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Frederico F. Martins Dr. Ángel Sánchez-González Jose Lanuza Dr. Haralampos N. Miras Prof. Xabier Lopez Dr. Nuno A. Bandeira Dr. Adrià Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(35):8977-8984
Phosphoester hydrolysis is an important chemical step in DNA repair. One archetypal molecular model of phosphoesters is para-nitrophenylphosphate (pNPP). It has been shown previously that the presence of molecular metal oxide [Mo7O24]6− may catalyse the hydrolysis of pNPP through the partial decomposition of polyoxomolybdate framework resulting in a [(PO4)2Mo5O15]6− product. Real-time monitoring of the catalytic system using electrospray ionisation mass spectrometry (ESI-MS) provided a glance into the species present in the reaction mixture and identification of potential catalytic candidates. Following up on the obtained spectrometric data, Density Functional Theory (DFT) calculations were carried out to characterise the hypothetical intermediate [Mo5O15(pNPP)2(H2O)6]6− that would be required to form under the hypothesised transformation. Surprisingly, our results point to the dimeric [Mo2O8]4− anion resulting from the decomposition of [Mo7O24]6− as the active catalytic species involved in the hydrolysis of pNPP rather than the originally assumed {Mo5O15} species. A similar study was carried out involving the same species but substituting Mo by W. The mechanism involving W species showed a higher barrier and less stable products in agreement with the non-catalytic effect found in experimental results. 相似文献
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McGlone T Vilà-Nadal L Miras HN Long DL Poblet JM Cronin L 《Dalton transactions (Cambridge, England : 2003)》2010,39(48):11599-11604
Two titanium embedded polyoxometalates with unprecedented structural features are presented: a monotitanium containing tungstoantimonate Na(13)H(3)[TiO(SbW(9)O(33))(2)]·33 H(2)O featuring a {Ti=O}(2+) moiety (1) and a hexatitanium containing tungstoarsenate K(6)[Ti(4)(H(2)O)(10)(AsTiW(8)O(33))(2)]·30 H(2)O containing a {Ti(4)(H(2)O)(10)}(16+) moiety (2). Both compounds have been fully characterised by single crystal X-ray diffraction, elemental analysis, IR and TGA. 1 is constructed from two α-B-{Sb(III)W(9)O(33)} fragments linked by five sodium cations and an unprecedented square pyramidal Ti(O)O(4) group with a terminal Ti=O bond, and 2 exhibits a Krebs-type structure composed of two {AsTiW(8)O(33)} fragments, where one W(VI) centre has been substituted for a Ti(IV) centre in each, fused together via a belt of four additional Ti(IV) centres. This system represents the tungsten Ti-incorporated polyoxoanion with one of the highest Ti:W ratios so far reported. Additionally, 2 could also be isolated as an n-tetrabutylammonium salt and has been further characterised by electrochemistry and electrospray ionisation (ESI) MS studies. Due to the unique nature of these systems, both have been fully investigated using DFT calculations yielding highly interesting results. Structure 1 has been optimised with five sodium atoms in the belt position, which in addition to reducing the high charge of the cluster influence a stabilisation of the antimony lone pairs. Electrostatic potential calculations highlight the high electronegativity of the terminal oxygen on the titanium centre, enhancing real potentiality as a reactive site for catalysis. 相似文献
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We consider the representation dimension, for fixed n ≥ 2, of ordinary and quantised Schur algebras S(n, r) over a field k. For k of positive characteristic p we give a lower bound valid for all p. We also give an upper bound in the quantum case, when k has characteristic 0. 相似文献
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Vanadate(V)-templated Dawson-type capsules {V(IV)M(VI)(17)(VO(4))(2)} (M = Mo, W; 1-2) have been synthesized and investigated by electrochemical methods in aqueous and organic media using spectroscopic techniques, EPR, UV-vis/NIR, IR, and CSI-MS (cryospray ionization mass spec.), and the clusters have been examined in the solid state by magnetic studies. The collision-induced dissociation (CID-MS) studies confirmed the solution structures as well as helped pinpoint the position of the vanadium ion on the {VM(17)}-type shell, which was corroborated by EPR and theoretical studies. 相似文献
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Miras HN Long DL Kögerler P Cronin L 《Dalton transactions (Cambridge, England : 2003)》2008,(2):214-221
A family of polyoxometalates with the composition [H2V3M17O62](6-) features a Dawson-like architecture containing two tetrahedral {VVO4} templates rather than main group hetero-anions ({PO4} or {SO4} etc.) typically associated with classical heteropolyacids, situated within a mixed-metal {MVI17VIVO54} cage and these clusters were first discovered using mass spectrometry. 相似文献