The hydrogen‐bonded complex bis(tert‐butylammonium) 2,6‐dichlorophenolate 2,4‐dichlorophenol–2,4‐dichlorophenolate tetrahydrofuran disolvate containing a chiral R53(10) hydrogen‐bonded ring as a supramolecular synthon

A fixed hydrogen‐bonding motif with a high probability of occurring when appropriate functional groups are involved is described as a `supramolecular hydrogen‐bonding synthon'. The identification of these synthons may enable the prediction of accurate crystal structures. The rare chiral hydrogen‐bonding motif R₅³(10) was observed previously in a cocrystal of 2,4,6‐trichlorophenol, 2,4‐dichlorophenol and dicyclohexylamine. In the title solvated salt, 2C₄H₁₂N⁺·C₆H₃Cl₂O⁻·(C₆H₃Cl₂O⁻·C₆H₄Cl₂O)·2C₄H₈O, five components, namely two tert‐butylammonium cations, one 2,4‐dichlorophenol molecule, one 2,4‐dichlorophenolate anion and one 2,6‐dichlorophenolate anion, are bound by N—H…O and O—H…O hydrogen bonds to form a hydrogen‐bonded ring, with the graph‐set motif R₅³(10), which is further associated with two pendant tetrahydrofuran molecules by N—H…O hydrogen bonds. The hydrogen‐bonded ring has internal symmetry, with a twofold axis running through the centre of the 2,6‐dichlorophenolate anion, and is isostructural with a previous and related structure formed from 2,4‐dichlorophenol, dicyclohexylamine and 2,4,6‐trichlorophenol. In the title crystal, helical columns are built by the alignment and twisting of the chiral hydrogen‐bonded rings, along and across the c axis, and successive pairs of rings are associated with each other through C—H…π interactions. Neighbouring helical columns are inversely related and, therefore, no chirality is sustained, in contrast to the previous case.     

π‐stacking and C—X...D (X = H,NO2; D = O, π) interactions in the crystal network of both C—H...N and π‐stacked dimers of 1,2‐bis(4‐bromophenyl)‐1H‐benzimidazole and 2‐(4‐bromophenyl)‐1‐(4‐nitrophenyl)‐1H‐benzimidazole

Molecules of 1,2‐bis(4‐bromophenyl)‐1H‐benzimidazole, C₁₉H₁₂Br₂N₂, (I), and 2‐(4‐bromophenyl)‐1‐(4‐nitrophenyl)‐1H‐benzimidazole, C₁₉H₁₂BrN₃O₂, (II), are arranged in dimeric units through C—H...N and parallel‐displaced π‐stacking interactions favoured by the appropriate disposition of N‐ and C‐bonded phenyl rings with respect to the mean benzimidazole plane. The molecular packing of the dimers of (I) and (II) arises by the concurrence of a diverse set of weak intermolecular C—X...D (X = H, NO₂; D = O, π) interactions.     

4,4′‐Bipyridine‐1,1′‐diium acetylenedicarboxylate: a new member of the (H2bipy)[Cu(ox)2] (bipy is 4,4′‐bipyridine and ox is oxalate) family

4,4′‐Bipyridine‐1,1′‐diium (H₂bipy) acetylenedicarboxylate, C₁₀H₁₂N₂²⁺·C₄O₄²⁻, (1), is a new member of a family of related structures with similar unit‐cell parameters. The structures in this family reported previously [Chen et al. (2012). CrystEngComm, 14 , 6400–6403] are (H₂bipy)[Cu(ox)₂] (ox is oxalate), (2), (H₂bipy)[NaH(ox)₂], (3), and (H₂bipy)[H₂(ox)₂], (4). Compound (1) has a one‐dimensional structure, in which H₂bipy²⁺ cations and acetylenedicarboxylate (ADC²⁻) anions are linked through a typical supramolecular synthon, i.e.R₂²(7), and form linear `–cation–anion–' ribbons. Through an array of nonclassical C—H...O hydrogen bonds, adjacent ribbons interact to give two‐dimensional sheets. These sheets stack to form a layered structure viaπ–π interactions between the H₂bipy²⁺ cations of neighbouring layers. The supramolecular isostructurality of compounds (1)–(4) is ascribed to the synergistic effect of multiple interactions in these structures. The balanced strong and weak intermolecular interactions stabilizing this structure type include strong charge‐assisted N—H...O hydrogen bonds, C—H...O contacts and π–π interactions.     

[2,5‐Bis(2,2′‐bipyridyl‐6‐yl)‐3,4‐diazahexa‐2,4‐diene]dichloridomanganese(II): from a mononuclear compound to a three‐dimensional supramolecular framework through C—H...Cl hydrogen bonds and π–π stacking interactions

The title compound, [MnCl₂(C₂₄H₂₀N₆)], has been synthesized and characterized based on the multifunctional ligand 2,5‐bis(2,2′‐bipyridyl‐6‐yl)‐3,4‐diazahexa‐2,4‐diene (L). The Mn^II centre is five‐coordinate with an approximately square‐pyramidal geometry. The L ligand acts as a tridendate chelating ligand. The mononuclear molecules are bridged into a one‐dimensional chain by two C—H...Cl hydrogen bonds. These chains are assembled into a two‐dimensional layer through π–π stacking interactions between adjacent uncoordinated bipyridyl groups. Furthermore, a three‐dimensional supramolecular framework is attained through π–π stacking interactions between adjacent coordinated bipyridyl groups.     

Weak hydrogen and halogen bonding in 4‐[(2,2‐difluoroethoxy)methyl]pyridinium iodide and 4‐[(3‐chloro‐2,2,3,3‐tetrafluoropropoxy)methyl]pyridinium iodide

To enable a comparison between a C—H…X hydrogen bond and a halogen bond, the structures of two fluorous‐substituted pyridinium iodide salts have been determined. 4‐[(2,2‐Difluoroethoxy)methyl]pyridinium iodide, C₈H₁₀F₂NO⁺·I⁻, (1), has a –CH₂OCH₂CF₂H substituent at the para position of the pyridinium ring and 4‐[(3‐chloro‐2,2,3,3‐tetrafluoropropoxy)methyl]pyridinium iodide, C₉H₉ClF₄NO⁺·I⁻, (2), has a –CH₂OCH₂CF₂CF₂Cl substituent at the para position of the pyridinium ring. In salt (1), the iodide anion is involved in one N—H…I and three C—H…I hydrogen bonds, which, together with C—H…F hydrogen bonds, link the cations and anions into a three‐dimensional network. For salt (2), the iodide anion is involved in one N—H…I hydrogen bond, two C—H…I hydrogen bonds and one C—Cl…I halogen bond; additional C—H…F and C—F…F interactions link the cations and anions into a three‐dimensional arrangement.     

A comparative experimental and theoretical investigation of hydrogen‐bond,halogen‐bond and π–π interactions in the solid‐state supramolecular assembly of 2‐ and 4‐formylphenyl arylsulfonates

To explore the operational role of noncovalent interactions in supramolecular architectures with designed topologies, a series of solid‐state structures of 2‐ and 4‐formylphenyl 4‐substituted benzenesulfonates was investigated. The compounds are 2‐formylphenyl 4‐methylbenzenesulfonate, C₁₄H₁₂O₄S, 3a , 2‐formylphenyl 4‐chlorobenzenesulfonate, C₁₃H₉ClO₄S, 3b , 2‐formylphenyl 4‐bromobenzenesulfonate, C₁₃H₉BrO₄S, 3c , 4‐formylphenyl 4‐methylbenzenesulfonate, C₁₄H₁₂O₄S, 4a , 4‐formylphenyl 4‐chlorobenzenesulfonate, 4b , C₁₃H₉ClO₄S, and 4‐formylphenyl 4‐bromobenzenesulfonate, C₁₃H₉BrO₄S, 4c . The title compounds were synthesized under basic conditions from salicylaldehyde/4‐hydroxybenzaldehydes and various aryl sulfonyl chlorides. Remarkably, halogen‐bonding interactions are found to be important to rationalize the solid‐state crystal structures. In particular, the formation of O…X (X = Cl and Br) and type I X…X halogen‐bonding interactions have been analyzed by means of density functional theory (DFT) calculations and characterized using Bader's theory of `atoms in molecules' and molecular electrostatic potential (MEP) surfaces, confirming the relevance and stabilizing nature of these interactions. They have been compared to antiparallel π‐stacking interactions that are formed between the arylsulfonates.     

Syntheses and crystal structures of two heterometallic iodoplumbates containing mixed‐valence copper(I/II)

Mixed‐valence copper(I/II) atoms have been introduced successfully into a Pb/I skeleton to obtain two heterometallic iodoplumbates, namely poly[bis(tetra‐n‐butylammonium) [bis(μ₃‐dimethyldithiocarbamato)dodeca‐μ₃‐iodido‐hexa‐μ₂‐iodido‐tetracopper(I)copper(II)hexalead(II)]], {(C₁₆H₃₆N)₂[Cu₄^ICu^IIPb₆(C₃H₆NS₂)₂I₁₈]}_n , (I), and poly[[μ₃‐iodido‐tri‐μ₂‐iodido‐iodido[bis(1,10‐phenanthroline)copper(I)]copper(I)copper(II)lead(II)] hemiiodine], {[Cu^ICu^IIPbI₅(C₁₂H₈N₂)₂]·0.5I₂}_n , (II), under solution and solvothermal conditions, respectively. Compound (I) contains two‐dimensional anionic layers, which are built upon the linkages of Cu^II(S₂CNMe₂)₂ units and one‐dimensional anionic Pb/I/Cu^I chains. Tetra‐n‐butylammonium cations are located between the anionic layers and connected to them via C—H…I hydrogen‐bonding interactions. Compound (II) exhibits a one‐dimensional neutral structure, which is composed of [PbI₅] square pyramids, [Cu^II₄] tetrahedra and [Cu^IIN₄I] trigonal bipyramids. Face‐to‐face aromatic π–π stacking interactions between adjacent 1,10‐phenanthroline ligands stabilize the structure and assemble compound (II) into a three‐dimensional supramolecular structure. I₂ molecules lie in the voids of the structure.     

Three zinc(II) and cadmium(II) complexes containing 4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole and polynitrile ligands: synthesis,molecular and supramolecular structures,and photoluminescence properties

Three photoluminescent complexes containing either Zn^II or Cd^II have been synthesized and their structures determined. Bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)zinc(II), [Zn(C₁₂H₁₀N₆)₂(C₂N₃)₂], (I), bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₂N₃)₂], (II), and bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(tricyanomethanido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₄N₃)₂], (III), all crystallize in the space group P , with the metal centres lying on centres of inversion, but neither analogues (I) and (II) nor Cd^II complexes (II) and (III) are isomorphous. A combination of N—H…N and C—H…N hydrogen bonds and π–π stacking interactions generates three‐dimensional framework structures in (I) and (II), and a sheet structure in (III). The photoluminescence spectra of (I)–(III) indicate that the energies of the π–π* transitions in the coordinated triazole ligand are modified by minor changes of the ligand geometry associated with coordination to the metal centres.     

Four supramolecular isomers of dichloridobis(1,10‐phenanthroline)cobalt(II): synthesis,structure characterization and isomerization

Crystal engineering can be described as the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding to design new solids with desired physical and chemical properties. Free‐energy differences between supramolecular isomers are generally small and minor changes in the crystallization conditions may result in the occurrence of new isomers. The study of supramolecular isomerism will help us to understand the mechanism of crystallization, a very central concept of crystal engineering. Two supramolecular isomers of dichloridobis(1,10‐phenanthroline‐κ²N,N′)cobalt(II), [CoCl₂(C₁₂H₈N₂)₂], i.e. (IA) (orthorhombic) and (IB) (monoclinic), and two supramolecular isomers of dichloridobis(1,10‐phenanthroline‐κ²N,N′)cobalt(II) N,N‐dimethylformamide monosolvate, [CoCl₂(C₁₂H₈N₂)₂]·C₃H₇NO, i.e. (IIA) (orthorhombic) and (IIB) (monoclinic), were synthesized in dimethylformamide (DMF) and structurally characterized. Of these, (IA) and (IIA) have been prepared and structurally characterized previously [Li et al. (2007). Acta Cryst. E 63 , m1880–m1880; Cai et al. (2008). Acta Cryst. E 64 , m1328–m1329]. We found that the heating rate is a key factor for the crystallization of (IA) or (IB), while the temperature difference is responsible for the crystallization of (IIA) or (IIB). Based on the crystallization conditions, isomerization behaviour, the KPI (Kitajgorodskij packing index) values and the density data, (IB) and (IIA) are assigned as the thermodynamic and stable kinetic isomers, respectively, while (IA) and (IIB) are assigned as the metastable kinetic products. The 1,10‐phenanthroline (phen) ligands interact with each other through offset face‐to‐face (OFF) π–π stacking in (IB) and (IIB), but by edge‐to‐face (EF) C—H...π interactions in (IA) and (IIA). Meanwhile, the DMF molecules in (IIB) connect to neighbouring [CoCl₂(phen)₂] units through two C—H...Cl hydrogen bonds, whereas there are no obvious interactions between DMF molecules and [CoCl₂(phen)₂] units in (IIA). Since OFF π–π stacking is generally stronger than EF C—H...π interactions for transition‐metal complexes with nitrogen‐containing aromatic ligands, (IIA) is among the uncommon examples that are stable and densely packed but that do not following Etter's intermolecular interaction hierarchy.     

Fourfold alkyl wrapping of a copper(II) porphyrin thwarts macrocycle π–π stacking in a compact supramolecular package

Porphyrins are valuable constituents in optoelectronic, catalytic, and other applications, yet control of intermolecular π–π stacking is invariably essential to attain the desired properties. Superstructures built onto the porphyrin, often via meso‐aryl groups, can afford facial encumbrance that suppresses π–π stacking, although some molecular designs have provided insufficient facial coverage and many have entailed cumbersome syntheses. In this study, a copper(II) porphyrin bearing four meso substituents, namely, {10,20‐bis[2,6‐bis(octyloxy)phenyl]‐5,15‐dibromoporphinato}copper(II), [Cu(C₆₄H₈₂Br₂N₄O₄)], was prepared by metalation of the corresponding free‐base porphyrin and was characterized by single‐crystal X‐ray diffraction. The crystal structure reveals a dihedral angle of 111.1 (2)° for the plane of the meso‐aryl group relative to the plane of the porphyrin, with both aryl groups tilted in the same direction. Each of the four octyloxy groups exhibits a gauche conformation for the –OCH₂CH₂– unit but is extended with four or five anti (–CH₂CH₂–/H) conformations thereafter, causing each octyl group to span the dimension of the macrocycle. In a global frame of reference where the two Br atoms define the north/south poles and the two aryl groups are at antipodes on the equator, two octyl groups of one aryl unit project over the northern hemisphere (covering pyrroles A and B), whereas those of the other aryl unit project over the southern hemisphere (covering pyrroles C and D). Together, the four octyl groups ensheath the two faces of the porphyrin in a self‐wrapped assembly. The closest approach of the Cu atom to an octyl methylene C atom (position 6) is 3.5817 (18) Å, the mean separations of neighboring porphyrin planes are 8.059 (4) and 4.693 (8) Å along the a and c axes, respectively, and the center‐to‐center distances between the Cu atoms of neighboring porphyrins are 10.2725 (4), 12.2540 (6), and 12.7472 (6) Å along the a, b, and c axes, respectively. The Hirshfeld surface analysis and two‐dimensional (2D) fingerprint plots provide information concerning contact interactions in the supramolecular assembly of the solid crystal.     

The Bright Future of Unconventional σ/π‐Hole Interactions

Non‐covalent interactions play a crucial role in (supramolecular) chemistry and much of biology. Supramolecular forces can indeed determine the structure and function of a host–guest system. Many sensors, for example, rely on reversible bonding with the analyte. Natural machineries also often have a significant non‐covalent component (e.g. protein folding, recognition) and rational interference in such ‘living’ devices can have pharmacological implications. For the rational design/tweaking of supramolecular systems it is helpful to know what supramolecular synthons are available and to understand the forces that make these synthons stick to one another. In this review we focus on σ‐hole and π‐hole interactions. A σ‐ or π‐hole can be seen as positive electrostatic potential on unpopulated σ* or π⁽*⁾ orbitals, which are thus capable of interacting with some electron dense region. A σ‐hole is typically located along the vector of a covalent bond such as X?H or X?Hlg (X=any atom, Hlg=halogen), which are respectively known as hydrogen and halogen bond donors. Only recently it has become clear that σ‐holes can also be found along a covalent bond with chalcogen (X?Ch), pnictogen (X?Pn) and tetrel (X?Tr) atoms. Interactions with these synthons are named chalcogen, pnigtogen and tetrel interactions. A π‐hole is typically located perpendicular to the molecular framework of diatomic π‐systems such as carbonyls, or conjugated π‐systems such as hexafluorobenzene. Anion–π and lone‐pair–π interactions are examples of named π‐hole interactions between conjugated π‐systems and anions or lone‐pair electrons respectively. While the above nomenclature indicates the distinct chemical identity of the supramolecular synthon acting as Lewis acid, it is worth stressing that the underlying physics is very similar. This implies that interactions that are now not so well‐established might turn out to be equally useful as conventional hydrogen and halogen bonds. In summary, we describe the physical nature of σ‐ and π‐hole interactions, present a selection of inquiries that utilise σ‐ and π‐holes, and give an overview of analyses of structural databases (CSD/PDB) that demonstrate how prevalent these interactions already are in solid‐state structures.     

Crystallographic report: Bis[tris(2‐pyridyl)amine]cadmium(II)‐di‐µ‐chloro‐dichloro‐cadmium(II), [(C5H4N)3N]2CdCl2CdCl2

In the dinuclear molecule of [(C₅H₄N)₃N]₂CdCl₂CdCl₂, one cadmium is octahedrally coordinated by a Cl₂N₄ donor set and the other cadmium is tetrahedrally coordinated by four chlorine atoms. The dinuclear units are connected by π–π interactions to give a two‐dimensional network. Copyright © 2003 John Wiley & Sons, Ltd.     

Crystallographic report: Diiodo[tris(2‐pyridyl)amine]zinc(II), [(C5H4N)3N]ZnI2

The zinc(II) atom in the molecule of [(C₅H₄N)₃N]ZnI₂ is tetrahedrally coordinated to two nitrogen atoms of the tris(2‐pyridyl)amine ligand and two iodides. The coordination moieties are connected to give a linear structure by intermolecular π–π interactions between the pyridyl rings. Copyright © 2003 John Wiley & Sons, Ltd.     

A copper(I) coordination polymer incorporation the corrosion inhibitor 1H‐benzotriazole: poly[μ3‐benzotriazolato‐κ3N1:N2:N3‐copper(I)]

The title complex, [Cu(C₆H₄N₃)]_n, was synthesized by the reaction of cupric nitrate, 1H‐benzotriazole (BTAH) and aqueous ammonia under hydrothermal conditions. The asymmetric unit contains three crystallographically independent Cu^I cations and two 1H‐benzotriazolate ligands. Two of the Cu^I cations, one with a linear two‐coordinated geometry and one with a four‐coordinated tetrahedral geometry, are located on sites with crystallographically imposed twofold symmetry. The third Cu^I cation, with a planar three‐coordinated geometry, is on a general position. Two Cu^I cations are doubly bridged by two BTA⁻ ligands to afford a noncentrosymmetric planar [Cu₂(BTA)₂] subunit, and two [Cu₂(BTA)₂] subunits are arranged in an antiparallel manner to form a centrosymmetric [Cu₂(BTA)₂]₂ secondary building unit (SBU). The SBUs are connected in a crosswise manner via the sharing of four‐coordinated Cu^I cations, Cu—N bonding and bridging by two‐coordinate Cu^I cations, resulting in a one‐dimensional chain along the c axis. These one‐dimensional chains are further linked by C—H...π and weak van der Waals interactions to form a three‐dimensional supramolecular architecture.     

Controllable assembly of a three‐dimensional metal–organic supramolecular framework displaying hydrogen‐bonding and π–π stacking interactions

The complex poly[[aqua(μ₂‐phthalato‐κ²O¹:O²){μ₃‐2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetato‐κ⁴N²,N³:O:O′}{μ₂‐2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetato‐κ³N²,N³:O}dizinc(II)] dihydrate], {[Zn₂(C₁₀H₈N₃O₂)₂(C₈H₄O₄)(H₂O)]·2H₂O}_n, has been prepared by solvothermal reaction of 2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetonitrile (PPAN) with zinc(II). Under hydrothermal conditions, PPAN is hydrolyzed to 2‐[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]acetate (PPAA⁻). The structure determination reveals that the complex is a one‐dimensional double chain containing cationic [Zn₄(PPAA)₄]⁴⁺ structural units, which are further extended by bridging phthalate ligands. The one‐dimensional chains are extended into a three‐dimensional supramolecular architecture via hydrogen‐bonding and π–π stacking interactions.     

The dual role of halogen,chalcogen, and pnictogen atoms as Lewis acid and base: Triangular XBr:SHX:PH2X complexes (X = F,Cl, Br,CN, NC,OH, NH2, and OCH3)

Using ab initio calculations, we have investigated the possibility of formation of triangular XBr:SHX:PH₂X complexes, where X = F, Cl, Br, CN, NC, OH, NH₂, and OCH₃. These complexes are formed through the interaction of a positive electrostatic potential region (σ‐hole) on a molecule with the negative region in another one. The results show that the combined halogen, chalcogen, and pnictogen interactions can give rise to stable cyclic structures. The interaction energies of these complexes span over a wide range, from ?3.55 to ?24.93 kcal/mol. Nice quadratic correlations are found between the interaction energies and binding distances in the trimers. To understand the nature of the interactions in these complexes, molecular electrostatic potential and quantum theory of atoms in molecule analyses are performed. © 2015 Wiley Periodicals, Inc.     

Crystallographic report: Dimethylammonium phenylphosphonate·2(phenylphosphonic acid)

Individual molecules of NH₂Me₂(HO)O₂PPh·2PhPO(OH)₂ are associated by hydrogen bonding, giving rise to a three‐dimensional supramolecular array. Copyright © 2003 John Wiley & Sons, Ltd.     

Bulk polarity of 3,5,7‐trinitro‐1‐azaadamantane mediated by asymmetric NO2(lone pair)…NO2(π‐hole) supramolecular bonding

Molecular crystals exhibiting polar symmetry are important paradigms for developing new electrooptical materials. Though accessing bulk polarity still presents a significant challenge, in some cases it may be rationalized as being associated with the specific molecular shapes and symmetries and subtle features of supramolecular interactions. In the crystal structure of 3,5,7‐trinitro‐1‐azaadamantane, C₉H₁₂N₄O₆, the polar symmetry of the molecular arrangement is a result of complementary prerequisites, namely the C_3v symmetry of the molecules is suited to the generation of polar stacks and the inherent asymmetry of the principal supramolecular bonding, as is provided by NO₂(lone pair)…NO₂(π‐hole) interactions. These bonds arrange the molecules into a trigonal network. In spite of the apparent simplicity, the structure comprises three unique molecules (Z′ =  +  + ), two of which are donors and acceptors of three N…O interactions and the third being primarily important for weak C—H…O hydrogen bonding. These distinct structural roles agree with the results of Hirshfeld surface analysis. A set of weak C—H…O and C—H…N hydrogen bonds yields three kinds of stacks. The orientation of the stacks is identical and therefore the polarity of each molecule contributes additively to the net dipole moment of the crystal. This suggests a special potential of asymmetric NO₂(lone pair)…NO₂(π‐hole) interactions for the supramolecular synthesis of acentric materials.