One dimensional inorganic oxovanadium polymers functionalized with manganese(II) complexes: Structural and magnetic characterization

Abstract: Two organo-inorganic hybrid manganese(II) vanadates [Mn(phen)2(VO3)2]∞ (1) and [{Mn(bipy)(VO3)2}{VO2(bipy)}(VO3)(V2O6)]∞ (2) were synthesized hydrothermally. Compound 1 is a chain consisting in VO3 units propagating along the b axis, decorated with {Mn(phen)2}+2 subunits. Compound 2 is a ladder like structure propagating along the a axis, consisting of two helical chains connected by the heterobinuclear {Mn(bipy)VO4 (2,2′-bipy)} moieties, generating a double helical structure. Magnetization measurements reveal that dominant antiferromagnetic interactions are mediated between the manganese(II) centers for both structures through oxovanadate bridges. Magnetic data of compound 1 were fitted with the analytical expression for a regular chain model, estimating a J value of −0.30cm−1. The DAVE code was use to fit experimental data and calculate the values of the super exchange constants for 2, assuming four different exchange pathways, J 12 =−0.17cm−1; J 23 =−0.12cm−1; J 13 =−0.08cm−1; J 24 =−0.05cm−1. DFT calculations on a tetranuclear fragment of 2, using diamagnetic substitutions, gave super exchange values of J 12 =−17.5cm−1 and J 23 =−8.5cm−1, corroborating the antiferromagnetic nature of the interactions as observed experimentally. [Copyright &y& Elsevier]