Crystallization of organically templated phosphomolybdate cluster-based solids from aqueous solution

Abstract

The paper reports the synthesis and structural characterization of several organic-inorganic solids involving phosphomolybdate clusters. The Strandberg-type {P2Mo5VIO23} and the lower-valent {P4Mo6V O31} cluster based solids were isolated in the presence of en (ethylenediamine) by controlling pH of the reaction medium. The lower-valent cluster invariably requires the presence of a suitable metal cation for further stabilization. A detailed investigation of the system was carried out where three different weak acids viz. oxalic acid, succinic acid and glycine were used in the entire pH range (1-12). Our results establish that the organic amine (en) is alone capable of reducing the molybdenum core in the absence of an organic acid at a suitable pH. Hence, pH of the reaction medium combined with suitable temperature favors the formation of lower-valent phosphomolybdate cluster. Higher pH favors the precipitation of a new sodium hydrogen phosphate. © 2012 Indian Academy of Sciences.