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1.  Different weak inter­actions in the crystals of three isomeric (E)-N-methyl-N′-(nitro­benzyl­idene)-2-(thio­phen-2-yl)acetohydrazides 
Three isomeric methyl­ated 2-(thio­phen-2-yl)acetohydrazides show little consistency in the pattern of weak (C—H⋯O, C—H⋯π and π–π) inter­actions in their crystal structures.
The crystal structures of three isomeric (E)-N-methyl-N′-(nitro­benzyl­idene)-2-(thio­phen-2-yl)acetohydrazides (formula C14H13N3O3S) are described, with the nitro group in ortho, meta and para positions in the benzene ring. In each crystal structure, mol­ecules are linked by various weak inter­actions (C—H⋯O and C—H⋯π bonds, and π–π stacking), leading to three-dimensional networks in each case, but with little similarity between them.
PMCID: PMC5137586  PMID: 27980808
crystal structure; carbohydrazide; methyl­ation; weak hydrogen bonds
2.  Two di­alkyl­ammonium salts of 2-amino-4-nitro­benzoic acid: crystal structures and Hirshfeld surface analysis 
The structures of two ammonium salts of 2-amino-4-nitro­benzoic acid are described. Substantial hydrogen bonding leads to supra­molecular layers in the [Me2NH2]+ salt and a three-dimensional architecture in the case of the [n-Bu2NH2]+ salt.
The crystal structures of two ammonium salts of 2-amino-4-nitro­benzoic acid are described, namely di­methyl­aza­nium 2-amino-4-nitro­benzoate, C2H8N+·C7H5N2O4 −, (I), and di­butyl­aza­nium 2-amino-4-nitro­benzoate, C8H20N+·C7H5N2O4 −, (II). The asymmetric unit of (I) comprises a single cation and a single anion. In the anion, small twists are noted for the carboxyl­ate and nitro groups from the ring to which they are connected, as indicated by the dihedral angles of 11.45 (13) and 3.71 (15)°, respectively; the dihedral angle between the substituents is 7.9 (2)°. The asymmetric unit of (II) comprises two independent pairs of cations and anions. In the cations, different conformations are noted in the side chains in that three chains have an all-trans [(+)-anti­periplanar] conformation, while one has a distinctive kink resulting in a (+)-synclinal conformation. The anions, again, exhibit twists with the dihedral angles between the carboxyl­ate and nitro groups and the ring being 12.73 (6) and 4.30 (10)°, respectively, for the first anion and 8.1 (4) and 12.6 (3)°, respectively, for the second. The difference between anions in (I) and (II) is that in the anions of (II), the terminal groups are conrotatory, forming dihedral angles of 17.02 (8) and 19.0 (5)°, respectively. In each independent anion of (I) and (II), an intra­molecular amino-N—H⋯O(carboxyl­ate) hydrogen bond is formed. In the crystal of (I), anions are linked into a jagged supra­molecular chain by charge-assisted amine-N—H⋯O(carboxyl­ate) hydrogen bonds and these are connected into layers via charge-assisted ammonium-N—H⋯O(carboxyl­ate) hydrogen bonds. The resulting layers stack along the a axis, being connected by nitro-N—O⋯π(arene) and methyl-C—H⋯O(nitro) inter­actions. In the crystal of (II), the anions are connected into four-ion aggregates by charge-assisted amino-N—H⋯O(carboxyl­ate) hydrogen bonding. The formation of ammonium-N—H⋯O(carboxyl­ate) hydrogen bonds, involving all ammonium-N—H and carboxyl­ate O atoms leads to a three-dimensional architecture; additional C—H⋯O(nitro) inter­actions contribute to the packing. The Hirshfeld surface analysis confirms the importance of the hydrogen bonding in both crystal structures. Indeed, O⋯H/H⋯O inter­actions contribute nearly 50% to the entire Hirshfeld surface in (I).
PMCID: PMC5137589  PMID: 27980811
crystal structure; carboxyl­ate; salt; hydrogen bonding; Hirshfeld surface analysis
3.  Crystal structure and Hirshfeld surface analysis of 2-{[2,8-bis­(tri­fluoro­meth­yl)quinolin-4-yl](hy­droxy)meth­yl}piperidin-1-ium 2-hy­droxy-2-phenyl­acetate hemihydrate 
The l-shaped cations in the centrosymmetric title salt are related across a non-crystallographic centre of inversion. In the crystal, hydrogen-bonded layers are linked by π–π and C—H⋯F⋯π inter­actions.
The asymmetric unit of the title salt, C17H17F6N2O+·C8H7O3 −·0.5H2O, comprises a pair of pseudo-enanti­omeric (i.e. related by a non-crystallographic centre of symmetry) piperidin-1-ium cations, two carboxyl­ate anions and a water mol­ecule of crystallization. The cations have similar conformations approximating to a letter, L: one of them shows disorder of its –CF3 group over two sets of sites in a 0.775 (3):0.225 (3) ratio. Distinctive conformations are found for the anions, one with the carboxyl­ate group lying to one side of the plane through the phenyl ring and the other where the oxygen atoms lie to either side of the plane. In the latter, an intra­molecular hy­droxy-O—H⋯O(carboxyl­ate) charge-assisted hydrogen bond is found. The packing features extensive O—H⋯O,N hydrogen bonding, often charge-assisted; C—H⋯π inter­actions are also formed. The hydrogen bonding results in the formation of five distinctive supra­molecular synthons and assembles mol­ecules in the ac plane. The quinolinyl rings lie to either side of the layer and inter-digitate with layers on either side, are approximately parallel to the b axis and are connected by π–π [inter-centroid separation = 3.6904 (18) Å] as well as C—F⋯π(quinolin­yl) inter­actions to consolidate the three-dimensional crystal. The dominance of the conventional hydrogen bonding in the mol­ecular packing is confirmed by an analysis of the Hirshfeld surface.
PMCID: PMC5095847  PMID: 27840722
crystal structure; salt; hydrogen bonding; mefloquine
4.  N′-[(1E)-(5-Nitro­furan-2-yl)methyl­idene]thio­phene-2-carbohydrazide: crystal structure and Hirshfeld surface analysis 
The title mol­ecule is curved as seen in the dihedral angle [27.4 (2)°] between the outer rings. Supra­molecular chains about a 41 screw axis are formed by amide-N—H⋯O(carbon­yl) hydrogen bonding.
In the title carbohydrazide, C10H7N3O4S, the dihedral angle between the terminal five-membered rings is 27.4 (2)°, with these lying to the same side of the plane through the central CN2C(=O) atoms (r.m.s. deviation = 0.0403 Å), leading to a curved mol­ecule. The conformation about the C=N imine bond [1.281 (5) Å] is E, and the carbonyl O and amide H atoms are anti. In the crystal, N—H⋯O hydrogen bonds lead to supra­molecular chains, generated by a 41 screw-axis along the c direction. A three-dimensional architecture is consolidated by thienyl-C—H⋯O(nitro) and furanyl-C—H⋯O(nitro) inter­actions, as well as π–π inter­actions between the thienyl and furanyl rings [inter-centroid distance = 3.515 (2) Å]. These, and other, weak inter­molecular inter­actions, e.g. nitro-N—O⋯π(thien­yl), have been investigated by Hirshfeld surface analysis, which confirms the dominance of the conventional N—H⋯O hydrogen bonding to the overall mol­ecular packing.
PMCID: PMC4992931  PMID: 27555956
crystal structure; carbohydrazide; hydrogen bonding; conformation; Hirshfeld surface analysis
5.  Weak inter­actions in the crystal structures of two indole derivatives 
The weak inter­molecular inter­actions in two indole derivatives are described.
We describe the syntheses and crystal structures of two indole derivatives, namely a second monoclinic polymorph of ethyl 5-chloro-1H-indole-2-carboxyl­ate C11H10ClNO2, (I), and ethyl 5-chloro-3-iodo-1H-indole-2-carboxyl­ate, C11H9ClINO2, (II). In their crystal structures, both compounds form inversion dimers linked by pairs of N—H⋯O hydrogen bonds, which generate R 2 2(10) loops. The dimers are linked into double chains in (I) and sheets in (II) by a variety of weak inter­actions, including π–π stacking, C—I⋯π, C—Cl—π inter­actions and I⋯Cl halogen bonds.
PMCID: PMC4992916  PMID: 27555941
crystal structure; indole; N—H⋯O hydrogen bonds; inversion dimers; weak inter­actions
6.  A kryptoracemic salt: 2-{[2,8-bis­(tri­fluoro­meth­yl)quinolin-4-yl](hy­droxy)meth­yl}piperidin-1-ium (+)-3,3,3-tri­fluoro-2-meth­oxy-2-phenyl­propanoate 
The l-shaped cations in the title compound are related across a non-crystallographic centre of inversion and therefore, are kryptoracemic. Supra­molecular chains arise in the crystal packing as a result of O—H⋯O and N—H⋯N hydrogen bonding.
The asymmetric unit of the title salt, C17H17F6N2O+·C10H8F3O3 −, comprises two piperidin-1-ium cations and two carboxyl­ate anions. The cations, each having an l-shaped conformation owing to the near orthogonal relationship between the quinolinyl and piperidin-1-ium residues, are pseudo-enanti­omeric. The anions have the same absolute configuration but differ in the relative orientations of the carboxyl­ate, meth­oxy and benzene groups. Arguably, the most prominent difference between the anions occurs about the Cq—Om bond as seen in the Cc—Cq—Om—Cm torsion angles of −176.1 (3) and −67.1 (4)°, respectively (q = quaternary, m = meth­oxy and c = carboxyl­ate). The presence of Oh—H⋯Oc and Np—H⋯Oc hydrogen bonds leads to the formation of a supra­molecular chain along the a axis (h = hy­droxy and p = piperidin-1-ium); weak intra­molecular Np—H⋯Oh hydrogen bonds are also noted. Chains are connected into a three-dimensional architecture by C—H⋯F inter­actions. Based on a literature survey, related mol­ecules/cations adopt a uniform conformation in the solid state based on the letter L.
PMCID: PMC4908568  PMID: 27308063
crystal structure; salt; krypto­racemate; hydrogen bonding
7.  Different N—H⋯π inter­actions in two indole derivatives 
The most important inter­molecular inter­actions in the two indole derivatives described here are N—H⋯π bonds, which lead to chains in one case and inversion dimers in the other; C—H⋯π inter­actions appear to reinforce the N—H⋯π bonds in each case.
We describe the syntheses and crystal structures of two indole derivatives, namely 6-isopropyl-3-(2-nitro-1-phenyl­eth­yl)-1H-indole, C19H20N2O2, (I), and 2-(4-meth­oxy­phen­yl)-3-(2-nitro-1-phenyl­eth­yl)-1H-indole, C23H20N2O3, (II); the latter crystallizes with two mol­ecules (A and B) with similar conformations (r.m.s. overlay fit = 0.139 Å) in the asymmetric unit. Despite the presence of O atoms as potential acceptors for classical hydrogen bonds, the dominant inter­molecular inter­action in each crystal is an N—H⋯π bond, which generates chains in (I) and A+A and B+B inversion dimers in (II). A different aromatic ring acts as the acceptor in each case. The packing is consolidated by C—H⋯π inter­actions in each case but aromatic π–π stacking inter­actions are absent.
PMCID: PMC4908542  PMID: 27308022
crystal structure; indole; N—H⋯π inter­action; chains; inversion dimers
8.  Crystal structures of four indole derivatives with a phenyl substituent at the 2-position and a carbonyl group at the 3-position: the C(6) N—H⋯O chain remains the same, but the weak reinforcing inter­actions are different 
Four related indole derivatives crystallize with a consistent C(6) N—H⋯O chain motif, but in each case the reinforcing inter­actions and crystal symmetries are different.
We describe the crystal structures of four indole derivatives with a phenyl ring at the 2-position and different carbonyl-linked substituents at the 3-position, namely 1-(2-phenyl-1H-indol-3-yl)ethanone, C16H13NO, (I), 2-cyclo­hexyl-1-(2-phenyl-1H-indol-3-yl)ethanone, C22H23NO, (II), 3,3-dimethyl-1-(2-phenyl-1H-indol-3-yl)butan-1-one, C20H21NO, (III), and 3-benzoyl-2-phenyl-1H-indole, C21H15NO, (IV). In each case, the carbonyl-group O atom lies close to the indole-ring plane and points towards the benzene ring. The dihedral angles between the indole ring system and 2-phenyl ring for these structures are clustered in a narrow range around 65°. The dominant inter­molecular inter­action in each case is an N—H⋯O hydrogen bond, which generates a C(6) chain, although each structure possesses a different crystal symmetry. The C(6) chains are consolidated by different (C—H⋯O, C—H⋯π and π–π stacking) weak inter­actions, with little consistency between the structures.
PMCID: PMC4778824  PMID: 27006809
crystal structure; indole; N—H⋯O hydrogen bond; C(6) chain; weak inter­actions
9.  Synthesis and Biological Activities of Camphor Hydrazone and Imine Derivatives 
Scientia Pharmaceutica  2015;84(3):467-483.
Both sonochemical and classical methodologies have been employed to convert camphor, 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one, C9H16C=O, into a number of derivatives including hydrazones, C9H16C=N-NHAr 3, imines, C9H16C=N-R 7, and the key intermediate nitroimine, C9H16C=N-NO2 6. Reactions of nitroamine 6 with nucleophiles by classical methods provided the desired compounds in a range of yields. In evaluations of activity against Mycobacterium tuberculosis, compound 7j exhibited the best activity (minimal inhibitory concentration (MIC) = 3.12 µg/mL), comparable to that of the antitubercular drug ethambutol. The other derivatives displayed modest antimycobacterial activities at 25–50 µg/mL. In in vitro tests against cancer cell lines, none of the synthesized camphor compounds exhibited cytotoxic activities.
PMCID: PMC5064238
camphor; sonochemistry; hydrazones; imines; tuberculosis
10.  Different hydrogen-bonded chains in the crystal structures of three alkyl N-[(E)-1-(2-benzyl­idene-1-methyl­hydrazin­yl)-3-hy­droxy-1-oxopropan-2-yl]carbamates 
Three closely related methyl­ated hydrazine carbamates show different hydrogen-bonding patterns, although they all result in chains.
The crystal structures of three methyl­ated hydrazine carbamate derivatives prepared by multi-step syntheses from l-serine are presented, namely benzyl N-{(E)-1-[2-(4-cyanobenzylidene)-1-methylhydrazinyl]-3-hydroxy-1-oxopro­pan-2-yl}carbamate, C20H20N4O4, tert-butyl N-{(E)-1-[2-(4-cyanobenzylidene)-1-methylhydrazinyl]-3-hydroxy-1-oxopropan-2-yl}carbamate, C17H22N4O4, and tert-butyl N-[(E)-1-(2-benzylidene-1-methylhydrazinyl)-3-hydroxy-1-oxopro­pan-2-yl]carbamate, C16H23N3O4. One of them shows that an unexpected racemization has occurred during the mild-condition methyl­ation reaction. In each crystal structure, the mol­ecules are linked into chains by O—H⋯O hydrogen bonds, but with significant differences between them.
PMCID: PMC4518986  PMID: 26279859
Carbohydrazide; methyl­ation; hydrogen bonds; chain; crystal structure
11.  Crystal structures of four indole derivatives as possible cannabinoid allosteric antagonists 
The crystal structures of four indole derivatives with various substituents at the 2-, 3- and 5-positions of the ring system are described. The dominant inter­molecular inter­action in each case is an N—H⋯O hydrogen bond, which generates either chains or inversion dimers. Weak C—H⋯O, C—H⋯π and π–π inter­actions occur in these structures but there is no consistent pattern amongst them. Two of these compounds act as modest enhancers of CB1 cannabanoid signalling and two are inactive.
The crystal structures of four indole derivatives with various substituents at the 2-, 3- and 5-positions of the ring system are described, namely, ethyl 3-(5-chloro-2-phenyl-1H-indol-3-yl)-3-phenyl­propano­ate, C25H22ClNO2, (I), 2-bromo-3-(2-nitro-1-phenyl­eth­yl)-1H-indole, C16H13BrN2O2, (II), 5-meth­oxy-3-(2-nitro-1-phenyl­eth­yl)-2-phenyl-1H-indole, C23H20N2O3, (III), and 5-chloro-3-(2-nitro-1-phenyl­eth­yl)-2-phenyl-1H-indole, C22H17ClN2O2, (IV). The dominant inter­molecular inter­action in each case is an N—H⋯O hydrogen bond, which generates either chains or inversion dimers. Weak C—H⋯O, C—H⋯π and π–π inter­actions occur in these structures but there is no consistent pattern amongst them. Two of these compounds act as modest enhancers of CB1 cannabanoid signalling and two are inactive.
PMCID: PMC4459378  PMID: 26090143
crystal structure; indole; cannabin­oid allosteric antagonist; N—H⋯O hydrogen bond
12.  Crystal structure of (E)-4-hy­droxy-N′-(3-hy­droxy­benzyl­idene)benzohydrazide monohydrate 
In the title benzohydrazide hydrate, C14H12N2O3·H2O, the dihedral angle between the aromatic rings is 58.11 (6)° and the C=O and N—H groups adopt an anti orientation. The main twist in the mol­ecule occurs about the C(=O)—Car (ar = aromatic) bond, with an N—C(=O)—Car—Car torsion angle of −43.5 (2)°. In the crystal, the components are linked by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds. These inter­actions generate [10-1] chains, with adjacent organic mol­ecules linked by inversion symmetry generating either pairs of N—H⋯O links [R 2 2(16) loops] or pairs of O—H⋯O links [R 2 2(20) loops]. Pairs of water mol­ecules are located in the R 2 2(20) loops and form their own O—H⋯O and O—H⋯N hydrogen bonds to adjacent organic mol­ecules in the chain. Finally, an inter­chain O—H⋯O hydrogen-bond link from the 4-hy­droxy group generates (010) sheets.
PMCID: PMC4186143  PMID: 25309238
crystal structure; benzohydrazide; hydrate; hydrogen bonding
13.  Crystal structures of potassium tri­fluorido­(4-meth­oxy­phen­yl)borate and potassium tri­fluorido(4-fluoro­phen­yl)borate 
Despite their different compositions and space groups, the irregular KF8 coordination polyhedra of the potassium cations in these structures are almost identical. The layer stacking sequences are AAA… in the p-methoxy compound and ABAB… in the p-fluoro compound.
The title compounds, K+·C7H7BF3O−, (I), and K+·C6H4BF4 −, (II), are mol­ecular salts containing para-substituted phenyl­tri­fluorido­borate anions. In each compound, the B atom adopts a distorted tetra­hedral BCF3 geometry. Despite their different compositions and space groups, the irregular KF8 coordination polyhedra of the potassium cations in the structures are almost identical. These polyhedra share faces and edges, generating infinite (010) layers in (I) and infinite (001) layers in (II). In (I), adjacent layers are stacked in an AAA… fashion, whereas in (II), they are stacked in an ABAB… sequence.
PMCID: PMC4158529  PMID: 25249857
crystal structure; boron; Lewis acid; layered structure
14.  7-Chloro-4-(2-hy­droxy­ethyl­amino)­quinolin-1-ium chloride 
In the title salt, C11H12ClN2O+·Cl−, the ten non-H atoms comprising the quinolinium residue are coplanar (r.m.s. deviation = 0.041 Å) and the hy­droxy­ethyl group is approximately perpendicular to this plane [Cring—N—Cmethyl­ene—C torsion angle = −74.61 (18)°]. A supra­molecular chain aligned along [101] mediated by charge-assisted O/N—H⋯Cl− hydrogen bonds features in the crystal packing. Chains are connected into a three-dimensional architecture by C—H⋯O(hy­droxy) inter­actions.
PMCID: PMC3998632  PMID: 24826110
15.  2-(2-Amino-4-nitro­phen­yl)-7-nitro-4H-3,1-benzoxazin-4-one 
In the title compound, C14H8N4O6, the benzoxazin-4-one fused-ring system (r.m.s. deviation = 0.018 Å) is coplanar with the attached benzene ring [dihedral angle = 0.81 (4)°], there being an intra­molecular N—H⋯N hydrogen bond between them. Each nitro group is twisted out of the plane of the attached benzene ring [O—N—C—C torsion angles = 167.94 (11) and 170.38 (11)°]. In the crystal, amine–nitro N—H⋯O hydrogen bonds lead to centrosymmetric dimeric aggregates that are connected into a three-dimensional architecture by oxazin­yl–nitro C—H⋯O and π–π inter­actions [inter-centroid distance between the oxazinyl and terminal benzene rings = 3.5069 (7) Å].
PMCID: PMC3998318  PMID: 24764879
16.  2-[(E)-2-(3,4-Di­chloro­benzyl­idene)hydrazin-1-yl]quinoxaline 
The 21 non-H atoms of the title compound, C15H10Cl2N4, are almost planar (r.m.s. deviation = 0.032 Å); the conformation about the N=C bond [1.277 (6) Å] is E. In the crystal, zigzag supra­molecular chains along the c axis (glide symmetry) are formed via N—H⋯N hydrogen bonds. These associate along the b axis by π–π inter­actions between the fused and terminal benzene rings [inter­centroid distance = 3.602 (3) Å] so that layers form in the bc plane.
PMCID: PMC3998292  PMID: 24764853
17.  3,3-Dimethyl-cis-9a,13a-diphenyl-2,3,9a,11,12,13a-hexa­hydro-1H-benzo[h][1,4]dioxino[2′,3′:5,6][1,4]dioxino[2,3-f]chromene 
In the title di­hydro­dioxin, C31H28O5, the dioxane ring has a chair conformation, whereas each of the pyran and dioxine rings has an envelope conformation with methyl­ene and quaternary C atoms, respectively, being the flap atoms. The phenyl rings are cis and form a dihedral angle of 82.11 (10)°. The molecular structure is stabilized by C—H⋯O contacts. In the crystal packing, supra­molecular layers parallel to (101) are sustained by C—H⋯π inter­actions.
PMCID: PMC3884479  PMID: 24427106
18.  (2E)-N′-[(E)-2-Hy­droxy­benzyl­idene]-3-phenyl­prop-2-enohydrazide 
In the non-planar title compound, C16H14N2O2, the dihedral angle between the phenyl rings is 16.67 (8)°. An E conformation is found for each of the imine [1.286 (2) Å] and ethyl­ene [1.335 (2) Å] bonds. The amide O and H atoms are anti, and an intra­molecular hy­droxy O—H⋯N hydrogen bond is noted. The formation of N—H⋯O(hy­droxy) hydrogen bonds in the crystal packing leads to helical chains along the b axis. Supra­molecular layers in the ab plane are formed as the chains are linked by C—H⋯O inter­actions.
PMCID: PMC3394040  PMID: 22798905
19.  (2E)-N′-[(E)-Benzyl­idene]-3-phenyl­prop-2-enohydrazide from synchrotron radiation 
In the title compound, C16H14N2O, the dihedral angle between the phenyl rings is 25.48 (12)°. An E conformation is found for each of the imine [1.269 (3) Å] and ethyl­ene [1.313 (3) Å] bonds. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, leading to zigzag chains along [010]. Supra­molecular layers in the ab plane are formed, whereby the chains are linked by C—H⋯N and C—H⋯π inter­actions.
PMCID: PMC3394041  PMID: 22798906
20.  4-(3-Fluoro­anilino)thieno[2,3-b]pyridine-6-carb­oxy­lic acid 
In the title compound, C14H9FN2O2S, the thieno[2,3-b]pyridine residue is almost planar (r.m.s. deviation = 0.0194 Å), with the carb­oxy­lic acid group [dihedral angle = 11.9 (3)°] and the benzene ring [71.1 (4)°] being twisted out of this plane to different extents. An intra­molecular N—H⋯O(carbon­yl) hydrogen bond closes an S(6) ring. Supra­molecular chains along [01-1] mediated by O—H⋯N(pyridine) hydrogen bonds feature in the crystal. A three-dimensional architecture is completed by π–π inter­actions occurring between the benzene ring and the two rings of the thieno[2,3-b]pyridine residue [centroid–centroid distances = 3.6963 (13) and 3.3812 (13) Å]. The F atom is disordered over the two meta sites in a near statistical ratio [0.545 (5):0.455 (5)].
PMCID: PMC3394012  PMID: 22798877
21.  N-(4-Chloro­phen­yl)-5-(4,5-dihydro-1H-imidazol-2-yl)thieno[2,3-b]pyridin-4-amine 
In the title compound, C16H13ClN4S, the thienopyridine fused-ring system is nearly planar (r.m.s. deviation = 0.0333 Å) and forms a dihedral angle of 4.4 (3)° with the attached dihydro­imidazole ring (r.m.s. deviation = 0.0429 Å) allowing for the formation of an intra­molecular (exocyclic amine)N—H⋯N(imine) hydrogen bond. The benzene rings of the disordered (50:50) –N(H)—C6H4Cl residue form dihedral angles of 59.1 (3) and 50.59 (15)° with the fused ring system. In the crystal, (imidazole amine)N—H⋯N(pyridine) hydrogen bonds lead to a supra­molecular helical chain along the b axis. The chains assemble into layers (ab plane) with inter-digitation of the chloro­benzene rings which results in weak C—H⋯Cl inter­actions in the c-axis direction.
PMCID: PMC3393946  PMID: 22798811
22.  4-[(E)-2-(2-Chloro­benzyl­idene)hydrazin-1-yl]quinolin-1-ium chloride dihydrate 
In the title hydrated salt, C16H13ClN3 +·Cl−·2H2O, a small twist is evident in the cation so that the chloro­benzene ring is not coplanar with the central hydrazinyl group [the N—C—C—C torsion angle = −4.8 (12)°]. The conformation about the imine N=C bond [1.284 (10) Å] is E. The components of the structure are connected into a three-dimensional architecture via O—H⋯O, O—H⋯Cl and N—H⋯Cl hydrogen bonds. One water H atom is disposed over two sites of equal occupancy.
PMCID: PMC3379418  PMID: 22719616
23.  4-[(E)-2-(2,4-Dichloro­benzyl­idene)hydrazin-1-yl]quinolin-1-ium chloride monohydrate 
In the title hydrated salt, C16H12Cl2N3 +·Cl−·H2O, there is a small twist in the cation as seen in the torsion angle linking the benzene ring to the rest of the mol­ecule [171.96 (17)°]. In the crystal, the quinolinium H atom forms a hydrogen bond to the lattice water mol­ecule, which also forms hydrogen bonds to two Cl− anions. Each Cl− ion also accepts a hydrogen bond from the hydrazine H atom. The three-dimensional architecture is also stabilized by π–π inter­actions between centrosymmetrically related quinoline residues [centroid–centroid distance = 3.5574 (11) Å].
PMCID: PMC3344163  PMID: 22606166
24.  7-Chloro-4-[(E)-2-(2,5-dimeth­oxy­benzyl­idene)hydrazin-1-yl]quinoline 
In the nearly planar title compound (r.m.s. deviation for the 24 non-H atoms = 0.064 Å), C18H16ClN3O2, the conformation about the N=C bond is E. Supra­molecular chains propagated by glide symmetry along [001] are found in the crystal packing. These are sustained by N—H⋯N hydrogen bonds with the quinoline N atom being the acceptor. The chains are connected into a three-dimensional architecture by π–π inter­actions involving all three aromatic rings [centroid–centroid distances = 3.5650 (9)–3.6264 (9) Å].
PMCID: PMC3344174  PMID: 22606177
25.  7-Chloro-4-[(E)-2-(3,4,5-trimeth­oxy­benzyl­idene)hydrazin-1-yl]quinoline 
In the title compound, C19H18ClN3O3, the r.m.s. deviation through the 23 non-H and non-meth­oxy atoms is 0.088 Å, indicating a planar mol­ecule with the exception of the meth­oxy groups. One meth­oxy group, surrounded on either side by the other meth­oxy groups, is almost normal to the benzene ring to which it is connected [C—O—Car—Car torsion angle = 81.64 (15)°]. In the crystal, N—H⋯O, C—H⋯O and π–π inter­actions [between quinoline residues; centroid–centroid distance = 3.4375 (8) Å] link mol­ecules into a three-dimensional architecture.
PMCID: PMC3344149  PMID: 22606152

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