Synthesis, structure, and photochemistry of an organic Heptamolybdate-Monomolybdate

Abstract

Treatment of MoO3 with butan-1-amine (BuNH2) or pyrrolidine (PyrNH(2)) results in the formation of (BuNH3)(8)[(Mo7O24)-(MoO4)].3H(2)O (1; BuNH3 = butan-1-aminium) or (PyrNH(2))(6)-[(Mo7O24].2H(2)O (2; PyrNH(2) = pyrrolidinium), respectively. On irradiation with sunlight, compound 1, which is an organic heptamolybdate [Mo7O24](6-) that contains a cocrystallized monomolybdate [MoO4](2-) in the same compound, is transformed to an oxido-bridged diheptamolybdate(BuNH3)(10)(-)[(Mo7O22)(mu(2)-O)(2)(Mo7O22)].5.5H(2)O (1b). The [Mo7O24](6-) units in 1 and 2 are made up of edge-sharing [MoO6] octahedra, whereas the central unit in 1b is a bis(mu(2)-O)-bridged heptamolybdate dimer. Hydrogen bonding among the lattice water molecules in 1 results in the formation of a water octamer, whereas hydrogen bonding between the lattice water molecules and [Mo7O24](6-) in 2 results in the formation of a one-dimensional water-linked heptamolybdate chain. Supramolecular structures, photochemistry, and thermal properties of 1, 1b, and 2 are reported. For comparison of photochemical behavior, two more polyoxomolybdates, (PrNH3)(6)[Mo7O24].3H(2)O (3; PrNH3 = propan-1-aminium) and (PentNH(3))(6)(-)[Mo7O24].3H(2)O (4; PentNH(3) = pentan-1-aminium), were prepared and characterized.