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A copper(II) complex of the non-symmetric bidentate ligand 2-{[6-(dimethylamino)pyrimidin-4-yl]sulfanyl}pyrimidine-4,6-diamine (L1) is reported. The single-crystal X-ray structure of aqua[aqua/chlorido(0.49/0.51)](2-{[6-(dimethylamino)pyrimidin-4-yl]sulfanyl}pyrimidine-4,6-diamine)copper(II) 0.49-chloride 1.51-hydrate, [CuCl1.51(C10H13N7S)(H2O)1.49]Cl0.49·1.51H2O or [(L1)Cl1.51(H2O)1.49Cu]0.49Cl·1.51H2O, exhibits distorted square-pyramidal geometry around the metal centre, with disorder in the axial position, occupied by chloride or water. The six-membered metal–chelate ring is in a boat conformation, and short intermolecular S...S interactions are observed. In addition to its capacity for bidentate metal coordination, the ligand has the ability to engage in further supramolecular interactions as both a hydrogen-bond donor and acceptor, and multiple interactions with lattice solvent water molecules are present in the reported structure.

The crystal structure of tricaesium citrate monohydrate, 3Cs+·C6H5O73−·H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. This compound is isostructural to the K+ and Rb+ compounds with the same formula. The three independent Cs cations are eight-, eight-, and seven-coordinate, with bond-valence sums of 0.91, 1.22, and 1.12 valence units. The coordination polyhedra link into a three-dimensional framework. The hydroxy group forms the usual S(5) hydrogen bond with the central carboxylate group, and the water molecule acts as a donor in two strong hydrogen bonds.

The crystal structure of dicesium hydrogen citrate, 2Cs+·C6H6O72−, has been solved using laboratory X-ray single-crystal diffraction data, refined using laboratory powder X-ray data, and optimized using density functional techniques. The Cs+ cation is nine-coordinate, with a bond-valence sum of 0.92 valence units. The CsO9 coordination polyhedra share edges and corners to form a three-dimensional framework. The citrate anion is located on a mirror plane. Its central hydroxy/carboxylate O—H...O hydrogen bond is short, and (unusually) intermolecular. The centrosymmetric end-end carboxylate hydrogen bond is exceptionally short (O...O = 2.416 Å) and strong. These hydrogen bonds contribute 16.5 and 21.7 kcal mol−1, respectively, to the crystal energy. The hydrophobic methylene groups occupy pockets in the framework.

The crystal structure of disodium hydrogen citrate sesquihydrate, 2Na2+·C6H6O72−·1.5H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. The asymmetric unit contains two independent hydrogen citrate anions, four sodium cations and three water molecules. The coordination polyhedra of the cations (three with a coordination number of six, one with seven) share edges to form isolated 8-rings. The un-ionized terminal carboxylic acid groups form very strong hydrogen bonds to non-coordinating O atoms, with O...O distances of 2.46 Å.