[Spectral study of the compounds with [(PO4)2Mo5O15]]

Three novel organic-molybdenum phosphates with [(PO4)2Mo5O15], namely (NH3CH2CH2NH3)2.5[(PO4)(HPO4) Mo5O15].7.5H2O (I), (H3NCH2CH2NH3)3.[(PO4)2Mo5O15].3H2O (II) and (H3NCH2CH2NH3)2.[Cu(en)] [(PO4)2Mo5O15].5H2O (III), were synthesized. The relationship between their properties and structures were studied by using FTIR, NIR-Raman, UV-Vis DRS and fluorescence spectra. Among these compounds, compound I and II possess isolating [(PO4)2Mo5O15] cage, while compound III is rather novel whose [(PO4)2Mo5O15] cages are bridging into chains by [Cuen] groups. The characteristic vibrational frequencies of molybdenum phosphates are related to the structures of these compounds. In the UV-Vis DRS spectra, there are two characteristic peaks of heteropoly compounds at 200 and 260 nm. The fluorescence spectra of these three compounds have been studied, which have emission peaks at about 400 nm excited by 240 nm, which are caused by O mu-Mo, while compound III produces 604 nm emission excited by 570 nm, which is caused by the LMCT of [Cuen] group.