l‐Valyl‐l‐serine trihydrate

The valine side chains in the crystal structure of the title compound [systematic name: 2‐(2‐ammonio‐3‐methyl­butan­amido)‐3‐hydroxy­propano­ate tri­hydrate], C₈H₁₆N₂O₄·3H₂O, stack along an a axis of 4.77 Å to form hydro­phobic columns surrounded by remarkable water/hydroxyl shells. The peptide main chains are connected by hydrogen bonds in two‐dimensional layers. The peptide mol­ecules in each layer are related only by translation, and generate a very rare pattern. This is rendered possible through the formation of the shortest C^α—H·O(carboxyl­ate) inter­action ever recorded.     

Zwitterionic 4‐piperidine­carboxyl­ic acid monohydrate

The title compound, 4‐piperidinio­carboxyl­ate (isonipecotic acid), crystallizes as a zwitterion and incorporates one water mol­ecule, i.e. C₆H₁₁NO₂·H₂O. The piperidine ring adopts a chair conformation and the α‐carboxyl­ate group is oriented in the equatorial position. The combination of the interactions between the α‐amino and α‐carboxyl­ate groups and the water mol­ecules builds a three‐dimensional assembly of hydrogen bonds.     

catena‐Poly[[copper(II)‐μ‐2‐[bis­(2‐pyridylmeth­yl)amino]butyrato‐κ4N,N′,N′′,O:κO′] perchlorate]

The copper(II) ion in the syn–anti carboxyl­ate‐bridged one‐dimensional zigzag chain title complex, {[Cu(C₁₆H₁₈N₃O₂)]ClO₄}_n, exhibits a distorted trigonal–bipyramidal environment. Two N atoms and one carboxyl­ate O atom of the ligand form the basal plane, while the axial positions are filled by an N atom of the ligand and one O atom belonging to the carboxyl­ate group of an adjacent mol­ecule. The crystal packing is enhanced by C—H⋯O(perchlorate) hydrogen bonds.     

2‐Ethyl­phenyl acridine‐9‐carboxyl­ate and 2,5‐dimethyl­phenyl acridine‐9‐carboxyl­ate

The title compounds, 2‐ethyl­phenyl acridine‐9‐carboxyl­ate, C₂₂H₁₇NO₂, (I), and 2,5‐dimethyl­phenyl acridine‐9‐carboxyl­ate, C₂₂H₁₇NO₂, (II), form triclinic and monoclinic crystals, respectively. Related by a centre of symmetry, adjacent molecules of (I) are linked in the lattice via a network of C—H·π and non‐specific dispersive interactions. As a result, acridine moieties and independent phenyl moieties of (I) are parallel in the lattice. The molecules of (II), arranged in a `head‐to‐tail' manner and related by a centre of symmetry, form pairs stabilized via C—H·π interactions. These are linked in the crystal via dispersive interactions. Acridine and independent phenyl moieties lie parallel within the pairs, while adjacent pairs are perpendicular, forming a herring‐bone pattern.     

7‐Vinyl‐8‐aza‐7‐de­aza‐2′‐deoxy­adenosine monohydrate

In the title compound, 4‐amino‐1‐(2‐deoxy‐β‐d ‐eythro‐pento­furan­osyl)‐3‐vinyl‐1H‐pyrazolo­[3,4‐d]­pyrimidine monohydrate, C₁₂H₁₅N₅O₃·H₂O, the conformation of the gly­cosyl bond is anti. The furan­ose moiety is in an S conformation with an unsymmetrical twist, and the conformation at the exocyclic C—C(OH) bond is +sc (gauche, gauche). The vinyl side chain is bent out of the heterocyclic ring plane by 147.5 (5)°. The three‐dimensional packing is stabilized by O—H·O, O—H·N and N—H·O hydrogen bonds.     

N‐Benzyl­tetra­hydro­pyrido‐anellated thio­phene derivatives: new anti­cholinesterases

The title compounds, tert‐butyl 6‐benzyl‐2‐(3,3‐diethyl­ureido)‐4,5,6,7‐tetra­hydro­thieno[2,3‐c]pyridine‐3‐carboxyl­ate, C₂₄H₃₃N₃O₃S, (I), 7‐benzyl‐2‐diethyl­amino‐5,6,7,8‐tetra­hydro‐3‐oxa‐9‐thia‐1,7‐diaza­fluoren‐4‐one, C₂₀H₂₃N₃O₂S, (II), and N‐(7‐benzyl‐4‐oxo‐5,6,7,8‐tetra­hydro‐4H‐3,9‐dithia‐1,7‐diaza­fluoren‐2‐yl)benzamide, C₂₃H₁₉N₃O₂S₂, (III), form monoclinic crystal systems. In (I) and (II), the mol­ecules are linked into a three‐dimensional framework by weak inter­molecular C—H⋯O=C hydrogen bonds, whereas in (III) stronger inter­molecular N—H⋯O=C inter­actions are observed. The conformation of (I) is further stabilized by an intra­molecular N—H⋯O=C hydrogen bond, which effects the planarity of the ureido­thio­phene­carboxyl­ate moiety.     

Eth­yl 5‐isoprop­oxy‐4‐meth­yl‐β‐carboline‐3‐carboxyl­ate: structural determinants of benzodiazepine‐receptor antagonism

Mol­ecules of the title compound, C₁₈H₂₀N₂O₃, are linked into ribbons by N—H·O and N—H·N hydrogen bonds. Stereochemical comparison with Ro 15‐1788 (viz. eth­yl 8‐fluoro‐5,6‐dihydro‐5‐meth­yl‐6‐oxo‐4H‐imidazo[1,5‐a][1,4]benzodiazepine‐3‐carboxyl­ate) has identified three electronegative N and O atoms in the mol­ecule as features likely to be responsible for its activity as a benzodiazepine‐receptor antagonist.     

A single‐strand helical coordination polymer: catena‐poly­[[[tri­aqua­nickel(II)]‐μ‐2,2′‐bi­pyridine‐3,3′‐di­carboxyl­ato‐κ3N,N′:O] monohydrate]

The asymmetric unit of the title compound, {[Ni(C₁₂H₆N₂O₄)(H₂O)₃]·H₂O}_n, is composed of a lattice water mol­ecule and a nickel(II) ion that is coordinated by three water mol­ecules and the two N atoms of a 2,2′‐bi­pyridine‐3,3′‐di­carboxyl­ate ligand. The twist of the 2,2′‐bi­pyridine‐3,3′‐di­carboxyl­ate unit and the coordination of one carboxyl­ate group to a symmetry‐related Ni^II atom generate a helical chain that runs along the b axis. Intrahelical hydrogen bonds participate in controlling the orientation of the helices, and both right‐handed and left‐handed helices are connected by interhelical hydrogen bonds into two‐dimensional sheets.     

Three methoxy‐substituted diethyl 4‐­phenyl‐2,6‐di­methyl‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate compounds

Diethyl 4‐(2,5‐di­methoxy­phenyl)‐2,6‐di­methyl‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate, C₂₁H₂₇NO₆, (I), diethyl 4‐(3,4‐di­methoxy­phenyl)‐2,6‐di­methyl‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate, C₂₁H₂₇NO₆, (II), and diethyl 2,6‐di­methyl‐4‐(3,4,5‐tri­methoxy­phenyl)‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate, C₂₂H₂₉NO₇, (III), crystallize with hydrogen‐bonding networks involving the H atom bonded to the N atom of the 1,4‐di­hydro­pyridine ring and carbonyl O atoms in (I) and (II). Unusually, (III) shows O atoms of methoxy groups serving as hydrogen‐bond acceptors.     

N‐Cinnamo­ylsaccharin

The title compound [systematic name: 2‐cinnamoyl‐1,2‐benzisothiazol‐3(2H)‐one 1,1‐dioxide], C₁₆H₁₁NO₄S, contains both saccharin and cinnamo­yl groups. The mol­ecule is approximately planar in the solid state, and adjacent mol­ecules are connected by C—H·O and C—H·π(phen­yl) inter­actions. In the C—H·π inter­action, the C·CgA distance is 3.916 (4) Å (CgA is the non‐fused benzene ring centroid) and the C—H·π angle is 156 (2)°. A feature of the mol­ecular geometry is the narrow C—S—N angle of 92.51 (9)° in the five‐membered ring. This angle relieves strain from the ring and makes it possible for the whole saccharin group to become quite planar.     

1,3‐Propane­di­ammonium bis(3′‐nitro‐trans‐cinnamate) and trans‐1,2‐cyclo­hexane­di­ammonium bis(3′‐nitro‐trans‐cinnamate)

In the title two adducts, C₃H₁₂N₂²⁺·2C₉H₆NO₄^?, (I), and C₆H₁₆N₂²⁺·2C₉H₆NO₄^?, (II), hydrogen bonds between the di­ammonium and carboxyl­ate ions form a two‐dimensional network parallel to the ab plane in (I) and one‐dimensional chains along the c axis in (II). The cyclo­hexane­di­ammonium ion in (II) has a crystallographic twofold axis.     

Bis­(di­cyclo­hexyl­ammonium) adipate monohydrate

In the asymmetric unit of the title compound, 2C₁₂H₂₄N⁺·C₆H₈O₄^2?·H₂O, the carboxyl­ate ion lies about an inversion center, the water mol­ecule is on a twofold axis and the sec‐ammonium cation is in a general position. Cations link the oxy­gen ends of two adjacent carboxyl­ate anions to form an eight‐membered ring [N?O 2.683 (3) and 2.711 (3) Å]. The ion pair propagates as a linear chain and adjacent chains are linked through the water mol­ecules [O?O 2.966 (3) Å] into layers.     

Ethyl N‐phenyl­oxamate

The oxamate group in the title compound, C₁₀H₁₁NO₃, is almost coplanar with the phenyl ring because of intramol­ecular hydrogen‐bonding interactions, and the structure can be described as an anilide single bonded to an ethyl carboxyl­ate group. The supramolecular structure is achieved through intermolecular hard N—H⋯O and soft C—H⋯X (X = O and phenyl) hydrogen‐bonding interactions.     

Proton‐transfer and non‐transfer in compounds of quinoline and quinaldic acid with l‐tartaric acid

The structures of two compounds of l ‐tartaric acid with quinoline, viz. the proton‐transfer compound quinolinium hydrogen (2R,3R)‐tartrate monohydrate, C₉H₈N⁺·C₄H₅O₆⁻·H₂O, (I), and the anhydrous non‐proton‐transfer adduct with quinaldic acid, bis­(quinolinium‐2‐carboxyl­ate) (2R,3R)‐tar­taric acid, 2C₁₀H₇NO₂·C₄H₆O₆, (II), have been determined at 130 K. Compound (I) has a three‐dimensional honeycomb substructure formed from head‐to‐tail hydrogen‐bonded hydrogen tartrate anions and water mol­ecules. The stacks of π‐bonded quinolinium cations are accommodated within the channels and are hydrogen bonded to it peripherally. Compound (II) has a two‐dimensional network structure based on pseudo‐centrosymmetric head‐to‐tail hydrogen‐bonded cyclic dimers comprising zwitterionic quinaldic acid species which are inter­linked by tartaric acid mol­ecules.     

Aqua­bis(2‐nitro­benzoato‐κO)(1,10‐phenanthroline‐κ2N,N′)­zinc(II)

The title compound, [Zn(C₇H₄NO₄)₂(C₁₂H₈N₂)(H₂O)], has been synthesized. X‐Ray analysis reveals that it is a neutral zinc(II) mononuclear carboxyl­ate complex based on mixed N‐ and O‐donor ligands. The Zn atom is five‐coordinate in a distorted trigonal–bipyramidal coordination environment involving two O atoms of two monodentate 2‐nitro­benzoate mol­ecules, two N atoms of a 1,10‐phenanthroline mol­ecule and one O atom of a water mol­ecule. The axial positions are occupied by a carboxyl­ate O atom from the 2‐nitro­benzoate ligand and an N atom from the 1,10‐phenanthroline ligand [N—Zn—O = 167.66 (9)°].     

Hydrogen‐bonding patterns in six derivatives of 2,4‐dimethyl­pyrrole

The crystal and mol­ecular structures of 4‐ethyl‐3,5‐dimethyl­pyrrole‐2‐carbaldehyde, C₁₀H₁₅NO, (I), benzyl 3,5‐dimethyl­pyrrole‐2‐carboxyl­ate, C₁₄H₁₅NO₂, (II), benzyl 4‐acetyl‐3,5‐dimethyl­pyrrole‐2‐carboxyl­ate, C₁₆H₁₇NO₃, (III), dimethyl 3,5‐dimethyl­pyrrole‐2,4‐dicarboxyl­ate, C₁₀H₁₃NO₄, (IV), 4‐ethyl‐3,5‐dimethyl‐2‐(p‐tos­ylacet­yl)pyrrole, C₁₇H₂₁NO₃S, (V), and ethyl 4‐(2‐ethoxy­carbonyl‐2‐hydroxy­acrylo­yl)‐3,5‐dimethyl­pyrrole‐2‐carboxyl­ate, C₁₅H₁₉NO₆, (VI), were determined at 130 K. Compounds (I), (II), (IV), (V) and (VI) form hydrogen‐bonded dimers [N—H⋯O=C = 1.97 (2)–2.03 (3) Å]. Four dimers, viz. (I) and (IV)–(VI), have inversion symmetry, while the dimer of (II) has twofold symmetry. Only (III) forms polymeric chains involving hydrogen bonds between the pyrrole H atom and the acetyl carbonyl group [H⋯O = 1.97 (2) Å] and is further stabilized by CH₃⋯O inter­actions (C—H⋯O = 2.28–2.49 Å). Compound (VI) was found to occur as the enol ether in the crystal.     

Bis(1,10‐phenanthroline‐κ2N,N′)(squarato‐κO)copper(II) trihydrate

The title mononuclear [Cu(sq)(phen)₂]·3H₂O complex [sq is squarate (C₄O₄) and phen is 1,10‐phenanthroline (C₁₂H₈N₂)] has been synthesized and the structure consists of a neutral mononuclear [Cu(sq)(phen)₂] unit and three solvate water mol­ecules. The Cu^II ion has distorted square‐pyramidal coordination geometry, comprised of one carboxyl­ate O atom from a monodentate squarate ligand and four N atoms from two chelating phen ligands. An extensive three‐dimensional network of OW—H⋯O/OW hydrogen bonds, face‐to‐face π–­π interactions between the 1,10‐phenanthroline aromatic rings and a weak π–ring interaction are responsible for crystal stabilization.     

Conformation of N‐methyl‐4‐piperidyl 2,4‐dinitrobenzoate

The crystal structure of N‐methyl‐4‐piperidyl 2,4‐di­nitro­benzoate, C₁₃H₁₅N₃O₆, (I), at 130 (2) K reveals that, in the solid state, the mol­ecule exists in the equatorial conformation, (Ieq). Thus, the through‐bond interaction present in the axial conformation, (Iax), is not strong enough to overcome the syn–diaxial interactions between the axial methyl substituent and the axial H atoms on the two piperidyl ring C atoms either side of the ester‐linked ring C atom. The carboxyl­ate group in (I) is orthogonal to the aromatic ring, in contrast with other 2,4‐di­nitro­benzoates, which are coplanar. The piperidyl–ester C—O bond distance is 1.467 (3) Å, which is actually shorter than other equatorial cyclo­hexyl–ester C—O distances. This shorter piperidyl–ester C—O bond distance is due to the reduced electron demand of the orthogonal ester group.     

8‐Hydroxyquinaldinic acid and its nickel(II) complex

The molecules of 8‐hydroxy­quinolinium‐2‐carboxyl­ate, C₁₀H₇NO₃, have a planar structure, in which the carboxyl group is ionized and the ring N atom is protonated. The derived nickel(II) complex, bis(8‐hydroxy­quinoline‐2‐carboxyl­ato‐κ³O²,N,O⁸)­nickel(II) trihydrate, [Ni(C₁₀H₆NO₃)₂]·3H₂O, contains an octahedral central Ni^II ion coordinated by the hydroxyl O atom, the ring N atom and the carboxyl­ate O atom of each of the two tridentate ligands, with a perpendicular orientation of the quinoline rings.     

7‐Carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate at 100 K

Both 7‐carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate, C₁₁H₉NO₃·H₂O, (I), and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate, C₁₁H₁₀NO₃⁺·Cl⁻·H₂O, (II), crystallize in the centrosymmetric P space group. Both compounds display an intramolecular O—H⋯O hydrogen bond involving the hydroxy group; this hydrogen bond is stronger in (I) due to its zwitterionic character [O⋯O = 2.4449 (11) Å in (I) and 2.5881 (12) Å in (II)]. In both crystal structures, the HN⁺ group participates in the stabilization of the structure via intermolecular hydrogen bonds with water mol­ecules [N⋯O = 2.7450 (12) Å in (I) and 2.8025 (14) Å in (II)]. In compound (II), a hydrogen‐bond network connects the Cl⁻ anion to the carboxylic acid group [Cl⋯O = 2.9641 (11) Å] and to two water mol­ecules [Cl⋯O = 3.1485 (10) and 3.2744 (10) Å].