Directed Synthesis of Noncentrosymmetric Molybdates Using Composition Space Analysis

Abstract

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.

Synthesis, crystal structures and thermal behaviour of organic–inorganic hybrids incorporating a chiral diamine

“…The TG curve shows that the compound is stable to approximately 105 C. The first transformation occurs in the temperature range 105e145 C. The weight loss of 5.834% is in agreement with the departure of 1.5$H 2 O molecules (calculated weight loss, 5.892%). This phenomenon is accompanied with an endothermic peak on the DTA curve, at 125 C. The second weight loss of 17.532%, observed between 145 and 215 C, (endothermic peak at 171 C on the DTA curve) corresponds to the departure of the last water molecules (calculated weight loss, 17 Fig. 5c.…”

“…This technique has been used with success in a variety of systems [5,17,38]. The role of 2-methylpiperazinediium cations in these reactions is three-fold.…”

“…The trend in these distances mirrors the sizes of the included organic cations. The Flack parameters for these compounds refined to À0.016 (15) and À0.016 (17), indicating absolute configurations. The enantiomeric structures are inverses of one another and are isostructural with a related copper phase [5].…”

Noncentrosymmetric Inorganic Oxide Materials: Synthetic Strategies and Characterisation Techniques

“…[51][52][53] As stated previously, the first challenge in synthesising NCS materials is to use inherently asymmetric NCS polyhedra. In using the SOJT-distorted Mo 6þ , Norquist et al synthesised materials where the d 0 cation is substantially displaced from the centre of its oxide octahedra.…”

“…The lone-pair cation coordination environment may be considered as pre-distorted, [38] as these cations are almost always found in local NCS environments. Halasyamani et al, [38][39][40][41][42][43][44][45][46][47][48][49][50] Norquist et al, [51][52][53] and others [54][55][56][57][58][59][60][61][62][63] have used SOJT-distorted cations in the design and synthesis of new NCS materials.…”