Carbonate encapsulation from dissolved atmospheric CO2 into a polyoxovanadate capsule

摘要

An aqueous synthesis, involving the reduction of the VO3- anion in a mild alkaline pH in the presence of alpha-Bi2O3, led to the formation of a fully reduced polyoxovanadate (POV) capsule, with CO32- anion encapsulation in its internal cavity, in the compound [Na-6(H2O)(24)][H(8)VIV15O(36)(CO3)]center dot 3N(2)H(4)center dot 10H(2)O (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 alpha-Bi2O3. Compound 1 crystals, upon exposure to HCl acid vapor, exclude CO2 gas that can react with the Grignard reagent (PhMgBr) to form triphenylcarbinol and benzoic acid; during this solid-vapor interface reaction, compound 1 itself transforms into an amorphous material that includes the Cl- anion but could not be characterized unambiguously. Thus, we have synthesized a chloride ion (Cl-) encapsulated compound [Na-10(H2O)(24)][H(3)VIV15O(36)(Cl)]center dot 6H(2)O (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 states. The temperature-dependent magnetic susceptibilities for compounds 1 and 2 have been recordred at 0.1 T in the temperature range of 3-300 K. The temperature-dependent magnetic susceptibilities of compounds 1 and 2 are shown in the form of chi(M)vs. T and their product chi T-M vs. T plots.