Structural Chemistry And Properties Study Of Polyoxomolybdate With Organophosphorus (Nitrogen-heterocyclic) Compounds

The polyoxometalates (POMs) are discrete anionic metal-oxygen clusters which exhibit a great diversity of sizes, nuclear and shape. The metallic cations and organic ligands could be coordinated with the POM via the oxygen atoms that located on the surface of the POMs to construct organic-inorganic hybrid compounds with multi-dimensional structures. While these species have been known for almost two centuries, they have always been an important research area based on their large domains of application ranging from catalysis, electrochemistry, magnetism to medicine.Based on the summary and investigation of the literatures related to this field at home and abroad, there’re nine metal/organic-POM compounds have been prepared by the hydrothermal method in this paper and we have found out the relationship between structures and spectral properties. Moreover, we also make the exploration on the magnetism property and the rhodamine B (RhB) photocatalytic degradation for part of the synthesized compounds. The main work is as follows:1. Nine novel polyoxomolybdates were obtained under hydrothermal condition and X-Ray single crystal diffraction was carried out to determine those structures further. Compounds 1-6 all contain Strandberg type molybdophenylphosphonates. In compound 2, the cations and anions are linked via the hydrogen bonds to form left-handed spiral chain. In compounds 4 and 5, a three-dimensional framework and a two-dimensional layer are constructed through the coordination between the metallic ions and organic ligands/anionic clusters respectively. Compounds 7 and 8 both contain Keggin type polyoxomolybdate, and one folded configuration present in 8. In compound 9, the{[Mo3O10]2-} cluster subunits with heart-shaped are linked together to form one-dimensional infinite chain. In this thesis, we also introduce TOPOS 4.0 to the structure topology analysis for compounds 4,5 and 9. We also summarized the structural building rule of the molybdenum oxide compounds.2. The IR spectra of nine compounds displays obvious characteristic vibration absorption of the groups in anionic clusters and organic ligands. The charge transferabsorption bands of O/Nâ†'M and the d-d transfer absorption bands of transition metallic ion are found in the UV-vis DRS spectra. The 2D-IR COS characterization were performed for some compounds. The temperature-induced 2D-IR COS indicates that the stretching vibration of Mo=OÏ„ in anionic clusters are more sensitive than Mo-Oμ for the thermal perturbation. Besides, the magnetism-induced 2D-IR COS exhibit the sensitive response of Mo-O stretching vibration as well as the nitrogen heterocyclic organic ligands which coordinated with the magnetic particles. The result from spectroscopic characterization are consistent with the structural analysis.3. The studies of the variable temperature magnetic susceptibility indicate that compounds 1 and 2 both display the paramagnetic properties. The phenomenon of a decrease in χmT at low T may be caused by the single-ion "D" effects which was due to the Jane-Teller effect. In the experiments of photo-catalytic degradation of RhB, we found that the compound 1,6 and 7 all display a good catalytic ability and improve the efficiency of degradation substantially. Furthermore, we also found the photo-catalytic activity of Keggin type polyoxomolybdate is better than the Strandberg type one.4. Quantum chemical calculation on the Strandberg type cluster anion was carried out in compound 6. Visualization of the HOMO-LUMO showed that the active centers are in OT and Oμ. Simulated infrared spectra verifies the correspondence between the Mo-0 vibration and IR peaks. It provides a theoretical basis for the further study of the spectral properties of these compounds.