Showing papers in "Acta Crystallographica Section C-crystal Structure Communications in 2016"

Redetermination of the crystal structure of boron subphthalocyanine chloride (Cl‐BsubPc) enabled by slow train sublimation

Abstract: The crystal structure of boron subphthalocyanine chloride [systematic name: chlorido­(subphthalocyaninato)boron], C24H12BClN6, a material of widespread inter­est in organic electronic device applications, has been redetermined with a higher precision using large single crystals obtained via slow train sublimation. Details are given for the construction and operation of the train sublimation system, which has been designed to reproducibly yield single crystals suitable for diffraction experiments in a manner which approximates the vacuum deposition conditions commonly used to fabricate organic electronic devices. Diffraction experiments were conducted using two crystal samples and four temperatures (90, 123, 147 and 295 K), enabling a discussion of changes in the unit cell and inter­molecular inter­actions with respect to temperature and in comparison to two previously published structures of Cl-BsubPc. The redetermined structure confirms the original structure published 41 years ago [Meller & Ossko (1972). Monatsh. Chem. 103, 150–155], with significantly improved precision for the geo­metric parameters. Analysis of the crystal structure revealed three inter­secting ribbon motifs formed through a combination of π–π and halogen–π (specifically B—Cl⋯π) inter­actions. H atoms were refined independently in order to facilitate a thorough discussion of these inter­molecular inter­actions using Hirshfeld surface analysis.

Hawley's Condensed Chemical Dictionary. Sixteenth Edition. By M. D. Larrañaga, R. J. Lewis Sr & R. A. Lewis. Wiley, 2016. Hardback, Pp. XIII+1547. Price GBP 96.78. ISBN 9781118135150.

Abstract: The first question which arises when considering such a book is: who in 2016 is still using a dictionary instead of an inter­net search engine? Beginning my review, I had no clear answer to this question, but, since it is an impressive book (more than 1500 pages), and since it was on my desk, I decided to give it a chance. I began to search systematically for the chemical words I encountered in my teaching and research work. I have been impressed by the quality of the definitions given and by the number of words present in this dictionary. I then decided to explore the content of the dictionary for compounds, i.e. their commercial names (e.g. Ludox®), trade names, acronyms (e.g. RDGE) or `official' names. Again, the number of entries of these types present in the book is very extensive and the information is very consisely presented. I have also been convinced by the definitions of fundamentals, basic concepts (solids and colloids, for instance), processes (e.g. the viscose process) and chemical reactivity rules (e.g. Saytzeff rule). The names of great chemists, as well as Nobel Prize winners, are also included. Although, this dictionary is not a classical handbook of chemistry and physics, nor is it a Merck® Index, it does give some properties and CAS numbers of some compounds, as well as some chemical formulae, indications of toxicity and medicinal values. When comparing the results obtained using the dictionary with those obtained from an inter­net search, in all cases the definitions I found in this book were, if not the only one, then by far the most pertinent. After two months of intensive use and hundreds of searches in the dictionary, very few words (only three in fact) and acronyms were found to be missing: `TEMPO' (CAS 2564-83-2), RAFT for `Reversible Addition Fragmentation chain Transfer' and, quite astonishingly, `ionic liquid'. Considering the huge amount of work the dictionary represents (it is almost unbelievable that there are only three co-authors), it is very good value for money. Clearly, I consider that this dictionary is a very valuable tool for all those who work in the various fields of chemistry or in multidisciplinary research. Masters or PhD students beginning in a new field will appreciate this data bank for handling a literature survey. In my opinion, a copy should be owned by every research team and be present in the library of each institution providing Bachelor and Masters degrees in chemistry and related sciences.

The challenging case of the theophylline-benzamide cocrystal.

Abstract: Theophylline has been used as an active pharmaceutical ingredient (API) in the treatment of pulmonary diseases, but due to its low water solubility reveals very poor bioavailability. Based on its different hydrogen-bond donor and acceptor groups, theophylline is an ideal candidate for the formation of cocrystals. The crystal structure of the 1:1 benzamide cocrystal of theophylline, C7H8N4O2·C7H7NO, was determined from synchrotron X-ray powder diffraction data. The compound crystallizes in the tetra­gonal space group P41 with four independent mol­ecules in the asymmetric unit. The mol­ecules form a hunter's fence packing. The crystal structure was confirmed by dispersion-corrected DFT calculations. The possibility of salt formation was excluded by the results of Raman and 1H solid-state NMR spectroscopic analyses.

Synthesis, structural characterization and thermal properties of a new copper(II) one-dimensional coordination polymer based on bridging N,N'-bis(2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine and dicyanamide ligands.

Abstract: The design and synthesis of polymeric coordination compounds of 3d transition metals are of great interest in the search for functional materials. The coordination chemistry of the copper(II) ion is of interest currently due to potential applications in the areas of molecular biology and magnetochemistry. A novel coordination polymer of Cu(II) with bridging N,N'-bis(2-hydroxyphenyl)-2,2-dimethylpropane-1,3-diamine (H2L-DM) and dicyanamide (dca) ligands, catena-poly[[[μ2-2,2-dimethyl-N,N'-bis(2-oxidobenzylidene)propane-1,3-diamine-1:2κ(6)O,N,N',O':O,O']dicopper(II)]-di-μ-dicyanamido-1:2'κ(2)N(1):N(5);2:1'κ(2)N(1):N(5)], [Cu2(C19H20N2O2)(C2N3)2]n, has been synthesized and characterized by CHN elemental analysis, IR spectroscopy, thermal analysis and X-ray single-crystal diffraction analysis. Structural studies show that the Cu(II) centres in the dimeric asymmetric unit adopt distorted square-pyramidal geometries, as confirmed by the Addison parameter (τ) values. The chelating characteristics of the L-DM(2-) ligand results in the formation of a Cu(II) dimer with a double phenolate bridge in the asymmetric unit. In the crystal, the dimeric units are further linked to adjacent dimeric units through μ1,5-dca bridges to produce one-dimensional polymeric chains.

Nobiletin: a citrus flavonoid displaying potent physiological activity.

Abstract: Nobiletin [systematic name: 2-(3,4-di­meth­oxy­phen­yl)-5,6,7,8-tetra­meth­oxy-4H-chromen-4-one; C21H22O8] is a flavonoid found in citrus peels, and has been reported to show a wide range of physiological properties, including anti-inflammatory, anti­cancer and anti­dementia activities. We have solved the crystal structure of nobiletin, which revealed that the chromene and arene rings of its flavone moiety, as well as the two meth­oxy groups bound to its arene ring, were coplanar. In contrast, the C atoms of the four meth­oxy groups bound to the chromene ring are out of the plane, making the mol­ecule conformationally chiral. A comparison of the crystal structures of nobiletin revealed that it could adopt a variety of different conformations through rotation of the covalent bond between the chromene and arene rings, and the orientations of meth­oxy groups bound to the chromene ring.

Synthesis and crystal structures of C24-epimeric 20(R)-ocotillol-type saponins.

Abstract: Ocotillol-type saponins have a wide spectrum of biological activities. Previous studies indicated that the configuration at the C24 position may be responsible for their stereoselectivity in pharmacological action and pharmacokinetics. Natural ocotillol-type saponins share a 20(S)-form but it has been found that the 20(R)-stereoisomers have different pharmacological effects. The semisynthesis of 20(R)-ocotillol-type saponins has not been reported and it is therefore worthwhile clarifying their crystal structures. Two C24 epimeric 20(R)-ocotillol-type saponins, namely (20R,24S)-20,24-epoxydammarane-3β,12β,25-triol, C30H52O4, (III), and (20R,24R)-20,24-epoxydammarane-3β,12β,25-triol monohydrate, C30H52O4·H2O, (IV), were synthesized, and their structures were elucidated by spectral studies and finally confirmed by single-crystal X-ray diffraction. The (Me)C-O-C-C(OH) torsion angle of (III) is 146.41 (14)°, whereas the corresponding torsion angle of (IV) is -146.4 (7)°, indicating a different conformation at the C24 position. The crystal stacking in (III) generates an R4(4)(8) motif, through which the molecules are linked into a one-dimensional double chain. The chains are linked via nonclassical C-H...O hydrogen bonds into a two-dimensional network, and further stacked into a three-dimensional structure. In contrast to (III), epimer (IV) crystallizes as a hydrate, in which the water molecules act as hydrogen-bond donors linking one-dimensional chains into a two-dimensional network through intermolecular O-H...O hydrogen bonds. The hydrogen-bonded chains extend helically along the crystallographic a axis and generate a C4(4)(8) motif.

Crystal structure and photoluminescence properties of a new Cd(II) coordination polymer catena-poly[bis[4-bromo-2-({[2-(pyrrolidin-1-yl)ethyl]imino}methyl)phenolato-κ(3)N,N',O]di-μ3-chlorido-di-μ2-chlorido-bis(methanol-κO)tricadmium(II)].

Abstract: Schiff base-metal complexes have been used widely as catalysts for many organic reactions, such as ring-opening polymerization and oxidation. In view of the importance of Cd(II) coordination polymers and in an effort to enlarge the library of such complexes, the title novel polymeric Cd(II) tridentate Schiff base complex, [Cd3(C13H16BrN2O)2Cl4(CH4O)2]n, has been synthesized and characterized by elemental analyses, UV and IR spectroscopies, and single-crystal X-ray diffraction. The complex crystallizes in the triclinic P-1 space group with two symmetry-independent Cd(II) atoms, one of which lies on an inversion centre, and analysis of the crystal structure shows that both Cd(II) atoms are six-coordinated; the environment around one Cd(II) atom can be described as distorted octahedral, while that around the second Cd(II) atom is octahedral. The Cd(II) atoms are linked by chloride ligands to form a one-dimensional coordination polymer. The nonbonding intermolecular Cd...Cd distances are 3.7009 (4) and 4.3563 (5) A. Furthermore, the photoluminescence properties of the complex have been investigated and it displays a strong red emission in the solid state at room temperature.

Absolute structure determination using CRYSTALS.

Abstract: A study of post-refinement absolute structure determination using previously published data was carried out using the CRYSTALS software package. We show that absolute structure determination may be carried out optimally using the analyses available in CRYSTALS, and that it is not necessary to have the separate procedures absolute structure determination and no inter­est in absolute structure as proposed by Flack [Chimia (2014), 68, 26–30].

Nontypical iodine-halogen bonds in the crystal structure of (3E)-8-chloro-3-iodomethylidene-2,3-dihydro-1,4-oxazino[2,3,4-ij]quinolin-4-ium triiodide.

Abstract: Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C12H8ClINO+·I3-, described by X-ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. Lastly, the influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.

Syntheses and structures of four new mixed-amide phosphoric triamides.

Abstract: Phosphoric triamides have extensive applications in biochemistry and are also used as O-donor ligands. Four new mixed-amide phosphoric triamide structures, namely rac-N-tert-butyl-N',N''-dicyclohexyl-N''-methylphosphoric triamide, C17H36N3OP, (I), rac-N,N'-dicyclohexyl-N'-methyl-N''-(p-tolyl)phosphoric triamide, C20H34N3OP, (II), N,N',N''-tricyclohexyl-N''-methylphosphoric triamide, C19H38N3OP, (III), and 2-[cyclohexyl(methyl)amino]-5,5-dimethyl-1,3,2λ(5)-diazaphosphinan-2-one, C12H26N3OP, (IV), have been synthesized and studied by X-ray diffraction and spectroscopic methods. Structures (I) and (II) are the first diffraction studies of acyclic racemic mixed-amide phosphoric triamides. The P-N bonds resulting from the different substituent -N(CH3)(C6H11), (C6H11)NH-, 4-CH3-C6H4NH-, (tert-C4H9)NH- and -NHCH2C(CH3)2CH2NH- groups are compared, along with the different molecular volumes and electron-donor strengths. In all four structures, the molecules form extended chains through N-H...O hydrogen bonds.

An iron(II) complex tripodally chelated with 1,1,1-tris(pyridin-2-yl)ethane showing room-temperature spin-crossover behaviour.

Abstract: The spin-crossover phenomenon is a reversible low- and high-spin transition caused by external stimuli such as heat. In the novel iron(II) complex salt tetra­phenyl­phospho­nium tris­(thio­cyanato-κN)[1,1,1-tris­(pyridin-2-yl)ethane-κ3N,N′,N′′]ferrate(II), (C24H20P)[Fe(NCS)3(C17H15N3)], the Fe—N bond lengths are in the range 2.027 (2)–2.089 (2) A, indicating that the specimen consists of comparable molar fractions of the low- and high-spin species at 296 K. A magnetic study confirmed that spin-crossover takes place at around 290 K.

Synthesis, structure and characterization of five new organically templated metal sulfates with 2-aminopyridinium.

Abstract: The chemistry of organically templated metal sulfates has attracted interest from the materials science community and the development of synthetic strategies for the preparation of organic-inorganic hybrid materials with novel structures and special properties is of current interest. Sulfur-oxygen-metal linkages provide the possibility of using sulfate tetrahedra as building units to form new solid-state materials. A series of novel organically templated metal sulfates of 2-aminopyridinium (2ap) with aluminium(III), cobalt(II), magnesium(II), nickel(II) and zinc(II) were obtained from the respective aqueous solutions and studied by single-crystal X-ray diffraction. The compounds crystallize in centrosymmetric triclinic unit cells in three structure types: type 1 for 2-aminopyridinium hexaaquaaluminium(III) bis(sulfate) tetrahydrate, (C5H7N2)[Al(H2O)6](SO4)2·4H2O, (I); type 2 for bis(2-aminopyridinium) tris[hexaaquacobalt(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Co(H2O)6]3(SO4)4·2H2O, (II), and bis(2-aminopyridinium) tris[hexaaquamagnesium(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Mg(H2O)6]3(SO4)4·2H2O, (III); and type 3 for bis(2-aminopyridinium) hexaaquanickel(II) bis(sulfate), (C5H7N2)2[Ni(H2O)6](SO4)2, (IV), and bis(2-aminopyridinium) hexaaquazinc(II) bis(sulfate), (C5H7N2)2[Zn(H2O)6](SO4)2, (V). The templating role of the 2ap cation in all of the reported crystalline substances is governed by the formation of characteristic charge-assisted hydrogen-bonded pairs with sulfate anions and the presence of π-π interactions between the cations. Additionally, both coordinated and uncoordinated water molecules are involved in hydrogen-bond formation. As a consequence, extensive three-dimensional hydrogen-bonding patterns are formed in the reported crystal structures.

Two pseudo-enantiomeric forms of N-benzyl-4-hydroxy-1-methyl-2,2-dioxo-1H-2λ(6),1-benzothiazine-3-carboxamide and their analgesic properties.

Abstract: The fact that molecular crystals exist as different polymorphic modifications and the identification of as many polymorphs as possible are important considerations for the pharmaceutic industry. The molecule of N-benzyl-4-hydroxy-1-methyl-2,2-dioxo-1H-2λ(6),1-benzothiazine-3-carboxamide, C17H16N2O4S, does not contain a stereogenic atom, but intramolecular hydrogen-bonding interactions engender enantiomeric chiral conformations as a labile racemic mixture. The title compound crystallized in a solvent-dependent single chiral conformation within one of two conformationally polymorphic P212121 orthorhombic chiral crystals (denoted forms A and B). Each of these pseudo-enantiomorphic crystals contains one of two pseudo-enantiomeric diastereomers. Form A was obtained from methylene chloride and form B can be crystallized from N,N-dimethylformamide, ethanol, ethyl acetate or xylene. Pharmacological studies with solid-particulate suspensions have shown that crystalline form A exhibits an almost fourfold higher antinociceptive activity compared to form B.

A comparative study of the packing of two polymorphs of the nickel(II) pincer complex [2,6-bis(di-tert-butylphosphinoyl)-4-(3,5-dinitrobenzoyloxy)phenyl-κ(3)P,C(1),P']chloridonickel(II).

Abstract: Pincer complexes can act as catalysts in organic transformations and have potential applications in materials, medicine and biology. They exhibit robust structures and high thermal stability attributed to the tridentate coordination of the pincer ligands and the strong σ metal–carbon bond. Nickel derivatives of these ligands have shown high catalytic activities in cross-coupling reactions and other industrially relevant transformations. This work reports the crystal structures of two polymorphs of the title NiII POCOP pincer complex, [Ni(C29H41N2O8P2)Cl] or [NiCl{C6H2-4-[OCOC6H4-3,5-(NO2)2]-2,6-(OPtBu2)2}]. Both pincer structures exhibit the NiII atom in a distorted square-planar coordination geometry with the POCOP pincer ligand coordinated in a typical tridentate manner via the two P atoms and one arene C atom via a C—Ni σ bond, giving rise to two five-membered chelate rings. The coordination sphere of the NiII centre is completed by a chloride ligand. The asymmetric units of both poly­morphs consist of one mol­ecule of the pincer complex. In the first polymorph, the arene rings are nearly coplanar, with a dihedral angle between the mean planes of 27.9 (1)°, while in the second polymorph, this angle is 82.64 (1)°, which shows that the arene rings are almost perpendicular to one another. The supra­molecular structure is directed by the presence of weak C—H⋯O=X (X = C or N) inter­actions, forming two- and three-dimensional chain arrangements.

X-ray characterization and magnetic properties of di­oxy­gen-bridged CuII and MnIII Schiff base complexes

Abstract: The coordination chemistry of multinuclear metal compounds is important because of their relevance to the multi-metal active sites of various metallo­proteins and metalloenzymes. Multinuclear CuII and MnIII compounds are of inter­est due to their various properties in the fields of coordination chemistry, inorganic biochemistry, catalysis, and optical and magnetic materials. Oxygen-bridged binuclear MnIII complexes generally exhibit anti­ferromagnetic inter­actions and a few examples of ferromagnetic inter­actions have also been reported. Binuclear CuII complexes are important due to the fact that they provide examples of the simplest case of magnetic inter­action involving only two unpaired electrons. Two novel di­oxy­gen-bridged copper(II) and manganese(III) Schiff base complexes, namely bis­(μ-4-bromo-2-{[(3-oxidoprop­yl)imino]­meth­yl}phenolato)dicopper(II), [Cu2(C10H10BrNO2)2], (1), and bis­(di­aqua­{4,4′-di­chloro-2,2′-[(1,1-di­methyl­ethane-1,2-di­yl)bis­(nitrilo­methanylyl­idene)]diphenolato}man­ganese(III)) bis­{μ-4,4′-di­chloro-2,2′-[(1,1-di­methyl­ethane-1,2-di­yl)bis­(nitrilo­methanylyl­idene)]di­phenol­ato}bis­[aqua­manganese(III)] tetra­kis­(perchlorate) ethanol disolvate, [Mn(C18H16Cl2N2O2)(H2O)2]2[Mn2(C18H16Cl2N2O2)2(H2O)2](ClO4)4·2C2H5OH, (2), have been synthesized and single-crystal X-ray diffraction has been used to analyze their crystal structures. The structure analyses of (1) and (2) show that each CuII atom is four-coordinated, with long weak Cu⋯O interactions of 2.8631 (13) A linking the dinuclear halves of the centrosymmetric tetranucelar molecules, while each MnIII atom is six-coordinated. The shortest intra- and inter­molecular nonbonding Mn⋯Mn separations are 3.3277 (16) and 5.1763 (19) A for (2), while the Cu⋯Cu separations are 3.0237 (3) and 3.4846 (3) A for (1). The magnetic susceptibilities of (1) and (2) in the solid state were measured in the temperature range 2–300 K and reveal the presence of anti­ferromagnetic spin-exchange inter­actions between the transition metal ions.

Designing a heterotrinuclear Cu(II)-Ni(II)-Cu(II) complex from a mononuclear Cu(II) Schiff base precursor with dicyanamide as a coligand: synthesis, crystal structure, thermal and photoluminescence properties.

Abstract: Schiff bases are considered `versatile ligands' in coordination chemistry. The design of polynuclear complexes has become of inter­est due to their facile pre­parations and varied synthetic, structural and magnetic properties. The reaction of the `ligand complex' [CuL] {H2L is 2,2′-[propane-1,3-diylbis(nitrilo­methanylyl­idene)]diphenol} with Ni(OAc)2·4H2O (OAc is acetate) in the presence of dicyanamide (dca) leads to the formation of bis­(dicyanamido-1κN1)bis­(dimethyl sulfoxide)-2κO,3κO-bis­{μ-2,2′-[propane-1,3-diylbis(nitrilo­methan­yl­yl­idene)]diphenolato}-1:2κ6O,O′:O,N,N′,O′;1:3κ6O,O′:O,N,N′,O′-di­cop­per(II)nickel(II), [Cu2Ni(C17H16N2O2)2(C2N3)2(C2H6OS)2]. The complex shows strong absorption bands in the frequency region 2155–2269 cm−1, which clearly proves the presence of terminal bonding dca groups. A single-crystal X-ray study revealed that two [CuL] units coordinate to an NiII atom through the phenolate O atoms, with double phenolate bridges between CuII and NiII atoms. Two terminal dca groups complete the distorted octa­hedral geometry around the central NiII atom. According to differential thermal analysis–thermogravimetric analysis (DTA–TGA), the title complex is stable up to 423 K and thermal decomposition starts with the release of two coordinated dimethyl sulfoxide mol­ecules. Free H2L exhibits photoluminescence properties originating from intra­ligand (π–π*) transitions and fluorescence quenching is observed on complexation of H2L with CuII.

The dangerous new synthetic drug α-PVP as the hydrated chloride salt α-pyrrolidinopentiophenone hydrochloride 0.786-hydrate.

Abstract: α-Pyrrolidinovalerophenone (α-PVP), a dangerous designer drug, is now being marketed around the world as a harmless `bath salt', when in reality it is a powerful β-ketone phenethylamine stimulant. A sample of the free base from a recent law-enforcement seizure was crystallized as the HCl salt [systematic name: 1-(1-oxo-1-phenylpentan-2-yl)pyrrolidin-1-ium chloride 0.786-hydrate], C15H22NO(+)·Cl(-)·0.786H2O. In the crystal structure, the propyl chain is nearly perpendicular to both the phenyl ring and the carbonyl group. The hydrogen-bonding scheme involves the quaternary N atom, the Cl(-) anion and the partially occupied (0.786) water molecule, forming centrosymmetric dimers.

Structural and spectroscopic characterization of two new blue luminescent pyridylbenzimidazole zinc(II) complexes.

Abstract: Luminescent metal complexes are used in photooptical devices. Zinc(II) complexes are of interest because of the ability to tune their color, their high thermal stability and their favorable carrier transport character. In particular, some zinc(II) complexes with aryl diimine and/or heterocyclic ligands have been shown to emit brightly in the blue region of the spectrum. Zinc(II) complexes bearing derivatized imidazoles have been explored for possible optoelectronic applications. The structures of two zinc(II) complexes of 5,6-dimethyl-2-(pyridin-2-yl)-1-[(pyridin-2-yl)methyl]-1H-benzimidazole (L), namely dichlorido(dimethylformamide-κO){5,6-dimethyl-2-(pyridin-2-yl-κN)-1-[(pyridin-2-yl)methyl]-1H-benzimidazole-κN(3)}zinc(II) dimethylformamide monosolvate, [ZnCl2(C20H18N4)(C3H7NO)]·C3H7NO, (I), and bis(acetato-κ(2)O,O'){5,6-dimethyl-2-(pyridin-2-yl-κN)-1-[(pyridin-2-yl)methyl]-1H-benzimidazole-κN(3)}zinc(II) ethanol monosolvate, [Zn(C2H3O2)2(C20H18N4)]·C2H5OH, (II), are reported. Complex (I) crystallized as a dimethylformamide solvate and exhibits a distorted trigonal bipyramidal coordination geometry. The coordination sphere consists of a bidentate L ligand spanning axial to equatorial sites, two chloride ligands in equatorial sites, and an O-bound dimethylformamide ligand in the remaining axial site. The other complex, (II), crystallized as an ethanol solvate. The Zn(II) atom has a distorted trigonal prismatic coordination geometry, with two bidentate acetate ligands occupying two edges and a bidentate L ligand occupying the third edge of the prism. Complexes (I) and (II) emit in the blue region of the spectrum. The results of density functional theory (DFT) calculations suggest that the luminescence of L results from π*←π transitions and that the luminescence of the complexes results from interligand charge-transfer transitions. The orientation of the 2-(pyridin-2-yl) substituent with respect to the benzimidazole system was found to have an impact on the calculated HOMO-LUMO gap (HOMO is highest occupied molecular orbital and LUMO is lowest unoccupied molecular orbital).

A new three-dimensional zinc(II) coordination polymer involving 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole and benzene-1,4-dicarboxylate ligands.

Abstract: Metal–organic frameworks (MOFs) based on multidentate N-heterocyclic ligands involving imidazole, triazole, tetra­zole, benzimidazole, benzotriazole or pyridine present intriguing mol­ecular topologies and have potential appli­cations in ion exchange, magnetism, gas sorption and storage, catalysis, optics and biomedicine. The 2-[(1H-1,2,4-triazol-1-yl)meth­yl]-1H-benzimidazole (tmb) ligand has four potential N-atom donors and can act in monodentate, chelating, bridging and tridentate coordination modes in the construction of complexes, and can also act as both a hydrogen-bond donor and acceptor. In addition, the tmb ligand can adopt different coordination conformations, resulting in complexes with helical structures due to the presence of the flexible methyl­ene spacer. A new three-dimensional coordination polymer, poly[[bis(μ2-benzene-1,4-di­carboxyl­ato)-κ4O1,O1′:O4,O4′;κ2O1:O4-bis{μ2-2-[(1H-1,2,4-tri­azol-1-yl)methyl-κN4]-1H-benzimidazole-κN3}dizinc(II)] trihydrate], {[Zn(C8H4O4)(C10H9N5)]·1.5H2O}n, has been synthesized by the reaction of ZnCl2 with tmb and benzene-1,4-di­carb­oxy­lic acid (H2bdic) under solvothermal conditions. There are two crystallographically distinct bdic2− ligands [bdic2−(A) and bdic2−(B)] in the structure which adopt different coordination modes. The ZnII ions are bridged by tmb ligands, leading to one-dimensional helical chains with different handedness, and adjacent helices are linked by bdic2−(A) ligands, forming a two-dimensional network structure. The two-dimensional layers are further connected by bdic2−(B) ligands, resulting in a three-dimensional framework with the topological notation 66. The IR spectra and thermogravimetric curves are consistent with the results of the X-ray crystal structure analysis and the title polymer exhibits good fluorescence in the solid state at room temperature.

Conformational differences and intermolecular C—H…N interactions in three polymorphs of a bis(pyridinyl)‐substituted benzimidazole

Abstract: The structural characterization of several polymorphic forms of a compound allow the inter­play between mol­ecular conformation and inter­molecular inter­actions to be studied, which can contribute to the development of strategies for the rational preparation of materials with desirable properties and the tailoring of inter­molecular inter­actions to produce solids with predictable characteristics of inter­est in crystal engineering. The crystal structures of two new polymorphs of 5,6-dimethyl-2-(pyridin-2-yl)-1-[(pyridin-2-yl)meth­yl]-1H-benzimidazole, C20H18N4, are reported. The previously reported polymorph, (1) [Geiger & DeStefano (2014). Acta Cryst. E70, o365], exhibits the space group C2/c, whereas polymorphs (2) and (3) presented here are in the Pnma and P\overline{1} space groups, respectively. The mol­ecular structures of the three forms differ in their orientations of the 2-(pyridin-2-yl)- and 1-[(pyridin-2-yl)meth­yl]- substituents. Density functional theory (DFT) calculations show that the relative energies of the mol­ecule in the three conformations follows the order (1) < (2) < (3), with a spread of 10.6 kJ mol−1. An analysis of the Hirshfeld surfaces shows that the three polymorphs exhibit inter­molecular C—H⋯N inter­actions, which can be classified into six types. Based on DFT calculations involving pairs of mol­ecules having the observed inter­actions, the C—H⋯N energy in the systems explored is approximately −11.2 to −14.4 kJ mol−1.

Cyclic heterotetrameric and low-dimensional hydrogen-bonded polymeric structures in the morpholinium salts of ring-substituted benzoic acid analogues

Abstract: The morpholinium (tetra­hydro-2H-1,4-oxazin-4-ium) cation has been used as a counter-ion in both inorganic and organic salt formation and particularly in metal complex stabilization. To examine the influence of inter­active substituent groups in the aromatic rings of benzoic acids upon secondary structure generation, the anhydrous salts of morpholine with salicylic acid, C4H10NO+·C7H5O3−, (I), 3,5-di­nitro­salicylic acid, C4H10NO+·C7H3N2O7−, (II), 3,5-di­nitro­benzoic acid, C4H10NO+·C7H3N2O6−, (III), and 4-nitro­anthranilic acid, C4H10NO+·C7H5N2O4−, (IV), have been prepared and their hydrogen-bonded crystal structures are described. In the crystal structures of (I), (III) and (IV), the cations and anions are linked by moderately strong N—H⋯Ocarboxyl hydrogen bonds, but the secondary structure propagation differs among the three, viz. one-dimensional chains extending along [010] in (I), a discrete cyclic hetero­tetra­mer in (III), and in (IV), a hetero­tetra­mer with amine N—H⋯O hydrogen-bond extensions along b, giving a two-layered ribbon structure. With the hetero­tetra­mers in both (III) and (IV), the ion pairs are linked though inversion-related N—H⋯Ocarboxylate hydrogen bonds, giving cyclic R44(12) motifs. With (II), in which the anion is a phenolate rather than a carboxyl­ate, the stronger assocation is through a symmetric lateral three-centre cyclic R12(6) N—H⋯(O,O′) hydrogen-bonding linkage involving the phenolate and nitro O-atom acceptors of the anion, with extension through a weaker O—H⋯Ocarboxyl hydrogen bond. This results in a one-dimensional chain structure extending along [100]. In the structures of two of the salts [i.e. (II) and (IV)], there are also π–π ring inter­actions, with ring-centroid separations of 3.5516 (9) and 3.7700 (9) A in (II), and 3.7340 (9) A in (IV).

A cyanide-bridged heterometallic coordination polymer constructed from square-planar [Ni(CN)4](2-): synthesis, crystal structure, thermal decomposition, electron paramagnetic resonance (EPR) spectrum and magnetic properties.

Abstract: Square-planar complexes are commonly formed by transition metal ions having a d(8) electron configuration. Planar cyanometallate anions have been used extensively as design elements in supramolecular coordination systems. In particular, square-planar tetracyanometallate(II) ions, i.e. [M(CN)4](2-) (M(II) = Ni, Pd or Pt), are used as good building blocks for bimetallic Hofmann-type assemblies and their analogues. Square-planar tetracyanonickellate(II) complexes have been extensively developed with N-donor groups as additional co-ligands, but studies of these systems using O-donor ligands are scarce. A new cyanide-bridged Cu(II)-Ni(II) heterometallic compound, poly[[diaquatetra-μ2-cyanido-κ(8)C:N-nickel(II)copper(II)] monohydrate], {[Cu(II)Ni(II)(CN)4(H2O)2]·H2O}n, has been synthesized and characterized by X-ray single-crystal diffraction analyses, vibrational spectroscopy (FT-IR), thermal analysis, electron paramagnetic resonance (EPR) and magnetic moment measurements. The structural analysis revealed that it has a two-dimensional grid-like structure built up of cationic [Cu(H2O)2](2+) and anionic [Ni(CN)4](2-) units connected through bridging cyanide ligands. The overall three-dimensional supramolecular network is expanded by a combination of interlayer O-H...N and intralayer O-H...O hydrogen-bond interactions. The first decomposition reactions take place at 335 K under a static air atmosphere, which illustrates the existence of guest water molecules in the interlayer spaces. The electron paramagnetic resonance (EPR) spectrum confirms that the Cu(II) cation has an axial coordination symmetry and that the unpaired electrons occupy the d(x(2)-y(2)) orbital. In addition, magnetic investigations showed that antiferromagnetic interactions exist in the Cu(II) atoms through the diamagnetic [Ni(CN)4](2-) ion.

A phase transition from monoclinic C2 with Z′ = 1 to triclinic P1 with Z′ = 4 for the quasiracemate l‐2‐aminobutyric acid–d‐methionine (1/1)

Abstract: Racemates of hydro­phobic amino acids with linear side chains are known to undergo a unique series of solid-state phase transitions that involve sliding of mol­ecular bilayers upon heating or cooling. Recently, this behaviour was shown to extend also to quasiracemates of two different amino acids with opposite handedness [Gorbitz & Karen (2015). J. Phys. Chem. B, 119, 4975–4984]. Previous investigations are here extended to an l-2-amino­butyric acid–d-me­thio­nine (1/1) co-crystal, C4H9NO2·C5H11NO2S. The significant difference in size between the –CH2CH3 and –CH2CH2SCH3 side chains leads to extensive disorder at room temperature, which is essentially resolved after a phase transition at 229 K to an unprecedented triclinic form where all four d-me­thio­­nine mol­ecules in the asymmetric unit have different side-chain conformations and all three side-chain rotamers are used for the four partner l-2-amino­butyric acid mol­ecules.

Supramolecular architectures in Co(II) and Cu(II) complexes with thiophene-2-carboxylate and 2-amino-4,6-dimethoxypyrimidine ligands.

Abstract: The coordination chemistry of mixed-ligand complexes continues to be an active area of research since these compounds have a wide range of applications. Many coordination polymers and metal-organic framworks are emerging as novel functional materials. Aminopyrimidine and its derivatives are flexible ligands with versatile binding and coordination modes which have been proven to be useful in the construction of organic-inorganic hybrid materials and coordination polymers. Thiophenecarboxylic acid, its derivatives and their complexes exhibit pharmacological properties. Cobalt(II) and copper(II) complexes of thiophenecarboxylate have many biological applications, for example, as antifungal and antitumor agents. Two new cobalt(II) and copper(II) complexes incorporating thiophene-2-carboxylate (2-TPC) and 2-amino-4,6-dimethoxypyrimidine (OMP) ligands have been synthesized and characterized by X-ray diffraction studies, namely (2-amino-4,6-dimethoxypyrimidine-κN)aquachlorido(thiophene-2-carboxylato-κO)cobalt(II) monohydrate, [Co(C5H3O2S)Cl(C6H9N3O2)(H2O)]·H2O, (I), and catena-poly[copper(II)-tetrakis(μ-thiophene-2-carboxylato-κ(2)O:O')-copper(II)-(μ-2-amino-4,6-dimethoxypyrimidine-κ(2)N(1):N(3))], [Cu2(C5H3O2S)4(C6H9N3O2)]n, (II). In (I), the Co(II) ion has a distorted tetrahedral coordination environment involving one O atom from a monodentate 2-TPC ligand, one N atom from an OMP ligand, one chloride ligand and one O atom of a water molecule. An additional water molecule is present in the asymmetric unit. The amino group of the coordinated OMP molecule and the coordinated carboxylate O atom of the 2-TPC ligand form an interligand N-H...O hydrogen bond, generating an S(6) ring motif. The pyrimidine molecules also form a base pair [R2(2)(8) motif] via a pair of N-H...N hydrogen bonds. These interactions, together with O-H...O and O-H...Cl hydrogen bonds and π-π stacking interactions, generate a three-dimensional supramolecular architecture. The one-dimensional coordination polymer (II) contains the classical paddle-wheel [Cu2(CH3COO)4(H2O)2] unit, where each carboxylate group of four 2-TPC ligands bridges two square-pyramidally coordinated Cu(II) ions and the apically coordinated OMP ligands bridge the dinuclear copper units. Each dinuclear copper unit has a crystallographic inversion centre, whereas the bridging OMP ligand has crystallographic twofold symmetry. The one-dimensional polymeric chains self-assemble via N-H...O, π-π and C-H...π interactions, generating a three-dimensional supramolecular architecture.

A new antibacterial silver(I) complex incorporating 2,5-dimethylpyrazine and the anti-inflammatory diclofenac.

Abstract: AgI-containing coordination complexes have attracted attention because of their photoluminescence properties and antimicrobial activities and, in principle, these properties depend on the nature of the structural topologies. A novel two-dimensional silver(I) complex with the anti-inflammatory diclofenac molecule, namely bis{μ-2-[2-(2,6-dichloroanilino)phenyl]acetato-κ3O,O':O}bis(μ-2,5-dimethylpyrazine-κ2N:N')silver(I), [Ag2(C14H10Cl2NO2)2(C6H8N2)]n, (I), has been synthesized and characterized by single-crystal X-ray diffraction, revealing that the AgI ions are chelated by the carboxylate groups of the anionic 2-[2-(2,6-dichloroanilino)phenyl]acetate (dicl) ligand in a μ3-η1:η2 coordination mode. Each dicl ligand links three AgI atoms to generate a one-dimensional infinite chain. Adjacent chains are connected through 2,5-dimethylpyrazine (dmpyz) ligands to form a two-dimensional layer structure parallel to the crystallographic bc plane. The layers are further connected by C-H...π interactions to generate a three-dimensional supramolecular structure. Additionally, the most striking feature is that the structure contains an intramolecular C-H ...Ag anagostic interaction. Furthermore, the title complex has been tested for its in vitro antibacterial activity and is determined to be highly effective on the studied microorganisms.

Comparison of the crystal structures of the potent anticancer and anti-angiogenic agent regorafenib and its monohydrate.

Abstract: Regorafenib {systematic name: 4-[4-({[4-chloro-3-(tri­fluoro­methy)phen­yl]car­bam­o­yl}amino)-3-fluoro­phen­oxy]-1-methyl­pyridine-2-carboxamide}, C21H15ClF4N4O3, is a potent anti­cancer and anti-angiogenic agent that possesses various activities on the VEGFR, PDGFR, raf and/or flt-3 kinase signaling mol­ecules. The compound has been crystallized as polymorphic form I and as the mono­hydrate, C21H15ClF4N4O3·H2O. The regorafenib mol­ecule consists of bi­aryl­urea and pyridine-2-carboxamide units linked by an ether group. A comparison of both forms shows that they differ in the relative orientation of the bi­aryl­urea and pyridine-2-carboxamide units, due to different rotations around the ether group, as measured by the C—O—C bond angles [119.5 (3)° in regorafenib and 116.10 (15)° in the monohydrate]. Meanwhile, the conformational differences are reflected in different hydrogen-bond networks. Polymorphic form I contains two inter­molecular N—H⋯O hydrogen bonds, which link the regorafenib mol­ecules into an infinite mol­ecular chain along the b axis. In the monohydrate, the presence of the solvent water mol­ecule results in more abundant hydrogen bonds. The water mol­ecules act as donors and acceptors, forming N—H⋯O and O—H⋯O hydrogen-bond inter­actions. Thus, R42(28) ring motifs are formed, which are fused to form continuous spiral ring motifs along the a axis. The (tri­fluoro­meth­yl)phenyl rings protrude on the outside of these motifs and inter­digitate with those of adjacent ring motifs, thereby forming columns populated by halogen atoms.

Crystallization experiments with the dinuclear chelate ring complex di-μ-chlorido-bis[(η2-2-allyl-4-methoxy-5-{[(propan-2-yloxy)carbonyl]methoxy}phenyl-κC1)platinum(II)].

Abstract: Crystallization experiments with the dinuclear chelate ring complex di-μ-chlorido-bis­[(η2-2-allyl-4-meth­oxy-5-{[(propan-2-yl­oxy)carbon­yl]meth­oxy}phenyl-κC1)platinum(II)], [Pt2(C15H19O4)2Cl2], containing a derivative of the natural compound eugenol as ligand, have been performed. Using five different sets of crystallization conditions resulted in four different complexes which can be further used as starting compounds for the synthesis of Pt complexes with promising anti­cancer activities. In the case of vapour diffusion with the binary chloro­form–diethyl ether or methyl­ene chloride–diethyl ether systems, no change of the mol­ecular structure was observed. Using evaporation from aceto­nitrile (at room temperature), di­methyl­formamide (DMF, at 313 K) or dimethyl sulfoxide (DMSO, at 313 K), however, resulted in the displacement of a chloride ligand by the solvent, giving, respectively, the mononuclear complexes (aceto­nitrile-κN)(η2-2-allyl-4-meth­oxy-5-{[(propan-2-yl­oxy)carbon­yl]meth­oxy}phenyl-κC1)chlorido­platinum(II) monohydrate, [Pt(C15H19O4)Cl(CH3CN)]·H2O, (η2-2-allyl-4-meth­oxy-5-{[(propan-2-yl­oxy)carbon­yl]meth­oxy}phenyl-κC1)chlorido­(di­methyl­formamide-κO)platinum(II), [Pt(C15H19O4)Cl(C2H7NO)], and (η2-2-allyl-4-meth­oxy-5-{[(propan-2-yl­oxy)carbon­yl]meth­oxy}phenyl-κC1)chlorido­(dimethyl sulfoxide-κS)platinum(II), determined as the analogue {η2-2-allyl-4-meth­oxy-5-[(ethoxycarbonyl)meth­oxy]phenyl-κC1}chlorido­(dimethyl sulfoxide-κS)platinum(II), [Pt(C14H17O4)Cl(C2H6OS)]. The crystal structures confirm that aceto­nitrile inter­acts with the PtII atom via its N atom, while for DMSO, the S atom is the coordinating atom. For the replacement, the longest of the two Pt—Cl bonds is cleaved, leading to a cis position of the solvent ligand with respect to the allyl group. The crystal packing of the complexes is characterized by dimer formation via C—H⋯O and C—H⋯π inter­actions, but no π–π inter­actions are observed despite the presence of the aromatic ring.

Concomitant polymorphs of 1,3-bis(3-fluorophenyl)urea.

Abstract: Hydrogen bonding between urea functionalities is a common structural motif employed in crystal-engineering studies. Crystallization of 1,3-bis(3-fluoro­phenyl)urea, C13H10F2N2O, from many solvents yielded concomitant mixtures of at least two polymorphs. In the monoclinic form, one-dimensional chains of hydrogen-bonded urea molecules align in an antiparallel orientation, as is typical of many di­phenyl­ureas. In the ortho­rhom­bic form, one-dimensional chains of hydrogen-bonded urea molecules have a parallel orientation rarely observed in symmetrically substituted di­phenyl­ureas.

Six polycyclic pyrimidoazepine derivatives: syntheses, molecular structures and supramolecular assembly.

Abstract: A versatile synthetic method has been developed for the formation of variously substituted polycyclic pyrimidoazepine derivatives, formed by nucleophilic substitution reactions on the corresponding chloro-substituted compounds; the reactions can be promoted either by conventional heating in basic solutions or by microwave heating in solvent-free systems. Thus, (6RS)-6,11-dimethyl-3,5,6,11-tetrahydro-4H-benzo[b]pyrimido[5,4-f]azepin-4-one, C14H15N3O, (I), was isolated from a solution containing (6RS)-4-chloro-8-hydroxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine and benzene-1,2-diamine; (6RS)-4-butoxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-8-ol, C18H23N3O2, (II), was formed by reaction of the corresponding 6-chloro compound with butanol, and (RS)-4-dimethylamino-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-8-ol, C16H20N4O, (III), was formed by reaction of the chloro analogue with alkaline dimethylformamide. (6RS)-N-Benzyl-8-methoxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-4-amine, C22H24N4O, (IV), (6RS)-N-benzyl-6-methyl-1,2,6,7-tetrahydropyrimido[5',4':6,7]azepino[3,2,1-hi]indol-8-amine, C22H22N4, (V), and (7RS)-N-benzyl-7-methyl-2,3,7,8-tetrahydro-1H-pyrimido[5',4':6,7]azepino[3,2,1-ij]quinolin-9-amine, C23H24N4, (VI), were all formed by reaction of the corresponding chloro compounds with benzylamine under microwave irradiation. In each of compounds (I)-(IV) and (VI), the azepine ring adopts a conformation close to the boat form, with the C-methyl group in a quasi-equatorial site, whereas the corresponding ring in (V) adopts a conformation intermediate between the twist-boat and twist-chair forms, with the C-methyl group in a quasi-axial site. No two of the structures of (I)-(VI) exhibit the same range of intermolecular hydrogen bonds: different types of sheet are formed in each of (I), (II), (V) and (VI), and different types of chain in each of (III) and (IV).

Triclinic and monoclinic polymorphs of meso-(E,E)-1,1'-[1,2-bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene): the high-yield synthesis of an unexpected product, concomitant polymorphism and configurational disorder.

Abstract: Pyrazolidine-3,5-diones and their derivatives exhibit a wide range of biological activities. Seeking to explore the effect of combining a hydro­carbyl ring substituent, as present in sulfinpyrazone (used to treat gout), with a chlorinated aryl ring, as present in muzolimine (a diuretic), we explored the reaction between 1-phenyl­pyrazolidine-3,5-dione and 4-chloro­benzaldehyde under mildly basic conditions in the expectation of producing the simple condensation product 4-(4-chloro­benzyl­idene)-1-phenyl­pyrazolidine-3,5-dione. However, the reaction product proved to be meso-(E,E)-1,1′-[1,2-bis(4-chloro­phen­yl)ethane-1,2-di­yl]bis­(phenyl­diazene), C26H20Cl2N4, and a tentative mechanism is proposed. Crystallization from ethanol produces two concomitant polymorphs, i.e. a triclinic form, (I), in the space group P\overline{1}, and a monoclinic form, (II), in the space group C2/c. In both polymorphs, the mol­ecules lie across centres of inversion, but in (II), the mol­ecules are subject to whole-mol­ecule disorder equivalent to configurational disorder with occupancies of 0.6021 (19) and 0.3979 (19). There are no hydrogen bonds in the crystal structure of polymorph (I), but the mol­ecules of polymorph (II) are linked by C—H⋯π(arene) hydrogen bonds into complex chains, which are further linked into sheets by C—H⋯N inter­actions.