Radmila Krupková

A new series of 3,5-diamino-1,2,4-triazolium(1+) inorganic salts and their potential in crystal engineering of novel NLO materials

Seven inorganic salts of 3,5-diamino-1,2,4-triazole (dat) with inorganic acids were prepared within our project focused on the crystal engineering of novel NLO materials and their X-ray structures were determined. Three triclinic compounds, dat(1+) selenate dihydrate, dat(1+) sulphate dihydrate and dat(1+) perchlorate, crystallize in the space group P. Three monoclinic structures of dat(1+) – i.e. nitrate, chloride hemihydrate and hydrogen phosphite crystallize in P21/c, P21/n and P21/c, respectively. Finally, the most promising structure of dat(1+) dihydrogen phosphate is orthorhombic (the space group Fdd2). The structure is formed by anionic layers parallel to the ac plane and the cationic chains parallel to the c axis. The FTIR and Raman spectra of the title compounds have been recorded and discussed. The assignment of the spectra is based on a quantum-chemical calculation and the factor group analysis. Quantitative powder measurements of the second harmonic generation of the only non-centrosymmetric dat(1+) dihydrogen phosphate at 1064 nm were performed and a relative efficiency equal to KDP (i.e. potassium dihydrogen phosphate) was observed. The consequent study of single crystal samples enabled the estimation of NLO tensor coefficients of this material.

Semi-organic salts of aniline with inorganic acids: prospective materials for the second harmonic generation

Three novel inorganic salts of aniline with sulfuric and selenic acids were prepared and characterized by X-ray structural analysis. Anilinium(1+) selenate, (C6H5NH3+)2SeO42−, and anilinium sulfate, (C6H5NH3+)2SO42−, crystallize in the monoclinic space groupC2. The crystal structures are based on hydrogen bonded layers of alternating anilinium cations and inorganic anions. Anilinium(1+) selenate dihydrate, (C6H5NH3+)2SeO42−·2H2O, crystallizes in the monoclinic space groupC2/c. The crystal structure is formed by a network of alternating anilinium cations, selenate anions and water molecules connected by a system of intermolecular hydrogen bonds. The FTIR and Raman spectra of all the compounds have been recorded and discussed as well as their crystal structures. According to the DSC curves and temperature dependence of lattice parameters, anilinium sulfate exhibits phase transitions at 217 and 182 K. The appropriate changes of vibrational spectra were also recorded during cooling of the sample especially in the N–H stretching and sulfate antisymmetric stretching (ν3SO42−) spectral regions. The quantitative measurements of the second harmonic generation at 1064 nm were performed using powdered samples of anilinium sulfate, anilinium chloride and anilinium selenate, and the relative efficiencies deff = 0.05dKDP, deff = 2.33dKDP and deff = 0.05dKDP (KDP; i.e.KH2PO4) have been observed, respectively.

Mixed crystals of 2-carbamoylguanidinium with hydrogen fluorophosphonate and hydrogen phosphite in the ratios 1:0, 0.76 (2):0.24 (2) and 0.115 (7):0.885 (7).

The title compounds, 2-carbamoylguanidinium hydrogen fluorophosphonate, C(2)H(7)N(4)O(+)·HFO(3)P(-), (I), 2-carbamoylguanidinium-hydrogen fluorophosphonate-hydrogen phosphite (1/0.76/0.24), C(2)H(7)N(4)O(+)·0.76HFO(3)P(-)·0.24H(2)O(3)P(-), (II), and 2-carbamoylguanidinium-hydrogen fluorophosphonate-hydrogen phosphite (1/0.115/0.885), C(2)H(7)N(4)O(+)·0.115HFO(3)P(-)·0.885H(2)O(3)P(-), (III), are isostructural with guanylurea hydrogen phosphite, C(2)H(7)N(4)O(+)·H(2)O(3)P(-) [Fridrichová, Němec, Císařová & Němec (2010). CrystEngComm, 12, 2054-2056]. They constitute structures where the hydrogen phosphite anion has been fully or partially replaced by hydrogen fluorophosphonate. The title structures are the fourth example of isostructural compounds which differ by the presence of hydrogen fluorophosphonate and hydrogen phosphite or fluorophosphonate and phosphite anions. Moreover, the present study reports structures with these mixed anions for the first time. In the reported mixed salts, the P and O atoms of either anion overlap almost exactly, as can be judged by comparison of their equivalent isotropic displacement parameters, while the P-F and P-H directions are almost parallel. There are strong O-H···O hydrogen bonds between the anions, as well as strong N-H···O hydrogen bonds between the 2-carbamoylguanidinium cations in the title structures. Altogether they form a three-dimensional hydrogen-bond pattern. Interestingly, rare N-H···F interactions are also present in the title structures. Another exceptional feature concerns the P-O(H) distances, which are about as long as the P-F distance. The dependence of P-F distances on the longest P-O distances in FO(3)P(2-) or HFO(3)P(-) is presented. The greater content of hydrogen phosphite in the mixed crystals causes a larger deformation of the cations from planarity.

Ammonium dipotassium hydrogen di­fluoro­phosphate at room temperature

(NH4)0.926K2.074[H(PO3F)2] crystallized from aqueous solution after mixing stoichiometric amounts of (NH4)2PO3F and K2PO3F in a 1:1 ratio. The structure contains two sites that are occupied by symmetry-independent cations; one site is occupied by potassium and ammonium in an approximate 1:1 ratio, while the other cation site is occupied exclusively by K. The anions are connected by a very short symmetry-restricted O⋯H⋯O hydrogen bond (∼2.47 A) into pairs [H(PO3F)2]3−. Ammonium is connected to anion O atoms by two- and three-centred N—H⋯O hydrogen bonds. Fluorines do not take part in the hydrogen-bond pattern.

PbTiO3 SrTiO3, and PbTiO3-Al2O3 composite and multilayer films prepared by sol-gel technique

Abstract PbTiO3 and SrTiO3 single phase films and PbTiO3−Al2O3 composite and multilayer films were prepared by the sol-gel method using dip- and spincoating deposition techniques. The films were characterized by optical microscopy. X-ray diffractometry, Alpha Step profilometer, Rutherford back-scattering and Fourier transform far infrared spectroscopy. It was found that the presence of Al2O3 in composite films blocks the PbTiO3 crystallization even at the temperature 800°C whereas in multilayer films the crystallization is retarded to a certain extent only. FT FIR spectroscopy has revealed in PbTiO3 films the well-pronounced soft mode at frequency 82cm−1 slightly lower than in bulk crystals which indicates some compressive internal stresses. In SrTiO3 films the effective soft mode damping increases with decreasing film thickness, which demonstrates the role of stresses induced by the substrate.

Tris(2-carbamoylguanidinium) hydrogen fluoro­phospho­nate fluoro­phospho­nate monohydrate

The title structure, 3C2H7N4O+·HFPO3 −·FPO3 2−·H2O, contains three independent 2-carbamoylguanidinium cations, one fluorophosphonate, one hydrogen fluorophosphonate and one water molecule. There are three different layers in the structure that are nearly perpendicular to the c axis. Each layer contains a cation and the layers differ by the respective presence of the water molecule, the hydrogen fluorophosphonate and fluorophosphonate anions. N—H⋯O hydrogen bonds between the guanylurea molecules that interconnect the molecules within each layer are strong. The layers are interconnected by strong and weak O—H⋯O hydrogen bonds between the anions and water molecules, respectively. Interestingly, the configuration of the layers is quite similar to that observed in 2-carbamoylguanidinium hydrogen fluorophosphonate [Fábry et al. (2012). Acta Cryst. C68, o76–o83]. There is also present a N—H⋯F hydrogen bond in the structure which occurs quite rarely.

Two polymorphs of bis(2-carbamoylguanidinium) fluorophosphonate dihydrate.

Two polymorphs of bis(2-carbamoylguanidinium) fluorophosphonate dihydrate, 2C(2)H(7)N(4)O(+)·FO(3)P(2-)·2H(2)O, are presented. Polymorph (I), crystallizing in the space group Pnma, is slightly less densely packed than polymorph (II), which crystallizes in Pbca. In (I), the fluorophosphonate anion is situated on a crystallographic mirror plane and the O atom of the water molecule is disordered over two positions, in contrast with its H atoms. The hydrogen-bond patterns in both polymorphs share similar features. There are O-H···O and N-H···O hydrogen bonds in both structures. The water molecules donate their H atoms to the O atoms of the fluorophosphonates exclusively. The water molecules and the fluorophosphonates participate in the formation of R(4)(4)(10) graph-set motifs. These motifs extend along the a axis in each structure. The water molecules are also acceptors of either one [in (I) and (II)] or two [in (II)] N-H···O hydrogen bonds. The water molecules are significant building elements in the formation of a three-dimensional hydrogen-bond network in both structures. Despite these similarities, there are substantial differences between the hydrogen-bond networks of (I) and (II). The N-H···O and O-H···O hydrogen bonds in (I) are stronger and weaker, respectively, than those in (II). Moreover, in (I), the shortest N-H···O hydrogen bonds are shorter than the shortest O-H···O hydrogen bonds, which is an unusual feature. The properties of the hydrogen-bond network in (II) can be related to an unusually long P-O bond length for an unhydrogenated fluorophosphonate anion that is present in this structure. In both structures, the N-H···F interactions are far weaker than the N-H···O hydrogen bonds. It follows from the structure analysis that (II) seems to be thermodynamically more stable than (I).

Bis(ammonium) fluorophosphate at room temperature

The title room-temperature phase of (NH(4))(2)(PO(3)F) is orthorhombic (Pna2(1)) and is related to the beta-K(2)SO(4) structure family. The title structure consists of ammonium cations, NH(4)(+), and fluorophosphate anions, (PO(3)F)(2-). These ions are connected by N-H.O hydrogen bonds. Two-centre N-H.F hydrogen bonds are not present in the structure. Phase transitions were detected at 251+/-2 and 274+/-2 K during cooling and heating, respectively.

Dependences of Space-Group Type Incidences of Organic and Metal-Organic Compounds on Reduced Unit-Cell Volumes

The dependences of occurrences of the most frequent space-group types P, P2 1 , P2 1 /c, C2/c, P2 1 2 1 2 1 and Pbca on reduced (primitive) unit-cell volumes up to 8000 Å3 were investigated for organic and metal-organic compounds with different number of residues (1–3), i.e. for the compounds with different number of molecular constituents. The dependences for these space-group types are similar, single-peaked; their maxima are proportional to the number of asymmetric units (a compact symmetry-independent part of the unit cell) affected by Z′ (number of formula units per asymmetric unit) in the pertinent space-group types. The dependences of Z′ < 1, Z′ = 1, Z′ > 1 within each space group type on reduced unit-cell volumes are also similar in shape. From these dependences it can be inferred that ability for crystallization of organic and metal-organic molecules ceases for the structures with the reduced unit-cell volumes above 8000 Å 3 . This volume corresponds roughly to 450 non-hydrogen atoms.

Tris(methylammonium) hydrogenphosphate dihydrogenphosphate

The title compound, 3CH6N+.HPO4(2-).H2PO4-, aggregates with the moieties interconnected by O-H...O and N-H...O hydrogen bonds, with O...O and N...O distances in the ranges 2.5366 (16)-2.5785 (14) and 2.7437 (16)-2.9967 (18) A, respectively. Three C-H...O hydrogen bonds are also present, with C...O distances in the range 3.2310 (18)-3.3345 (17) A. All H atoms are ordered. Structures with ordered hydrogenphosphate and dihydrogenphosphate components are rare.