Exo conformers of N‐(pyridin‐2‐yl)‐ and N‐(pyridin‐3‐yl)norbornene‐5,6‐dicarboximide crystals

Two isomeric pyridine‐substituted norbornenedicarboximide derivatives, namely N‐(pyridin‐2‐yl)‐exo‐norbornene‐5,6‐dicarboximide, (I), and N‐(pyridin‐3‐yl)‐exo‐norbornene‐5,6‐dicarboximide, (II), both C₁₄H₁₂N₂O₄, have been crystallized and their structures unequivocally determined by single‐crystal X‐ray diffraction. The molecules consist of norbornene moieties fused to a dicarboximide ring substituted at the N atom by either pyridin‐2‐yl or pyridin‐3‐yl in an anti configuration with respect to the double bond, thus affording exo isomers. In both compounds, the asymmetric unit consists of two independent molecules (Z′ = 2). In compound (I), the pyridine rings of the two independent molecules adopt different conformations, i.e. syn and anti, with respect to the methylene bridge. The intermolecular contacts of (I) are dominated by C—H...O interactions. In contrast, in compound (II), the pyridine rings of both molecules have an anti conformation and the two independent molecules are linked by carbonyl–carbonyl interactions, as well as by C—H...O and C—H...N contacts.     

Three closely related 1‐(naphthalen‐2‐yl)prop‐2‐en‐1‐ones: pseudosymmetry,disorder and supramoleular assembly mediated by C—H…π and C—Br…π interactions

It has been observed that when electron‐rich naphthyl rings are present in chalcones they can participate in π–π stacking interactions, and this can play an important role in orientating inhibitors within the active sites of enzymes, while chalcones containing heterocyclic substituents additionally exhibit fungistatic and fungicidal properties. With these considerations in mind, three new chalcones containing 2‐naphthyl substituents were prepared. 3‐(4‐Fluorophenyl)‐1‐(naphthalen‐2‐yl)prop‐2‐en‐1‐one, C₁₉H₁₃FO, (I), crystallizes with Z ′ = 2 in the space group P and the four molecules in the unit cell adopt an arrangement which resembles that in the space group P 2₁/a . Although 3‐(4‐bromophenyl)‐1‐(naphthalen‐2‐yl)prop‐2‐en‐1‐one, C₁₉H₁₃BrO, (II), with Z ′ = 1, is not isostructural with (I), the molecules of (I) and (II) adopt very similar conformations. In 1‐(naphthalen‐2‐yl)‐3‐(thiophen‐2‐yl)prop‐2‐en‐1‐one, C₁₇H₁₂OS, (III), the thiophene unit is disordered over two sets of atomic sites, with occupancies of 0.780 (3) and 0.220 (3), which are related by a near 180° rotation of the thiophene unit about its exocyclic C—C bond. The molecules of compound (I) are linked by three independent C—H…π(arene) hydrogen bonds to form centrosymmetric octamolecular aggregates, whereas the molecules of compound (II) are linked into molecular ladders by a combination of C—H…π(arene) and C—Br…π(arene) interactions, and those of compound (III) are linked into centrosymmetric dimers by C—H…π(thiophene) interactions.     

5‐Amino‐4‐(4‐diethyl­amino­phenyl)‐2‐(4‐hydroxy­phenyl)‐7‐(pyrrolidin‐1‐yl)‐1,6‐naphthyridine‐8‐carbo­nitrile

In the title compound, C₂₉H₃₀N₆O, the naphthyridine moiety is planar with a dihedral angle between the fused rings of 1.9 (1)°. The phenol ring is nearly coplanar, while the diethyl­amino­phenyl substituent is orthogonal to the central naphthyridine ring and the pyrrolidine ring makes an angle of 11.2 (1)° with it. The O atom of the hydroxy substituent is coplanar with the phenyl ring to which it is attached. The molecular structure is stabilized by a C—H?N‐type intramolecular hydrogen bond and the packing is stabilized by intermolecular C—H?π, O—H?N and N—H?O hydrogen bonds.     

4‐(Pyrrol‐1‐yl)‐1,2,4‐triazole

The asymmetric unit of the title compound, C₆H₆N₄, comprises one and a half molecules with a C₂ axis through the second molecule. Each molecule consists of two planar five‐membered rings connected by a triazole–pyrrole N—N bond with the triazole ring close to being at right angles to the pyrrole ring. The molecules are linked by C—H...N hydrogen bonds and weaker offset face‐to‐face π–π interactions.     

Reactions between arylhydrazinium chlorides and 2‐chloroquinoline‐3‐carbaldehydes: molecular and supramolecular structures of a hydrazone,a 4,9‐dihydro‐1H‐pyrazolo[3,4‐b]quinoline and two 1H‐pyrazolo[3,4‐b]quinolines

Hydrazone derivatives exhibit a wide range of biological activities, while pyrazolo[3,4‐b]quinoline derivatives, on the other hand, exhibit both antimicrobial and antiviral activity, so that all new derivatives in these chemical classes are potentially of value. Dry grinding of a mixture of 2‐chloroquinoline‐3‐carbaldehyde and 4‐methylphenylhydrazinium chloride gives (E)‐1‐[(2‐chloroquinolin‐3‐yl)methylidene]‐2‐(4‐methylphenyl)hydrazine, C₁₇H₁₄ClN₃, (I), while the same regents in methanol in the presence of sodium cyanoborohydride give 1‐(4‐methylphenyl)‐4,9‐dihydro‐1H‐pyrazolo[3,4‐b]quinoline, C₁₇H₁₅N₃, (II). The reactions between phenylhydrazinium chloride and either 2‐chloroquinoline‐3‐carbaldehyde or 2‐chloro‐6‐methylquinoline‐3‐carbaldehyde give, respectively, 1‐phenyl‐1H‐pyrazolo[3,4‐b]quinoline, C₁₆H₁₁N₃, (III), which crystallizes in the space group Pbcn as a nonmerohedral twin having Z′ = 3, or 6‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]quinoline, C₁₇H₁₃N₃, (IV), which crystallizes in the space group R. The molecules of compound (I) are linked into sheets by a combination of N—H…N and C—H…π(arene) hydrogen bonds, and the molecules of compound (II) are linked by a combination of N—H…N and C—H…π(arene) hydrogen bonds to form a chain of rings. In the structure of compound (III), one of the three independent molecules forms chains generated by C—H…π(arene) hydrogen bonds, with a second type of molecule linked to the chains by a second C—H…π(arene) hydrogen bond and the third type of molecule linked to the chain by multiple π–π stacking interactions. A single C—H…π(arene) hydrogen bond links the molecules of compound (IV) into cyclic centrosymmetric hexamers having (S₆) symmetry, which are themselves linked into a three‐dimensional array by π–π stacking interactions.     

Ethyl β‐{2‐[4‐(dimethylamino)phenyliminomethyl]‐1‐(phenylsulfonyl)indol‐3‐yl}acrylate

The title compound, C₂₈H₂₇N₃O₄S, crystallizes in the centrosymmetric space group P2₁/n, with one mol­ecule in the asymmetric unit. In the indole ring, the dihedral angle between the fused rings is 3.6 (1)°. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 79.2 (1)° with the best plane of the indole moiety. The phenyl ring of the di­methyl­amino­phenyl group is orthogonal to the phenyl ring of the phenyl­sulfonyl group. The dihedral angle formed by the weighted least‐squares planes through the pyrrole ring and the phenyl ring of the di­methyl­amino­phenyl group is 7.8 (1)°. The molecular structure is stabilized by C—H?O and C—H?N interactions.     

1‐(Thiophen‐3‐yl)ethanone

The structure of the title compound, C₆H₆OS, exhibits a flip‐type disorder of the thiophene ring [occupancy ratio = 0.848 (3):0.152 (3)], which is typical for many thiophene derivatives. The puckered thiophene ring is essentially coplanar with the plane formed by the non‐H atoms of the acetyl substituent, similar to its simple analogues, i.e. 3‐acetyl‐2‐carboxythiophene, 4‐acetyl‐3‐carboxythiophene and 3,5‐diacetyl‐2‐ethylamino‐4‐methylthiophene. In the crystal structure, molecules are connected by C—H...π hydrogen bonds, forming a sheet parallel to the (001) plane. Moreover, an inspection of the crystal lattice reveals that there are short S...O contacts connecting the molecules of adjacent sheets. Comparison of the title crystal structure with its simple 3‐methoxythiophene analogue shows a close similarity in the herringbone arrangement of molecules and in the presence of C—H...π interactions and S...O contacts.     

Synthesis and structures of photoactive rhenium carbonyl complexes derived from 2‐(pyridin‐2‐yl)‐1,3‐benzothiazole, 2‐(quinolin‐2‐yl)‐1,3‐benzothiazole and 1,10‐phenanthroline

Carbon monoxide (CO) has recently been identified as a gaseous signaling molecule that exerts various salutary effects in mammalian pathophysiology. Photoactive metal carbonyl complexes (photoCORMs) are ideal exogenous candidates for more controllable and site‐specific CO delivery compared to gaseous CO. Along this line, our group has been engaged for the past few years in developing group‐7‐based photoCORMs towards the efficient eradication of various malignant cells. Moreover, several such complexes can be tracked within cancerous cells by virtue of their luminescence. The inherent luminecscent nature of some photoCORMs and the change in emission wavelength upon CO release also provide a covenient means to track the entry of the prodrug and, in some cases, both the entry and CO release from the prodrug. In continuation of the research circumscribing the development of trackable photoCORMs and also to graft such molecules covalently to conventional delivery vehicles, we report herein the synthesis and structures of three rhenium carbonyl complexes, namely, fac‐tricarbonyl[2‐(pyridin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₂H₈N₂S)(CO)₃](CF₃SO₃), ( 1 ), fac‐tricarbonyl[2‐(quinolin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₆H₁₀N₂S)(CO)₃](CF₃SO₃), ( 2 ), and fac‐tricarbonyl[1,10‐phenanthroline‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₂H₈N₂)(CO)₃](CF₃SO₃), ( 3 ). In all three complexes, the Re^I center resides in a distorted octahedral coordination environment. These complexes exhibit CO release upon exposure to low‐power UV light. The apparent CO release rates of the complexes have been measured to assess their comparative CO‐donating capacity. The three complexes are highly luminescent and this in turn provides a convenient way to track the entry of the prodrug molecules within biological targets.     

Structures and packing of ferrocenylmethyl methacrylate and ferrocene‐1,1′‐diylbis(methylene) dimethacrylate

Electroactive metallocene polymers are of interest due to the possibility that they offer a muscle‐like response, and in gel systems very large volume changes are possible. The ferrocenyl moiety exhibits physical and electrochemical stability of the neutral and oxidized forms and could be a candidate for use as the redox‐active group in these materials. The title compounds, [Fe(C₅H₅)(C₁₀H₁₁O₂)], (I), and [Fe(C₁₀H₁₁O₂)₂], (II), comprise a typical ferrocene core with coplanar and approximately eclipsed cyclopentadienyl (Cp) rings. In (I), there is a single methyl methacrylate substituent, with the other Cp ring unsubstituted. In (II), a methyl methacrylate substituent on each Cp ring completes the structure. In both compounds, there is an s‐trans geometry of the vinyl and carbonyl components of the methacrylate group. Inversion dimers formed through C—H...O contacts dominate the crystal packing of both molecules. Weak C—H...π(ring) contacts and, in the case of (I), an unusual C—H...π(alkene) contact further stabilize the structures.     

5‐Formylsalicylic acid and 5‐(benzimidazolium‐2‐yl)salicylate

Both title compounds are derivatives of salicylic acid. 5‐Formylsalicylic acid (systematic name: 5‐formyl‐2‐hydroxybenzoic acid), C₈H₆O₄, possesses three good hydrogen‐bond donors and/or acceptors coplanar with their attached benzene ring and abides very well by Etter's hydrogen‐bond rules. Intermolecular O—H...O and some weak C—H...O hydrogen bonds link the molecules into a planar sheet. Reaction of this acid and o‐phenylenediamine in refluxing ethanol produced in high yield the new zwitterionic compound 5‐(benzimidazolium‐2‐yl)salicylate [systematic name: 5‐(1H‐benzimidazol‐3‐ium‐2‐yl)‐2‐hydroxybenzoate], C₁₄H₁₀N₂O₃. Each imidazolium N—H group and its adjacent salicyl C—H group chelate one carboxylate O atom via hydrogen bonds, forming seven‐membered rings. As a result of steric hindrance, the planes of the molecules within these pairs of hydrogen‐bonded molecules are inclined to one another by ∼74°. There are also π–π stacking interactions between the parallel planes of the imidazole ring and the benzene ring of the salicyl component of the adjacent molecule on one side and the benzimidazolium component of the molecule on the other side.     

Experimental and Theoretical Studies of 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine: A Potential Antibacterial Agent

The title compound ( 1 ), 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine (C₂₀H₁₆Cl₂N₆), was synthesized and structurally characterized by elemental analysis, ¹H NMR and ¹³C NMR and single crystal X‐ray diffraction. The compound crystallizes as a colourless needle shaped in the triclinic system, space group P‐1 with cell constants: a = 10.7557(11) Å, b = 12.7078(17) Å, c = 15.511(2) Å, α = 68.029(4)0, β = 86.637(5)0, γ = 87.869(4)0; V = 1962.4 (4) ų, Z = 4. There are two structurally similar but crystallographically independent molecules (A and B) in the asymmetric unit of the title compound, which is linked via N‐H…Cl hydrogen bond. An intramolecular C‐H…N hydrogen also occurs in each molecule. In the crystal, each of independent molecules forms a centrosymmetric dimer with an R²₂(8) ring motifs through a pair of N‐H…N hydrogen bonds. These dimers are further connected by intermolecular N‐H…Cl and C‐H…Cl hydrogen bonds, forming an infinite two dimensional supramolecular network lying parallel to the [010] plane. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6‐311G (d, p) basis set and compared with the experimental data. Mulliken population analyses on atomic charges, HOMO‐LUMO energy levels, Molecular electrostatic potential and chemical reactivity of the title compound were investigated by theoretical calculations. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. The in vitro antibacterial activity has been screened against Gram‐positive (Bacillus cerus and Staphylococcus epidermidis) and Gram‐Negative (Escherichia coli, Acinetobacter baumannii and Proteus vulgaris). The results revealed that the compound exhibited good to moderate antibacterial activity.     

A chain of π‐stacked molecules in 4‐(2‐chlorophenyl)pyrrolo[1,2‐a]quinoxaline and a hydrogen‐bonded sheet in (4RS)‐4‐(1,3‐1,3‐benzodioxol‐6‐yl)‐4,5‐dihydropyrrolo[1,2‐a]quinoxaline

In the molecule of 4‐(2‐chlorophenyl)pyrrolo[1,2‐a]quinoxaline, C₁₇H₁₁ClN₂, (I), the bond lengths are consistent with electron delocalization in the two outer rings of the fused tricyclic system, with a localized double bond in the central ring. The molecules of (I) are linked into chains by a π–π stacking interaction. In (4RS)‐4‐(1,3‐benzodioxol‐6‐yl)‐4,5‐dihydropyrrolo[1,2‐a]quinoxaline, C₁₈H₁₄N₂O₂, (II), the central ring of the fused tricyclic system adopts a conformation intermediate between screw‐boat and half‐chair forms. A combination of N—H...O and C—H...π(arene) hydrogen bonds links the molecules of (II) into a sheet. Comparisons are made with related compounds.     

Synthesis,Structure, and Solution Study of a Mercury(II) Complex with the Ligand [1‐(2‐Methoxyphenyl)‐3‐(4‐chlorophenyl)]triazene

The title ligand, [1‐(2‐methoxyphenyl)‐3‐(4‐chlorophenyl)]triazene, H L ( 1 ), was prepared. In a reaction with Hg(NO₃)₂ it forms the complex [Hg(C₂₆H₂₂Cl₂N₆O₂)], [Hg L ₂] ( 2 ). Both compounds were characterized by means of X‐ray crystallography, CHN analysis, FT‐IR, ¹H NMR, and ¹³C NMR spectroscopy. In the structure of compound 1 , two independent fragments are present in the unit cell. They exhibit trans arrangement about the –N=N– double bond. The dihedral angles between two benzene rings in both fragments are 4.36 and 18.79 Å, respectively. Non‐classic C–H ··· N hydrogen bonding and C–H ··· π interactions form a layer structure along the crystallographic ab plane [110]. In compound 2 , the Hg^II atom is hexacoordinated by two tridentate [1‐(2‐methoxyphenyl)‐3‐(4‐chlorophenyl)]triazenide ligands through a N₂O₂ set. In addition, in the structure of 2 , monomeric complexes are connected to each other by C–H ··· π stacking interactions, resulting in a 2D architecture. These C–H ··· π edge‐to‐face interactions are present with H ··· π distances of 3.156 and 3.027 Å. The results of studies of the stoichiometry and formation of complex 2 in methanol solution were found to support its solid state stoichiometry.     

2‐Ethyl‐1‐[5‐(4‐methylphenyl)pyrazol‐3‐yl]‐3‐(thiophene‐2‐carbonyl)isothiourea: molecular ribbons containing three types of hydrogen‐bonded ring

The title compound, C₁₈H₁₈N₄OS₂, was prepared by reaction of S,S‐diethyl 2‐thenoylimidodithiocarbonate with 5‐amino‐3‐(4‐methylphenyl)‐1H‐pyrazole using microwave irradiation under solvent‐free conditions. In the molecule, the thiophene unit is disordered over two sets of atomic sites, with occupancies of 0.814 (4) and 0.186 (4), and the bonded distances provide evidence for polarization in the acylthiourea fragment and for aromatic type delocalization in the pyrazole ring. An intramolecular N—H...O hydrogen bond is present, forming an S(6) motif, and molecules are linked by N—H...O and N—H...N hydrogen bonds to form a ribbon in which centrosymmetric R₂²(4) rings, built from N—H...O hydrogen bonds and flanked by inversion‐related pairs of S(6) rings, alternate with centrosymmetric R₂²(6) rings built from N—H...N hydrogen bonds.     

(5RS)‐6H‐Spiro[pyrazolo[1,5‐c]quinazoline‐5,4′‐thiochroman]: efficient synthesis under mild conditions,molecular structure and supramolecular assembly

Pyrazolo[1,5‐c]quinazolines are fused‐quinazoline derivatives which have been reported as potential agents against neurological disorders. The normal synthesis routes to these compounds require harsh reaction conditions, long reaction times or multistep sequences. The title compound, C₁₈H₁₅N₃S, has been prepared under very mild conditions by condensation of thiochroman‐4‐one with 5‐(2‐aminophenyl)‐1H‐pyrazole, which had itself been prepared by the reaction of hydrazine hydrate with 4‐hydroxyquinoline mediated by a brief period of microwave heating. Within the molecule in the crystal structure, the reduced pyrimidine ring adopts an envelope conformation, whereas the thiane ring adopts a half‐chair conformation. Molecules are linked into sheets by a combination of one N—H...S hydrogen bond and two independent C—H...π(arene) hydrogen bonds, which utilize the same aryl ring as the acceptor, with one C—H bond donating to each face of the ring. Comparisons are made with some related compounds.     

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.     

(±)‐(4‐Oxo‐4H‐chromen‐2‐yl)(phenyl)methyl acetate

The title compound, C₁₈H₁₄O₄, forms a supramolecular structure viaπ–π stacking and weak C—H⋯O and C—H⋯π interactions. The benzo­pyran moiety is almost planar. The benzene ring of the phenyl­methyl acetate substituent is nearly perpendicular to the fused benzene and pyran rings and also to the methyl acetate group.     

3‐[(E)‐(3‐tert‐Butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)iminomethyl]quinolin‐2(1H)‐one: chains built by π‐stacking of hydrogen‐bonded R22(8) dimers

In the title compound, C₂₃H₂₂N₄O, there is evidence for some bond fixation in the aryl component of the quinolinone unit. Pairs of molecules related by inversion are linked into R₂²(8) dimers by almost linear N—H...O hydrogen bonds, and dimers related by inversion are linked into chains by a single aromatic π–π stacking interaction.     

Octyl 1‐(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)‐2‐(4‐chlorophenyl)‐1H‐benzimidazole‐5‐carboxylate: complex sheets built from N—H...N,C—H...N and C—H...O hydrogen bonds

In the title compound, C₂₉H₃₅ClN₄O₂, the bond lengths provide evidence for aromatic delocalization in the pyrazole ring but bond fixation in the fused imidazole ring, and the octyl chain is folded, rather than adopting an all‐trans chain‐extended conformation. A combination of N—H...N, C—H...N and C—H...O hydrogen bonds links the molecules into sheets, in which the hydrogen bonds occupy the central layer with the tert‐butyl and octyl groups arranged on either side, such that the closest contacts between adjacent sheets involve only the octyl groups. Comparisons are made with the supramolecular assembly in some simpler analogues.     

(E)‐2‐(1,3‐Benzothiazol‐2‐yl)‐3‐(4‐fluorophenyl)acrylonitrile: a chain of π‐stacked hydrogen‐bonded rings

The title compound, C₁₆H₉FN₂S, crystallizes as a nonmerohedral twin with twin rotation about the reciprocal‐lattice vector [10]*. The molecules are nearly planar and the dihedral angle between the planes of the two aryl rings is only 4.4 (2)°. The molecules are linked by pairs of C—H...N hydrogen bonds to form cyclic centrosymmetric R₂²(18) dimers, which are linked into chains by an aromatic π–π stacking interaction. Comparisons are made with some related 3‐aryl‐2‐thienylacrylonitriles.