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

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 −0.30 cm−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, J12 = −0.17 cm−1; J23 = −0.12 cm−1; J13 = −0.08 cm−1; J24 = −0.05 cm−1. DFT calculations on a tetranuclear fragment of 2, using diamagnetic substitutions, gave super exchange values of J12 = −17.5 cm−1 and J23 = −8.5 cm−1, corroborating the antiferromagnetic nature of the interactions as observed experimentally.

Graphical abstractBoth [Mn(phen)2(VO3)2]∞ (1) and [{Mn(bipy)(VO3)2}{VO2(bipy)}(VO3)(V2O6)]∞ (2) present weak antiferromagnetic behavior. Analytical models, numerical approximation fitting models and DFT calculations were used to obtain a better insight of the magnetic behavior. The scheme corresponds to the ladder-like structure of (2).Figure optionsDownload full-size imageDownload as PowerPoint slide