Noncentrosymmetry in New Templated Gallium Fluorophosphates

Two new noncentrosymmetric polar gallium fluorophosphates have been synthesized under mild hydrothermal conditions through the use of enantiomorphically pure sources of either R-2-methylpiperazine or S-2-methylpiperazine. A centrosymmetric analogue was also prepared using a racemic source of the amine. Novel [Ga3F(PO4)(4)](n)(4n-) layers, constructed from [Ga3O3F(PO4)(4)] building units, are observed in all three compounds. The use of racemic 2-methylpiperazine results in crystallographic disorder of the amines and creation of inversion centers, while using a single enantiomer destroys the inversion symmetry and orders the amines. Second harmonic generation measurements were performed on [(R)-C5H14N2](2)[Ga3F(PO4)(4)]center dot 5.5H(2)O and [(S)-C5H14N2](2)[Ga3F(PO4)(4)]center dot 4.75H(2)O, both of which display type 1 phase-matching capabilities and exhibit activities of similar to 50 x alpha-SiO2. The structures of these compounds were determined using single crystal X-ray diffraction, infrared spectroscopy, and thermal analyses. [C5H14N2](2)[Ga3F(PO4)(4)]center dot 5.25H(2)O, a = 13.0863(5). angstrom, c = 9.9023(4) angstrom, trigonal, P-3 (No. 147), Z = 2; [(R)- C5H14N2](2)[Ga3F(PO4)(4)]center dot 5.5H(2)O, a = 13.0887(2), angstrom, c = 29.9439(4) angstrom, trigonal, P3(1) (No. 144), Z = 6; [(S)- C5H14N2](2)[Ga3F(PO4)(4)]center dot 4.75H(2)O, a = 13.0871(2) angstrom, c = 29.8350(6) angstrom, trigonal, P3(2) (No. 145), Z = 6.