Study on the source of magnetic properties of three novel boratopolyoxovanadates via two-dimensional infrared correlation spectroscopy

摘要

Three novel polyoxovanadoborates namely [V12B18O46(OH)(14)(H2O)(0.75)]center dot 20.5H(2)O 1, Na-2[V12B18O48(OH)(12)(H2O)(0.5)]center dot 26.5H(2)O 2 and Cd-0.5{[Na(H2O)(2)]2[Na(H2O)](2)[Na(H2O)(3)]2V(12)B(18)O(53)(OH)(7)(H2O)(0.5)}center dot 11H(2)O 3 have been hydrothermally synthesized and structurally characterized. The boratopolyoxovanadate cage [V12B18O60] backbones in 1-3 are constructed by the combination of two hexameric oxovanadate units [V6O9] and one puckered [B18O42] ring via sharing O atoms. All three compounds were obtained under alkaline conditions, and the cluster anions were all [V12B18O60]. But the cations were different, it is inferred that the protonation of the three compound cluster ions is different, respectively [V12B18O46(OH)(14)(H2O)(0.75)] in 1, [V12B18O48(OH)(12)(H2O)(0.5)](2-) in 2 and [V12B18O53(OH)(7)(H2O)(0.5)](7-) in 3. The V oxidation states ratio of V-IV to V-V were 2:1 confirmed by valence bond calculation and XPS. We studied the magnetic properties of three compounds by two methods: The variable temperature magnetic susceptibility and the 2D IR COS under magnetic perturbation. Fromthe 2D IR COS under magnetic perturbation map, it is showed that all three: (1) the presence of V-IV. (2) Certain quasi-aromaticity from B3O3 six-membered ring. (3) The difference of protonation and the charge of the cluster anions. This work enriches the theory of two-dimensional correlation spectroscopy and also provides a new approach to the study of magnetic materials. (c) 2019 Elsevier B.V. All rights reserved.