Two-dimensional Correlation Infrared Spectroscopy Study on Vanadoborate Anionic Skeleton Regulated by Countercations.

Two novel vanadoborate compounds, [Cu(en)2]3[Li(H2O)]4[Li(H2O)3]2[V12B18O50(OH)10(H2O)]2 & sdot;33.5H2O (1) and (H2en)4[Li(H2O)]4[V12B18O55(OH)5(H2O)]& sdot;14H2O (2), were synthesized via hydrothermal synthesis under identical conditions except for temperature. Structural analysis revealed that although both contain [V12B18O60]n- cluster anion, the different countercations potentially lead to variations in the [V12B18O60]ncluster anion skeletons. In compound 1, the V4+/V5+ ratio was 10:2; while in compound 2 the ratio was 11:1. It is speculated that different countercations may influence the valence states of cluster anions. In this study, quantum chemical calculations revealed that the aromaticity and activity of the two compounds were different, and twodimensional correlation infrared spectroscopy (2D-COS-IR) under magnetic perturbation confirmed that distinct response peaks of functional group vibrations to the magnetic field due to the different V4+/V5+ ratios and aromaticity of the two compounds. An electrochemical analysis revealed that compound 2 exhibits higher electrocatalytic activity. The results of quantum chemical calculations are aligned not only with the changes in the 2D-COS-IR spectra but also with the conclusions obtained from experiments on electrochemical properties. Overall, this work proposes a novel strategy for interpreting the alteration of vanadoborate anionic skeleton due to the introduction of different countercations by combining 2D-COS-IR with quantum chemical calculations.