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The transformation processes of non-solvated ibrutinib into a series of halogenated benzene solvates are explored in detail here. The transformation was studied in real time by X-ray powder diffraction in a glass capillary. Crystal structures of chlorobenzene, bromobenzene and iodobenzene solvates are isostructural, whereas the structure of fluorobenzene solvate is different. Four different mechanisms for transformation were discovered despite the similarity in the chemical nature of the solvents and crystal structures of the solvates formed. These mechanisms include direct transformations and transformations with either a crystalline or an amorphous intermediate phase. The binding preference of each solvate in the crystal structure of the solvates was examined in competitive slurry experiments and further confirmed by interaction strength calculations. Overall, the presented system and online X-ray powder diffraction measurement provide unique insights into the formation of solvates., (open access.)

The structure-property relations are examined for apremilast cocrystals and solvates in this work. A unique and large dataset of multicomponent crystal forms is presented including 7 cocrystals and 12 solvates. In total, 15 of the presented multicomponent forms and their crystal structures are published here for the first time. This dataset is unique owing to the extreme crystal packing similarity of all 19 crystal forms. This fact makes the evaluation of structure-property relations significantly easier and more precise since the differences in the crystal lattice arrangement are close to negligible. Properties of the guest molecules used here can be directly correlated with the macroscopic properties of the corresponding multicomponent forms. Interestingly, a considerable correlation was found between the intrinsic dissolution rate of the multicomponent forms and their solubility, as well as the solubility of their guest molecules in the dissolution medium. The latter is of particular interest as it can aid in the design of multicomponent forms with tuned properties., (© Jan Jirat et al. 2022.)

The structure determinations of phases (II) and (III) of barium dicalcium hexakis(propanoate) {or poly[hexa-μ 4 -propanoato-bariumdicalcium], [BaCa 2 (C 3 H 5 O 2 ) 6 ] n } are reported at 240 and 130 K, respectively [phase (I) was determined previously by Stadnicka & Glazer (1980). Acta Cryst. B36, 2977-2985; our structure determination of phase (I) at room temperature is included in the supporting information]. In the high-temperature phase, the Ba 2+ cation is surrounded by six carboxylate groups in bidentate bridging modes. In the low-temperature phases, five carboxylate groups act in bidentate bridging modes and one acts in a monodentate bridging mode around Ba 2+ . The Ca 2+ cations are surrounded by six carboxylate O atoms in a trigonal antiprism in all the structures. The Ba 2+ and Ca 2+ cations are underbonded and significantly overbonded, respectively, in all the phases. The bonding of the Ba 2+ cation increases slightly at the cost of the bonding of Ca 2+ cations during cooling to the low-temperature phases. The phase transitions during cooling are accompanied by ordering of the ethyl chains. In room-temperature phase (I), all six ethyl chains are positionally disordered over two positions in the crossed mode, with additional splitting of the ethyl α- and β-C atoms. In phase (II), on the other hand, there are three disordered ethyl chains, one with positionally disordered ethyl α- and β-C atoms, and the other two with positionally disordered ethyl β-C atoms only, and in the lowest-temperature phase (III) there are four ordered ethyl chains and two disordered ethyl chains with positionally disordered ethyl β-C atoms only.

The crystal structures of two single-enantiomer amidophosphoesters with an (O) 2 P(O)(N) skeleton and one single-enantiomer phosphoric triamide with an (N) 2 P(O)(N) skeleton were studied. The compounds are diphenyl [(R)-(+)-α-4-dimethylbenzylamido]phosphate, (I), and diphenyl [(S)-(-)-α-4-dimethylbenzylamido]phosphate, (II), both C 21 H 22 NO 3 P, and N-(2,6-difluorobenzoyl)-N',N''-bis[(R)-(+)-α-ethylbenzyl]phosphoric triamide, C 25 H 28 F 2 N 3 O 2 P, (III). The asymmetric units contain two amidophosphoester molecules for (I) and (II), and one phosphoric triamide molecule for (III). In the crystal structures of (I) and (II), molecules are assembled in a similar one-dimensional chiral ribbon architecture, but with almost a mirror-image relationship with respect to each other through N-H...O(P) and C-H...O(P) hydrogen bonds along [010]. In the crystal structure of (III), the chiral tape architecture along [100] is mediated by N-H...O(P) and N-H...O(C) hydrogen bonds, and the tapes are connected into slabs by C-H...O interactions (along the ab plane). The differences/similarities of the two diastereotopic phenoxy groups in (I)/(II) and the two chiral amine fragments in (III) were studied on the grounds of geometry, conformation and contribution to the crystal packing, as well as 1 H and 13 C signals in a solution NMR study.

The conformational flexibilities are studied in two new organotin(IV) complexes, namely, trans-dichloridodimethylbis[N,N',N''-tris(2-chlorobenzyl)phosphoric triamide]tin(IV), [Sn(CH 3 ) 2 (C 21 H 21 Cl 3 N 3 OP) 2 Cl 2 ] or Sn(CH 3 ) 2 Cl 2 {OP[NHCH 2 C 6 H 4 (2-Cl)] 3 } 2 , (I), and bis(dipropylammonium) tetrachloridodimethylstannate(IV), [(CH 3 CH 2 CH 2 ) 2 NH 2 ] 2 [Sn(CH 3 ) 2 Cl 4 ], (II), and their analogous structures from the Cambridge Structural Database (CSD). The conformations are considered based on the N-P=O-Sn torsion angles for (I) and the C-C-C-N, C-C-N-C, C-N-C-C and N-C-C-C torsion angles for the two symmetry-independent [CH 3 CH 2 CH 2 NH 2 CH 2 CH 2 CH 3 ] + cations in (II), and the ±ac±sp±ac (ac = anticlinal and sp = synperiplanar) and ±ap±ap±ap±ap (ap = antiperiplanar) conformations are observed, respectively. In both structures, the four atoms in the corners of the square-planar segment of the octahedral shape around the Sn atom participate in normal hydrogen-bonding interactions as acceptors, which include two O and two Cl atoms for (I), and four Cl atoms for (II). However, the phosphoric triamide ligands block the environment around the Sn atom and limit the hydrogen-bond pattern to form a supramolecular ribbon assembly, while in the presence of small organic cations in (II), a two-dimensional hydrogen-bonded architecture is achieved. The weak interactions π-π, C-H...π and C-Cl...π in (I), and C-H...Cl in (II) do not change the dimensionality of the hydrogen-bond pattern. The 62 CSD structures analogous to (I), i.e. with an SnOPN 3 segment (including 83 entries) fall into four categories of conformations based on the N-P=O-Sn torsion angles. The 132 [(CH 3 CH 2 CH 2 ) 2 NH 2 ] + cations from 85 CSD structures are classified into seven groups based on the torsion angles noted for (II). Most of the CSD structures adopt the same associated conformations noted for (I) and (II). 15 [Sn(CH 3 ) 2 Cl 4 ] 2- anions extracted from the CSD are compared with the structure of (II).

The crystal structure, Hirshfeld surface analysis and spectroscopic analysis of a new polyoxometalate (POM) compound, namely, nonakis(2-methoxyaniline) bis(diphosphopentamolybdate) trihydrate, (C 7 H 9 NO) 9 [P 2 Mo 5 O 23 ] 2 ·3H 2 O, is reported. The title compound was synthesized using the solution method and was structurally characterized by single-crystal X-ray diffraction, which revealed P-1 symmetry. A study of the intermolecular interactions using Hirshfeld surface analysis confirmed that the hydrogen-bonding interactions play the dominant role in the stability of the crystal structure. The refinement was complicated by extensive disorder affecting 11 of the 16 ions and molecules in the asymmetric unit. IR and UV-Vis spectroscopic techniques were used to identify the vibrational modes and to classify this compound as an insulator.

Two new N-oxide compounds, namely glycinium 2-carboxy-1-(λ 1 -oxidaneyl)-1λ 4 -pyridine-6-carboxylate-glycine-water (1/1/1), C 2 H 6 NO 2 + ·C 7 H 4 NO 5 - ·C 2 H 5 NO 2 ·H 2 O or [(2,6-HpydcO)(HGLY)(GLY)(H 2 O)], 1, and methyl 6-carboxy-1-(λ 1 -oxidaneyl)-1λ 4 -pyridine-2-carboxylate, C 8 H 7 NO 5 or 2,6-HMepydcO, 2, were prepared and identified by elemental analysis, FT-IR, Raman spectroscopy and single-crystal X-ray diffraction. The X-ray analysis of 1 revealed an ionic compound containing a 2,6-HpydcO - anion, a glycinium cation, a neutral glycine molecule and a water molecule. Compound 2 is a neutral compound with two independent units in its crystal structure. In addition to the hydrogen bonds, the crystal network is stabilized by π-π stacking interactions of the types pyridine-carboxylate and carboxylate-carboxylate. The thermodynamic stability and charge-distribution patterns for isolated molecules of 2,6-H 2 pydcO and 2,6-HMepydcO, and their two similar derivatives, pyridine-2,6-dicarboxylic acid (2,6-H 2 pydc) and dimethyl 1-(λ 1 -oxidaneyl)-1λ 4 -pyridine-2,6-dicarboxylate (2,6-Me 2 pydcO), were studied by density functional theory (DFT) and natural bond orbital (NBO) analysis, respectively. The ability of these compounds and their analogues to interact with nine selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) was investigated using docking calculations.

From the system CuCl 2 -biq-NaN(CN) 2 (biq is 2,2'-biquinoline), the binuclear molecular complex bis(μ-dicyanamido-κ 2 N 1 :N 5 )bis[(2,2'-biquinoline-κ 2 N,N')(dicyanamido-κN 1 )copper(II)], [Cu 2 (C 2 N 3 ) 4 (C 18 H 12 N 2 ) 2 ] or [Cu 2 (biq) 2 (dca) 2 (μ 1,5 -dca) 2 ] (1) [dca is dicyanamide, N(CN) 2 - ] was isolated and characterized by crystal structure analysis, and spectral, thermal and magnetic measurements. IR spectroscopy confirmed the presence of the biq and dca ligands in 1. Its solid-state structure consists of discrete centrosymmetric binuclear copper(II) units with double end-to-end dca bridges. Each Cu II atom is in a distorted square-pyramidal environment with the equatorial plane formed by two nitrile N atoms from bridging dca groups, one of the two N atoms of the chelate biq molecule and one nitrile N atom from a terminal dca ligand, whereas the second biq N atom occupies the axial position. Thermal decomposition of 1 in an air atmosphere proceeds gradually, with copper(I) cyanide being the final decomposition product. Magnetic measurements revealed the formation of alternating spin chains and a relatively strong exchange interaction within the binuclear units was also confirmed by Broken Symmetry DFT (density functional theory) calculations.

The two single-enantiomer phosphoric triamides N-(2,6-difluorobenzoyl)-N',N''-bis[(S)-(-)-α-methylbenzyl]phosphoric triamide, [2,6-F 2 -C 6 H 3 C(O)NH][(S)-(-)-(C 6 H 5 )CH(CH 3 )NH] 2 P(O), denoted L-1, and N-(2,6-difluorobenzoyl)-N',N''-bis[(R)-(+)-α-methylbenzyl]phosphoric triamide, [2,6-F 2 -C 6 H 3 C(O)NH][(R)-(+)-(C 6 H 5 )CH(CH 3 )NH] 2 P(O), denoted D-1, both C 23 H 24 F 2 N 3 O 2 P, have been investigated. In their structures, chiral one-dimensional hydrogen-bonded architectures are formed along [100], mediated by relatively strong N-H...O(P) and N-H...O(C) hydrogen bonds. Both assemblies include the noncentrosymmetric graph-set motifs R 2 2 (10), R 2 1 (6) and C 2 2 (8), and the compounds crystallize in the chiral space group P1. Due to the data collection of L-1 at 120 K and of D-1 at 95 K, the unit-cell dimensions and volume show a slight difference; the contraction in the volume of D-1 with respect to that in L-1 is about 0.3%. The asymmetric units of both structures consist of two independent phosphoric triamide molecules, with the main difference being seen in one of the torsion angles in the OPNHCH(CH 3 )(C 6 H 5 ) part. The Hirshfeld surface maps of these levo and dextro isomers are very similar; however, they are near mirror images of each other. For both structures, the full fingerprint plot of each symmetry-independent molecule shows an almost asymmetric shape as a result of its different environment in the crystal packing. It is notable that NMR spectroscopy could distinguish between compounds L-1 and D-1 that have different relative stereocentres; however, the differences in chemical shifts between them were found to be about 0.02 to 0.001 ppm under calibrated temperature conditions. In each molecule, the two chiral parts are also different in NMR media, in which chemical shifts and P-H and P-C couplings have been studied.

The complex (2,2'-biquinoline-κ 2 N,N')(carbamoylcyanonitrosomethanide-κ 2 N,O)chloridocopper(II) acetonitrile monosolvate, [Cu(C 3 H 2 N 3 O 2 )Cl(C 18 H 12 N 2 )]·CH 3 CN or [Cu(ccnm)Cl(biq)]·acn (acn is acetonitrile, biq is 2,2'-biquinoline and ccnm is carbamoylcyanonitrosomethanide), (I), was prepared as a result of nucleophilic addition of water to the dicyanonitrosomethanide ion in the presence of Cu II and biq. IR spectroscopy confirmed the presence of ccnm, biq and acn in (I). The solid-state structure consists of the neutral complex containing ccnm and biq ligands, coordinated to the Cu II atom in a bidendate chelating manner, and a chloride ligand, resulting in a distorted tetragonal pyramidal coordination of Cu II . The asymmetric unit is supplemented by one molecule of solvated acn which, along with the nitrile group of ccnm, serves as an acceptor in intermolecular hydrogen bonding, creating infinite chains along the b axis. Magnetic measurements revealed a paramagnetic behaviour with a very small Weiss temperature Θ = -0.32 K and high anisotropy of the g tensor (g x = 2.036, g y = 2.120 and g z = 2.205).

The solid-state phase transitions and intermediate structures of S -2-amino-butanoic acid (l-2-aminobutyric acid), S -2-aminopentanoic acid (l-norvaline), S -2-aminohexanoic acid (l-norleucine) and l-methionine between 100 and 470 K, identified by differential scanning calorimetry, have been characterized in a comprehensive single-crystal X-ray diffraction investigation. Unlike other enantiomeric amino acids investigated until now, this group featuring linear side chains displays up to five distinct phases. The multiple transitions between them involve a number of different processes: alteration of the hydrogen-bond pattern, to our knowledge the first example of this observed for an amino acid, sliding of molecular bilayers, seen previously only for racemates and quasiracemates, concerted side-chain rearrangements and abrupt as well as gradual modifications of the side-chain disorder. Ordering of l-norleucine upon cooling even proceeds via an incommensurately modulated structure. l-Methionine has previously been described as being fully ordered at room temperature. An accurate refinement now reveals extensive disorder for both molecules in the asymmetric unit, while two previously unknown phases occur above room temperature.

Orthophthalaldehyde (o-phthalaldehyde, OPA) is an aromatic dialdehyde bearing two electron-withdrawing carbonyl groups. The reactions of OPA with primary amines are broadly applied for the synthesis of important heterocyclic compounds with biological relevance. A number of such reactions have been investigated recently and several structures of condensation products have been reported, however, the complex reaction mechanism is still not fully understood and comprises concurrent as well as consecutive reactions. The reaction products depend on the primary amine which reacts with OPA, the reaction environment (solvent) and the proportion of the reactants. The title molecule, C11H13NO, the product of the reaction of OPA with isopropylamine, contains a five-membered pyrrole C4N ring with a carbonyl substituent, which forms part of the isoindolinone unit. Though this pyrrole ring contains one C atom in the sp(3)-hybridized state, it is fairly planar. The title molecule has been compared with similar structures retrieved from the Cambridge Structural Database in order to study this phenomenon. The planarity of this fragment has been explained by the presence of partially delocalized C-C, C-N and C-O bonds, and by an inner angle in the planar pentagonal ring (∼108°), which is close to the ideal tetrahedral value for the sp(3)-hybridized state of the constituent C atom. Due to this propitious angle, this C atom can be present in states intermediate between sp(3)- and sp(2)-hybridized in different structures, while still maintaining the planarity of the ring. There are only weak intermolecular C-H...O hydrogen bonds and C-H...π-electron ring interactions in the structure. In particular, it is the pyrrole ring which is involved in these interactions.

Hirshfeld surfaces and two-dimensional fingerprint plots are used to analyse the intermolecular interactions in two new phosphorothioic triamide structures, namely N,N',N''-tris(3,4-dimethylphenyl)phosphorothioic triamide acetonitrile hemisolvate, P(S)[NHC6H3-3,4-(CH3)2]3·0.5CH3CN or C24H30N3PS·0.5CH3CN, (I), and N,N',N''-tris(4-methylphenyl)phosphorothioic triamide-3-methylpiperidinium chloride (1/1), P(S)[NHC6H4(4-CH3)]3·[3-CH3-C5H9NH2](+)·Cl(-) or C21H24N3PS·C6H14N(+)·Cl(-), (II). The asymmetric unit of (I) consists of two independent phosphorothioic triamide molecules and one acetonitrile solvent molecule, whereas for (II), the asymmetric unit is composed of three components (molecule, cation and anion). In the structure of (I), the different components are organized into a six-molecule aggregate through N-H···S and N-H···N hydrogen bonds. The components of (II) are aggregated into a two-dimensional array through N-H···S and N-H···Cl hydrogen bonds. Moreover, interesting features of packing arise in this structure due to the presence of a double hydrogen-bond acceptor (the S atom of the phosphorothioic triamide molecule) and of a double hydrogen-bond donor (the N-H unit of the cation). For both (I) and (II), the full fingerprint plot of each component is asymmetric as a consequence of the presence of three fragments. These analyses reveal that H···H interactions [67.7 and 64.3% for the two symmetry-independent phosphorothioic triamide molecules of (I), 30.7% for the acetonitrile solvent of (I), 63.8% in the phosphorothioic triamide molecule of (II) and 62.9% in the 3-methylpiperidinium cation of (II)] outnumber the other contacts for all the components in both structures, except for the chloride anion of (II), which only receives the Cl···H contact. The phosphorothioic triamide molecules of both structures include unsaturated C atoms, thus presenting C···H/H···C interactions: 17.6 and 21% for the two symmetry-independent phosphorothioic triamide molecules in (I), and 22.7% for the phosphorothioic triamide molecule of (II). Furthermore, the N-H···S hydrogen bonds in both (I) and (II), and the N-H...Cl hydrogen bonds in (II), are the most prominent interactions, appearing as large red spots on the Hirshfeld surface maps. The N···H/H···N contacts in structure (I) are considerable, whereas for (II), they give a negligible contribution to the total interactions in the system.

The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the α-NaFeO2 structure type in agreement with the ratio of the ionic radii r(3+)/r(+). KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S-S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S(2-)) and the bond-valence sums.

The structure of N,N',N''-tribenzylphosphorothioic triamide, C21H24N3PS, (I), and analysis of the bond-angle sums at the N atoms for this compound, and for 74 structures with a P(S)[N]3 skeleton and the N atom in a three-coordinate geometry found in the Cambridge Structural Database [CSD; Groom & Allen (2014). Angew. Chem. Int. Ed. 53, 662-671], are reported. For (I), the bond-angle sum at one of the N atoms [359 (1)°] shows a nearly planar configuration, while the other two show a nonplanar geometry with bond-angle sums of 342 (1) and 347 (1)°. The location of the atoms attached to the nonplanar N atoms suggests an anti orientation of the corresponding lone electron pairs (LEPs) on these N atoms with respect to the P=S group. For 74 structures with a P(S)[N]3 skeleton and with the N atom in a three-coordinate geometry, the bond-angle sums at the N atoms were found to be in the range 293-360°. Among 307 such three-coordinate N atoms, 39% (120 N atoms) have bond-angle sums in the range 359-360°, in accordance with sp(2) hybridization, and 45% (138 N atoms) have bond-angle sums in the range 352-359°, with hybridization close to sp(2). For the orientation of the LEP with respect to the P=S group, the anti orientation was found to be a general rule for N atoms, with the corresponding bond-angle sums deviating by more than 8° from the planar value of 360°. In the title structure, the S atom takes part in intermolecular (N-H···)(N-H···)S hydrogen bonds, connecting the molecules into extended chains parallel to the b axis. The co-operation of one N atom in an N-H···S hydrogen bond as an H-atom donor, and in an N-H···N hydrogen bond as an acceptor, is a novel feature of the crystal structure.

The structures of 4-chloro-3-nitroaniline, C6H5ClN2O2, (I), and 4-iodo-3-nitroaniline, C6H5IN2O2, (II), are isomorphs and both undergo continuous (second order) phase transitions at 237 and 200 K, respectively. The structures, as well as their phase transitions, have been studied by single-crystal X-ray diffraction, Raman spectroscopy and difference scanning calorimetry experiments. Both high-temperature phases (293 K) show disorder of the nitro substituents, which are inclined towards the benzene-ring planes at two different orientations. In the low-temperature phases (120 K), both inclination angles are well maintained, while the disorder is removed. Concomitantly, the b axis doubles with respect to the room-temperature cell. Each of the low-temperature phases of (I) and (II) contains two pairs of independent molecules, where the molecules in each pair are related by noncrystallographic inversion centres. The molecules within each pair have the same absolute value of the inclination angle. The Flack parameter of the low-temperature phases is very close to 0.5, indicating inversion twinning. This can be envisaged as stacking faults in the low-temperature phases. It seems that competition between the primary amine-nitro N-H···O hydrogen bonds which form three-centred hydrogen bonds is the reason for the disorder of the nitro groups, as well as for the phase transition in both (I) and (II). The backbones of the structures are formed by N-H···N hydrogen bonding of moderate strength which results in the graph-set motif C(3). This graph-set motif forms a zigzag chain parallel to the monoclinic b axis and is maintained in both the high- and the low-temperature structures. The primary amine groups are pyramidal, with similar geometric values in all four determinations. The high-temperature phase of (II) has been described previously [Garden et al. (2004). Acta Cryst. C60, o328-o330].

The compound N,N',N''-tricyclohexylphosphorothioic triamide, C18H36N3PS or P(S)[NHC6H11]3, (I), crystallizes in the space group Pnma with the molecule lying across a mirror plane; one N atom lies on the mirror plane, whereas the bond-angle sum at the other N atom has a deviation of some 8° from the ideal value of 360° for a planar configuration. The orientation of the atoms attached to this nonplanar N atom corresponds to an anti orientation of the corresponding lone electron pair (LEP) with respect to the P=S group. The P=S bond length of 1.9785 (6) Å is within the expected range for compounds with a P(S)[N]3 skeleton; however, it is in the region of the longest bond lengths found for analogous structures. This may be due to the involvement of the P=S group in N-H···S=P hydrogen bonds. In O,O'-diethyl (2-phenylhydrazin-1-yl)thiophosphonate, C10H17N2O2PS or P(S)[OC2H5]2[NHNHC6H5], (II), the bond-angle sum at the N atom attached to the phenyl ring is 345.1°, whereas, for the N atom bonded to the P atom, a practically planar environment is observed, with a bond-angle sum of 359.1°. A Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B58, 380-388] analysis shows a shift of the maximum population of P=S bond lengths in compounds with a P(S)[O]2[N] skeleton to the shorter bond lengths relative to compounds with a P(S)[N]3 skeleton. The influence of this difference on the collective tendencies of N···S distances in N-H···S hydrogen bonds for structures with P(S)[N]3 and P(S)[O]2[N] segments were studied through a CSD analysis.

The title structures NaGdS2 (sodium gadolinium sulfide), NaLuS2 (sodium lutetium sulfide) and NaYS2 (sodium yttrium sulfide) were redetermined in order to improve the structural information available for the family of group 1 and thallium rare earth sulfides, which are isostructural with the rhombohedral α-NaFeO2 structure type. In particular, the present investigation has been directed at the rhombohedral sodium rare earth sulfides. The observed dependence of the fractional coordinate z(S(2-)) on the identity of the rare earth element in the newly determined structures is in agreement with the known structures of the potassium and rubidium analogues. Crystals of NaGdS2 and NaLuS2 display obverse-reverse twinning.

In the title salts, C12H14N2(2+)·2ClO4(-), (I), and C12H14N2(2+)·S2O8(2-), (II), the dication is organized around an inversion centre located at the centre of the -CH2CH2- bridge and the two pyridine segments are anti with respect to one another. The peroxodisulfate anion in (II) also exhibits inversion symmetry. Hirshfeld surface analysis shows closely similar Hirshfeld surface shapes for the dications in the two salts, reflecting similar intermolecular contacts and similar conformations. The two-dimensional fingerprint plots (FPs) are quite asymmetric, due to the presence of more than one component (cation and anion). The most striking of the complementary features for each of the FPs of the dications is the broad green spike in the region d(e) > d(i), without the presence of a corresponding spike in the region d(e) < d(i), reflecting the absence of O···H contacts. Moreover, H···O interactions (51% in the dications of both salts) outnumber other contacts in both crystal structures.