Compounds containing copper(I) are of interest for their role in biological processes. The nature of short (< ∼3.2 Å) Cu...Cu contacts within these compounds has been debated, being either described as weakly attractive (bonding) `cuprophilic' interactions, or simply as short metal–metal distances constrained by ligand geometry or largely ionic in nature. The title three-dimensional Cu<sup>+</sup>-containing coordination polymer, [Cu<sub>3</sub>(C<sub>7</sub>H<sub>7</sub>N<sub>2</sub>O<sub>2</sub>)Cl<sub>2</sub>]<sub>n</sub>, was formed from the in situ reduction of CuCl<sub>2</sub> in the presence of 3,5-diaminobenzoic acid and KOH under hydrothermal conditions. Its complex crystal structure contains ten distinct Cu<sup>I</sup> atoms, two of which lie on crystallographic inversion centres. The copper coordination geometries include near-linear CuOCl and CuN<sub>2</sub>, T-shaped CuOCl<sub>2</sub> and distorted tetrahedral CuOCl<sub>3</sub> groups. Each Cu<sup>I</sup> atom is also associated with two adjacent metal atoms, with Cu...Cu distances varying from 2.7350 (14) to 3.2142 (13) Å; if all these are regarded as `cuprophilic' interactions, then infinite [01] zigzag chains of Cu^I atoms occur in the crystal. The structure is consolidated by N—H...Cl hydrogen bonds.

Oxazolidin-2-ones are widely used as protective groups for 1,2-amino alcohols and chiral derivatives are employed as chiral auxiliaries. The crystal structures of four differently substituted oxazolidinecarbohydrazides, namely N′-[(E)-benzylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C₁₂H₁₂N₃O₃, (I), N′-[(E)-2-chlorobenzylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C₁₂H₁₂ClN₃O₃, (II), (4S)-N′-[(E)-4-chlorobenzylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C₁₂H₁₂ClN₃O₃, (III), and (4S)-N′-[(E)-2,6-dichlorobenzylidene]-N,3-dimethyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C₁₃H₁₃Cl₂N₃O₃, (IV), show that an unexpected mild-condition racemization from the chiral starting materials has occurred in (I) and (II). In the extended structures, the centrosymmetric phases, which each crystallize with two molecules (A and B) in the asymmetric unit, form A+B dimers linked by pairs of N—H...O hydrogen bonds, albeit with different O-atom acceptors. One dimer is composed of one molecule with an S configuration for its stereogenic centre and the other with an R configuration, and possesses approximate local inversion symmetry. The other dimer consists of either R,R or S,S pairs and possesses approximate local twofold symmetry. In the chiral structure, N—H...O hydrogen bonds link the molecules into C(5) chains, with adjacent molecules related by a 2₁ screw axis. A wide variety of weak interactions, including C—H...O, C—H...Cl, C—H...π and π–π stacking interactions, occur in these structures, but there is little conformity between them.

The syntheses and characterisation of a new family of isostructural mixed-metal selenites based on the zemannite-type framework are described. These BaM₂(SeO₃)₃·3H₂O phases are built up from three-dimensional networks of MO₆ (M = Co, Ni, Mn, Mg) octahedra and SeO₃ pyramids. The octahedral groups form isolated M₂O₉ face-sharing pairs, which are linked by the selenite anions into a three-dimensional anionic framework. The framework encapsulates one-dimensional 12-ring channels occupied by the barium cations and water molecules. There are two types of channels: in one, the cations and water molecules are well ordered, and the channels are fully occupied; in the other, the same species are disordered, and the channels are partially occupied. There is little if any evidence of zeolitic reversible de/rehydration and cation ion-exchange behaviour for these materials.