The monohydrates of the four polar dipeptides l‐seryl‐l‐asparagine,l‐seryl‐l‐tyrosine,l‐tryptophanyl‐l‐serine and l‐tyrosyl‐l‐tryptophan

The crystal structures of the four dipeptides l ‐seryl‐l ‐asparagine monohydrate, C₇H₁₃N₃O₅·H₂O, l ‐seryl‐l ‐tyrosine monohydrate, C₁₂H₁₆N₂O₅·H₂O, l ‐tryptophanyl‐l ‐serine monohydrate, C₁₄H₁₇N₃O₄·H₂O, and l ‐tyrosyl‐l ‐tryptophan monohydrate, C₂₀H₂₁N₃O₄·H₂O, are dominated by extensive hydrogen‐bonding networks that include cocrystallized solvent water molecules. Side‐chain conformations are discussed on the basis of previous observations in dipeptides. These four dipeptide structures greatly expand our knowledge on dipeptides incorporating polar residues such as serine, asparagine, threonine, tyrosine and tryptophan.     

l‐Phenyl­alanyl‐l‐alanine dihydrate

A new type of molecular arrangement for dipeptides is observed in the crystal structure of l ‐phenyl­alanyl‐l ‐alanine dihydrate, C₁₂H₁₆N₂O₃·2H₂O. Two l ‐Phe and two l ‐Ala side chains aggregate into large hydro­phobic columns within a three‐dimensional hydrogen‐bond network.     

N‐(tert‐Butoxycarbonyl)‐L‐valyl‐L‐valine methyl ester: a twisted parallel β‐sheet in the crystal structure of a protected dipeptide

The title compound, C₁₆H₃₀N₂O₅, crystallizes with three molecules in the asymmetric unit, each adopting a β‐strand/polyproline II backbone conformation. The main‐chain functional groups are hydrogen bonded into tapes having the characteristics of parallel β‐sheets. Each tape has a left‐handed twist and thus forms a helix, with six peptide molecules needed to complete a full 360° rotation. A comparison of hydrogen‐bond lengths and twisting modes is made with other related structures of protected dipeptides and with a hexapeptide derived from amyloid‐β containing the Val–Val segment. Additionally, a comparison of the backbone conformation is made with that of the Val141–Val142 segment of the water channel aquaporin‐4 (AQP4).     

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.     

l‐Seryl‐l‐phenyl­alanine

The peptide bond in the crystal structure of the title compound, C₈H₁₆N₂O₄, deviates substantially from planarity in the same manner as in other l ‐Ser‐l ‐Xaa dipeptides, where Xaa is a hydro­phobic residue.     

Ammonium N‐acetyl‐l‐threoninate and methyl­ammonium N‐acetyl‐l‐threoninate

Ammonium N‐acetyl‐l ‐threoninate, NH₄⁺·C₆H₁₀NO₄^?, and methyl­ammonium N‐acetyl‐l ‐threoninate, CH₆N⁺·­C₆H₁₀NO₄^?, crystallize in the orthorhombic P2₁2₁2₁ and monoclinic P2₁ space groups, respectively. The two crystals present the same packing features consisting of infinite ribbons of screw‐related N‐acetyl‐l ‐threoninate anions linked together through pairs of hydrogen bonds. The cations interconnect neighbouring ribbons of anions involving all the nitrogen‐H atoms in three‐dimensional networks of hydrogen bonds. The hydrogen‐bond patterns include asymmetric `three‐centred' systems. In both structures, the Thr side chain is in the favoured (g^?g⁺) conformation.     

catena‐Poly[[[triaquazinc(II)]‐μ‐2‐nitroterephthalato‐κO1:κ2O4,O4′] monohydrate]

The title complex, {[Zn(C₈H₃NO₆)(H₂O)₃]·H₂O}_n, has a one‐dimensional chain structure. The two carboxylate groups of the dianionic 2‐nitroterephthalate ligand adopt mono‐ and bidentate chelating modes. The Zn atom shows distorted octahedral coordination, bonded to three O atoms from two carboxylate groups and three O atoms of three non‐equivalent coordinated water molecules. The one‐dimensional chains are aggregated into two‐dimensional layers through inter‐chain hydrogen bonding. The whole three‐dimensional structure is further stabilized by inter‐layer hydrogen bonds.     

Hydrogen‐bonding patterns in three substituted N‐benzyl‐N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)acetamides

The molecules of N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)‐2‐chloro‐N‐(4‐methoxybenzyl)acetamide, C₂₃H₂₆ClN₃O₂, are linked into a chain of edge‐fused centrosymmetric rings by a combination of one C—H...O hydrogen bond and one C—H...π(arene) hydrogen bond. In N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)‐2‐chloro‐N‐(4‐chlorobenzyl)acetamide, C₂₂H₂₃Cl₂N₃O, a combination of one C—H...O hydrogen bond and two C—H...π(arene) hydrogen bonds, which utilize different aryl rings as the acceptors, link the molecules into sheets. The molecules of S‐[N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)‐N‐(4‐methylbenzyl)carbamoyl]methyl O‐ethyl carbonodithioate, C₂₆H₃₁N₃O₂S₂, are also linked into sheets, now by a combination of two C—H...O hydrogen bonds, both of which utilize the amide O atom as the acceptor, and two C—H...π(arene) hydrogen bonds, which utilize different aryl groups as the acceptors.     

catena‐Poly[[[pentaaquathulium(III)]‐μ‐5‐sulfonatobenzene‐1,3‐dicarboxylato] 4,4′‐bipyridyl 1.5‐solvate hemihydrate]

The crystal structure of the title compound, {[Tm(C₈H₃O₇S)(H₂O)₅]·1.5C₁₀H₈N₂·0.5H₂O}_n, is built up from two [Tm(SIP)(H₂O)₅] molecules (SIP³⁻ is 5‐sulfonatobenzene‐1,3‐dicarboxylate), three 4,4′‐bipyridyl (bpy) molecules and one solvent water molecule. One of the bpy molecules and the solvent water molecule are located on an inversion centre and a twofold rotation axis, respectively. The Tm^III ion coordination is composed of four carboxylate O atoms from two trianionic SIP³⁻ ligands and five coordinated water molecules. The Tm³⁺ ions are linked by the SIP³⁻ ligands to form a one‐dimensional zigzag chain propagating along the c axis. The chains are linked by interchain O—H...O hydrogen bonds to generate a two‐dimensional layered structure. The bpy molecules are not involved in coordination but are linked by O—H...N hydrogen bonds to form two‐dimensional layers. The two‐dimensional layers are further bridged by the bpy molecules as pillars and the solvent water molecules through hydrogen bonds, giving a three‐dimensional supramolecular structure. π–π stacking interactions between the parallel aromatic rings, arranged in an offset fashion with a face‐to‐face distance of 3.566 (1) Å, are observed in the crystal packing.     

cis‐Dichloridobis(1,10‐phenanthroline‐5,6‐diol‐κ2N,N′)manganese(II): a supramolecular chain formed via O—H...Cl bonds and aromatic stacking

The title compound, [MnCl₂(C₁₂H₈N₂O₂)₂], displays a novel supramolecular chain formed by intermolecular O—H...Cl hydrogen bonds and aromatic stacking. The molecule has crystallographically imposed twofold symmetry with the Mn^II atom on the twofold axis. In the 1,10‐phenanthroline‐5,6‐diol ligand, each H atom of the two hydroxy groups is oriented towards the other hydroxy O atom. Both hydroxy groups form intermolecular O—H...Cl hydrogen bonds with a single Cl atom of an adjacent molecule. These hydrogen bonds connect the molecules via operation of the molecular twofold axis and the centre of inversion of the crystal lattice, forming a doubly‐bridged one‐dimensional structure with Mn atoms as the nodes. Strong aromatic π‐stacking between two antiparallel neighbouring 1,10‐phenanthroline‐5,6‐diol ligands also helps to stabilize the chain.     

2‐[(E)‐(4‐Hydroxy‐3‐methoxybenzylidene)amino]‐N‐(2‐methylphenyl)‐4,5,6,7‐tetrahydro‐1‐benzothiophene‐3‐carboxamide

The title compound, C₂₄H₂₄N₂O₃S, exhibits antifungal and antibacterial properties. The compound crystallizes with two molecules in the asymmetric unit, with one molecule exhibiting `orientational disorder' in the crystal structure with respect to the cyclohexene ring. The o‐toluidine groups in both molecules are noncoplanar with the respective cyclohexene‐fused thiophene ring. In both molecules, there is an intramolecular N—H...N hydrogen bond forming a pseudo‐six‐membered ring which locks the molecular conformation and eliminates conformational flexibility. The crystal structure is stabilized by O—H...O hydrogen bonds; both molecules in the asymmetric unit form independent chains, each such chain consisting of alternating `ordered' and `disordered' molecules in the crystal lattice.     

Pearls on a string: a Z′ = 7 structure for glycyl‐l‐valine

The title peptide, C₇H₁₄N₂O₃, crystallizes with seven independent mol­ecules in the asymmetric unit. All have essentially the same overall conformation, but some flexibility is exhibited by the glycine residue. It appears that the high Z′ value, observed only three times before for an organic compound, permits formation of shorter hydrogen bonds in one of the two head‐to‐tail chains involving the N‐terminal amino groups and the C‐terminal carboxyl­ate groups than found in a hypothetical model structure of glycyl‐l ‐valine with Z′ = 1, and that it furthermore alleviates strain associated with an eclipsed orientation of the amino group.     

Poly[[diaqua(μ3‐3‐nitrophthalato)calcium(II)] monohydrate]

The title 3‐nitrophthalate–calcium coordination polymer, {[Ca(C₈H₃NO₆)(H₂O)₂]·H₂O}_n, crystallizes as a one‐dimensional framework. The Ca^II centre has a distorted pentagonal–bipyramidal geometry, being seven‐coordinated by five O atoms from three different 3‐nitrophthalate groups and by two water molecules, resulting in a one‐dimensional zigzag chain along the a‐axis direction by the interconnection of the four O atoms from the two carboxylate groups. There is a D3 water cluster composed of the coordinated and the solvent water molecules within such chains. Adjacent chains are aggregated into two‐dimensional layers via hydrogen bonds in the c‐axis direction. The whole three‐dimensional structure is further stabilized by weak O—H...O hydrogen bonds between the O atoms of the nitro group and the water molecules.     

l‐Phenyl­alanyl‐l‐tryptophan 0.75‐hydrate

The title compound, C₂₀H₂₁N₃O₃·0.75H₂O, crystallizes as exceedingly thin fibers. The crystal packing arrangement is related to those of other hydro­phobic dipeptides with phenyl­alanine residues, but the structure has pseudo‐tetra­gonal symmetry in an ortho­rhom­bic space group with four peptide mol­ecules and three water mol­ecules in the asymmetric unit.     

Poly[[triaquazinc(II)]‐μ3‐4‐nitrophthalato‐κ3O1:O2:O2′]

In the title complex, [Zn(C₈H₃NO₆)(H₂O)₃]_n, the two carboxylate groups of the 4‐nitrophthalate dianion ligands have monodentate and 1,3‐bridging modes, and Zn atoms are interconnected by three O atoms from the two carboxylate groups into a zigzag one‐dimensional chain along the b‐axis direction. The Zn atom shows distorted octahedral coordination as it is bonded to three O atoms from carboxylate groups of three 4‐nitrophthalate ligands and to three O atoms of three non‐equivalent coordinated water molecules. The one‐dimensional chains are aggregated into two‐dimensional layers through inter‐chain hydrogen bonding. The whole three‐dimensional structure is further maintained and stabilized by inter‐layer hydrogen bonds.     

Hydrogen‐bonding features in the 1:2 adduct of 4‐aminobenzoic acid and l‐proline

The title adduct, 4‐aminobenzoic acid–l ‐proline–water (1/2/1), C₇H₇NO₂·2C₅H₉NO₂·H₂O, contains two independent proline chains with a C(5) motif, each of the head‐to‐tail type and each held together by N—H...O hydrogen bonds, propagated parallel to the b and c axes of the unit cell. Thus, the proline residues aggregate parallel to the ac plane. 4‐Aminobenzoic acid (PABA) residues are arranged on both sides of the proline aggregate and are connected through water O atoms, which act as acceptors for PABA and as hydrogen‐bond donors to the amino acids. The characteristic features of PABA, viz. twisting of the carboxyl plane from the aromatic ring and the formation of a head‐to‐tail chain motif [C(8)] along the b axis, are observed. A distinct feature of the structure is that no proton transfer occurs between proline and PABA.     

Synthesis and characterization of a novel long‐alkyl‐chain ester‐substituted benzimidazole gelator and its octan‐1‐ol solvate

The synthesis of a novel benzimidazole derivative with a long‐chain‐ester substituent, namely methyl 8‐[4‐(1H‐benzimidazol‐2‐yl)phenoxy]octanoate, (3), is reported. Ester (3) shows evidence of aggregation in solution and weak gelation ability with toluene. The octan‐1‐ol solvate, methyl 8‐[4‐(1H‐benzimidazol‐2‐yl)phenoxy]octanoate octan‐1‐ol monosolvate, C₂₂H₂₆N₂O₃·C₈H₁₈O, (4), exhibits a four‐molecule hydrogen‐bonded motif in the solid state, with N—H…O hydrogen bonds between benzimidazole molecules and O—H…N hydrogen bonds between the octan‐1‐ol solvent molecules and the benzimidazole unit. The alkyl chains of the ester and the octan‐1‐ol molecules are in unfolded conformations. The phenylene ring is canted by 10.27 (6)° from the plane of the benzimidazole ring system. H…C contacts make up 20.7% of the Hirshfeld surface coverage. Weak C—H…π interactions involving the benzimidazole alkyl chain and three aromatic rings are observed.     

l‐Prolinium picrate and 2‐methyl­pyridinium picrate

In the structure of l ‐prolinium picrate, C₅H₁₀NO₂⁺·C₆H₂N₃O₇⁻, the C^γ atom of the pyrrolidine ring has conformational disorder. Both the major and minor conformers of the pyrrolidine ring adopt conformations inter­mediate between a half‐chair and an envelope. Both the cation and anion are packed through chelated three‐centred N—H⋯O hydrogen bonds. The prolinium cation connects two different picrate anions, leading to an infinite chain running along the b axis. In 2‐methyl­pyridinium picrate, C₆H₈N⁺·C₆H₂N₃O₇⁻, the cations and anions are packed separately along the a axis and are inter­connected by N—H⋯O hydrogen bonds. Intra­molecular contacts between phenolate O atoms and adjacent nitro groups are identified in both structures. A graph‐set motif of R₁²(6) is observed in both structures.     

2‐tert‐Butylamino‐4‐chloro‐6‐ethylamino‐1,3,5‐triazine: a structure with Z′ = 4 containing two different molecular conformations and two independent chains of hydrogen‐bonded R22(8) rings

The title compound (trivial name terbutylazine), C₉H₁₆ClN₅, (I), crystallizes with Z′ = 4 in the space group Pca2₁, 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 R₂²(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.     

Unusual hydrate stabilization in the two‐dimensional layered structure of quinacrinium bis(2‐carboxy‐4,5‐dichlorobenzoate) tetrahydrate,a proton‐transfer compound of the drug quinacrine

The crystal structure of the hydrated proton‐transfer compound of the drug quinacrine [rac‐N′‐(6‐chloro‐2‐methoxyacridin‐9‐yl)‐N,N‐diethylpentane‐1,4‐diamine] with 4,5‐dichlorophthalic acid, C₂₃H₃₂ClN₃O²⁺·2C₈H₃Cl₂O₄⁻·4H₂O, has been determined at 200 K. The four labile water molecules of solvation in the structure form discrete ...O—H...O—H... hydrogen‐bonded chains parallel to the quinacrine side chain, the two N—H groups of which act as hydrogen‐bond donors for two of the water acceptor molecules. The other water molecules, as well as the acridinium H atom, also form hydrogen bonds with the two anion species and extend the structure into two‐dimensional sheets. Between these sheets there are also weak cation–anion and anion–anion π–π aromatic ring interactions. This structure represents the third example of a simple quinacrine derivative for which structural data are available but differs from the other two in that it is unstable in the X‐ray beam due to efflorescence, probably associated with the destruction of the unusual four‐membered water chain structures.