A Spectroscopic Method for Distinguishing Two Novel Sandwich-Type Tungsten Oxide Cluster Compounds.

This study introduces two novel sandwich-type tungsten-oxygen cluster compounds synthesized by hydrothermal methods, H4(C6H12N2H2)3{Na(H2O)2[Mn2(H2O)(GeW9O34)]}2 (Compound 1) and H2(C6H12N2H2)3.5{Na3(H2O)4[Co2(H2O)(GeW9O34)]2}·17H2O (Compound 2). The two compounds comprise cluster anions [GeW9O34]10- coordinated with transition metal atoms, either Mn or Co, and are stabilized by organic ligands. These compounds are crystallized in the hexagonal crystal system and P63/m space group. The two compounds were characterized through various techniques. Fourier transform infrared (IR) spectroscopy showed absorption peaks of anionic backbone vibrations of the Keggin cluster at 500-1000 cm-1, IR spectral peaks of δ(N-H) and νas(C-N) of the ligand triethylenediamine at 1000-2000 cm-1, and IR spectral peaks of the ligand νas(N-H) and νas(O-H) of water at 3000-3500 cm-1. Despite similar one-dimensional (1D) IR spectra due to the same cluster anions and similar molecular structures, the two compounds exhibited distinct responses in two-dimensional correlation spectroscopy with IR under magnetic and thermal perturbations. Under magnetic perturbation, Compound 1 showed a strong response peak for νas(W-Ob-W), while Compound 2 exhibited a strong response peak for νas(W=Od), possibly linked to differing magnetic particles. Similarly, Compound 1 displayed a strong response peak under thermal perturbation for νas(W-Oc-W). In contrast, Compound 2 showed a strong response peak for νas(W=Od); these results may be attributed to the different hydrogen bonding connections between the two compounds, which affect the groups in distinct ways through vibration and transmit these vibrations to the W-O bonds. The research presented in this paper expands the theoretical and experimental data of 2D correlation IR spectroscopy.

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

Three novel polyoxovanadoborates namely [V12B18O46(OH)14(H2O)0.75]·20.5H2O 1, Na2[V12B18O48(OH)12(H2O)0.5]·26.5H2O 2 and Cd0.5{[Na(H2O)2]2[Na(H2O)]2[Na(H2O)3]2V12B18O53(OH)7(H2O)0.5}·11H2O 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 VIV to VV 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. From the 2D IR COS under magnetic perturbation map, it is showed that all three: (1) the presence of VIV. (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.