Magnetic properties of hybrid organo-inorganic copper(II) oxovanadate(V) phosphate and phosphonate bridged systems
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The hybrid organo-inorganic compounds [Cu4(bipy)4V4O11(PO4)2]nH2O (n 5) (1), [Cu2(phen)2(PO4)(H2PO4)2(VO2) Ã† 2H2O] (2) and [Cu2(phen)2(O3PCH2PO3)(V2O5) (H2O)]H2O (3) which present different bridging forms of the phosphate/phosphonate group, show different bulk magnetic properties. We herein analyze the magnetic behaviour of these compounds in terms of their structural parameters. We also report a theoretical study for compound (1) assuming four different magnetic exchange pathways between the copper centres present in the tetranuclear unit. For compound (1) the following J values were obtained J1 = +3.29; J2 = 0.63; J3 = 2.23; J4 = 46.14 cm 1. Compound (2) presents a Curieâ€“Weiss behaviour in the whole range of temperature (3â€“300 K), and compound (3) shows a maximum for the magnetic susceptibility at 64 K, typical for antiferromagnetic interactions. These data where fitted using a model previously reported in the literature, assuming two different magnetic exchange pathways between the four copper(II) centres, with J1 = 30.0 and J2 = 8.5 cm 1.