Binary chalcogen halogen EX species represent intriguing systems in terms of chemical bonding theories, such as hypervalency and stereoactivity of lone electron pairs. Instead of a simple molecular EX structure, selenium tetrachloride forms an ionic pair, ClSeCl, that assembles into a tetrameric (SeCl) structure, namely, tetra-μ-chlorido-dodecachloridotetraselenium. This article describes the charge-density analysis of the tetrameric molecule of β-SeCl based on the aspherical model obtained from Hirshfeld Atom Refinement of the tetrameric molecule and of an explicit cluster of 15 tetramers that simulates the crystal packing. Deformation density, electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) were used to evaluate the bonding situation, the electron-density distribution around the Se atom and the interaction energy of the tetramer.

Two novel Cu-based metal-organic frameworks (MOFs), namely, poly[[aquadichlorido[μ-4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylato][μ-4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylato]tricopper(II)] monohydrate], {[Cu(CHNO)Cl(HO)]·HO} or {[Cu(PTP)Cl(HO)]·HO}, (I), and poly[[diaquabis[μ-4'-(pyridin-3-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylato]bis(μ-terephthalato)tricopper(II)] dihydrate], {[Cu(CHNO)(CHO)(HO)]·2HO} or {[Cu(BDC)(MTP)(HO)]·2HO}, (II), have been synthesized successfully with 4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylic acid (HPTP) and 4'-(pyridin-3-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylic acid (HMTP) as the ligands, respectively. Crystal structure analysis reveals that (II) possesses a 2D coordinated layer structure, in which adjacent 2D coordination layers are linked into 3D frameworks through π-π interactions, while the structure of (I) displays dual coordination layers, in which adjacent coordination layers are connected into a 3D framework through hydrogen-bonding interactions. The photophysical properties of the two MOFs were investigated by fluorescence spectroscopy. Complex (II) shows an obvious `turn-on' fluorescence enhancement effect towards flazasulfuron and its potential application for sensing flazasulfuron in water with high selectivity and sensitivity was also investigated in detail.

A new crystalline compound, catena-poly[hexa-μ-acetato-(acetic acid)-μ-oxido-triangulo-triiron(III)]-μ-acetato], [Fe(CHO)O(CHO)], incorporating the basic ferric acetate unit, has been obtained from an acetic anhydride solution of hydrated iron(III) nitrate. The crystals have the composition FeO(OAc)(HOAc) (HOAc is acetic acid) and include the well-known [FeO(OAc)] unit, in which the Fe centres are linked to a central coplanar μ-oxido ligand. Acetate ions provide bridges between pairs of Fe centres. These individual [FeO(OAc)] units are linked by additional bridging acetate anions to form zigzag chains. The bridging acetate ions coordinate to a position trans to the oxido group on two of the Fe centres. Remarkably, the trans site on the third Fe centre is occupied by the carbonyl group of an acetic acid molecule. This is the first reported case of an acetic acid molecule coordinating to an Fe centre. Not surprisingly, the acetic acid molecule is only weakly coordinating, resulting in a short Fe-O(oxido) bond trans to the carbonyl group. The trans influence apparent in this structure provides an interesting contrast with the structurally similar Mn analogue, in which the corresponding pair of trans bonds are both elongated because of the Jahn-Teller effect.

Taurine is part of the cysteine cycle and is one of the few naturally occuring organosulfur-based molecules in the human body. As implied by modern studies, protonated taurine is of biological impact. The first attempts to isolate its protonated species in the binary superacidic system HF/SbF were performed by Hopfinger, resulting in the isolation of monoprotonated taurine. Since the chosen conditions seemed rather harsh, investigations in less acidic systems were performed at room temperature to explore the involved protonated species. Herein, we present the structure of 2-[dihydroxy(oxo)sulfanyliumyl]ethanaminium bis[hexafluoridoarsenate(V)], [HOSCHNH][AsF], the diprotonated form of 2-aminoethanesulfonic acid (taurine). It was synthesized in the binary superacidic system HF/AsF and crystallizes as colourless needles. Diprotonated taurine was structurally characterized by single-crystal X-ray diffraction analysis, low-temperature vibrational spectroscopy and NMR spectroscopy.

The reactions of oxalyl chloride were investigated in the binary superacidic systems HF/SbF and DF/SbF. O-Monoprotonated oxalyl chloride was isolated and represents the first example of a protonated acyl chloride. Diprotonated oxalyl chloride is only stable in solution. Salts of the ClCO cation were synthesized from the reactions of oxalyl chloride or COClF with SbF in 1,1,1,2-tetrafluoroethane (R-134a, CFCFH). The colourless salts were characterized by low-temperature vibrational spectroscopy, NMR spectroscopy and single-crystal X-ray diffraction. (1,2-Dichloro-2-oxoethylidene)oxidanium hexafluoridoantimonate(V), [CO(OH)Cl][SbF], crystallizes in the monoclinic space group P2 and carbonyl chloride hexadecafluoridotriarsenate(V) [ClCO][SbF], in the trigonal space group P3, with two and three formula units per unit cell, respectively. Monoprotonated oxalyl chloride and the ClCO cation both display very short C-Cl bonds with a strong double-bond character.

A recent communication on Ru-catalyzed C-H bond arylation with 4-aminoantipyrine (AP) reported the synthesis of AP benzamides. In order to provide additional support to the published structures of AP benzamides, crystallization by high-throughput (HTP) encapsulated nanodroplet crystallization (ENaCt) was undertaken. This allowed for conclusive structure determination by single-crystal X-ray diffraction analysis (SCXRD). This article describes the crystallization and X-ray crystal structure of N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-methylbenzamide, CHNO, as a benzamide bearing 4-aminoantipyrine, providing structural confirmation. X-ray structure analysis reveals intermolecular hydrogen-bonding interactions between the AP benzamide N-H proton and the carbonyl O atom of the AP moiety.

The synthesis, single-crystal X-ray structure determination and thermal analysis are reported for a novel heteronuclear oxalate compound synthesized from a mixture of Fe and Na salts, oxalic acid and N,N-dimethylformamide (DMF) in aqueous solution. The new metallooxalate compound was obtained and identified as a dimethylammonium tris(oxalato)ferrate(III), namely, poly[[bis(dimethylammonium) [tri-μ-oxalato-sodium(I)iron(III)]]-dimethylamine-water (3/1/1)], [NH(CH)][NaFe(CO)]·0.33NH(CH)·0.33HO, which crystallizes in the orthorhombic noncentrosymmetric space group C222. In this novel structure, each Fe atom is hexacoordinated by three non-equivalent bidentate oxalate ligands, while the four Na atoms adopt different coordination numbers, i.e. 6, 7 and 8. The structure consists of bimetallic anionic A layers, {[NaFe(CO)]}, displaying a layered structure with infinitely linked FeNa tetramers on the ab plane. Two kinds of bimetallic parallel layers (A1 and A2) are present alternately and are found to be staggered, while only the A2 layer is crossed by a twofold axis parallel to the a axis through two Na atoms. The [NH(CH)] (HDMA) cations occupy the voids between the anionic layers, while the free molecules, i.e. NH(CH) (DMA) and HO, are located between two different anionic layers. In addition to ionic bonds, the stability of the structure is ensured by hydrogen-bond interactions involving the oxalate ligands and the nitrogenous and water molecules. The layered structure appears to be different in the family of oxalate-bridged Na-Fe compounds. It is in agreement with the predicted 2D or layered structure of bimetallic complexes containing anionic tris(oxalato)metallate(III) with the [XR] counter-ion template (X = N, P or S, and R = alkyl group or H). The thermal decomposition of the compound shows the final residual product to be NaFeO.

The effects of Eu doping on the crystal structure and charge distribution of BiSiO (BSO) bisilicate, based on first principles and density functional theory (DFT), were calculated and analyzed using Materials Studio software. The effect of different proportions (1/12, 1/6 and 1/3) of Eu doping on BSO crystals was investigated using the virtual crystal approximation method. Through Mulliken charge analysis, it is found that a high proportion of Eu doping will destroy the symmetry of the crystal structure. With an increase of the Eu-doping ratio, the Eu-O bond length first increased and then decreased, showing the characteristics of covalent bonds, and the Eu-O bond length reached the minimum value when the Eu-doping ratio was increased to 1/3. With an increase in the Eu-doping ratio, the Bi-O bond length decreases sequentially and also reaches the minimum value when the Eu-doping ratio was increased to 1/3. This indicates that the covalence between the Eu-O and Bi-O atoms is enhanced when the doping ratio is 1/3 when BSO crystals are doped with Eu.

Three dinuclear zinc(II) acetate complexes of the general formula [Zn{L}(AcO)], namely, di-μ-acetato-κO:O'-bis[({2-[(pyridin-2-ylmethylidene)amino]phenyl}sulfanido-κN,N',S)zinc(II)], [Zn(CHNS)(CHO)] (n = 1), 4, μ-acetato-1:2κO:O'-acetato-2κO-[μ-(2-{[1-(pyridin-2-yl)ethylidene]amino}phenyl)sulfanido-1κS:2κN,N',S][(2-{[1-(pyridin-2-yl)ethylidene]amino}phenyl)sulfanido-1κN,N',S]dizinc(II), [Zn(CHNS)(CHO)] (n = 2), 5, and μ-acetato-1:2κO:O'-acetato-2κO-[μ-(2-{[phenyl(pyridin-2-yl)methylidene]amino}phenyl)sulfanido-1κS:2κN,N',S][(2-{[phenyl(pyridin-2-yl)methylidene]amino}phenyl)sulfanido-1κN,N',S]dizinc(II)-bis(2-aminophenyl) disulfide (2/1), [Zn(CHNS)(CHO)]·0.5CHNS (n = 3), 6·0.5(2-APS), were obtained from the reaction of 2-R-(pyridin-2-yl)benzothiazoline precursors (R = H, 1; R = Me, 2; R = Ph, 3) with zinc acetate dihydrate in a 1:1 ratio. All the complexes crystallized as dinuclear species and complex 6 cocrystallized with one molecule of bis(2-aminophenyl) disulfide (2-APS). The anionic Schiff base ligands {L} displayed a κN,κS-tridentate coordination mode with the formation of two five-membered chelate rings. In 4, 5 and 6·0.5(2-APS), both Zn ions are pentacoordinated and the coordination sphere of 4 was different with respect to those in 5 and 6·0.5(2-APS). For 4, the X-ray diffraction study showed a dinuclear complex containing two bridging acetate ligands linked to both Zn ions. For 5 and 6·0.5(2-APS), the dinuclear complexes displayed one bridging acetate ligand linked to both Zn ions, where the first Zn ion includes a dative bond with one S atom from an adjacent anionic Schiff base {L}, while the second Zn ion is coordinated to one terminal acetate ligand. In each dinuclear complex, the geometry is the same for both Zn metal centres. The local geometry of the Zn cation in 4 is halfway between trigonal bipyramidal and square pyramidal local geometries; in 5 and 6, the local geometries are described as distorted square pyramidal. Hirshfeld surface analysis of 5 and 6 showed the predominance of H...H interactions, as well as the contribution of C-H...C, C-H...O and C-H...S noncovalent interactions to the cohesion of the crystalline network of the Zn complexes.

Biologically active compounds are highly sought-after materials for developing novel structures applicable to industry. Cytosine and pyridine-2,3-dicarboxylic acid (quinolinic acid) are notably significant environmentally. Cytosine, a pyrimidine derivative, features a six-membered ring with a ketone and an amino group, constituting a fundamental nitrogenous base found in deoxyribonucleic acid (DNA). The present synthesis yielded a salt of dipyridine-2,3-dicarboxylic acid with cytosine, wherein a proton was transferred from a carboxyl group of quinolinic acid to a ring N atom in the cytosine molecule giving the salt 6-amino-2-oxo-2,3-dihydropyrimidin-1-ium 3-carboxypyridine-2-carboxylate, CHNO·CHNO. A Hirshfeld surface analysis was conducted to examine the contribution of contacts within the salt. The structure of the salt was compared to other structures containing quinolinic acid in the Cambridge Structural Database (CSD).

This work focused on analyzing the properties of N-(5-nitrothiazol-2-yl)furan-2-carboxamide (CHNOS, NTFC) as a possible inhibitor of the rheumatoid arthritis process. The synthesis of NTFC was carried out and good-quality crystals were obtained and studied by NMR (H and C), DEPT 135, UV-Vis, IR, MS and single-crystal X-ray diffraction. The structure of NTFC consists of two rings, thiazole and furan, and a central C-N-C(=O)-C segment, which appears to be planar. This central amide segment forms angles of 2.61 (10) and 7.97 (11)° with the planes of the thiazole and furan rings, respectively. The crystal structure of NTFC exhibits N-H...N, N-H...O and C-H...O hydrogen bonds, and C-H...π and π-π interactions that facilitate self-assembly and the formation of hydrogen-bonded dimers, which implies the appearance of R(8) graph-set motifs in this interaction. The stability of the dimeric unit is complemented by the formation of strong intramolecular C-S...O interactions of chalcogen character, with an S...O distance of 2.6040 (18) Å. Hirshfeld surface (HS) analysis revealed that O...H/H...O interactions were dominant, accounting for 36.8% of the total HS, and that N-H...N interactions were fundamental to the formation of the dimeric structure. The molecular electrostatic potential (MEP) map showed a maximum energy of 46.73 kcal mol and a minimum of -36.06 kcal mol. The interaction energies of molecular pairs around NTFC are highest for those interactions linked by N-H hydrogen bonds. The properties of the NTFC ligand as a potential inhibitor of the DHODH (dihydroorotate dehydrogenase) enzyme were evaluated by molecular docking, showing coupling energies very close to those obtained with the control drug for rheumatoid arthritis, i.e. leflunomide.

In this study, we introduce a novel indole-containing pyridine-based Schiff base, (E)-2-({[bis(pyridin-2-yl)methylidene]hydrazin-1-ylidene}methyl)-1H-indole, CHN (2-DPHI), and its cadmium(II) complex poly[[2-({[bis(pyridin-2-yl)methylidene]hydrazin-1-ylidene}methyl)-1H-indole]di-μ-chlorido-cadmium(II)], [CdCl(CHN)] (pCd2), as potential anticancer agents. The Schiff base was synthesized by reacting dipyridylmethanone hydrazone with indole-2-formaldehyde, while the cadmium complex was prepared by combining CdCl and 2-DPHI in methanol at room temperature. Both compounds were evaluated for their cytotoxicity against three human cancer cell lines (A375, A549 and HeLa) and a normal cell line (HFF-1). The ligand 2-DPHI exhibited notable antitumour activity, with an IC value of 12.22 µM against A375 and 15.17 µM against A549 after 48 h, while the pCd2 complex showed an even stronger inhibition of A375 cells, with an IC value of 4.88 µM, outperforming both 2-DPHI and CdCl. Both compounds demonstrated lower toxicity towards normal cells compared to cancer cells. The structures of 2-DPHI and pCd2 were fully characterized using single-crystal X-ray diffraction, elemental analysis, high-resolution mass spectrometry and FT-IR, H NMR, C NMR and UV-Vis spectroscopy.

Three salts, namely, 2,4,6-triaminopyrimidin-1-ium sorbate dihydrate, CHN·CHO·2HO, (I), 2,4,6-triaminopyrimidin-1-ium N-phenylanthranilate, CHN·CHNO, (II), and 2,4,6-triaminopyrimidin-1-ium p-toluenesulfonate, CHN·CHOS, (III), were synthesized, characterized by X-ray diffraction techniques and their supramolecular interactions investigated. In all three crystal structures, protonation of the pyrimidine moiety occurs at the N1 position and is reflected in a widening of the C-N-C bond angle. In salts (I)-(III), the primary acid-base interaction occurs through a pair of N-H...O hydrogen bonds to give a heterodimeric R(8) synthon. Salts (II) and (III) form a discrete centrosymmetric base pair that produces a homodimeric R(8) synthon and salt (I) forms a water-mediated base pair resulting in a tetrameric R(12) synthon. The supramolecular patterns exhibited by sulfonate salt (III) mimic the patterns of carboxylate salt (II) and both exhibit a DADA array (D = donor and A = acceptor) quadruple hydrogen-bonded pattern. The crystal structures of salts (I) and (III) are stabilized by offset and face-to-face aromatic π-π stacking interactions, respectively. The resulting architectures in salts (I)-(III) are a supramolecular sheet with a rosette-like architecture in (I), a supramolecular sheet-like architecture in (II) and a three-dimensional supramolecular network in (III).

Starting from (p-tolylsulfinyl)ferrocene (1), a mixture of the complete series [CpFe{CH(SOTol-p)}] (n = 2-4) (2-4) in all regioisomers was obtained. After chromatographic separation, crystals of 1,2-bis[(4-methylbenzene)sulfinyl]ferrocene, 2a, and 1,3-bis[(4-methylbenzene)sulfinyl]ferrocene, 2b, both [Fe(CH)(CHOS)], as well as of 1,2,3-tris[(4-methylbenzene)sulfinyl]ferrocene, [Fe(CH)(CHOS)], 3a, and 1,2,3,4-tetrakis[(4-methylbenzene)sulfinyl]ferrocene ethyl acetate 0.75-solvate, [Fe(CH)(CHOS)]·0.75CHO, 4, could be isolated. Their molecular and crystal structures are compared with each other and also with the so far unreported structures of related 1,2-bis(phenylsulfanyl)ferrocene, [Fe(CH)(CHS)], 5, and 1,2,3,4-tetrakis(phenylsulfanyl)ferrocene, [Fe(CH)(CHS)], 6. In all the sulfinyl structures, the O atoms of the S=O groups are in equatorial positions, except for that in tetrasubstituted 4. All the arene rings of these compounds (except for one ring in 4) are in axial positions directed away from the Fe atom, mostly in a near perpendicular orientation with respect to the plane of the cyclopentadienyl ring. The main intermolecular interactions in the crystals are C-H...H-C, C-H...π and C-H...O, while C-H...S interactions are much less important, except for tetrasulfanyl compound 6. π-π interactions (intramolecular) are only important in compound 3a. Hirshfeld analysis shows that dispersion terms are dominant for the interaction energies of all six compounds. In general, the calculated total interaction energies increase with increasing number of substituents and are higher for the sulfinyl than for the sulfanyl groups.

2,4,6-Triaminopyrimidine is an interesting and challenging molecule due to the presence of multiple hydrogen-bond donors and acceptors. Its noncovalent interactions with a variety of carboxylic acids provide several supramolecular aggregates with frequently occurring molecular synthons. The present work focuses on the supramolecular interactions of 2,4,6-triaminopyrimidinium 3-(indol-3-yl)propionate-3-(indol-3-yl)propionic acid (1/1), CHN·CHNO·CHNO, (I), 2,4,6-triaminopyrimidinium 2-(indol-3-yl)acetate, CHN·CHNO, (II), 2,4,6-triaminopyrimidinium 5-bromothiophene-2-carboxylate, CHN·CHBrOS, (III), and 2,4,6-triaminopyrimidinium 5-chlorothiophene-2-carboxylate, CHN·CHClOS, (IV). All four salts exhibit robust homomeric and heteromeric R(8) ring motifs. Salts (I) and (II) develop sextuple [in (I)] and quadruple [in (I) and (II)] hydrogen-bonded arrays through fused-ring motifs. Salt (II) exhibits a rosette-like architecture. Salt (IV) is isostructural and isomorphous with salt (III), exhibiting an identical crystal structure with a different composition and an identical supramolecular architecture. In salts (III) and (IV), a linear hetero-tetrameric motif is formed and, in addition, both salts exhibit halogen-π interactions which enhance the crystal stability. All four salts develop a supramolecular hydrogen-bonded pattern facilitated by several N-H...O and N-H...N hydrogen bonds with multiple furcated donors and acceptors.

The introduction of the cerium(III) analogue (1-Ce, Ln = Ce) of (tert-butoxido)chloridopentakis(tetrahydrofuran)lanthanide(III) tetraphenylborate tetrahydrofuran disolvate, [Ln{OC(CH)}Cl(CHO)][B(CH)]·2CHO or [Ln(OBu)Cl(THF)](BPh)·2THF (1-Ln) has been achieved with a structural comparison between the existing solid-state structures of other rare earth analogues and the title compound at 100 and 180 K. The cation in 1-Ce is targeted as the cerium(III) ion possesses the criteria to exhibit slow magnetic relaxation in axial point-charge crystal fields, akin to the dysprosium(III) ion in 1-Dy. AC magnetic susceptibility experiments reveal no such behaviour for 1-Ce, putting the viability of cerium-based SMMs into question.

The binuclear paddle-wheel copper(II) complex tetrakis(μ-3,4-diethoxybenzoato-κO:O')bis[(ethanol-κO)copper(II)], [Cu(CHO)(CHO)], has been synthesized and characterized. In each molecule, two Cu centres are bridged in a syn-syn fashion by four equatorial 3,4-diethoxybenzoate ligands, the two axial positions being occupied by ethanol molecules. The thermal stability has been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The magnetic behaviour, studied by SQUID magnetometry, shows a Cu-Cu antiferromagnetic exchange interaction with 2J = -288 cm, a value that fits with a magnetic structure correlation established for compounds of this kind.

Research concerning coordination polymers has been intense due to their significant variability and structural stability. With this in mind, an ionic neodymium coordination polymer was synthesized, composed of an anionic one-dimensional polymer interconnected to a cationic three-dimensional porous polymer, poly[dodecaaquabis(μ-pyridine-4-carbohydrazide-κN:O)bis(μ-4-sulfobenzoato-κO:O')bis(μ-4-sulfobenzoato-κO:O':O'')trineodymium(III)] catena-poly[aquabis(μ-pyridine-4-carbohydrazide-κN:O)bis(μ-4-sulfobenzoato-κO:O')neodymium(III)] 4.33-hydrate, {[Nd(CHOS)(CHNO)(HO)][Nd(CHOS)(CHNO)(HO)]·4.33HO}. The ligands used were 4-sulfobenzoate (PSB) and pyridine-4-carbohydrazide, popularly known as isoniazid (INH), an antibiotic drug. The compound crystallizes in the monoclinic space group C2/c, with Z = 4. Solid-state calculations suggest that the crystal structure is mainly stabilized by hydrogen bonds, i.e. O-H...O and N-H...O interactions among the polymers, and by van der Waals interactions involving the organic side chains. This net is tetragonal, 2-nodal 3,4-connected, and can be described as the dmd (sqc 528) type.