Two New Ferrous Molybdophosphates as Temperature-Dependent Hydrothermal Reaction Products.

Two new ferrous molybdophosphates, (H2enMe)7FeII[Mo(HPO4)2(PO4)6(OH)6O24]·7H2O 1 and (H2enMe)6FeII[Mo(HPO4)4(PO4)4(OH)6O24]·4H2O 2 (enMe = 1,2-propanediamine), have been synthesized from an identical starting mixture through hydrothermal reactions using temperature as the only independent variable, and thoroughly characterized by IR, TG, single crystal X-ray diffraction and cyclic voltammetry. The structures of both 1 and 2 are built from the building blocks of the formula, {FeII[Mo6P4O31]2}, consisting of a network of MO6 (M = Fe, Mo) octahedra and PO4 tetrahedra linked through their vertices as anions, and protonated 1,2-propanediamine as cations, respectively. The most important aspect is that the non-hydrogen atomic ratio of Mo, Fe, P, O in the anions of 1 and 2 is the same, but the protonation of the PO4 groups is different in 1 and 2. Less protonation of the PO4 groups in 1 obtained at high temperature results in the anion carrying more charges and gives rise to more H2enMe cations per [FeII(P8Mo)] unit compared with that in 2 obtained at low temperature, and as a consequence, different interpenetrating hydrogen-bonded network structures are formed in the two different compounds in terms of packing efficiency and the system energy minimization. [ABSTRACT FROM AUTHOR]