Tris(5-amino-1H-1,2,4-triazol-4-ium) dihydrogenphosphate hydrogenphosphate trihydrate

In the crystal structure of the title molecular salt, 3C2H5N4 +·HPO4 2−·H2PO4 −·3H2O, the phosphate-based framework is built upon layers parallel to (010) made up from the H2PO4 − and HPO4 2− anions and water molecules, which are interconnected through O—H⋯O hydrogen bonds. The organic cations are located between the phosphate–water layers and are connected to them via N—H⋯O hydrogen bonds. The bond-length features are consistent with an imino resonance form for the exocyclic amino group, as is commonly found for a C—N single bond involving sp 2-hybridized C and N atoms.

In the crystal structure of the title molecular salt, 3C 2 H 5 N 4 + Á-HPO 4 2À ÁH 2 PO 4 À Á3H 2 O, the phosphate-based framework is built upon layers parallel to (010) made up from the H 2 PO 4 À and HPO 4 2À anions and water molecules, which are interconnected through O-HÁ Á ÁO hydrogen bonds. The organic cations are located between the phosphate-water layers and are connected to them via N-HÁ Á ÁO hydrogen bonds. The bond-length features are consistent with an imino resonance form for the exocyclic amino group, as is commonly found for a C-N single bond involving sp 2 -hybridized C and N atoms.
Their abilities to combine the rigidity and high cohesion of inorganic host matrices with the enhanced polarizability of organic guest chromophores within one molecular scale assists in better performance of optical signal-processing devices.
The use of organic-inorganic polar crystalline materials for quadratic nonlinear optical applications is supported by two observations: (i) the organic molecules, especially if they contain a delocalized π-system with asymmetric substitution by electron donor-acceptor groups, are highly polarizable entities idealy suited for NLO applications. Being organic materials, the nature of the substituents can be tailored so as to not affect optical transparency; (ii) the ionic inorganic host matrices are able to increase the packing cohesion, can induce noncentrosymmetry, and also shift the transparency of crystal towards blue wavelengths.
Within a systematic investigation of new materials resulting from the association of organic chromophores with inorganic species, we report here the synthesis and the characterization of a new hybrid phosphate-amine material, (C 2 H 5 N 4 ) 3 (HPO 4 )(H 2 PO 4 ).3H 2 O, which includes the 3-amino-1H-1,2,4-triazolium cations, a chromophore which could be efficient in the blue-U.V. wavelength region. The title compound could exhibit a richness of interesting physical properties such as ferroelectricity and nonlinear optic phenomena like second harmonic generation. It crystallizes in a non-centrosymmetric setting in the space group Pc. The structure of this organic-inorganic hybrid material consists of one dihydrogenmonophosphate anion, one monohydrogenmonophosphate dianion, three crystallographically independent 3amino-1H-1,2,4-triazolium cations and three water molecules (Fig. 1). The atomic arrangement is a typical layered organization as it is very often encountered in this kind of inorganic-organic hybrid compounds (Kaabi et al., 2004). The H 2 PO 4anions are hydrogen bonded with the HPO 4 2groups and one of the water molecules (that of O3) to form corrugated chains running parallel to the a-axis at (0, 0, 0) and (0, 0, 1/2). These chains are interconnected, via O(water) -H···O and O-H···O(water) hydrogen bonds, with the two remaining water molecules H 2 O(1) and H 2 O(2), associated through O1-H···O2 hydrogen bonds, on one hand, and with the HPO 4 2anions of the adjacent chain, trough O-H···O hydrogen bonds, on the other hand. These hydrogen bonds link the different inorganic units into infinite planar layers parallel to the (0 1 0) plane ( Fig. 2) crossing the unit cell at y = (2n +1)/2 (Fig. 3). Within the layers, various graph-set motifs (Bernstein et al., 1995) are apparent, including R 5 5 (10) and R 4 4 (12) loops. The 3-amino-1H-1,2,4-triazolium cations are interconnected via weak N-H···N hydrogen bonds, with D-H···A distances between 3.003 (1) and 3.064 (1) supplementary materials sup-2 Acta Cryst. (2012). E68, o3257-o3258 Å, to form organic chains spreading along the c-axis at x ~ (n + 1)/3 (Fig. 4). The chains are build from the three crystallographically independent organic cations, labelled A, B and C, in such a way that each N-H···N connected chain incorporates only one type of cation: Molecules of type A are located at x ~1/3, chains at x ~ 0 consist of molecules of type B, and the chains at x~2/3 are made up of molecules C. Alternating molecules in each of these chains are created by the c-glide plane. In two of the chains, that of molecules A and C, alternating molecules are roughly coplanar. In the third, molecules are twisted against each other by an angle of 34.37°. The chains are roughly parallel to each other and weakly π-stacked, with interplanar distances between the mean planes of chains between 3.21 Å (between A and C), and up to 3.52 Å (for A and B). Despite of the quite close interplanar distances, π-π stacking interactions are limited due to molecule offsets in parallel layers, and the non-coplanarity of neighboring molecules in the chains of molecules B. The organic chains are anchored to the inorganic layers through N-H···O hydrogen bonds whose geometrical characteristics are given in Table 2. The projection of the whole arrangement along the a-axis (Fig. 4) shows how the organic chains alternate as to fill the space separating parallel inorganic layers. In this structure, three 3-amino-1H-1,2,4-triazolium cationic groups compensate the negative charges of the dihydrogenmonophosphate and the monohydrogenmonophosphate anions, leading to charge neutrality for the structure as a whole.
The sum of the angles around the N1A, N1B and N1C nitrogen atoms are 360° and the C-N bond distances of the NH 2 groups are 1.332 (1) Å for N1A-C1A, 1.327 (1) Å for N1B-C1B and 1.330 (1) Å for N1C-C1C, which are short for C-N single bonds, but still not quite as contracted as one would expect for a fully established C=N double bond. These bond length features are consistent with an imino resonance form as it is commonly found for a C-N single bond involving sp 2 hybridized C and N atoms (Shanmuga Sundara Raj et al., 2000). In agreement with this, the amino groups are not pyramidal but the electron densities of the hydrogen atoms of the amino groups were found to be in plane with the 3-amino-1H-1,2,4-triazolium skeleton. The detailed geometry of the HP (1 A     Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.