Independent Formula Units Research Articles

XAFS study of mixed ligand benzimidazole copper complexes having distorted coordination geometry

X-ray absorption fine structure (XAFS) at the Cu K-edge in copper complexes, viz., [Cu(BzImH)4X2], where BzImH= benzimidazole and X= ClO4 (1), NO3 (2), ½ SO4 (3), Br (4), Cl (5) and their ‘inner complex’ [Cu(BzImH)2] (6) have been investigated using synchrotron radiation. The crystal structures of 4, 5 and 6 are not available. From EXAFS analysis, the structures of 4 and 5 have been estimated to be distorted square pyramidal and that of 6 to be tetrahedrally distorted square planar. Though, the crystal structure of the complexes 1 and 2 have been studied earlier using X-ray crystallography and found to be distorted square pyramidal, these complexes have been included in the study because each of these complexes has two independent formula units having two Cu sites in a molecule. In 2 the axial bond lengths are not similar at Cu1 and Cu2 sites. The electronic nature of Cu metal center in the complexes has been studied using XANES. The XANES spectra have been simulated and p-DOS and d-DOS calculated simultaneously for the Cu center in the complexes. The splitting of Cu K-edge into two edges K1 and K2 has been correlated with the p-DOS and the occurrence of pre-edge has been correlated with d-DOS.

Prevalence and Significance of Approximate Symmetry in Organic Pc Structures

AbstractA survey has been made of the well determined (R≤0.050) organic crystal structures that have only a single glide plane (e. g., are in space group Pc) and that have more than one crystallographically independent formula unit (Z′>1); the goal was to discover what fraction have additional approximate symmetry. Of the 377 unique structures examined 8 % should almost certainly been refined in a higher‐symmetry unit cell; 86 % of the remaining 347 have approximate symmetry that is periodic in at least one dimension. While these percentages are similar to those found for P1 structures (C. P. Brock, Acta Crystallogr., Sect. B 2022, 78, 576–588), the types of approximate symmetry differ because 89 % of the P1, Z′>1 structures were composed of enantiopure material. The 347 reliable Pc structures include 118 that are slightly distorted or mimicked Cc and P21/c structures, 15 of which were reported as having been determined at room temperature. The distortions in another 72 are so large that the approximate symmetry must be seen as periodic in two dimensions only. These results suggest that symmetry lowering may accompany transformation of a crystal nucleus to a macroscopic crystal.

Crystal structure of a host-guest complex of the tris-urea receptor, 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea, that encapsulates hydrogen-bonded chains of di-hydrogen phosphate anions with separate tetra-n-butyl-ammonium counter-ions.

The title compound, C25H25N9O9·C16H36N+·H2PO4 - (I) or (C25H25N9O9)·(n-Bu4N+)·(H2PO4 -) (systematic name: 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea tetra-butyl-ammonium di-hydrogen phosphate), comprises a tris-urea receptor (R), a di-hydrogen phosphate anion and a tetra-n-butyl-ammonium cation. It crystallizes with two independent formula units in the asymmetric unit. The conformations of the two tris-urea receptors are stabilized by N-H⋯O and C-H⋯O intra-molecular hydrogen bonds. Each di-hydrogen phosphate anion has two O-H⋯O inter-molecular hydrogen-bonding inter-actions with the other di-hydrogen phosphate anion. Inversion-related di-anion units are linked by further O-H⋯O hydrogen bonds, forming a chain propagating along the a-axis direction. Each di-hydrogen phosphate anion makes a total of four N-H⋯O(H2PO4 -) hydrogen bonds with two ureido subunits from two different tris-urea receptors, hence each tris-urea receptor provides the two ureido subunits for the encapsulation of the H2PO4 - hydrogen-bonded chain. There are numerous inter-molecular C-H⋯O hydrogen bonds present involving both receptor mol-ecules and the tetra-n-butyl-ammonium cations, so forming a supra-molecular three-dimensional structure. One of the butyl groups and one of the nitro groups are disordered over two positions of equal occupancy.

Conformational flexibility and pseudosymmetric aggregation in a betainium salt hydrate

The cation of 3-(trimethylammonium)-benzoic acid exhibits a considerable conformational flexibility connected to the orientation of carboxyl group, coupled to the proton position, and rotations of the trimethylammonium group. This conformational flexibility considerably affects the aggregation of ions and molecules of 3-(trimethylammonium)-benzoic acid iodide hydrate, which crystallizes in a low-symmetry structure with four symmetry-independent formula units (monoclinic space group Pc, Z’ = 4, model I). However this structure approximates the symmetry of space group P21/c in the same unit cell (Z’ = 2, model II), and also even a still more highly symmetric structure of space group P21/c in a half-smaller unit cell (Z’ = 1, model III). The independent formula units are differentiated by the conformations of trimethylammonium groups (ordered in model I, but disordered in models II and III), conformations of the carboxyl groups and positions of OH···O bonded water molecules (ordered in molecules I and II, and disordered in model III), while the bulks of the cations and iodide anions are consistent for all models. While the calorimetric study and varied-temperature structural determinations exclude phase transitions of the highly pseudosymmetric model I. This pseudosymmetry is independent of temperature between 100 K and the m.p. at 463 K, and illustrates subtle structural effects leading complex molecular aggregation in the crystal. Theoretical computations confirm the low energy differences between the conformers.Graphical abstractᅟ

An exceptional 5:4 enantiomeric structure.

The only crystals that could be grown from racemic solutions of the PF6(-) salt of the resolvable cation [Ru(2,9-dimethyl-1,10-phenanthroline)2(dipyrido[3,2-d:2',3'-f]quinoxaline)](2+) have translational symmetry only (space group P1), contain nine independent sets of ions, and include numerous independent solvent molecules (11 acetone, one diethyl ether and possibly several water molecules). Layers of hydrophobic cations alternate with layers containing most of the anions and solvent molecules. All nine cations have the same basic conformation, which is distorted by the presence of the methyl substituents on the two 1,10-phenanthroline ligands. Four pairs of enantiomeric cations within a layer are related by approximate inversion centers; the ninth cation, which shows no sign of disorder, makes the layer chiral. Within the cation layers stripes parallel to [110] of six cations alternate with stripes of three; the local symmetry and the cation orientations are different in the two stripes. These stripes are reflected in the organization of the anion/solvent layer. The ca 80:20 inversion twinning found indicates that enantiomeric preference is transmitted less perfectly across the anion/solvent layer than within the cation layer. The structure is exceptional in having nine independent formula units and an unbalanced set (ratio 4:5) of resolvable enantiomers. The difficulty in growing crystals of this material is consistent with its structural complexity.

Crystallographic identification of an unexpected by-product in an Ullman's reaction toward biphenyls: 1-(4-hexyloxy-3-hydroxyphenyl)ethanone.

The synthesis of 3,3'-diacetoxy-4,4'-bis(hexyloxy)biphenyl following the nickel-modified Ullmann reaction yielded a by-product which was identified successfully by crystallographic analysis as 1-(4-hexyloxy-3-hydroxyphenyl)ethanone, C14H20O3. This unexpected nonbiphenyl by-product exhibited IR, (1)H NMR, (13)C NMR and COSY (correlation spectroscopy) spectra fully consistent with the proposed structure. The compound crystallized in the orthorombic Pbca space group, with two independent formula units in the asymmetric unit (one of which was slightly disordered), and showed a supramolecular architecture in which molecules linked by hydroxy-ethanone O-H···O interactions are organized in columns separated by the aliphatic tails.

Crystal structure of 2-cyano-1-methyl-pyridinium perchlorate.

The asymmetric unit of the title salt, C7H7N2 +·ClO4 −, comprises two independent formula units. The solid-state structure comprises corrugated layers of cations and of anions, approximately parallel to (010). The supra­molecular layers are stabilized and connected by C—H⋯O hydrogen bonding to consolidate a three-dimensional architecture. A close pyridin­ium–perchlorate N⋯O contact [2.867 (5) Å] is noted. The crystal was refined as an inversion twin.

Crystal Structure and NMR Study of Tetrakis(acetonitrile)silver(I) Fluorosulfonate [Ag(CH3CN)4]+[SO3F]–

The title compound [Ag(CH3CN)4]+[SO3F]- crystallizes in the orthorhombic space group Pna21, a = 24:383(24), b = 8:632(11), c = 20:755(17) Å, V = 4368(6) Å3, Z = 12, with three independent formula units in the unit cell. A comparison with the isostructural compound [Ag(CH3CN)4]+ [ClO4]- is given. The salt has also been characterized by solution 1H and 19F NMR spectroscopy and the data compared to that of fluorosulfonic acid

Darstellung, strukturelle und spektroskopische Charakterisierung eines Pentaiodids [Rb(12-Krone-4)2]I5 / Preparation, Structural and Spectroscopic Characterization of a Pentaiodide [Rb(12-Crown-4)2]I5

Dark-green crystals of [Rb(12-crown-4)2]I5 were obtained by the reaction of stoichiometric amounts of RbI, I2 and 12-crown-4 from an ethanol=methanol solution (monoclinic space group P21=n with Z = 4, a = 8:9200(10), b = 24:069(2), c = 13:9950(10) Å and β = 91:984(9)°). The crystal structure contains one independent formula unit consisting of the polyiodide and the cation. The anionic part of the structure is an isolated, V-shaped pentaiodide I5 -. The cation is a sandwich complex with two 12-crown-4-molecules surrounding the alkali metal atom

Crystal structure of the Np(IV) compound [Np(DMSO)7(NO3)](ClO4)3 (DMSO = dimethyl sulfoxide)

The Np(IV) complex [Np(DMSO)7(NO3)](ClO4)3 was synthesized and studied by single crystal X-ray structural analysis. The crystal structure contains three crystallographically independent formula units. The complex cations [Np(DMSO)7(NO3)]3+ contain bidentate chelate nitrate ions and DMSO molecules coordinated to the Np atom via O atom. The coordination polyhedra (CPs) of the two crystallographically independent Np atoms can be described as base-monocapped tetragonal antiprisms, whereas the CP of the third crystallographically independent Np atom should be described as a trigonal prism tricapped at lateral faces. In contrast to many other structures of dimethyl sulfoxide complexes of actinide and lanthanide perchlorates, the DMSO molecules and perchlorate ions in the structure under consideration show no disordering.

7-Benzyl-3-methyl-6-phenylimidazo[2,1-b][1,3]thiazol-7-ium chloride 0.75-hydrate

Theasymmetric unit of the title salt, C19H17N2S+·Cl−·0.75H2O, contains two symmetrically independent formula units of the carbenium salt along with three water mol­ecules. The water mol­ecules are only 50% occupated, and one of them is positioned in a hydro­phobic pocket not forming any hydrogen bonds. The conformation of the independent cations is very similar, with dihedral angles of 61.0 (2) and 61.5 (3)° between the benzene rings. They form quasi-centrosymmetric couples via π–π stacking inter­actions between the benzene and imidazo[2,1-b]thia­zole rings [centroid–centroid distances = 3.718 (3) and 3.663 (3) Å]. In the crystal, O—H⋯Cl hydrogen bonds lead to the formation of a helical anion–water chain along the c-axis direction. The cations connect to the anion–water chain through C—H⋯Cl inter­actions, generating a three-dimensional supra­molecular network. O—H⋯S hydrogen bonds and C—H⋯O inter­actions also occur.

The first uranyl complexes with valerate ions

FT-IR spectroscopy and single-crystal X-ray structure analysis were used to characterize the discrete neutral compound diaquadioxidobis(n-valerato-κ(2)O,O')uranium(VI), [UO2(C4H9COO)2(H2O)2], (I), and the ionic compound potassium dioxidotris(n-valerato-κ(2)O,O')uranium(VI), K[UO2(C4H9COO)3], (II). The U(VI) cation in neutral (I) is at a site of 2/m symmetry. Potassium salt (II) has two U centres and two K(+) cations residing on twofold axes, while a third independent formula unit is on a general position. The ligands in both compounds were found to suffer severe disorder. The FT-IR spectroscopic results agree with the X-ray data. The composition and structure of the ionic potassium uranyl valerate are similar to those of previously reported potassium uranyl complexes with acetate, propionate and butyrate ligands. Progressive lengthening of the alkyl groups in these otherwise similar compounds was found to have an impact on their structures, including on the number of independent U and K(+) sites, on the coordination modes of some of the K(+) centres and on the minimum distances between U atoms. The evolution of the KUO6 frameworks in the four homologous compounds is analysed in detail, revealing a new example of three-dimensional topological isomerism in coordination compounds of U(VI).

(Cyclobutane-1,1-dicarboxylato-κ2O,O′)(1,10-phenanthroline-κ2N,N′)platinum(II) dihydrate

The title compound, [Pt(C6H6O4)(C12H8N2)]·2H2O, which crystallizes as two independent formula units, has the metal atom in a square-planar geometry defined by two O atoms of the chelating cyclo­butane-1,1-di­carboxyl­ate dianion and two N atoms of the chelating 1,10-phenanthroline mol­ecule (r.m.s. deviations of the PtO2N2 units = 0.026 and 0.026 Å). Adjacent complex and water mol­ecules are connected through inter­molecular O—H⋯O hydrogen bonds and C—H⋯O, C⋯O [shortest C⋯O distance = 3.140 (5) Å], π–π [shortest C⋯C distances = 3.234 (6) and 3.347 (6) Å] and Pt⋯π [shortest Pt⋯C distance = 3.358 (4) Å] inter­actions into a three-dimensional network.

Supramolecular synthesis based on piperidone derivatives and pharmaceutically acceptable co-formers

The target complexes, bis{(E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-oxopiperidinium} butanedioate, 2C27H36N3O(+)·C4H4O4(2-), (II), and bis{(E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-oxopiperidinium} decanedioate, 2C27H36N3O(+)·C10H16O4(2-), (III), were obtained by solvent-mediated crystallization of the active pharmaceutical ingredient (API) (E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-piperidone and pharmaceutically acceptable dicarboxylic (succinic and sebacic) acids from ethanol solution. They have been characterized by melting point, IR spectroscopy and single-crystal X-ray diffraction. For the sake of comparison, the structure of the starting API, (E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-piperidone methanol monosolvate, C27H35N3O·CH4O, (I), has also been studied. Compounds (II) and (III) represent salts containing H-shaped centrosymmetric hydrogen-bonded synthons, which are built from two parallel piperidinium cations and a bridging dicarboxylate dianion. In both (II) and (III), the dicarboxylate dianion resides on an inversion centre. The two cations and dianion within the H-shaped synthon are linked by two strong intermolecular N(+)-H···(-)OOC hydrogen bonds. The crystal structure of (II) includes two crystallographically independent formula units, A and B. The cation geometries of units A and B are different. The main N-C6H4-C=C-C(=O)-C=C-C6H4-N backbone of cation A has a C-shaped conformation, while that of cation B adopts an S-shaped conformation. The same main backbone of the cation in (III) is practically planar. In the crystal structures of both (II) and (III), intermolecular N(+)-H···O=C hydrogen bonds between different H-shaped synthons further consolidate the crystal packing, forming columns in the [100] and [101] directions, respectively. Salts (II) and (III) possess increased aqueous solubility compared with the original API and thus enhance the bioavailability of the API.

Tetraamminelithium triamminelithium trisulfide, [Li(NH3)4][Li(NH3)3S3

The title compound, [Li(NH3)4]+[Li(NH3)3S3]−, an ammo­niate of the previously unknown lithium tris­ulfide, was obtained from the reaction of lithium and sulfur in liquid ammonia. The asymmetric unit consists of two crystallographically independent formula units. The [Li(NH3)4]+ cations are close to regular LiN4 tetra­hedra. The anions contain LiSN3 tetra­hedra; the S—S—S bond angles are 110.43 (5) and 109.53 (5)°. In the crystal, the components are linked by multiple N—H⋯S hydrogen bonds. A weak N—H⋯N hydrogen bond is also present.

3-Aminopyridiniumtrans-diaquadioxalatochromate(III)

In the structure of the title compound, (C5H7N2)[Cr(C2O4)2(H2O)2], two crystallographically independent formula units are present. Both chromium atoms are six-coordinated in a distorted octa­hedral geometry by two chelating equatorial oxalato ligands and two axial water mol­ecules. The [Cr(C2O4)2(H2O)2]− anions and C5H7N2 + cations are linked through a complex three-dimensional hydrogen-bonding network consisting of N—H⋯O and O—H⋯O inter­actions.

Polysulfonylamine, CXCII [1]. Polynäre Verbindungen aus Di(4-fluorbenzolsulfonyl) amin (FAH), 1,1,3-Trimethylharnstoff (TrMU) und Dimethylamin (Me2NH): Bildung und Strukturen des Cokristalls FAH·TrMU (Z′ = 1), des Salzes Me2NH2 +·FA– (Z′ = 6) und des Salz-Cokristalls FAH·TrMU·Me2NH2 +·FA– (Z′ = 1). Bemerkungen zur Oxophobie von C–F-Gruppen in Kristallstrukturen / Polysulfonylamines, CXCII. Polynary Compounds Based upon Di(4-fluorobenzenesulfonyl)amine (FAH), 1,1,3-Trimethylurea (TrMU) and Dimethylamine (Me2NH): Formation

Cocrystallization of di(4-fluorobenzenesulfonyl)amine, (4-F-C6H4SO2)2NH (= FAH), with 1,3,3- trimethylurea (TrMU) from dichloromethane/petroleum ether afforded the molecular cocrystal FAH・TrMU (1, monoclinic, P21/n, Z′ = 1) and the salt cocrystal FAH・TrMU・Me2NH2 +・FA− (2, monoclinic, P21, Z′ = 1). The minor product 2 resulted from a hydrolysis reaction of TrMU and was obtained by serendipity. The salt component of 2, Me2NH2 +・FA− (3, monoclinic, C2, Z′ = 6), was prepared by metathesis of [Me2NH2]Cl with Ag[FA] and is not isomorphous to its previously reported congeners Me2NH2 +・(4-X-C6H4SO2)2N− (4 - 7 for X = Cl, Br, I or Me, all monoclinic, Cc, Z′ = 1). The three new structures display one-dimensional arrays (catemers) based upon classical two- or three-centre hydrogen bonds that use N-H or N+-H groups as donors and S=O, C=O or N− groups as acceptors. In 1, the catemers consist of alternating FAH and TrMU molecules, in 3 of alternating Me2NH2 + and FA− ions (six independent formula units), in 2 of alternating Me2NH2 + and FA− ions (one independent unit) and FAH・ ・ ・ TrMU・ ・ ・ heterodimers acting as side-groups to the ionic polymer. The packings of 1 - 3 are completely devoid of short fluorine-oxygen contacts below the van derWaals limit, as are all the known crystal structures containing FAH or FA− entities (“oxophobia” of the C-F groups). The Z′ = 6 structure of 3 may be interpreted as a stratagem to avoid short F・ ・ ・O contacts, in contrast to the Z′ = 1 structures of 4 - 6, which exhibit hydrogen-bonded ion catemers similar to the catemer of 3, and two halogen bonds C-X・ ・ ・O=S per formula unit

Dicyclohexylammonium thiocyanate: monoclinic polymorph

The title salt, C12H24N+·NCS−, represents a monoclinic polymorph of the previously reported ortho­rhom­bic form [Khawar Rauf et al. (2008 ▶). Acta Cryst. E64, o366]. Two independent formula units comprise the asymmetric unit with the major difference in their mol­ecular structures relating to the relative dispositions of the cyclo­hexyl rings [dihedral angles = 79.88 (6) and 67.72 (5)°]. Further, the independent anions form distinctive patterns of hydrogen-bonding inter­actions, i.e. 2 × N—H⋯N versus N—H⋯N and N—H⋯S. The resulting supra­molecular architecture is a supra­molecular chain along the c axis based on a square-wave topology.

A triclinic modification of 3,4-dihydroxybenzoic acid monohydrate

The unit cell of the title compound, C7H6O4·H2O, features four independent formula units; the individual carb­oxy­lic acid mol­ecules themselves are nearly planar (r.m.s. deviations = 0.0189, 0.0334, 0.0356 and 0.0441 Å). Two independent mol­ecules each form two hydrogen bonds by acid–carbonyl O—H⋯O inter­actions and the dimers are also nearly planar (r.m.s. deviations = 0.039 and 0.049 Å). The two independent dimers are aligned at 44.5 (1)°. Other O—H⋯O inter­actions involving the hy­droxy groups and water mol­ecules give rise to a three-dimensional network.

Morpholin-4-ium morpholine-4-carbodithioate

The title compound, C4H10NO+·C5H8NOS2 −, is built up of a morpholinium cation and a dithio­carbamate anion. In the crystal, two structurally independent formula units are linked via N—H⋯S hydrogen bonds, forming an inversion dimer, with graph-set motif R 4 4(12).