R. V. Krishnakumar

L-Prolinium tartrate

In the title salt, C(5)H(10)NO(2)(+).C(4)H(5)O(6)(-), proline exists as a cation and the tartaric acid as a semi-tartrate anion. The semi-tartrate ions form hydrogen-bonded strings along the c axis. These strings are interconnected through the proline molecules, forming a layered network parallel to the bc plane. The proline molecules, however, do not directly interact among themselves, except for a weak C-H.O hydrogen bond.

catena-Poly­[[cadmium(II)]-μ-β-alanine-di-μ-chloro]

In the title compound, [CdCl2(C3H7NO2)]n, the β-alanine residues exist in the zwitterionic form. The Cd atoms are coordinated by four Cl atoms and two O atoms, forming a distorted octahedral environment. These octahedra are linked through Cl—Cl edges and are bridged by the carboxyl groups of the β-alanine residues, to form a one-dimensional polymer chain that extends along [100].

dl‐Phenyl­alaninium maleate at 123 K

In the title compound, C9H12NO2+.C4H3O4-, the amino acid molecule exists in the cationic form with a positively charged amino group and an uncharged carboxylic acid group. The maleic acid molecules exits in the mono-ionized state. In the semi-maleate anion, the intramolecular O-H...O hydrogen bond is asymmetric. The phenylalaninium cations and the semi-maleate anions form hydrogen-bonded double layers, linked together by N-H...O and O-H...O hydrogen bonds, extending along 101].

Bis(dl‐serinium) oxalate dihydrate

# 2002 International Union of Crystallography Printed in Great Britain ± all rights reserved In the title compound, 2C3H8NO3 + .C2O4 2H2O, the serine molecule exists in the cationic form with an uncharged carboxylic acid group and a positively charged amino group. The oxalic acid molecule exists as a double negatively charged oxalate anion. Two independent oxalate anions lie across inversion centres. The aggregation of individual molecules differs distinctly from other similar complexes.

l‐Leucinium oxalate

In the title compound, C6H14NO2+.C2HO4-, the leucine molecule exists in the cationic form, with a protonated amino group and an uncharged carboxylic acid group. Oxalic acid exists in the mono-ionized state. Pseudo-inversion centres relate the leucinium cations and semi-oxalate anions. The leucinium and semi-oxalate ions form hydrogen-bonded, double-layered chains, extending parallel to the b axis. The leucinium cations are arranged in these double layers on opposite sides leading to alternating hydrophobic and hydrophilic layers.

dl‐Valine‐fumaric acid (2/1)

In the title compound, C5H11NO2.0.5C(4)H(4)O(4), the valine molecule exists as a zwitterion and the fumaric acid molecule in the unionized state, forming an adduct, a feature uncommon in similar crystal structures. The fumaric acid molecule has a centre of symmetry and is planar with a trans configuration about the central C=C bond. The fumaric acid molecules have no hydrogen-bonded interactions among themselves and only mediate interactions between DL-valine layers, leading to a three-dimensional network of molecules.

Syntheses and characterisation of amide adducts of uranyl bis (β-diketonates) the molecular structure of [UO2(DBM)2.C4H9CON(3-C5H11)(sec-C4H9)]

The first structurally characterised uranyl bis (β-diketonate)-amide adduct compound [UO2(DBM)2. C4H9CON (3-C5H11) (sec-C4H9)] (DBM = dibenzoylmethanate) shows that the amide ligand bonded through its amido oxygen atom to the uranyl group. The average bond distances for U–O(uranyl), U–O(DBM) and U–O(amide) are 1.778(5), 2.346(5) and 2.411(5)Å respectively.

Racemic 1-Acetyl-5-phenyl-3-styryl-2-pyrazoline

The asymmetric unit of the racemic title compound, C19H18N2O, contains two enantiomeric molecules of the pyrazoline, differing in the configuration at C3. All the rings in the molecules are essentially planar.

1′-Benzylspiro­[chromene-2,4′-piperi­dine]-4-carbonitrile

In the title compound, C21H20N2O, the piperidine ring adopts a chair conformation while the pyran ring adopts a screw-boat conformation. The piperidine ring forms dihedral angles of 65.75 (3) and 67.79 (5)° with the chroman and methyl-substituted benzene rings, respectively. The crystal structure features weak C—H⋯π and π–π [centroid–centroid distance = 3.8098 (8) Å] interactions.

Isomorphous methyl- and chloro-substituted small heterocyclic analogues obeying the chlorine–methyl (Cl–Me) exchange rule

The two new isomorphous structures [3-methyl-4-(4-methylphenyl)-1-phenyl-6-trifluoromethyl-1H-pyrazolo[3,4-b]pyridin-5-yl](thiophen-2-yl)methanone, C26H18F3N3OS, (I), and [4-(4-chlorophenyl)-3-methyl-1-phenyl-6-trifluoromethyl-1H-pyrazolo[3,4-b]pyridin-5-yl](thiophen-2-yl)methanone, C25H15ClF3N3OS, (II), are shown to obey the chlorine-methyl exchange rule. Both structures show extensive disorder, treatment of which greatly improves the quality of the description of the structures. In addition, it is worth noting that the presence of extensive disorder may make it difficult to detect the isomorphism automatically during data-mining procedures (such as searches of the Cambridge Structural Database).