Acta Crystallographica Section C

Crystal Structure Communications

Volume 62, Part 7 (July 2006)

organic compounds

 

Two crystals of doubly protonated melaminium salts: melaminium bis(trifluoroacetate) trihydrate and melaminium bis(trichloroacetate) dihydrate

G. J. Perpétuo and J. Janczak

Abstract: Crystals of 2,4,6-triamino-1,3,5-triazine-1,3-dium bis(trifluoroacetate) trihydrate, C₃H₈N₆²⁺·2CF₃COO^-·3H₂O, and 2,4,6-triamino-1,3,5-triazine-1,3-dium bis(trichloroacetate) dihydrate, C₃H₈N₆²⁺·2CCl₃COO^-·2H₂O, both contain doubly protonated melamine rings that lie on crystallographic twofold axes. In the former structure, one water molecule also lies on a twofold axis. While the trifluoroacetate compound crystallizes in a centrosymmetric space group, the trichloroacetate is non-centrosymmetric, so it is useful as a material for non-linear optics. The efficiency of second harmonic generation is about three times greater than that of KDP (KH₂PO₄). A combination of ionic and donor-acceptor hydrogen-bond interactions link the melaminium(2+) residues with trifluoroacetate or trichloroacetate ions and water molecules to form a three-dimensional network.

Formula: C₃H₈N₆²⁺·2C₂F₃O₂^-·3H₂O and C₃H₈N₆²⁺·2C₂Cl₃O₂^-·2H₂O

	Structure factor file (CIF format) (102.1 kbytes) [ doi:10.1107/S0108270106015873/fa3013Isup2.hkl ] Contains datablock I
	Structure factor file (CIF format) (109.6 kbytes) [ doi:10.1107/S0108270106015873/fa3013IIsup3.hkl ] Contains datablock c2

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