Hydrogen‐bonding and π–π stacking interactions in aquachloridobis(1,10‐phenanthroline)cobalt(II) chloride dichloridobis(1,10‐phenanthroline)cobalt(II) hexahydrate

The title compound, [CoCl(C₁₂H₈N₂)₂(H₂O)]Cl·[CoCl₂(C₁₂H₈N₂)₂]·6H₂O, is the first example of a new 1:1 cocrystal of the octahedral [CoCl₂(phen)₂] and [CoCl(phen)₂(H₂O)]⁺·Cl⁻ complexes (phen is 1,10‐phenanthroline). The latter form heterochiral dimers held by strong π–π stacking interactions via their phenathroline ligands, which confirms that π stacking is an important and reliable synthon in supramolecular design. In addition, the crystal structure is networked by H₂O...H₂O, H₂O...Cl⁻ and H₂O...Cl hydrogen bonds, which interconnect the different units of the cobalt complexes.     

Assembly of a two‐dimensional layer structure with 1,4‐bis(1H‐benzimidazol‐1‐ylmethyl)benzene dihydrate via hydrogen bonds and π–π interactions

In the title compound, C₂₂H₁₈N₄·2H₂O, the organic fragment lies across a centre of inversion in the P2₁/n space group. The water molecules form C(2)‐type hydrogen‐bonded chains which are linked to the 1,4‐bis(1H‐benzimidazol‐1‐ylmethyl)benzene molecules through O—H...N hydrogen bonds, forming sheets reinforced by π–π stacking interactions between the aromatic rings within the layers.     

A helical zinc(II) coordination polymer assembled from 1,3‐bis[(pyridin‐3‐yl)methoxy]benzene and benzene‐1,4‐dicarboxylic acid

In catena‐poly[[aqua[1,3‐bis(pyridine‐3‐ylmethoxy)benzene‐κN]zinc(II)]‐μ₂‐benzene‐1,4‐dicarboxylato‐κ²O¹:O⁴], [Zn(C₈H₄O₄)(C₁₈H₁₆N₂O₂)(H₂O)]_n, each Zn^II centre is tetrahedrally coordinated by two O atoms of bridging carboxylate groups from two benzene‐1,4‐dicarboxylate anions (denoted L²⁻), one O atom from a water molecule and one N atom from a 1,3‐bis[(pyridin‐3‐yl)methoxy]benzene ligand (denoted bpmb). (Aqua)O—H...N hydrogen‐bonding interactions induce the formation of one‐dimensional helical [Zn(L)(bpmb)(H₂O)]_n chains which are interlinked through (aqua)O—H...O hydrogen‐bonding interactions, producing two‐dimensional corrugated sheets.     

Pyridine–pyridine π–π stacking interactions in penta­carbonyl­[pyridine‐4(1H)‐thione]­tungsten(0)

In the title compound, [W(C₅H₅NS)(CO)₅], the pyridine‐4‐thiol ligand coordinates through the sulfur in the thione mode. The coordination sphere around the W atom is distorted from octahedral geometry by intermolecular hydrogen bonding and steric interactions between the pyridine ring and two CO ligands. An intermolecular pyridine–pyridine ring distance of 3.47 (1) Å indicates π–π stacking interactions between these ligand units.     

Intramolecular π–π stacking in diaquabis(2‐hydroxybenzoato‐κO)bis(1,10‐phenanthroline‐κ2N,N′)strontium(II)

In the title compound, [Sr(C₇H₅O₃)₂(C₁₂H₈N₂)₂(H₂O)₂], the Sr^II ion is located on a twofold rotation axis and assumes a distorted square‐antiprism SrN₄O₄ coordination geometry, formed by two phenanthroline (phen) ligands, two 2‐hydroxybenzoate anions and two water molecules. Within the mononuclear complex molecule, intramolecular π–π stacking is observed between nearly parallel coordinated phen ligands, while normal intermolecular π–π stacking occurs between parallel phen ligands of adjacent complex molecules. Classic O—H...O and weak C—H...O hydrogen bonding helps to stabilize the crystal structure.     

π–π stacking motifs in dialkylbis{5‐[(E)‐2‐aryldiazen‐1‐yl]‐2‐hydroxybenzoato}tin(IV) complexes

The diorganotin(IV) complexes of 5‐[(E)‐2‐aryldiazen‐1‐yl]‐2‐hydroxybenzoic acid are of interest because of their structural diversity in the crystalline state and their interesting biological activity. The structures of dimethylbis{2‐hydroxy‐5‐[(E)‐2‐(4‐methylphenyl)diazen‐1‐yl]benzoato}tin(IV), [Sn(CH₃)₂(C₁₄H₁₁N₂O₃)₂], and di‐n‐butylbis{2‐hydroxy‐5‐[(E)‐2‐(4‐methylphenyl)diazen‐1‐yl]benzoato}tin(IV) benzene hemisolvate, [Sn(C₄H₉)₂(C₁₄H₁₁N₂O₃)₂]·0.5C₆H₆, exhibit the usual skew‐trapezoidal bipyramidal coordination geometry observed for related complexes of this class. Each structure has two independent molecules of the Sn^IV complex in the asymmetric unit. In the dimethyltin structure, intermolecular O—H…O hydrogen bonds and a very weak Sn…O interaction link the independent molecules into dimers. The planar carboxylate ligands lend themselves to π–π stacking interactions and the diversity of supramolecular structural motifs formed by these interactions has been examined in detail for these two structures and four closely related analogues. While there are some recurring basic motifs amongst the observed stacking arrangements, such as dimers and step‐like chains, variations through longitudinal slipping and inversion of the direction of the overlay add complexity. The π–π stacking motifs in the two title complexes are combinations of some of those observed in the other structures and are the most complex of the structures examined.     

Synthesis,crystal structure and photophysical properties of 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene: a new π building block

A dimerized 1,3‐diazaazulene derivative, namely 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene [or 2,2′‐(1,4‐phenylene)bis(1,3‐diazaazulene)], C₂₂H₁₄N₄, (I), has been synthesized successfully through the condensation reaction between 2‐methoxytropone and benzene‐1,4‐dicarboximidamide hydrochloride, and was characterized by ¹H NMR and ¹³C NMR spectroscopies, and ESI–MS. X‐ray diffraction analysis reveals that (I) has a nearly planar structure with good π‐electron delocalization, indicating that it might serve as a π building block. The crystal belongs to the monoclinic system. One‐dimensional chains were formed along the a axis through π–π interactions and adjacent chains are stabilized by C—H…N interactions, forming a three‐dimensional architecture. The solid emission of (I) in the crystalline form exhibited a 170 nm red shift compared with that in the solution state. The observed optical bandgap for (I) is 3.22 eV and a cyclic voltammetry experiment confirmed the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The calculated bandgap for (I) is 3.37 eV, which is very close to the experimental result. In addition, the polarizability and hyperpolarizability of (I) were appraised for its further application in second‐order nonlinear optical materials.     

A novel three‐dimensional copper(II) coordination polymer with 1,4‐bis(1,2,4‐triazol‐1‐ylmeth­yl)benzene and thio­cyanate

In the title complex, poly[copper(II)‐di‐μ₂‐thio­cyanato‐μ₂‐1,4‐bis­(1,2,4‐triazol‐1‐ylmeth­yl)benzene], [Cu(NCS)₂(C₁₂H₁₂N₆)]_n, the Cu^II atom lies on an inversion centre in a tetra­gonally distorted octa­hedral environment. Four N atoms from thio­cyanate and 1,4‐bis­(1,2,4‐triazol‐1‐ylmeth­yl)benzene (bbtz) ligands fill the equatorial positions, and S atoms from symmetry‐related thio­cyanate ligands fill the axial positions. The benzene ring of the bbtz ligand lies about an inversion centre. Single thio­cyanate bridges link the Cu^II atoms into two‐dimensional sheets containing an unprecedented 16‐membered [Cu₄(μ‐NCS‐N:S)₄] ring. The bbtz ligands further link the two‐dimensional sheets into a three‐dimensional network.     

Amide–π interactions between formamide and benzene

High‐level ab initio calculations have been carried out using a formamide–benzene model system to evaluate amide–π interactions. The interaction energies were estimated as a sum of the CCSD(T) correlation contribution and the HF energy at the complete basis set limit, for the geometries of the model structures at the energy minimum obtained by potential energy surface (PES) scans. NH/π geometry in a face‐on configuration was found to be the most attractive among the various geometries considered, with interaction energy of ?3.75 kcal/mol. An interaction energy of ?2.08 kcal/mol was calculated for the stacked N/Center type geometry, where the nitrogen atom of formamide points directly toward the center of the aromatic ring. The weakest C?O/π geometry, where a carbonyl oxygen atom points toward the plane of the aromatic ring, was found to have energy minimum at an intermolecular distance of 3.67 Å from the PES, with a repulsive interaction energy less than 1 kcal/mol. However, if there are simultaneous attractive interactions with other parts of the molecule besides the amide group, the weak repulsion could be easily overcome, to give a C?O/π geometry interaction. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

Controllable assembly of a three‐dimensional metal–organic supramolecular framework including π–π stacking interactions

The mixed‐ligand metal–organic complex poly[(μ₃‐phthalato)[μ₂‐3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐ido]dicopper(II)], [Cu₂(C₈H₄O₄)(C₈H₆N₃)₂]_n, has been synthesized by the reaction of copper(II) acetate with 2‐(1H‐pyrazol‐3‐yl)pyridine (HL) and phthalic acid. The binuclear chelating–bridging L units are further linked by bridging phthalate ligands into a two‐dimensional network parallel to the (010) plane. The two‐dimensional networks are extended into a three‐dimensional supramolecular architecture viaπ–π stacking interactions.     

Hydrogen bonding and π–π stacking in the three‐dimensional supra­molecular complex bis­(4,4′‐bipyridinium) diaqua­dioxalatoferrate(II) bis(hydrogen oxalate)

The title compound, (C₁₀H₁₀N₂)₂[Fe(C₂O₄)₂(H₂O)₂](C₂HO₄)₂, appears to be a modular associate consisting of a complex anion containing bivalent Fe as the central atom, a bridging hydrogen oxalate anion and a diprotonated 4,4‐bipyridine acting as the counter‐cation. The Fe^II ion in the complex anion occupies a position on a centre of inversion. Its coordination environment is formed by six O atoms from two bidentate oxalate ligands, forming a basal plane, and two water mol­ecules approximately perpendicular to the plane, representing a distorted octa­hedral geometry. These three kinds of ions are connected by strong hydrogen bonds, with donor–acceptor distances (N⋯O and O⋯O) lying in the range 2.54–2.98 Å, and π–π stacking inter­actions between the 4,4′‐bipyridinium cations, thus forming a three‐dimensional supra­molecular structure.     

A novel two‐dimensional metal–organic supramolecular framework including π–π stacking and hydrogen‐bond interactions

[μ‐N,N′‐Bis(pyridin‐3‐yl)benzene‐1,4‐dicarboxamide‐<!?show [forcelb]><!?tlsb=0.12pt>1:2κ²N:N′]bis{[N,N′‐bis(pyridin‐3‐yl)benzene‐1,4‐dicarboxamide‐κN]diiodidomercury(II)}, [Hg₂I₄(C₁₈H₁₄N₄O₂)₃], is an S‐shaped dinuclear molecule, composed of two HgI₂ units and three N,N′‐bis(pyridin‐3‐yl)benzene‐1,4‐dicarboxamide (L) ligands. The central L ligand is centrosymmetric and coordinated to two Hg^II cations via two pyridine N atoms, in a syn–syn conformation. The two terminal L ligands are monodentate, with one uncoordinated pyridine N atom, and each adopts a syn–anti conformation. The HgI₂ units show highly distorted tetrahedral (sawhorse) geometry, as the Hg^II centres lie only 0.34 (2) or 0.32 (2) Å from the planes defined by the I and pyridine N atoms. Supramolecular interactions, thermal stability and solid‐state luminescence properties were also measured.     

Triclinic and orthorhombic polymorphs of 2‐iodo‐4‐nitro­aniline: interplay of hydrogen bonds,nitro⃛I interactions and aromatic π–π‐stacking interactions

In the triclinic polymorph of 2‐iodo‐4‐nitro­aniline, C₆H₅IN₂O₂, space group P, the mol­ecules are linked by paired N—­H?O hydrogen bonds into C(8)[R(6)] chains of rings. These chains are linked into sheets by nitro?I interactions, and the sheets are pairwise linked by aromatic π–π‐stacking interactions. In the orthorhombic polymorph, space group Pbca, the mol­ecules are linked by single N—H?O hydrogen bonds into spiral C(8) chains; the chains are linked by nitro?O interactions into sheets, each of which is linked to its two immediate neighbours by aromatic π–π‐stacking inter­actions, so producing a continuous three‐dimensional ­structure.     

The role of π–π stacking and hydrogen‐bonding interactions in the assembly of a series of isostructural group IIB coordination compounds

The supramolecular chemistry of coordination compounds has become an important research domain of modern inorganic chemistry. Herein, six isostructural group IIB coordination compounds containing a 2‐{[(2‐methoxyphenyl)imino]methyl}phenol ligand, namely dichloridobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)zinc(II), [ZnCl₂(C₂₈H₂₆N₂O₄)], 1 , diiodidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)zinc(II), [ZnI₂(C₂₈H₂₆N₂O₄)], 2 , dibromidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)cadmium(II), [CdBr₂(C₂₈H₂₆N₂O₄)], 3 , diiodidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)cadmium(II), [CdI₂(C₂₈H₂₆N₂O₄)], 4 , dichloridobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)mercury(II), [HgCl₂(C₂₈H₂₆N₂O₄)], 5 , and diiodidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)mercury(II), [HgI₂(C₂₈H₂₆N₂O₄)], 6 , were synthesized and characterized by X‐ray crystallography and spectroscopic techniques. All six compounds exhibit an infinite one‐dimensional ladder in the solid state governed by the formation of hydrogen‐bonding and π–π stacking interactions. The crystal structures of these compounds were studied using geometrical and Hirshfeld surface analyses. They have also been studied using M06‐2X/def2‐TZVP calculations and Bader's theory of `atoms in molecules'. The energies associated with the interactions, including the contribution of the different forces, have been evaluated. In general, the π–π stacking interactions are stronger than those reported for conventional π–π complexes, which is attributed to the influence of the metal coordination, which is stronger for Zn than either Cd or Hg. The results reported herein might be useful for understanding the solid‐state architecture of metal‐containing materials that contain M^IIX₂ subunits and aromatic organic ligands.     

Substituted 4‐alkoxy‐7‐Cl‐quinolines exhibiting π–π stacking

The molecules of 4‐allyloxy‐7‐chloroquinoline, C₁₂H₁₀ClNO, (I), 7‐chloro‐4‐methoxyquinoline, C₁₀H₈ClNO, (II), and 7‐chloro‐4‐ethoxyquinoline, C₁₁H₁₀ClNO, (III), are all planar. In all three structures, π–π interactions between the quinoline ring systems are generated by unit‐cell translations along the a axes, irrespective of space group. These structures are the first reported for 4‐alkoxyquinolines.     

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.     

A triangular palladium(II) supramolecular coordination complex based on 1,4‐bis(1H‐imidazol‐1‐yl)benzene and (2,2′‐bipyridyl)palladium(II) nitrate: synthesis and crystal structure

The self‐assembly of ditopic bis(1H‐imidazol‐1‐yl)benzene ligands ( L ^H) and the complex (2,2′‐bipyridyl‐κ²N,N′)bis(nitrato‐κO)palladium(II) affords the supramolecular coordination complex tris[μ‐bis(1H‐imidazol‐1‐yl)benzene‐κ²N³:N^3′]‐triangulo‐tris[(2,2′‐bipyridyl‐κ²N,N′)palladium(II)] hexakis(hexafluoridophosphate) acetonitrile heptasolvate, [Pd₃(C₁₀H₈N₂)₃(C₁₂H₁₀N₄)₃](PF₆)₆·7CH₃CN, 2 . The structure of 2 was characterized in acetonitrile‐d₃ by ¹H/¹³C NMR spectroscopy and a DOSY experiment. The trimeric nature of supramolecular coordination complex 2 in solution was ascertained by cold spray ionization mass spectrometry (CSI–MS) and confirmed in the solid state by X‐ray structure analysis. The asymmetric unit of 2 comprises the trimetallic Pd complex, six PF₆^? counter‐ions and seven acetonitrile solvent molecules. Moreover, there is one cavity within the unit cell which could contain diethyl ether solvent molecules, as suggested by the crystallization process. The packing is stabilized by weak inter‐ and intramolecular C—H…N and C—H…F interactions. Interestingly, the crystal structure displays two distinct conformations for the L ^H ligand (i.e. syn and anti), with an all‐syn‐[Pd] coordination mode. This result is in contrast to the solution behaviour, where multiple structures with syn/anti‐ L ^H and syn/anti‐[Pd] are a priori possible and expected to be in rapid equilibrium.     

Synthesis and characterization of poly(1,4‐bis((E)‐2‐(3‐dodecylthiophen‐2‐yl)vinyl)benzene) derivatives

New amorphous semiconducting copolymers, poly(9,9‐dialkylfluorene)‐alt‐(3‐dodecylthienyl‐divinylbenzene‐3‐dodecylthienyl) derivatives (PEFTVB and POFTVB), were designed, synthesized, and characterized. The structure of copolymers was confirmed by H NMR, IR, and elemental analysis. The copolymers showed very good solubility in organic solvents and high thermal stability with high T_g of 178–185 °C. The weight average molecular weight was found to be 107,900 with polydispersity of 3.14 for PEFTVB and 76,700 with that of 3.31 for POFTVB. UV–vis absorption studies showed the maximum absorption at 428 nm (in solution) and 435 nm (in film) for PEFTVB and at 430 nm (in solution) and 436 nm (in film) for POFTVB. Photoluminescence studies showed the emission at 498 nm (in solution) and 557 nm (in film) for PEFTVB and at 498 nm (in solution) and 536 nm (in film) for POFTVB. The solution‐processed thin‐film transistors showed the carrier mobility of 2 × 10^?4 cm² V^?1 s^?1 for PEFTVB‐based devices and 2 × 10^?5 cm² V^?1 s^?1 for POFTVB‐based devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3942–3949, 2010     

μ‐4,4′‐Bipyridine‐κ2N:N′‐bis[triaqua(4,4′‐bipyridine‐κN)cadmium(II)] bis(3‐aminobenzoate) bis(perchlorate) dihydrate: a novel supramolecular system constructed by π–π and hydrogen‐bonding interactions

The title dicadmium compound, [Cd₂(C₁₀H₈N₂)₅(H₂O)₆](C₇H₆NO₂)₂(ClO₄)₂·2H₂O, is located around an inversion centre. Each Cd^II centre is coordinated by three N atoms from three different 4,4′‐bipyridine ligands and three O atoms from three coordinating water molecules in a distorted octahedral coordination environment. In the dicadmium cation unit, one 4,4′‐bipyridine (4,4′‐bipy) molecule acts as a bidentate bridging ligand between two Cd metal ions, while the other four 4,4′‐bipy molecules act only as monodentate terminal ligands, resulting in a rare `H‐type' [Cd₂(C₁₀H₈N₂)₅(H₂O)₆] host unit. These host units are connected to each other viaπ–π stacking interactions, giving rise to a three‐dimensional supramolecular grid network with large cavities. The 3‐aminobenzoate anions, perchlorate anions and water molecules are encapsulated in the cavities by numerous hydrogen‐bonding interactions. To the best of our knowledge, this is the first example of a coordination compound based on both 4,4′‐bipyridine ligands together with discrete 3‐aminobenzoate anions.     

σ–π Continuum in Indole–Palladium(II) Complexes

The intrinsic features of (hetero‐arene)–metal interactions have been elusive mainly because the systematic structure analysis of non‐anchored hetero‐arene–metal complexes has been hampered by their labile nature. We report successful isolation and systematic structure analysis of a series of non‐anchored indole–palladium(II) complexes. It was revealed that there is a σ–π continuum for the indole–metal interaction, while it has been thought that the dominant coordination mode of indole to a metal center is the Wheland‐intermediate‐type σ‐mode in light of the seemingly strong electron‐donating ability of indole. Several factors which affect the σ‐ or π‐character of indole–metal interactions are discussed.