More Than A Few Cases Of Tungstate Electrospray Mass Spectrometry

Polyoxometalates (POMs) is a rapidly developing class of metal oxide, their interesting electrochemical and molecular properties have led to many potential applications for POMs, in the areas of catalysis, medicine and materials science. One of the most intensity aspects of POM chemistry lies with the fact that the cluster can be viewed as transferable building blocks or synthons, the controlled assembly has been a hot topic in the recent years.In this paper, three types of eight polysoxotungstates are successfully tested using electrosopray ionization mass spectrometry (ESI-MS) through adjusting parameters.1> Two heterpolytungstate compounds [(n-C4H9)4N]2[W6O19](1)[(n-C4H9)4N]4[W10O32](2)2、Two silicotungste compounds K4[α-SiW12O40]·17H2O(3) K8[α-SiW11O39]·13H2O(4)3、four arsenotungste compouds Na3[AsW12O40]·xH2O(5) Na12[As2W18Cu3O66(H2O)3]·32H2O(6) Na10[As2W18Zn3O66(H2O)3]·51H2O(7) Na9[[Na(H2O)]3[Mn(C3H4N2)]3(AsW9O33)2]·27H2O(8)By choosing test parameters, we have obtained the distinguishing ESI-MS figures and summarized up the m/z peaks of fragment ions. By changing the collision voltage, the precursor fragments are further ionized to get the lower mass fragment ions and the possible mechanism of the disaggregation is simulated. For compound1and2, the major fragmentation yields a series of dianionic isopolytungstate [WxO3x+1]2-(x=2-8). For compound3,4and5, the major fragmentation yields a series of pairs of complementary ions, each pair comprising a dianionic isopolytungstate ([WxO3x+1]2-) and a heteropolytungstate ([MW12-xO39-3x]"n-,M=Si, As, x=6-9, n=2,1). The total stoichiometry and charge of each pair of complementary product ions match those of the precursor anion. For compound6,7and8, ESI-MS yields a series of dianionic heteropolytungstates ([AsWxO3x+2]2")(x=1-6). Besides, a new inorganic-organic polyoxometalates based on the Keggin ion [SiW12O40]4-has been synthesized by hydrothermally synthesis, and characterized by single crystal X-ray diffraction, elemental analysis, fluorescent spectrum and IR.[Cu(H2O)2(C12H10N4)]2[SiW12O40]·9H2O(9)The Keggin ion is connected via four O-Cu-O bonds to form2D (4,4) network. The compound9has been also used as a modifier to fabricate chemically modified carbon paste electrode (CMCPE), and the result shows that CMCPE presents five reversible redox peaks, and has good electrocatalytic activity toward the nitrite.