Carbonate encapsulation from dissolved atmospheric CO2 into a polyoxovanadate capsule
An aqueous synthesis, involving the reduction of VO3‒ anion in a mild alkaline pH in the presence of α-Bi2O3, leads to the formation of a fully reduced polyoxovanadate (POV) capsule, with CO32‒ anion encapsulation in its internal cavity, in compound [Na6(H2O)24][H8VIV15O36(CO3)]·3N2H4·10H2O (1). This CO32‒ anion encapsulation, the source of which is absorbed aerial CO2 in the pertinent aqueous alkaline reaction mixture, occurs only in the presence of α-Bi2O3. Compound 1 crystals, upon exposure to HCl acid vapor, exclude CO2 gas that can be reacted to Grignard reagent, PhMgBr to form triphenyl carbinol and benzoic acid; during this solid-vapor interface reaction, compound 1 itself is transformed into an amorphous material that includes Cl‒ anion, but could not be characterized unambiguously. Thus, we have synthesized a chloride ion (Cl‒) encapsulated compound [Na10(H2O)24][H3V15O36(Cl)]·6H2O (2) in a direct synthesis protocol, which has been characterized by crystallography as well as by other spectroscopic methods. Compounds 1 and 2, each having fifteen vanadium(IV) centers, exhibit interesting magnetism in their solid state. The temperature dependence magnetic susceptabilities for compounds 1 and 2 have been recordred at 0.1 T in the temperature range of 3‒300 K. The temperature dependence magnetic susceptabilities of compounds 1 and 2 are shown in the form of χM vs T and their product χMT vs T plots.