l-Tryptophan 4-nitro-phenol tris-olvate.

The title compound, C(11)H(12)N(2)O(2)·3C(6)H(5)NO(3), comprises a zwitterionic amino acid formed by two nearly planar groups: (i) the indole ring and Cß, and (ii) the carboxyl group, Cα, as well as the amine N atom, with r.m.s. deviations of 0.0084 and 0.0038 Å, respectively. The angle between these idealized planes is 39.47 (9)°. The amine group of the amino acid is in a syn (-sc) arrangement relative to the ring system. The overall crystal structure results from the packing of sheets parallel to the (001) planes. These sheets are formed by a pair of screw axis related parallel networks bound by hydrogen-bond and π-π stacking interactions. The intermolecular cohesion of all organic residues in each of the latter two-dimensional networks is achieved via strong hydrogen bonding, nitro-π and π-π stacking interactions.

2-Amino-5-nitro-pyridinium tetraoxido-rhenate(VII) monohydrate.

All the residues of the title compound, (C(5)H(6)N(3)O(2))[ReO(4)]·H(2)O, are located on general crystallographic positions. The 2-amino-5-nitro-pyridinium cation has a typical planar conformation with one of the nitro O atoms -0.058 (5) Šout of plane; the amine H atoms are also a little out of the main ring plane towards the opposite side of the aforementioned O atom [by 0.02 (4) and 0.04 (4) Å]. The perrhenate anion is nearly ideally tetra-hedral. Three distinct N-H⋯O hydrogen bonds give rise to C(8) zigzag chains running along [100]. R(4) (4)(12) rings involving the two hydrogen bonds in which the water mol-ecules inter-act with the perrhenate anions are also present.

Bis[glycinium(0.5+)] perrhenate.

All the residues of the title compound, (C(2)H(5.5)NO(2))(2)[ReO(4)], are located in general crystallographic positions. The glycine mol-ecules have usual conformations [Rodrigues Matos Beja et al. (2006 ▶). Acta Cryst. C62, o71-o72] with the H atom of the carboxylate group half-occupied, thus bearing a formal half-positive charge per molecule. The perrhenate anion has nearly ideal tetra-hedral geometry. A large number of strong hydrogen bonds give rise to the overall three-dimensional network. A two-dimensional network, parallel to (100), is made up of strong O-H⋯O hydrogen bonds with a donor acceptor distance of 2.445 (2) Å. A large number of weaker O-H⋯O and N-H⋯O hydrogen bonds consolidates the structure into an overall three-dimensional network.

2,2,6,6-Tetramethyl-4-oxopiperidinium nitrate.

In the title compound, C(9)H(18)NO(+).NO(3)(-), the piperidinium ring adopts a slightly deformed chair conformation and the nitrate anion is disordered. The ions are arranged in hydrogen-bonded chains parallel to [001], in which the cations alternate with the anions. The intrachain hydrogen bonds are bifurcated and link the O atoms of the anions to the N atoms of the cations.

L-Phenylalanine-4-nitrophenol (1/1).

In the 1:1 adduct formed between L-phenylalanine and 4-nitrophenol [alternative IUPAC name: (2S)-2-ammonio-3-phenylpropanoate-4-nitrophenol (1/1)], C9H11NO2.C6H5NO3, the L-phenylalanine molecule is in the zwitterionic state. The overall structure is stabilized via strong hydrogen bonding between polar zones and van der Waals interactions between non-polar zones, which alternate with the polar zones.

Supramolecular structure and second harmonic generation in strontium bis(hydrogen L-malate) hexahydrate.

The title compound, tetraaquabis(hydrogen L-malato)strontium(II) dihydrate, [Sr(C4H5O5)2(H2O)4].2H2O, is a new non-linear optical semi-organic material with a second harmonic generation efficiency approximately 3.5 times greater than that of potassium dihydrogen phosphate. The malate anions are interconnected through directional O-H...O hydrogen bonding, in a head-to-tail arrangement, creating extended anionic chains along [001]. Neighbouring parallel chains are crosslinked by water molecules, resulting in a three-dimensional architecture. The Sr2+ ion is coordinated by eight O atoms. This material is a new candidate for non-linear optical applications since the crystals are stable and easy to grow.

Glycinium trichloroacetate.

The title compound, C2H6NO2+.C2Cl3O2-, crystallizes in the P4(1) space group with two glycinium cations and two trichloroacetate anions in the asymmetric unit. The glycinium cations have nearly Cs point-group symmetry which is only broken by the H atoms of the amine group. The trichloroacetate anions show typical bond lengths and angles, one of the trichloromethyl groups being disordered. Chains of alternating anions and cations run along the c axis. Within these chains, consecutive anion-cation pairs are bound via strong hydrogen bonds involving the carboxylate anions and the carboxyl or amine groups of the cations. Weaker hydrogen bonds bind neighbouring chains together.

Glycinium trifluoroacetate.

In the title compound, C(2)H(6)NO(2)(+).C(2)F(3)O(2)(-), the main N-C-COOH skeleton of the glycinium cation is almost perfectly planar. The trifluoroacetate anion has a staggered conformation with typical bond distances and angles. The CF(3) group is slightly disordered. The structure is stabilized by an extensive network of strong O-H.O hydrogen bonds and weaker N-H.O bonds.