The directed synthesis of two noncentrosymmetric sulfated molybdates has been achieved through the use of chiral organic amines. Reaction gels containing either (R)-2-methylpiperazine or (S)-2-methylpiperazine, MoO 3 , H 2 SO 4 , and H 2 O were subjected to mild hydrothermal conditions, resulting in the growth of single crystals of [(R)-C 5 H 14 N 2 ][(MoO 3 ) 3 (SO 4 )]‚H 2 O and [(S)-C 5 H 14 N 2 ][(MoO 3 ) 3 (SO 4 )]‚H 2 O. These materials crystallize in the noncentroysmmetric space group P2 1 2 1 2 1 (No. 19), which exhibits the enantiomorphic crystal class 222 (D 2 ). The second harmonic generation activities were measured on sieved powders.
A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown. The relative phase stabilities for these products are dependent upon the reactant mole fractions in the initial reaction gel. This phase stability information was used to direct the synthesis of two new noncentrosymmetric compounds, using either (S)-(-)-3-aminoquinuclidine dihydrochloride or (R)-(+)-3-aminoquinuclidine dihydrochloride. [(R)-C7H16N2]2[Mo8O26] and [(S)-C7H16N2]2[Mo8O26] both crystallize in the noncentrosymmetric space group P2(1) (No. 4), which has the polar crystal class 2 (C2). The second-harmonic generation activities were measured on sieved powders. The structure-directing properties of the molybdate components in each compound were determined using bond valence sums. The structures of all five compounds were determined using single-crystal X-ray diffraction.
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