The role of stereoactive lone pairs in templated vanadium tellurite charge density matching.

The role of charge density matching was investigated in the formation of templated vanadium tellurites under mild hydrothermal conditions. Reactions were conducted using a fixed NaVTeO(5):amine ratio in an ethanol/water solution to isolate the effects of amine structure. The use of 1,4-diaminobutane, 1,3-diaminopropane, and piperazine resulted in three distinct vanadium tellurite connectivities, [V(2)Te(2)O(10)](n)(2n-) chains, [V(2)TeO(8)](n)(2n-) layers, and [V(2)Te(2)O(10)](n)(2n-) layers, respectively. Charge density matching with the protonated amines is the primary influence over the structure of each vanadium tellurite anion, as quantified by molecular surface area and geometric decomposition methods. Electron localization functions were calculated using the Stuttgart tight-binding linear muffin-tin orbital, atomic sphere approximation code, to visualize the location and relative size, shape, and orientation of the stereoactive lone pair in the tellurite groups. [C(4)H(14)N(2)][V(2)Te(2)O(10)]: a = 5.649(5) A, b = 6.348(5) A, c = 9.661(5) A, alpha = 84.860(5) degrees , beta = 85.380(5) degrees , gamma = 81.285(5) degrees , triclinic, P1 (No. 2), Z = 1.

Synthetic approaches for noncentrosymmetric molybdates.

The use of second-order Jahn-Teller active Mo (VI) centers and chiral organic amines is discussed as an approach to crystallographic noncentrosymmetry. Several series of reactions, conducted under mild hydrothermal conditions, were designed to probe important reaction variables. Correlations between reagent and solvent concentrations and the molybdate structure were investigated using composition space analysis, which allows for the isolation of specific reaction variables. The effects of amine structure variation were probed using multiple series of related amines, which consisted of either linear diamines or ethylenediamine derivatives. The addition of fluoride results in the loss of amine-based structural variations. Chiral organic amines were used to demonstrate the viability of using such components to control the three-dimensional symmetry in new materials. The synthesis, structure, and characterization of eight new organically templated polyoxomolybdates and polyoxofluoromolybdates are reported.