RESUMEN
Pancake bonding phenomenology is applied for the first time in a bioorganic system, the pigment eumelanin, via a hydration-induced decrease of the interplanar distance down to 3.19 Å. The observation explains the long-term inconsistency between electron paramagnetic resonance and muon spin relaxation data for eumelanin.
RESUMEN
Reaction of [(C6H6)RuCl2]2 and Na8[Ta6O19] gives two new hybrid organometallic POM complexes, Na10[{(C6H6)RuTa6O18}2(µ-O)]·39.4H2O (Na10-1) and Na4(trans-[{(C6H6)Ru}2Ta6O19]·20H2O (Na4-2). In both cases the half-sandwich fragments {(C6H6)Ru}(2+) are coordinated as additional vertices to the {Ta3(µ2-O)3} triangles of the hexatantalate. According to NMR and ESI-MS data, the dimeric complex [{(C6H6)RuTa6O18}2(µ-O)](10-) dissociates in water with the formation of monomeric [(C6H6)RuTa6O19](6-) species (1a). X-ray structural characterization and aqueous speciation of the complexes by (13)C, (1)H, and DOSY NMR; ESI-MS; and capillary electrophoresis (CE) have been carried out.
RESUMEN
Unambiguous identification of polyoxometalate (POM) species generated in self-assembly reactions in solution is rather problematic due to close similarity of their properties such as solubility and spectral characteristics. The situation is made more complex by protonation equilibria (which can change their analytical signals) and the lack of individual compounds to serve as standards for individual members of these mixtures. In the present work a new approach to the study of such POMs has been suggested, taking molybdovanadates [PMo12-xVxO40]-3-x as a model. The key feature of this approach consists of generation of so-called "conditional model systems" that include most of the expected components of a mixture formed by self-assembly, tracked down by reliable detection techniques, e.g., 51V NMR-spectroscopy in this particular case. Then the proposed composition of the mixture is verified and corrected by means of high-performance liquid chromatography coupled with inductively coupled plasma atomic emission spectrometry (HPLC-ICP-AES).
RESUMEN
The reaction between solid (NMP)n{[BiBr4]}n (1) (NMP = N-methylpyridinium) and Br2, generated in situ in HBr solution, results in the formation of (NMP)3[Bi2Br9]·Br2 (2). In the structure of 2, dibromine molecules connect discrete binuclear [Bi2Br9](3-) anions into an extended network. Complex 2 is thermally stable (up to 150 °C).
RESUMEN
Reaction of [Nb6O19](8-) with [Pt(OH)4(H2O)2] upon heating yielded first characterized platinum polyniobates. A dimeric complex [Nb6O19{Pt(OH)2}]2(12-) (1) is produced in a 1 : 1 molar ratio. Increasing the Pt/Nb6 molar ratio to 1 : 2 yields a mixture of 1 and a sandwich-type complex [Pt(Nb6O19)2](12-) (2).
RESUMEN
New hybrid POM based on Lindqvist-type polyoxometalates [M6O19](8-) (M = Nb, Ta) and organometallic fragment {Cp*Rh}(2+) have been isolated and characterized. X-ray quality crystals of K4[(Cp*Rh)2Nb6O19]·20H2O () and Cs4[(Cp*Rh)2Ta6O19]·18H2O () were obtained from solutions with {Cp*Rh} : [M6O19](8-) stoichiometry 2 : 1. The solution behavior of the hybrid polyoxoanions was studied with ESI-MS and (1)H DOSY NMR. Amongst the poorly investigated chemistry of polyoxotantalates, complex is the first complex bearing a grafted organometallic fragment. The formation of 1 : 1 complexes was detected by ESI-MS techniques.
RESUMEN
Reaction between monolacunary {BW(11)} tungstoborate and oxothiocationic building block, {Mo(2)O(2)S(2)}, results in the formation of a new polyoxothiometalate with a unique architecture in which two [H(2)BW(12)O(43)](9-) tungstoborate subunits are linked together with a hexamolybdate [Mo(V)(6)O(6)S(6)(OH)(4)(H(2)O)(2)](2+) bridge.