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The organic component of the title compound, C22H20N2O5·2H2O, exhibits approximate but noncrystallographic mirror symmetry. The molecules of the organic component are linked by a combination of one O—H...O hydrogen bond and two N—H...O hydrogen bonds to form sheets containingR22(8),R22(16) andR66(40) rings. These sheets are linked into a continuous three-dimensional framework structure by cyclic centrosymmetricR42(8) water tetramers. Comparisons are made with some simpler analogues.

The title compound, C27H25Cl2N3, is an unexpected but high-yield product from the microwave-mediated reaction between 3-tert-butyl-N-4-chlorobenzyl-1-phenyl-1H-pyrazol-5-amine and 4-chlorobenzaldehyde. Inversion-related pairs of molecules are linked by C—H...π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, and dimers of this type are linked into sheets by two independent π–π stacking interactions.

In the molecules of both methyl (1RS,3SR,3aRS,6aSR)-1-methyl-3-(3-methyl-1-phenyl-1H-pyrazol-4-yl)-4,6-dioxo-5-phenyloctahydropyrrolo[3,4-c]pyrrole-1-carboxylate, C25H24N4O4, (I), and methyl (1RS,3SR,3aRS,6aSR)-5-(4-chlorophenyl)-1-methyl-3-(3-methyl-1-phenyl-1H-pyrazol-4-yl)-4,6-dioxooctahydropyrrolo[3,4-c]pyrrole-1-carboxylate, C25H23ClN4O4, (II), the two rings of the pyrrolopyrrole fragment are both nonplanar, with conformations close to half-chair forms. The overall conformations of the molecules of (I) and (II) are very similar, apart from the orientation of the ester function. The molecules of (I) are linked into sheets by a combination of an N—H...π(pyrrole) hydrogen bond and three independent C—H...O hydrogen bonds. The molecules of (II) are also linked into sheets, which are generated by a combination of an N—H...N hydrogen bond and two independent C—H...O hydrogen bonds, weakly augmented by a C—H...π(arene) hydrogen bond.

In the title compound, C31H29N3O2, the reduced pyridine ring adopts a conformation intermediate between the envelope and half-chair forms. The aryl rings of the benzyl and phenyl substituents are nearly parallel and overlap, indicative of an intramolecular π–π stacking interaction. A combination of two C—H...O hydrogen bonds and one C—H...N hydrogen bond links the molecules into a bilayer havingtert-butyl groups on both faces.

A fully ordered structure is reported for the polymorph of triphenylsilanol–4,4′-bipyridyl (4/1), 4C18H16OSi·C10H8N2, havingZ′ = 4. The asymmetric unit contains four similar but distinct five-molecule aggregates, in which the central bipyridyl unit is linked to two molecules of triphenylsilanolviaO—H...N hydrogen bonds, with a further pair of triphenylsilanol molecules linked to the first pairviaO—H...O hydrogen bonds. An extensive series of C—H...π(arene) hydrogen bonds links these aggregates into complex sheets. This structure is compared with a previously reported structure [Bowes, Ferguson, Lough & Glidewell (2003).Acta Cryst.B59, 277–286], which was based on an erroneous disordered structural model arising from a false direct-methods solution with reference to a strong pseudo-inversion centre.

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.

(2RS,4SR)-7-Bromo-2-(2-methylphenyl)-2,3,4,5-tetrahydro-1H-naphtho[1,2-b]azepin-4-ol, C21H20BrNO, (I), and (2RS,4SR)-2-(3-methylthiophen-2-yl)-2,3,4,5-tetrahydro-1H-naphtho[1,2-b]azepin-4-ol, C19H19NOS, (II), both crystallize withZ′ = 2 in the space groupsP21/candCc, respectively; compound (II) crystallizes as a nonmerohedral twin, with twin fractions 0.183 (2) and 0.817 (2). The molecules of (I) are linked by O—H...O and O—H...N hydrogen bonds to form a cyclic centrosymmetricR44(16) tetramer. The molecules of (II) are linked by O—H...O hydrogen bonds to form aC22(4) chain and these chains are weakly linked by a single C—H...π(thienyl) interaction to form a three-dimensional array. Comparisons are made with some related compounds.

The racemic title dipyrrolopyrrolizine compound crystallizes from dimethylformamide as a disolvate, C55H39Cl2N7O6·2C3H7NO. None of the four fused heterocyclic rings is planar; one adopts an envelope conformation, two others adopt half-chair conformations and the fourth adopts a conformation intermediate between an envelope and a half-chair. The arrangement of the ring fusions is such as to preclude the possibility of internal mirror symmetry. The three independent molecular components are weakly linked by C—H...O hydrogen bonds, and the dipyrrolopyrrolizine molecules are linked by a combination of four C—H...O and one C—H...π(arene) hydrogen bond to form a three-dimensional framework, from which the dimethylformamide solvent molecules are pendent. However, aromatic π–π stacking interactions are absent in the structure.

1,5-Bis(4-chlorophenyl)-3-(2-oxo-1,2-dihydroquinolin-3-yl)pentane-1,5-dione, (Ia), and 1,5-bis(2-chlorophenyl)-3-(2-oxo-1,2-dihydroquinolin-3-yl)pentane-1,5-dione, (Ib), crystallize as an 84:16 mixture, 0.84C26H19Cl2NO3·0.16C26H19Cl2NO3, in the space groupI41/a, where the molecules of the two isomers occupy very similar sites in the unit cell. A combination of one N—H...O hydrogen bond and one C—H...O hydrogen bond links the molecules, regardless of isomeric form, into a single three-dimensional framework structure. The molecules of (9RS,10RS)-8,9-bis(4-chlorobenzyl)-10-(2-oxo-1,2-dihydroquinolin-3-yl)-5,6,9,10-tetrahydrophenanthridine, C36H22Cl2N2O4, (II), are linked by two hydrogen bonds, one each of the N—H...O and C—H...O types, into a molecular ribbon in which centrosymmetric rings ofR22(18) andR44(24) types alternate. The hydrogen-bonded ribbons enclose channels, which contain highly disordered solvent molecules.

(2RS,4RS)-7-Fluoro-2-(2-phenylethyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C18H18FNO, (I), and (2RS,4RS)-7-chloro-2-(2-phenylethyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C18H18ClNO, (II), are isomorphous but not strictly isostructural, as the slight differences in the unit-cell dimensions and molecular conformations are sufficient to preclude, in the structure of (I), the direction-specific intermolecular interactions present in the structure of (II), where the molecules are linked into sheets by a combination of C—H...N and C—H...π(arene) hydrogen bonds.

The structures are reported of nine closely related tetrahydro-1,4-epoxy-1-benzazepines carrying pendant heterocyclic substituents, namely: 2-exo-(5-nitrofuran-2-yl)-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C14H12N2O4, (I), 7-fluoro-2-exo-(1-methyl-1H-pyrrol-2-yl)-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C15H15FN2O, (II), 7-fluoro-2-exo-(5-methylfuran-2-yl)-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C15H14FNO2, (III), 7-fluoro-2-exo-(3-methylthiophen-2-yl)-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C15H14FNOS, (IV), 7-fluoro-2-exo-(5-methylthiophen-2-yl)-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C15H14FNOS, (V), 7-chloro-2-exo-(5-methylfuran-2-yl)-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C15H14ClNO2, (VI), 2-exo-(5-methylfuran-2-yl)-7-trifluoromethoxy-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C16H14F3NO3, (VII), 2-exo-(3-methylthiophen-2-yl)-7-trifluoromethoxy-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C16H14F3NO2S, (VIII), and 2-exo-(5-nitrofuran-2-yl)-7-trifluoromethoxy-2,3,4,5-tetrahydro-1,4-epoxy-1H-1-benzazepine, C15H11F3N2O5, (IX). All nine compounds crystallize in centrosymmetric space groups as racemic mixtures with configuration (2RS,4SR). There are no direction-specific interactions between the molecules in (V). The molecules in (III), (IV), (VI) and (VII) are linked into simple chains, by means of a single C—H...O hydrogen bond in each of (III), (VI) and (VII), and by means of a single C—H...π(arene) hydrogen bond in (IV), while the molecules in (VIII) are linked into a chain of rings. In each of (I) and (II), a combination of one C—H...O hydrogen bond and one C—H...π(arene) hydrogen bond links the molecules into sheets, albeit of completely different construction in the two compounds. In (IX), the sheet structure is built from a combination of four independent C—H...O hydrogen bonds and one C—H...π(arene) hydrogen bond. Comparisons are made with some related compounds.

The closely related compoundscis-(2RS,4SR)-2-(thiophen-2-yl)-2,3,4,5-tetrahydro-1H-1-benzazepin-4-ol, C14H15NOS, (I), andcis-(2RS,4SR)-2-(5-methylthiophen-2-yl)-2,3,4,5-tetrahydro-1H-1-benzazepin-4-ol, C15H17NOS, (II), both crystallize withZ′ = 2 in the space groupP\overline{1}. In (I), the thienyl substituent in one of the two independent molecules is disordered over two sets of atomic sites having occupancies of 0.856 (2) and 0.144 (2). In both compounds, the two independent hydroxy O atoms are both within 2.8 Å of the hydroxy O atoms of two neighbouring molecules, and all of the hydroxy H atoms are disordered, each over two sites. The resulting O—H...O hydrogen bonds generate two similar but distinctC44(8) chains, depending upon which hydroxy H-atom sites are occupied or vacant, with full correlation of the hydroxy H-atom occupancies within each chain. Comparisons are made with the supramolecular assembly in some related compounds.

Six closely related pyrazolo[3,4-b]pyridine derivatives, namely 6-chloro-3-methyl-1,4-diphenylpyrazolo[3,4-b]pyridine-5-carbaldehyde, C20H14ClN3O, (I), 6-chloro-3-methyl-4-(4-methylphenyl)-1-phenylpyrazolo[3,4-b]pyridine-5-carbaldehyde, C21H16ClN3O, (II), 6-chloro-4-(4-chlorophenyl)-3-methyl-1-phenylpyrazolo[3,4-b]pyridine-5-carbaldehyde, C20H13Cl2N3O, (III), 4-(4-bromophenyl)-6-chloro-3-methyl-1-phenylpyrazolo[3,4-b]pyridine-5-carbaldehyde, C20H13BrClN3O, (IV), 6-chloro-4-(4-methoxyphenyl)-3-methyl-1-phenylpyrazolo[3,4-b]pyridine-5-carbaldehyde, C21H16ClN3O2, (V), and 6-chloro-3-methyl-4-(4-nitrophenyl)-1-phenylpyrazolo[3,4-b]pyridine-5-carbaldehyde, C20H13ClN4O3, (VI), which differ only in the identity of a single small substituent on one of the aryl rings, crystallize in four different space groups spanning three crystal systems. The molecules of (I) are linked into a chain of rings by a combination of C—H...N and C—H...π(arene) hydrogen bonds; those of (II), (IV) and (V), which all crystallize in the space groupP\overline{1}, are each linked by two independent C—H...O hydrogen bonds to form chains of edge-fused rings running in different directions through the three unit cells; the molecules of (III) are linked into complex sheets by a combination of two C—H...O hydrogen bonds and one C—H...π(arene) hydrogen bond; finally, the molecules of (VI) are linked by a single C—H...O hydrogen bond to form a simple chain.

In 3-tert-butyl-1-(4-chloro­phen­yl)-4-phenyl­indeno­[1,2-b]pyra­zolo­[4,3-e]pyridin-5(1H)-one, C29H22ClN3O, (I), inversion-related pairs of mol­ecules are linked by C—H⋯O hydrogen bonds to form R22(18) dimers, which are themselves linked into a chain by a π–π stacking inter­action between inversion-related pairs of mol­ecules. In 3-tert-butyl-1-(4-chloro­phen­yl)-4-(4-meth­oxy­phen­yl)indeno­[1,2-b]pyrazolo­[4,3-e]pyridin-5(1H)-one, C30H24ClN3O2, (II), which crystallizes in the space group P\overline{1}, with Z′ = 2 and with different orientations for the meth­oxy groups in the two independent mol­ecules, a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds links the mol­ecules into chains of rings, which are further linked into sheets by a π–π stacking inter­action.

The title compound, C(15)H(16)N(2)O, crystallizes in the space group P2(1)2(1)2(1) with Z' = 1. The seven-membered ring adopts a chair-type conformation with the hydroxy and pyridyl substituents in equatorial sites. Molecules are linked into a three-dimensional framework structure by a combination of O-H···N, C-H···O and C-H···π(arene) hydrogen bonds, but N-H···O and N-H···π(arene) interactions are absent from the structure. Comparisons are made with some related compounds.

In the title compound, C(17)H(32)O(2)S(3), the dodecyl chain and the trithiocarbonate unit adopt a nearly planar all-trans conformation, while the carboxyl group is synclinal to this chain direction. The molecules are linked by pairs of inversion-related O-H...O hydrogen bonds to form centrosymmetric dimers of R(2)(2)(8) type, and dimers related by translation are linked by C-H...O hydrogen bonds to form a chain of edge-fused rings, or a molecular ladder, containing alternating R(2)(2)(8) and R(4)(4)(20) rings.

In the title compound, C(18)H(15)N(4)O(+).Cl(-).1.5H(2)O, one water site is fully ordered with unit occupancy while the other, which lies close to an inversion centre in the space group C2/c, has only 0.5 occupancy. The cation exhibits bond fixation in the fused carbocyclic ring and electronic polarization in the terminal heterocyclic ring. The components are linked into complex sheets by a combination of N-H...O, N-H...Cl, O-H...O, O-H...Cl and C-H...O hydrogen bonds.

The molecules of 8-methyl-7,10-diphenyl-5H-benzo[h]pyrazolo[3,4-b]quinoline-5,6(10H)-dione, C(27)H(17)N(3)O(2), (I), are weakly linked into chains by a single C-H...O hydrogen bond, and these chains are linked into sheets by a pi-pi stacking interaction involving pyridyl and aryl rings. In 8-methyl-7-(4-methylphenyl)-10-phenyl-5H-benzo[h]pyrazolo[3,4-b]quinoline-5,6(10H)-dione, C(28)H(19)N(3)O(2), (II), the molecules are linked into a three-dimensional framework structure by a combination of C-H...N, C-H...O and C-H...pi(arene) hydrogen bonds, together with a pi-pi stacking interaction analogous to that in (I).

In each of 2-amino-4-(piperidin-1-yl)-11H-pyrimido[4,5-b][1,5]benzodiazepin-6-ium chloride monohydrate, C(16)H(19)N(6)(+).Cl(-).H(2)O, (I), and 2-amino-4-[methyl(2-methylphenyl)amino]-11H-pyrimido[4,5-b][1,5]benzodiazepin-6-ium chloride-benzene-1,2-diamine (1/1), C(19)H(19)N(6)(+).Cl(-).C(6)H(8)N(2), (II), the seven-membered ring in the cation adopts a boat conformation. The pyrimidine ring in (II) adopts a twist-boat conformation, but the corresponding ring in (I) is essentially planar. The amino groups of the benzene-1,2-diamine component of (II) are both pyramidal. The independent components of (I) are linked into complex sheets by a combination of N-H...O, N-H...N, N-H...Cl and O-H...Cl hydrogen bonds. In the crystal structure of (II), one N-H...N hydrogen bond and six independent N-H...Cl hydrogen bonds combine to link the components into complex sheets.

The mol­ecules of the title compound, C26H19Cl2N5, are conformationally chiral, with none of the aryl groups coplanar with the pyrazolo[3,4-b]pyridine core of the mol­ecule. A single unique N—H⋯N hydrogen bond links the mol­ecules into two symmetry-related sets of C(11) chains running parallel to the [011] and [01\overline{1}] directions, respectively, and these two sets of chains are linked into a continuous three-dimensional framework structure by a single unique C—H⋯N hydrogen bond which forms a chain parallel to the [100] direction.

In O-ethyl N-benzoylthiocarbamate, C(10)H(11)NO(2)S, the molecules are linked into sheets by a combination of two-centre N-H...O and C-H...S hydrogen bonds and a three-centre C-H...(O,S) hydrogen bond. A combination of two-centre N-H...O and C-H...O hydrogen bonds links the molecules of O-ethyl N-(4-methylbenzoyl)thiocarbamate, C(11)H(13)NO(2)S, into chains of rings, which are linked into sheets by an aromatic pi-pi stacking interaction. In O,S-diethyl N-(4-methylbenzoyl)imidothiocarbonate, C(13)H(17)NO(2)S, pairs of molecules are linked into centrosymmetric dimers by pairs of symmetry-related C-H...pi(arene) hydrogen bonds, while the molecules of O,S-diethyl N-(4-chlorobenzoyl)imidothiocarbonate, C(12)H(14)ClNO(2)S, are linked by a single C-H...O hydrogen bond into simple chains, pairs of which are linked by an aromatic pi-pi stacking interaction to form a ladder-type structure.

The molecules of racemic 3-benzoylmethyl-3-hydroxyindolin-2-one, C(16)H(13)NO(3), (I), are linked by a combination of N-H...O and O-H...O hydrogen bonds into a chain of centrosymmetric edge-fused R(2)(2)(10) and R(4)(4)(12) rings. Five monosubstituted analogues of (I), namely racemic 3-hydroxy-3-[(4-methylbenzoyl)methyl]indolin-2-one, C(17)H(15)NO(3), (II), racemic 3-[(4-fluorobenzoyl)methyl]-3-hydroxyindolin-2-one, C(16)H(12)FNO(3), (III), racemic 3-[(4-chlorobenzoyl)methyl]-3-hydroxyindolin-2-one, C(16)H(12)ClNO(3), (IV), racemic 3-[(4-bromobenzoyl)methyl]-3-hydroxyindolin-2-one, C(16)H(12)BrNO(3), (V), and racemic 3-hydroxy-3-[(4-nitrobenzoyl)methyl]indolin-2-one, C(16)H(12)N(2)O(5), (VI), are isomorphous in space group P-1. In each of compounds (II)-(VI), a combination of N-H...O and O-H...O hydrogen bonds generates a chain of centrosymmetric edge-fused R(2)(2)(8) and R(2)(2)(10) rings, and these chains are linked into sheets by an aromatic pi-pi stacking interaction. No two of the structures of (II)-(VI) exhibit the same combination of weak hydrogen bonds of C-H...O and C-H...pi(arene) types. The molecules of racemic 3-hydroxy-3-(2-thienylcarbonylmethyl)indolin-2-one, C(14)H(11)NO(3)S, (VII), form hydrogen-bonded chains very similar to those in (II)-(VI), but here the sheet formation depends upon a weak pi-pi stacking interaction between thienyl rings. Comparisons are drawn between the crystal structures of compounds (I)-(VII) and those of some recently reported analogues having no aromatic group in the side chain.

In the molecule of the title compound, C25H21N3OS, which was prepared by mild oxidation of the corresponding 5,6,7,8,9,10-hexahydro analogue, the fused carbocyclic ring adopts an envelope conformation. Pairs of molecules are linked into cyclic centrosymmetric dimers by pairs of inversion-related N—H...O hydrogen bonds.

The bond distances in 2-cyano-N-(2,6-dimethoxypyrimidin-4-yl)-3-[4-(dimethylamino)phenyl]acrylamide, C(18)H(19)N(5)O(3), (I), and in the anionic component of the salt dimethylammonium 6-cyano-1,3-dimethyl-2,4,5-trioxo-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidin-8-ide, C(2)H(8)N(2)(+)center dot C(10)H(7)N(4)O(3)(-), (II), provide evidence for the occurrence of electronic polarization. There are no hydrogen bonds in the structure of (I), instead pairs of molecules are linked into centrosymmetric dimers by a single pi-pi stacking interaction. In (II), a combination of a two-centre N-H center dot center dot center dot O hydrogen bond, a three-centre N-H center dot center dot center dot(O)(2) hydrogen bond, together utilizing all three O atoms, and a two-centre C-H center dot center dot center dot N hydrogen bond, link the components into a ribbon containing R(1)(2)(6), R(2)(2)(10) and R(6)(6)(30) rings.

(3Z)-3-{1-[(5-Phenyl-1H-pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuran-2(3H)-one, C(15)H(15)N(3)O(2), (I), and the stoichiometric adduct (3Z)-3-{1-[(5-methyl-1H-pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuran-2(3H)-one-6-(2-hydroxyethyl)-2,5-dimethylpyrazolo[1,5-a]pyrimidin-7(4H)-one (1/1), C(10)H(13)N(3)O(2).C(10)H(13)N(3)O(2), (II), in which the two components have the same composition but different constitutions, are formed in the reactions of 2-acetyl-4-butyrolactone with 5-amino-3-phenyl-1H-pyrazole and 5-amino-3-methyl-1H-pyrazole, respectively. In each compound, the furanone component contains an intramolecular N-H...O hydrogen bond. The molecules of (I) are linked into a chain by a single intermolecular N-H...O hydrogen bond, while in (II), a combination of one O-H...N hydrogen bond, within the selected asymmetric unit, and two N-H...O hydrogen bonds link the molecular components into a ribbon containing alternating centrosymmetric R(4)(4)(20) and R(6)(6)(22) rings.

The molecules of (2RS,4SR)-2-exo-(5-bromo-2-thienyl)-7-chloro-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(14)H(11)BrClNOS, (I), are linked into cyclic centrosymmetric dimers by C-H...pi(thienyl) hydrogen bonds. Each such dimer makes rather short Br...Br contacts with two other dimers. In (2RS,4SR)-2-exo-(5-methyl-2-thienyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(15)H(15)NOS, (II), a combination of C-H...O and C-H...pi(thienyl) hydrogen bonds links the molecules into chains of rings. A more complex chain of rings is formed in (2RS,4SR)-7-chloro-2-exo-(5-methyl-2-thienyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(15)H(14)ClNOS, (III), built from a combination of two independent C-H...O hydrogen bonds, one C-H...pi(arene) hydrogen bond and one C-H...pi(thienyl) hydrogen bond.

4,4'-(Phenylmethylene)bis(6-allyl-3-chloro-2-methylaniline), C(27)H(28)Cl(2)N(2), (I), and 4,4'-(2-thienylmethylene)bis(6-allyl-3-chloro-2-methylaniline), C(25)H(26)Cl(2)N(2)S, (II), adopt similar molecular conformations, although the thienyl group in (II) exhibits orientational disorder over two sets of sites with occupancies of 0.614 (3) and 0.386 (3). The amino groups in both compounds are pyramidal. A single N-H...N hydrogen bond links the molecules of (I) into cyclic centrosymmetric dimers. Molecules of (II) are linked by an ordered C-H...pi(arene) hydrogen bond to form cyclic centrosymmetric dimers, and these dimers are linked into statistically interrupted chains by a second C-H...pi(arene) hydrogen bond involving a donor in the minor component of the disordered thienyl unit.

The organic components of 2-methoxy-3-methyl-6-oxo-4-(2,3,4-tri-O-acetyl-beta-D-xylopyranosylamino)-1,6-dihydropyrimidine-5-carbaldehyde 0.065-hydrate, C(18)H(23)N(3)O(10).0.065H(2)O, (I), which crystallizes with Z' = 2 in the space group P2(1)2(1)2(1), are linked into a three-dimensional framework structure by a combination of four C-H...O hydrogen bonds. In 2-methylsulfanyl-6-oxo-4-(2,3,4-tri-O-acetyl-beta-D-xylopyranosylamino)-1,6-dihydropyrimidine-5-carbaldehyde, C(17)H(21)N(3)O(9)S, (II), where the pyrimidine fragment is disordered with two different conformations for the methylsulfanyl substituent, molecules are linked into chains of rings by a combination of N-H...O and C-H...O hydrogen bonds.

In 6-(3,4,5-trimethoxyphenyl)-6,7-dihydro-5H-1,3-dioxolo[4,5-g]quinolin-8(5H)-one, C(19)H(19)NO(6), (I), the six-membered heterocyclic ring adopts a conformation intermediate between envelope and half-chair forms; it is disordered over two enantiomeric configurations, with occupancies of 0.879 (3) and 0.121 (3), leading to positional disorder of the 3,4,5-trimethoxyphenyl unit. In 6-(1,3-benzodioxol-5-yl)-6,7-dihydro-5H-1,3-dioxolo[4,5-g]quinolin-8-one, C(17)H(13)NO(5), (II), the molecules are similarly disordered, with occupancies of 0.866 (4) and 0.134 (4). The molecules in (I) are linked by one three-centre N-H...(O)(2) hydrogen bond and one two-centre C-H...O hydrogen bond to form a complex chain of rings whose formation is reinforced by two independent aromatic pi-pi stacking interactions. In (II), a single N-H...O hydrogen bond links the molecules into a simple chain, and pairs of chains are linked by a single aromatic pi-pi stacking interaction.

5-Benzylamino-3-tert-butyl-1-phenyl-1H-pyrazole, C(20)H(23)N(3), (I), and its 5-[4-(trifluoromethyl)benzyl]-, C(21)H(22)F(3)N(3), (III), and 5-(4-bromobenzyl)-, C(20)H(22)BrN(3), (V), analogues, are isomorphous in the space group C2/c, but not strictly isostructural; molecules of (I) form hydrogen-bonded chains, while those of (III) and (V) form hydrogen-bonded sheets, albeit with slightly different architectures. Molecules of 3-tert-butyl-5-(4-methylbenzylamino)-1-phenyl-1H-pyrazole, C(21)H(25)N(3), (II), are linked into hydrogen-bonded dimers by a combination of N-H...pi(arene) and C-H...pi(arene) hydrogen bonds, while those of 3-tert-butyl-5-(4-chlorobenzylamino)-1-phenyl-1H-pyrazole, C(20)H(22)ClN(3), (IV), form hydrogen-bonded chains of rings which are themselves linked into sheets by an aromatic pi-pi stacking interaction. Simple hydrogen-bonded chains built from a single N-H...O hydrogen bond are formed in 3-tert-butyl-5-(4-nitrobenzylamino)-1-phenyl-1H-pyrazole, C(20)H(22)N(4)O(2), (VI), while in 3-tert-butyl-5-(3,4,5-trimethoxybenzylamino)-1-phenyl-1H-pyrazole, C(23)H(29)N(3)O(3), (VII), which crystallizes with Z' = 2 in the space group P-1, pairs of molecules are linked into two independent centrosymmetric dimers, one generated by a three-centre N-H...(O)(2) hydrogen bond and the other by a two-centre N-H...O hydrogen bond.

The title compound, piperidinium 6-amino-3-methyl-5-nitroso-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-ide 6-amino-3-methyl-5-nitrosopyrimidine-2,4(1H,3H)-dione, C(5)H(12)N(+).C(5)H(5)N(4)O(3)(-).C(5)H(6)N(4)O(3), (I), crystallizes with Z' = 2 in the space group P1. There is an intramolecular N-H...O hydrogen bond in each pyrimidine unit and within the selected asymmetric unit the six independent components are linked by 11 hydrogen bonds, seven of the N-H...O type and four of the N-H...N type. These six-component aggregates are linked into sheets by five further hydrogen bonds, three of the N-H...O type and one each of the N-H...N and C-H...O types.

In the title compound, C(24)H(18)N(4)O(3)S.C(2)H(6)OS, the biindenylidene component shows evidence of polarization of the electronic structure. The dimethyl sulfoxide solvent molecules are disordered over two sites, and they are linked to the biindenylidenedione components via N-H...O and C-H...O hydrogen bonds. A combination of N-H...N and N-H...O hydrogen bonds links the nonsolvent components into a chain of edge-fused centrosymmetric R(2)(2)(8) and R(2)(2)(22) rings, and these chains are linked into sheets by a single aromatic pi-pi stacking interaction.

(2R,4S)-7-Bromo-2-phenyl-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, C(20)H(16)BrNO, (I), exhibits evidence of a modest degree (ca 10%) of inversion twinning, while both (2RS,4SR)-7-bromo-2-(4-chlorophenyl)-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, C(20)H(15)BrClNO, (II), and (2RS,4SR)-2-(4-fluorophenyl)-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, C(20)H(16)FNO, (III), crystallize as genuine racemic mixtures. The molecules of (I) are linked into sheets by a combination of one C-H...O hydrogen bond and two C-H...pi(arene) hydrogen bonds, while those of (II) are linked into sheets of pi-stacked hydrogen-bonded chains. A combination of one C-H...O hydrogen bond and four independent C-H...pi(arene) hydrogen bonds links the molecules of (III) into a three-dimensional framework. The significance of this study lies in its finding, via comparison with the structures of some closely-related epoxybenzazepine analogues, of significant changes in crystal structures consequent upon small changes in the peripheral substituents.

The title solvates, (I) and (II), both C18H16N6O3·C2H6OS, are isomeric. The conformations adopted by the 6-substituent are significantly different, with the 6-aminophenyl unit remote from the nitrophenyl ring in methoxypyrimidine (I) but adjacent to it in pyrimidinone (II). Pairs of pyrimidine molecules in (I) are linked by N—H...N hydrogen bonds to form cyclic centrosymmetric dimers from which the dimethyl sulfoxide molecules are pendent, while in (II) a combination of three independent N—H...O hydrogen bonds links the components into a chain containing bothR22(8) andR42(8) rings, in which the dimethyl sulfoxide component acts as a double acceptor of hydrogen bonds. The significance of this study lies in its observation of different conformations for the pyrimidine components in (I) and (II), and different hydrogen-bonded structures, apparently dominated by the different roles adopted by the dimethyl sulfoxide components.

2-Amino-4-chloro-5-formyl-6-[meth­yl(2-methyl­phen­yl)­amino]pyrimidine, C13H13ClN4O, (I), and 2-amino-4-chloro-5-formyl-6-[(2-methoxy­phen­yl)methyl­amino]pyrimidine, C13H13ClN4O2, (II), are isostructural and essentially isomorphous. Although the pyrimidine rings in each compound are planar, the ring-substituent atoms show significant displacements from this plane, and the bond distances provide evidence for polarization of the electronic structures. In each compound, a combination of N—H⋯N and N—H⋯O hydrogen bonds links the mol­ecules into sheets built from centrosymmetric R22(8) and R66(32) rings. The significance of this study lies in its observation of the isostructural nature of (I) and (II), and in the comparison of their crystal and mol­ecular structures with those of analogous compounds.

In each of 3-tert-butyl-1-phenyl-7-(4-trifluoromethylbenzyl)-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1'-cyclohexane-2',6'-dione, C(29)H(30)F(3)N(3)O(2), (I), and 3-tert-butyl-7-(4-methoxybenzyl)-1-phenyl-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1'-cyclohexane-2',6'-dione, C(29)H(33)N(3)O(3), (II), the reduced pyridine ring adopts a half-chair conformation. The molecules of compound (I) are linked by two C-H...O hydrogen bonds to form a C(5)C(5)[R(1)(2)(8)] chain of rings, while in compound (II), two C-H...O hydrogen bonds link the molecules into a C(6)C(7)[R(2)(2)(11)] chain of rings, which is further reinforced by a C-H...pi hydrogen bond. The significance of this study lies in its observation of significant differences in hydrogen-bonded structures consequent upon very minor changes in remote substituents.

2-Amino-4-methoxy-6-phenyl-11H-pyrimido[4,5-b][1,4]benzodiazepine, C(18)H(15)N(5)O, (I), and its 6-(2-fluorophenyl)-, 6-(3-nitrophenyl)- and 6-(4-methoxyphenyl)- analogues, viz. C(18)H(14)FN(5)O, (II), C(18)H(14)N(6)O(3), (III), and C(19)H(17)N(5)O(2), (IV), respectively, all adopt molecular conformations which are almost identical, containing boat-shaped seven-membered rings. In each structure, paired N-H...N hydrogen bonds link the molecules into centrosymmetric dimers. In each of (I)-(III), the dimers are further linked, forming a different three-dimensional framework in each case, while in compound (IV) the dimers are linked into sheets. The significance of this study lies in the observation of different crystal structures in four compounds whose molecular structures are very similar.

3-tert-Butyl-7-(4-chlorobenzyl)-4',4'-dimethyl-1-phenyl-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1'-cyclohexane-2',6'-dione ethanol hemisolvate, C(30)H(34)ClN(3)O(2) x 0.5C(2)H(6)O, (I), its 7-(4-bromobenzyl)- analogue, C(30)H(34)BrN(3)O(2) x 0.5C(2)H(6)O, (II), and its 7-(4-methylbenzyl)- analogue, C(31)H(37)N(3)O(2) x 0.5C(2)H(6)O, (III), are isomorphous, with the ethanol component disordered across a twofold rotation axis in the space group C2/c. In the corresponding 7-[4-(trifluoromethyl)benzyl]- compound, C(31)H(34)F(3)N(3)O(2) x 0.5C(2)H(6)O, (IV), the ethanol component is disordered across a centre of inversion in the space group P\overline{1}. In each of (I)-(IV), the reduced pyridine ring adopts a half-chair conformation. The heterocyclic components in (I)-(III) are linked into centrosymmetric dimers by a single C-H...pi interaction, with the half-occupancy ethanol component linked to the dimer by a combination of C-H...O and O-H...pi(arene) hydrogen bonds. The heterocyclic molecules in (IV) are linked into chains of centrosymmetric rings by C-H...O and C-H...pi hydrogen bonds, again with the half-occupancy ethanol component pendent from the chain. The significance of this study lies in the isomorphism of the related derivatives (I)-(III), in the stoichiometric hemisolvation by ethanol, where the disordered solvent molecule is linked to the heterocyclic component by a two-point linkage, and in the differences between the crystal structures of (I)-(III) and that of (IV).

In the title compound, C(24)H(26)O(4), (I), the central ring of the fused tricyclic ring system adopts a shallow boat conformation, while the two outer rings adopt envelope conformations. The molecules are linked into C(9) chains by a single C-H...O hydrogen bond. The significance of this study lies in its comparison of the conformation and supramolecular aggregation of (I) with those of related compounds in the published literature.

(2SR,4RS)-7-Fluoro-2-exo-(2-furyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(14)H(12)FNO(2), (I), crystallizes with Z' = 2 in the space group P2(1)/c. A combination of three C-H...O hydrogen bonds and one C-H...N hydrogen bond links the molecules into a complex chain of rings, and pairs of such chains are linked into a tube-like structure by two C-H...pi(arene) hydrogen bonds. There are no hydrogen bonds in the structure of racemic (2SR,4RS)-2-exo-(5-bromo-2-thienyl)-7-fluoro-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(14)H(11)BrFNOS, (II), while the molecules of (2S,4R)-2-exo-(5-bromo-2-thienyl)-7-trifluoromethoxy-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(15)H(14)BrF(3)NO(2)S, (III), are linked into sheets by a combination of two C-H...O hydrogen bonds and one C-H...pi(arene) hydrogen bond. The significance of this study lies in its observation of the wide variation in the patterns of supramolecular aggregation, consequent upon modest changes in the peripheral substituents.

In (2SR,4RS)-7-chloro-2-exo-(4-chlorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(16)H(13)Cl(2)NO, (I), the molecules are linked by a combination of C-H...O and C-H...N hydrogen bonds into a chain of edge-fused R(3)(3)(12) rings. The isomeric compound (2S,4R)-7-chloro-2-exo-(2-chlorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, (II), crystallizes as a single 2S,4R enantiomer and the molecules are linked into a three-dimensional framework structure by two C-H...O hydrogen bonds and one C-H...pi(arene) hydrogen bond. The molecules of (2S,4R)-7-chloro-2-exo-(1-naphthyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(20)H(16)ClNO, (III), are also linked into a three-dimensional framework structure, here by one C-H...O hydrogen bond and two C-H...pi(arene) hydrogen bonds. The significance of this study lies in its observation of the variations in molecular configuration and conformation, and in the variation in the patterns of supramolecular aggregation, consequent upon modest changes in the peripheral substituents.

The title compound (trivial name terbutylazine), C(9)H(16)ClN(5), (I), crystallizes with Z' = 4 in the space group Pca2(1), and equal numbers of molecules adopt two different conformations for the ethylamine groups. The four independent molecules form two approximately enantiomorphic pairs. Eight independent N-H...N hydrogen bonds link the molecules into two independent chains of R(2)(2)(8) rings, in which the arrangement of the alkylamine substituents in the independent molecules precludes any further crystallographic symmetry. The significance of this study lies in its finding of two distinct molecular conformations within the structure and two distinct ways in which the molecules are organized into hydrogen-bonded chains, and in its comparison of the hydrogen-bonded structure of (I) with those of analogous 1,3,5-triazines and pyrimidines.

Compounds trans-tetraaquadichloridocobalt(II)-piperazine-2,5-dione (1/1), [CoCl(2)(H(2)O)(4)].C(4)H(6)N(2)O(2), (I), and trans-tetraaquadichloridonickel(II)-piperazine-2,5-dione (1/1), [NiCl(2)(H(2)O)(4)].C(4)H(6)N(2)O(2), (II), are isomorphous. In each structure, the metal complex and the piperazinedione unit both lie across centres of inversion in the space group P2(1)/n. The [MCl(2)(H(2)O)(4)] units (M = Co or Ni) are linked by O-H...Cl hydrogen bonds into sheets of R(2)(2)(8) and R(4)(2)(12) rings, and these sheets are linked by the piperazinedione components via a combination of O-H...O and N-H...Cl hydrogen bonds into a three-dimensional framework. In catena-poly[[[trans-diaquacopper(II)]-di-mu-chlorido] piperazine-2,5-dione solvate], {[CuCl(2)(H(2)O)(2)].C(4)H(6)N(2)O(2)}(n), (III), the metal ion and the piperazine unit both lie across centres of inversion in the space group I2/a. The coordination polymer forms chains of centrosymmetric [CuCl(2)(H(2)O)(2)] units running parallel to [010] and these are linked by the piperazinedione units into a three-dimensional framework structure. In poly[mu(3)-nitrato-mu(2)-piperazine-2,5-dione-silver(I)], [Ag(NO(3))(C(4)H(6)N(2)O(2))](n), (IV), the silver and nitrate ions lie on mirror planes in the space group Pnma, while the piperazinedione unit lies across a centre of inversion. The compound is a coordination polymer containing five-coordinate approximately square-pyramidal Ag, in which the ligating O atoms are derived from three different nitrate ligands and two different piperazinedione ligands. The ionic components form sheets in which each anion is coordinated to three different cations, and these sheets are linked into a three-dimensional framework by the organic ligands, each of which coordinates to two different Ag centres. The significance of this study lies in its demonstration of a wide variety of framework types built from a common and very simple organic component with simple metal salts.

The molecules of ethyl 2-methoxy-6-[(triphenylphosphoranylidene)amino]nicotinate, C(27)H(25)N(2)O(3)P, (I), and ethyl 2-methylsulfanyl-6-[(triphenylphosphoranylidene)amino]nicotinate, C(27)H(25)N(2)O(2)PS, (II), have almost identical bond lengths and molecular conformations, and both show evidence for polarized electronic structures. However, the crystal structures, as illustrated by the weak hydrogen bonds linking the molecules, are significantly different. The significance of this study lies in the observation that two compounds which are almost identical in constitution, configuration and conformation nonetheless adopt different crystal structures.

In each of 6-amino-3-methyl-2-(morpholin-4-yl)-5-nitrosopyrimidin-4(3H)-one, C(9)H(13)N(5)O(3), (I), morpholin-4-ium 4-amino-2-(morpholin-4-yl)-5-nitroso-6-oxo-1,6-dihydropyrimidin-1-ide, C(4)H(10)NO(+) x C(8)H(10)N(5)O(3)(-), (II), and 6-amino-2-(morpholin-4-yl)-5-nitrosopyrimidin-4(3H)-one hemihydrate, C(8)H(11)N(5)O(3) x 0.5 H(2)O, (III), the bond distances within the pyrimidine components are consistent with significant electronic polarization, which is most marked in (II) and least marked in (I). Despite the high level of substitution, the pyrimidine rings are all effectively planar, and in each of the pyrimidine components, there are intramolecular N-H...O hydrogen bonds. In each compound, the organic components are linked by multiple N-H...O hydrogen bonds to form sheets of widely differing construction, and in compound (III) adjacent sheets are linked by the water molecules, so forming a three-dimensional hydrogen-bonded framework. This study also contains the first direct geometric comparison between the electronic polarization in a neutral aminonitrosopyrimidine and that in its ring-deprotonated conjugate anion in a metal-free environment.

The pyrimidine rings in ethyl (E)-3-[2-amino-4,6-bis(dimethylamino)pyrimidin-5-yl]-2-cyanoacrylate, C(14)H(20)N(6)O(2), (I), and 2-[(2-amino-4,6-di-1-piperidylpyrimidin-5-yl)methylene]malononitrile, C(18)H(23)N(7), (II), which crystallizes with Z' = 2 in the P1 space group, are both nonplanar with boat conformations. The molecules of (I) are linked by a combination of N-H...N and N-H...O hydrogen bonds into chains of edge-fused R(2)(2)(8) and R(4)(4)(20) rings, while the two independent molecules in (II) are linked by four N-H...N hydrogen bonds into chains of edge-fused R(2)(2)(8) and R(2)(2)(20) rings. This study illustrates both the readiness with which highly-substituted pyrimidine rings can be distorted from planarity and the significant differences between the supramolecular aggregation in two rather similar compounds.

The molecules of 5-amino-1-(4-methoxybenzoyl)-3-methylpyrazole, C(12)H(13)N(3)O(2), (I), and 5-amino-3-methyl-1-(2-nitrobenzoyl)pyrazole, C(11)H(10)N(4)O(3), (II), both contain intramolecular N-H...O hydrogen bonds. The molecules of (I) are linked into a chain of rings by a combination of N-H...N and N-H...pi(arene) hydrogen bonds, while those of (II) are linked into a three-dimensional framework structure by N-H...N and C-H...O hydrogen bonds.

Tetraaqua(18-crown-6)cerium(III) hexacyanoferrate(III) dihydrate, [Ce(C(12)H(24)O(6))(H(2)O)(4)][Fe(CN)(6)].2H(2)O, and tetraaqua(18-crown-6)neodymium(III) hexacyanoferrate(III) dihydrate, [Nd(C(12)H(24)O(6))(H(2)O)(4)][Fe(CN)(6)].2H(2)O, are isomorphous and isostructural in the C2/c space group, where the cations, which contain ten-coordinate lanthanoid centres, lie across twofold rotation axes and the anions lie across inversion centres. In these compounds, an extensive series of O-H...O and O-H...N hydrogen bonds links the components into a continuous three-dimensional framework. Triaqua(18-crown-6)lanthanoid(III) hexacyanoferrate(III) dihydrate, [Ln(C(12)H(24)O(6))(H(2)O)(3)][Fe(CN)(6)].2H(2)O, where Ln = Sm, Eu, Gd or Tb, are all isomorphous and isostructural in the P\overline{1} space group, as are triaqua(18-crown-6)gadolinium(III) hexacyanochromate(III) dihydrate, [Gd(C(12)H(24)O(6))(H(2)O)(3)][Cr(CN)(6)].2H(2)O, and triaqua(18-crown-6)gadolinium(III) hexacyanocobaltate(III) dihydrate, [Gd(C(12)H(24)O(6))(H(2)O)(3)][Co(CN)(6)].2H(2)O. In these compounds, there are two independent anions, both lying across inversion centres, and the lanthanoid centres exhibit nine-coordination; in the crystal structures, an extensive series of hydrogen bonds links the components into a three-dimensional framework.

In both 2,5-dimethyl-6,7-dihydrobenzo[h]pyrazolo[1,5-a]quinazoline, C(16)H(15)N(3), (I), and 2-tert-butyl-5-methyl-6,7-dihydrobenzo[h]pyrazolo[1,5-a]quinazoline, C(19)H(21)N(3), (II), which crystallizes with Z' = 2 in the space group P\overline{1}, the non-aromatic carbocyclic rings adopt screw-boat conformations. The molecules of (I) are linked into chains of rings by a combination of C-H...N and C-H...pi(arene) hydrogen bonds, while in (II) there are no hydrogen bonds of any kind.

The molecules of methyl 3-(2-nitrophenylhydrazono)butanoate, C(11)H(13)N(3)O(4), (I), and methyl 3-(2,4-dinitrophenylhydrazono)butanoate, C(11)H(12)N(4)O(6), (II), both prepared from methyl 3-oxobutanoate and the corresponding nitrophenylhydrazine, exhibit polarized molecular electronic structures; in each of (I) and (II), the molecules are linked into chains by a single C-H...O hydrogen bond. The molecules of 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole, C(10)H(10)N(2)O, (III), prepared by the reaction of methyl 3-oxobutanoate and phenylhydrazine, are linked into chains by a single O-H...N hydrogen bond. The reaction between methyl 3-oxobutanoate and 3-nitrophenylhydrazine yields 5-hydroxy-3-methyl-1-(3-nitrophenyl)-1H-pyrazole, (IV), which when crystallized from acetone yields 4-isopropylidene-3-methyl-1-(3-nitrophenyl)-1H-pyrazol-5(4H)-one, C(13)H(13)N(3)O(3), (V).