Poly[[aquabis(μ2‐isonicotinato‐κ3N:O,O′)cadmium(II)] 1,4‐di‐3‐pyridyl‐2,3‐diaza‐1,3‐butadiene hemisolvate]

The title compound, {[Cd(C₆H₄NO₂)₂(H₂O)]·0.5C₁₂H₁₀N₄}_n, presents an intricate three‐dimensional network with cavities traversing it in three orthogonal directions, where the (disordered) guest molecules lodge. The compound is a member of a series of coordination polymers presenting the same main host framework but with guests of variable size and geometry, to which the flexible skeleton seems to adapt. The disorder in the structure is explained in terms of an apparently well defined specificity in the position/orientation of the guest molecules, as determined by the main framework.     

Two (E)‐2‐arylidene‐1,4‐di‐p‐tosyl‐1,2,3,4‐tetrahydroquinoxaline compounds: supramolecular frameworks built with C—H...O and C—H...π(arene) hydrogen bonds and π–π stacking interactions

The pyrazine ring in two N‐substituted quinoxaline derivatives, namely (E)‐2‐(2‐methoxybenzylidene)‐1,4‐di‐p‐tosyl‐1,2,3,4‐tetrahydroquinoxaline, C₃₀H₂₈N₂S₂O₅, (II), and (E)‐methyl 2‐[(1,4‐di‐p‐tosyl‐1,2,3,4‐tetrahydroquinoxalin‐2‐ylidene)methyl]benzoate, C₃₁H₂₈N₂S₂O₆, (III), assumes a half‐chair conformation and is shielded by the terminal tosyl groups. In the molecular packing of the compounds, intermolecular C—H...O hydrogen bonds between centrosymmetrically related molecules generate dimeric rings, viz. R₂²(22) in (II) and R₂²(26) in (III), which are further connected through C—H...π(arene) hydrogen bonds and π–π stacking interactions into novel supramolecular frameworks.     

3‐Methyl‐7‐(2‐thienyl)pyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione: π‐stacked bilayers built from N—H...O,C—H...O and C—H...π hydrogen bonds

In the title compound, C₁₂H₉N₃O₂S, the thienyl substituent is disordered over two sets of sites with occupancies of 0.749 (3) and 0.251 (3). A combination of N—H...O, C—H...O and C—H...π hydrogen bonds links the molecules into bilayers and these bilayers are themselves linked into a continuous structure by π–π stacking interactions.     

5‐Amino‐1‐benzoyl‐3‐methylpyrazole: complex sheets built from N—H...N,C—H...O and C—H...π(arene) hydrogen bonds

Molecules of the title compound [systematic name: (5‐amino‐3‐methylpyrazol‐1‐yl)(phenyl)methanone], C₁₁H₁₁N₃O, contain an intramolecular hydrogen bond. The molecules are linked into sheets by a combination of N—H...N, C—H...O and C—H...π(arene) hydrogen bonds. Comparisons are made with the hydrogen‐bonded structures of some related compounds.     

Concerted coordination and hydrogen‐bonding network of the 1,4‐di‐4‐pyrid­yl‐2,3‐diaza‐1,3‐butadiene [Zn(MeOH)2(H2O)2](ClO4)2 3:1 complex

In the title compound, diaqua­bis(1,4‐di‐4‐pyrid­yl‐2,3‐diaza‐1,3‐butadiene)dimethanolzinc(II) bis­(perchlorate) 1,4‐di‐4‐pyrid­yl‐2,3‐diaza‐1,3‐butadiene methanol 1.72‐solvate 1.28‐hydrate, [Zn(C₁₂H₁₀N₄)₂(CH₄O)₂(H₂O)₂](ClO₄)₂·C₁₂H₁₀N₄·1.72CH₄O·1.28H₂O, determined at ca 110 K, the Zn cation and the extended dipyridyl ligand both lie across inversion centres in space group P. The structure consists of a network arrangement of the constituent species stabilized by a combination of coordination, hydrogen bonding and π–π forces. Uncoordinated methanol and water solvent mol­ecules occupy the otherwise void spaces within and between the networks.     

Weak C—H...O and C—H...π hydrogen bonds and π–π stacking interactions in a series of four N′‐[(E)‐(aryl)methylidene]‐N‐methyl‐2‐oxo‐1,3‐oxazolidine‐4‐carbohydrazides

Oxazolidin‐2‐ones are widely used as protective groups for 1,2‐amino alcohols and chiral derivatives are employed as chiral auxiliaries. The crystal structures of four differently substituted oxazolidinecarbohydrazides, namely N′‐[(E)‐benzylidene]‐N‐methyl‐2‐oxo‐1,3‐oxazolidine‐4‐carbohydrazide, C₁₂H₁₂N₃O₃, (I), N′‐[(E)‐2‐chlorobenzylidene]‐N‐methyl‐2‐oxo‐1,3‐oxazolidine‐4‐carbohydrazide, C₁₂H₁₂ClN₃O₃, (II), (4S)‐N′‐[(E)‐4‐chlorobenzylidene]‐N‐methyl‐2‐oxo‐1,3‐oxazolidine‐4‐carbohydrazide, C₁₂H₁₂ClN₃O₃, (III), and (4S)‐N′‐[(E)‐2,6‐dichlorobenzylidene]‐N,3‐dimethyl‐2‐oxo‐1,3‐oxazolidine‐4‐carbohydrazide, C₁₃H₁₃Cl₂N₃O₃, (IV), show that an unexpected mild‐condition racemization from the chiral starting materials has occurred in (I) and (II). In the extended structures, the centrosymmetric phases, which each crystallize with two molecules (A and B) in the asymmetric unit, form A+B dimers linked by pairs of N—H...O hydrogen bonds, albeit with different O‐atom acceptors. One dimer is composed of one molecule with an S configuration for its stereogenic centre and the other with an R configuration, and possesses approximate local inversion symmetry. The other dimer consists of either R,R or S,S pairs and possesses approximate local twofold symmetry. In the chiral structure, N—H...O hydrogen bonds link the molecules into C(5) chains, with adjacent molecules related by a 2₁ screw axis. A wide variety of weak interactions, including C—H...O, C—H...Cl, C—H...π and π–π stacking interactions, occur in these structures, but there is little conformity between them.     

The O–H···O, O–H···N and C–H···O hydrogen bonds in 1,4-dimethylpiperazine mono-betaine monohydrate

1,4-Dimethylpiperazine mono-betaine (1-carboxymethyl-1,4-dimethylpiperazinium inner salt, MBPZ) crystallizes as monohydrate. The crystals are orthorhombic, space group Pccn. Two MBPZ molecules and two water molecules form a cyclic oligomer, (MBPZ·H₂O)₂. The O–H···O and O–H···N hydrogen bonds are of 2.769(1) and 2.902(1) Å, respectively. The dimers interact with the neighboring molecules through the C–H···O hydrogen bonds of 3.234(1) Å. The piperazine ring assumes a chair conformation with the N(4)–CH₃ and N⁺(1)–CH₂COO⁻ groups in the equatorial position and the N⁺(1)–CH₃ group in the axial one. The FTIR spectrum is compared with that calculated by the B3LYP/6-31G(d,p) level of theory.     

4‐Methoxy‐1‐naphthol: chains formed by O—H...O hydrogen bonds and π–π stacking interactions

The structure of 4‐methoxy‐1‐naphthol, C₁₁H₁₀O₂, (I), contains an intermolecular O—H...O hydrogen bond which links the molecules into a simple C(2) chain running parallel to the shortest crystallographic b axis. This chain is reinforced by intermolecular π–π stacking interactions. Comparisons are drawn between the crystal structure of (I) and those of several of its simple analogues, including 1‐naphthol and some monosubstituted derivatives, and that of its isomer 7‐methoxy‐2‐naphthol. This comparison shows a close similarity in the packing of the molecules of its simple analogues that form π‐stacks along the shortest crystallographic axes. A substantial spatial overlap is observed between adjacent molecules in such stacks. In this group of monosubstituted naphthols, the overlap depends mainly on the position of the substituents carried by the naphthalene moiety, and the extent of the overlap depends on the substituent type. By contrast with (I), in the crystal structure of the isomeric 7‐methoxy‐2‐naphthol there are no O—H...O hydrogen bonds or π–π stacking interactions, and sheets are formed by O—H...π and C—H...π interactions.     

5‐Chloro‐2‐hydroxybenzophenone,featuring O—H...O,C—H...O,C—H...π and π–π interactions

Molecules of the title compound, C₁₃H₉ClO₂, contain an intramolecular O—H...O hydrogen bond, and the two aromatic rings are inclined at 57.02 (3)° with respect to one another. The crystal structure is supported by C—H...O, C—H...π and π–π interactions.     

Van Der Waals heterogeneous layer‐layer carbon nanostructures involving π···H‐C‐C‐H···π···H‐C‐C‐H stacking based on graphene and graphane sheets

Noncovalent interactions involving aromatic rings, such as π···π stacking, CH···π are very essential for supramolecular carbon nanostructures. Graphite is a typical homogenous carbon matter based on π···π stacking of graphene sheets. Even in systems not involving aromatic groups, the stability of diamondoid dimer and layer‐layer graphane dimer originates from C − H···H − C noncovalent interaction. In this article, the structures and properties of novel heterogeneous layer‐layer carbon‐nanostructures involving π···H‐C‐C‐H···π···H‐C‐C‐H stacking based on [n ]‐graphane and [n ]‐graphene and their derivatives are theoretically investigated for n = 16–54 using dispersion corrected density functional theory B3LYP‐D3 method. Energy decomposition analysis shows that dispersion interaction is the most important for the stabilization of both double‐ and multi‐layer‐layer [n ]‐graphane@graphene. Binding energy between graphane and graphene sheets shows that there is a distinct additive nature of CH···π interaction. For comparison and simplicity, the concept of H‐H bond energy equivalent number of carbon atoms (noted as NHEQ), is used to describe the strength of these noncovalent interactions. The NHEQ of the graphene dimers, graphane dimers, and double‐layered graphane@graphene are 103, 143, and 110, indicating that the strength of C‐H···π interaction is close to that of π···π and much stronger than that of C‐H···H‐C in large size systems. Additionally, frontier molecular orbital, electron density difference and visualized noncovalent interaction regions are discussed for deeply understanding the nature of the C‐H···π stacking interaction in construction of heterogeneous layer‐layer graphane@graphene structures. We hope that the present study would be helpful for creations of new functional supramolecular materials based on graphane and graphene carbon nano‐structures. © 2017 Wiley Periodicals, Inc.     

Ab initio and AIM studies on typical π‐type and pseudo‐π‐type halogen bonds: Comparison with hydrogen bonds

Series of typical π‐type and pseudo‐π‐type halogen‐bonded complexes B ··· ClY and B ··· BrY and hydrogen‐bonded complex B ··· HY (B = C₂H₄, C₂H₂, and C₃H₆; Y = F, Cl, and Br) have been investigated using the MP2/aug‐cc‐pVDZ method. A striking parallelism was found in the geometries, vibrational frequencies, binding energies, and topological properties between B ··· XY and B ··· HY (X = Cl and Br). It has been found that the lengths of the weak bond d(X ··· π)/d(H ··· π), the frequencies of the weak bond ν(X ··· π)/ν(H ··· π), the frequency shifts Δν(X? Y)/Δν(H? Y), the electron densities at the bond critical point of the weak bonds ρ_c(X ··· π)/ρ_c(H ··· π), and the electron density changes Δρ_c(X? Y)/Δρ_c(H? Y) could be used as measures of the strengths of typical π‐type and pseudo‐π‐type halogen/hydrogen bonds. The typical π‐type and pseudo‐π‐type halogen bond and hydrogen bond are noncovalent interactions. For the same Y, the halogen bond strengths are in the order B ··· ClY < B ··· BrY. For the same X, the halogen bond strength decreases according to the sequence F > Cl > Br that is in agreement with the hydrogen bond strengths B ··· HF > B ··· HCl > B ··· HBr. All of these typical π‐type and pseudo‐π‐type hydrogen‐bonded and halogen‐bonded complexes have the “conflict‐type” structure. Contour maps of the Laplacian of π electron density indicate that the formation of B ··· XY halogen‐bonded complex and B ··· HY hydrogen‐bonded complex is very similar. Charge transfer is observed from B to XY/HY and both the dipolar polarization and the volume of the halogen atom or hydrogen atom decrease on B ··· XY/B ··· HY complex formation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

N‐(2‐Iodobenzylidene)‐3‐nitroaniline: sheets formed by a combination of C—H⋯O hydrogen bonds and two aromatic π–π‐stacking interactions

Molecules of the title compound, C₁₃H₉IN₂O₂, are linked into [010] chains by a single C—H?O hydrogen bond and these chains are linked into (100) sheets by two independent aromatic π–π‐stacking interactions, each involving one of the two substituted arene rings.     

C—H⋯N and C—H⋯π interactions in 2‐ethoxy‐4,6‐diphenylpyridine‐3‐carbonitrile

The title compound, C₂₀H₁₆N₂O, has two mol­ecules in the asymmetric unit and the crystal structure shows that the central pyridine ring of each mol­ecule has a flat boat conformation. The terminal C atom in one of the mol­ecules is disordered over two positions, with relative occupancies of 0.594 (14) and 0.398 (14). Intermolecular C—H?N and C—H?π interactions and π–π stacking, along with intramolecular C—H?N and C—H?π interactions, help to stabilize the structure.     

C—H⋯π and π–π interactions in the supramolecular structure of 3‐methyl‐1,4‐diphenyl‐1H‐pyrazolo[3,4‐b]pyridine

The supramolecular structure of the title compound, C₁₉H₁₅N₃, is defined by π–π‐stacking and C—H?π interactions. There are no conventional hydrogen bonds in the structure.     

1‐(2‐Aminophenyl)‐3‐(4‐pyridyl)prop‐2‐en‐1‐one: a three‐dimensional framework structure built from N—H...N,C—H...O and C—H...π(arene) hydrogen bonds

The intramolecular dimensions of the title compound, C₁₄H₁₂N₂O, provide evidence for a polarized electronic structure. The molecule, which is almost completely planar, contains an intramolecular N—H...O hydrogen bond, and the molecules are linked by a combination of N—H...N, C—H...O and C—H...π(arene) hydrogen bonds to form a three‐dimensional framework structure.     

Cocrystals of 1,4‐diethynylbenzene with 1,3‐diacetylbenzene and benzene‐1,4‐dicarbaldehyde exhibiting strong nonconventional alkyne–carbonyl C—H…O hydrogen bonds between the components

Weak interactions between organic molecules are important in solid‐state structures where the sum of the weaker interactions support the overall three‐dimensional crystal structure. The sp‐C—H…N hydrogen‐bonding interaction is strong enough to promote the deliberate cocrystallization of a series of diynes with a series of dipyridines. It is also possible that a similar series of cocrystals could be formed between molecules containing a terminal alkyne and molecules which contain carbonyl O atoms as the potential hydrogen‐bond acceptor. I now report the crystal structure of two cocrystals that support this hypothesis. The 1:1 cocrystal of 1,4‐diethynylbenzene with 1,3‐diacetylbenzene, C₁₀H₆·C₁₀H₁₀O₂, (1), and the 1:1 cocrystal of 1,4‐diethynylbenzene with benzene‐1,4‐dicarbaldehyde, C₁₀H₆·C₈H₆O₂, (2), are presented. In both cocrystals, a strong nonconventional ethynyl–carbonyl sp‐C—H…O hydrogen bond is observed between the components. In cocrystal (1), the C—H…O hydrogen‐bond angle is 171.8 (16)° and the H…O and C…O hydrogen‐bond distances are 2.200 (19) and 3.139 (2) Å, respectively. In cocrystal (2), the C—H…O hydrogen‐bond angle is 172.5 (16)° and the H…O and C…O hydrogen‐bond distances are 2.25 (2) and 3.203 (2) Å, respectively.     

A mixed crystal of imperatorin and phellopterin,with C—H...O,C—H...π and π–π interactions

The crystal structure of 9‐(3‐methyl­but‐2‐enyl­oxy)­‐7H‐furo­[3,2‐g]­chro­men‐7‐one–4‐methoxy‐9‐(3‐methyl­but‐2‐enyl­oxy)‐7H‐­furo­[3,2‐g]­chromen‐7‐one (0.926/0.074), 0.926C₁₆H₁₄O₄·0.074C₁₇H₁₆O₅, is characterized by two independent imperatorin mol­ecules in the asymmetric unit, which exhibit different side‐chain conformations. A small amount of phellopterin overlaps with one of the two imperatorin mol­ecules. The supramol­ecular structure is supported by C—H...O, C—H...π and π–π interactions.     

Synthesis,X‐ray characterization and density functional theory studies of N6‐benzyl‐N6‐methyladenine–M(II) complexes (M = Zn,Cd): The prominent role of π–π, C–H···π and anion–π interactions

We report the synthesis and X‐ray characterization of the N⁶‐benzyl‐N⁶‐methyladenine ligand (L) and three metal complexes, namely [Zn(HL)Cl₃]·H₂O ( 1 ), [Cd(HL)₂Cl₄] ( 2 ) and [H₂L]₂[Cd₃(μ‐L)₂(μ‐Cl)₄Cl₆]·3H₂O ( 3 ). Complex 1 consists of the 7H‐adenine tautomer protonated at N3 and coordinated to a tetrahedral Zn(II) metal centre through N9. The octahedral Cd(II) in complex 2 is N⁹‐coordinated to two N⁶‐benzyl‐N⁶‐methyladeninium ligands (7H‐tautomer protonated at N3) that occupy apical positions and four chlorido ligands form the basal plane. Compound 3 corresponds to a trinuclear Cd(II) complex, where the central Cd atom is six‐coordinated to two bridging μ‐L and four bridging μ‐Cl ligands. The other two Cd atoms are six‐coordinated to three terminal chlorido ligands, to two bridging μ‐Cl ligands and to the bridging μ‐L through N3. Essentially, the coordination patterns, degree of protonation and tautomeric forms of the nucleobase dominate the solid‐state architectures of 1 – 3 . Additionally, the hydrogen‐bonding interactions produced by the endocyclic N atoms and NH groups stabilize high‐dimensional‐order supramolecular assemblies. Moreover, energetically strong anion–π and lone pair (lp)–π interactions are important in constructing the final solid‐state architectures in 1 – 3 . We have studied the non‐covalent interactions energetically using density functional theory calculations and rationalized the interactions using molecular electrostatic potential surfaces and Bader's theory of atoms in molecules. We have particularly analysed cooperative lp–π and anion–π interactions in 1 and π⁺–π⁺ interactions in 3 .     

Naphthalene‐1,6‐diol: a three‐dimensional framework built from O—H...O,O—H...π and C—H...O hydrogen bonds

The asymmetric unit of the title compound, C₁₀H₈O₂, contains two practically planar symmetry‐independent molecules linked by one O—H...O hydrogen bond. Molecules are further linked into a three‐dimensional network, which is built from R₆⁶(36), R₆⁶(18), R₆⁶(30) and R₄⁴(26) rings formed by the combined effect of three O—H...O and one C—H...O hydrogen bond. This network is additionally stabilized by an O—H...π interaction.     

C—H⋯O,C—H⋯π and π–π inter­actions in three benzofuran‐2‐yl ketone derivatives

The mol­ecules of 2‐benzoyl‐1‐benzofuran, C₁₅H₁₀O₂, (I), inter­act through double C—H⋯O hydrogen bonds, forming dimers that are further linked by C—H⋯O, C—H⋯π and π–π inter­actions, resulting in a three‐dimensional supramolecular network. The dihedral angle between the benzo­yl and benzofuran fragments in (I) is 46.15 (3)°. The mol­ecules of bis­(5‐bromo‐1‐benzofuran‐2‐yl) ketone, C₁₇H₈Br₂O₃, (II), exhibit C₂ symmetry, with the carbon­yl group (C=O) lying along the twofold rotation axis, and are linked by a combination of C—H⋯O and C—H⋯π inter­actions and Br⋯Br contacts to form sheets. The stability of the mol­ecular packing in 3‐mesit­yl‐3‐methyl­cyclo­but­yl 3‐methyl­naphtho[1,2‐b]furan‐2‐yl ketone, C₂₈H₂₈O₂, (III), arises from C—H⋯π and π–π stacking inter­actions. The fused naphthofuran moiety in (III) is essentially planar and makes a dihedral angle of 81.61 (3)° with the mean plane of the trimethyl­benzene ring.