paramagnetism of 1 is consistent with the extension of the network from the hydrogen donor site of the axial water, which is orthogonal to the d_xy magnetic orbital. Compound 2 forms one-dimensional chains with water molecules of adjacent monomers held together by hydrogen bonds to ether molecules (V–O–H⋯O_ether⋯H –O–V). The chain network radiates only through the equatorial plane of the complex where the water molecules are located. The presence of the intervening solvent molecule between hydrogen bonds of the primary coordination sphere magnetically insulates metal centers and compound 2 is also a simple paramagnet. Removal of the solvent turns on the magnetic interaction and neighboring spin centers couple antiferromagnetically. Compound 3 forms a layered structure via V–Cl⋯H–O–V hydrogen bonding, where all the hydrogen donor sites participate in the formation of the network. The vanadyl spin centers, at distances of 5.5 and 6.5 Å from each other, couple antiferromagnetically (J/k = −0.7 K). Thus, magnetic coupling among metal centers is achieved when the hydrogen bond network directly radiates from the coordination plane containing the magnetic orbital. These results further support the utility of hydrogen bond as a viable design element in the construction of low dimensional, magnetic solids.