l‐Prolinium tartrate

In the title salt, C₅H₁₀NO₂⁺·C₄H₅O₆^?, proline exists as a cation and the tartaric acid as a semi‐tartrate anion. The semi‐tartrate ions form hydrogen‐bonded strings along the c axis. These strings are interconnected through the proline mol­ecules, forming a layered network parallel to the bc plane. The proline mol­ecules, however, do not directly interact among themselves, except for a weak C—H?O hydrogen bond.     

2‐Amino‐5‐methyl­pyridinium (2‐amino‐5‐methyl­pyridine)trichloro­zincate(II)

The title compound, (C₆H₉N₂)[ZnCl₃(C₆H₈N₂)], consists of one 2‐amino‐5‐methyl­pyridinium cation and one (2‐amino‐5‐methyl­pyridine)trichloro­zincate(II) anion, which are held together by N—H·Cl hydrogen bonds and π–π inter­actions. The cation and the pyridine ligand show similar geometric features, except for the N—C bond lengths. Mol­ecules of the title compound are connected by N—H·Cl hydrogen bonds to form chiral chains; these chains are associated further by C—H·Cl hydrogen bonds to form layers, which are in turn linked by π–π inter­actions.     

4‐Di­methyl­amino­pyridinium bromide

The crystal and molecular structure of 4‐di­methyl­amino­pyridinium bromide, C₇H₁₁N₂^+.Br^?, (I), is built up by hydrogen‐bonded dimers of crystallographic 222 symmetry and four short C—H...halogen contacts. It is remarkable that (I) and 4‐di­methyl­amino­pyridinium chloride are not isostructural.     

Bis(2‐chloro‐N‐methyl­pyridinium) iodide triiodide

The title compound, 2C₆H₇ClN⁺·I^?·I₃^?, crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.     

Two‐dimensional networks in 2‐methylanilinium picrate and 2,5‐dichloroanilinium picrate

Both the title molecular adducts of 2‐methylaniline or 2,5‐dichloroaniline with picric acid are 1:1 organic salts, namely 2‐methylanilinium picrate, C₇H₁₀N⁺·C₆H₂N₃O₇⁻, (I), and 2,5‐dichloroanilinium picrate, C₆H₆Cl₂N⁺·C₆H₂N₃O₇⁻, (II). In both structures, the phenoxide O atoms accept two N—H hydrogen bonds in a bifurcated acceptor fashion, which link the component ions by N—H...O hydrogen bonds into continuous two‐dimensional zigzag layers, running parallel to the (100) plane in (I) and the (010) plane in (II). A π–π interaction is observed between symmetry‐related anilinium cations in (I), while in (II), Cl...O_nitro and Cl...Cl interactions are observed. This study indicates that a substitution on aniline can exert a pivotal influence on the construction of its supramolecular structure.     

Bis(2‐amino‐6‐methyl­pyridinium) tetra­chloro­zincate(II)

The title compound, (C₆H₉N₂)₂[Zn^IICl₄], consists of two 2‐amino‐6‐methyl­pyridinium (AMP) cations and one [ZnCl₄]²⁻ anion, which are held together by N—H·Cl hydrogen bonds. Bond lengths within the AMP cation indicate that the imine tautomer makes a significant contribution to the structure. The mol­ecules are associated by two different π–π interactions between identical antiparallel AMP cations, with face‐to‐face distances of 3.627 (4) and 3.342 (3) Å, to form a one‐dimensional chain.     

4‐[2‐(4‐Cyano­phenyl)ethenyl]‐N‐methyl­pyridinium tetra­phenyl­borate

In the title compound, C₁₅H₁₃N₂⁺·C₂₄H₂₀B⁻, the pyridyl ring of the cation makes a dihedral angle of 1.6° with the benzene ring. Each is rotated in the same direction with respect to the central –C—CH=CH—C– linkage, by 3.8 and 5.3°, respectively. The anions have a slightly distorted tetra­hedral geometry. Mol­ecular packing analysis was carried out using the packing energy portioning scheme in the program OPEC. Around each anion in the crystal structure there are eight anions, which inter­act with the central anion through C—H⋯π inter­actions. The cations are hydrogen bonded in a head‐to‐tail fashion, forming chains along [10].     

N‐(l‐2‐Aminobutyryl)‐l‐alanine and 2‐(l‐alanylamino)‐l‐butyric acid 0.33‐hydrate

The crystal structure of N‐(l ‐2‐amino­butyryl)‐l ‐alanine, C₇H₁₄N₂O₃, is closely related to the structure of l ‐alanyl‐l ‐alanine, both being tetragonal, while the retro‐analogue 2‐(l ‐alanyl­amino)‐l ‐butyric acid 0.33‐hydrate, C₇H₁₄N₂O₃·­0.33H₂O, forms a new type of molecular columnar structure with three peptide mol­ecules in the asymmetric unit.     

trans‐4‐[(4‐Di­methyl­amino­phenyl)­imino­methyl]‐N‐methyl­pyridinium para‐toluene­sulfonate

In the title compound, C₁₅H₁₈N₃⁺·C₇H₇O₃S^?, the phenyl­ene and pyridyl rings are somewhat twisted with respect to each other, forming a dihedral angle of 23.49 (6)°. The compound contains a dipolar chromophoric cation, but crystallizes in the centrosymmetric space group P2₁/n and is thus not expected to display quadratic non‐linear optical effects.     

Hydrogen‐bonded supramolecular motifs in 2‐amino‐4,6‐dimethoxypyrimidinium picrate and pyrimethaminium picrate dimethyl sulfoxide solvate

In the crystal structures of 2‐amino‐4,6‐dimethoxypyrimidinium 2,4,6‐trinitrophenolate (picrate), C₆H₁₀N₃O₂⁺·C₆H₂N₃O₇⁻, (I), and 2,4‐diamino‐5‐(4‐chlorophenyl)‐6‐ethylpyrimidin‐1‐ium (pyrimethaminium or PMN) picrate dimethyl sulfoxide solvate, C₁₂H₁₄ClN₄⁺·C₆H₂N₃O₇⁻·C₂H₆OS, (II), the 2‐amino‐4,6‐dimethoxypyrimidine and PMN cations are protonated at one of the pyrimidine N atoms. The picrate anion interacts with the protonated cations through bifurcated N—H...O hydrogen bonds, forming R₂¹(6) and R₁²(6) ring motifs. In (I), Z′ = 2. In (II), two inversion‐related PMN cations are connected through a pair of N—H...N hydrogen bonds involving the 4‐amino group and the uncharged N atom of the pyrimidine ring, forming a cyclic hydrogen‐bonded R₂²(8) motif. In addition to the pairing, the O atom of the dimethyl sulfoxide solvent molecule bridges the 2‐amino and 4‐amino groups on both sides of the paired bases, resulting in a self‐complementary …DADA… array of quadruple hydrogen‐bonding patterns.     

2‐(2‐Oxoimidazolidinyl)ethyl 2‐methyl­prop‐2‐enoate

In the crystal structure of the title compound, C₉H₁₄N₂O₃, the molecules are linked by N—H?O=C bonds into chains parallel to [001]. Large crystals are readily obtained, presumably because of the hydrogen bonds and an energetically stable conformation of the mol­ecule.     

1,4‐Di­methyl­pyridinium hexakis­(di­methyl­form­amide‐κO)­calcium(II) dodecamolybdophosphate

In the title compound, (C₇H₁₀N)[Ca(C₃H₇NO)₆][PMo₁₂O₄₀], two types of cations {viz. 1,4‐di­methyl­pyridinium and a [Ca(DMF)₆]²⁺ complex cation (DMF is di­methyl­form­amide)} and dodecamolybdophosphate (tetra­conta­oxo­phos­phido­dodeca­molybdate) anions form an infinite three‐dimensional assembly via electrostatic forces.     

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.     

Supramolecular structures of 2‐chloro‐5‐methyl­phenol and 4‐chloro‐3‐methyl­phenol (chlorocresol)

The crystal structures of the title compounds (both C₇H₇ClO) are characterized by two independent mol­ecules in each of the asymmetric units and feature O—H...O, C—H...π and π–π interactions. In addition, intermolecular C—H...Cl and intramolecular O—H...Cl interactions are present in 2‐chloro‐5‐methyl­phenol. For each crystal, the non‐covalent interactions emphasize the different spatial environments for the two independent mol­ecules.     

2‐(Nitro­methyl­ene)‐1,3‐dithietane

In the crystal structure of the title compound, C₃H₃NO₂S₂, the four‐membered C₂S₂ ring is planar, as is the whole mol­ecule. The short intramolecular S?O distance of 2.687 (2) Å shows the five‐atom system to be conjugated. The mol­ecules pack as a two‐dimensional network in the (010) plane through short intermolecular S?O [2.900 (2) and 3.077 (2) Å] interactions.     

2‐(4‐Acetyl‐3,5‐di­hydroxy‐2‐methyl­phenoxy)‐4,6‐di­methoxy‐3‐methyl­benzoic acid

In the title compound, C₁₉H₂₀O₈, the benzene rings are nearly perpendicular to each other [dihedral angle 80.2 (2)°]. The carboxy group is twisted out while both the methoxy and acetyl groups are almost coplanar with their attached benzene rings. The hydroxy group is involved in an intramolecular O—H?O hydrogen bond with the acetyl O atom and the compound is connected through an intermolecular O—H?O contact to form a dimer. The crystal structure is stabilized by intermolecular O—H?O hydrogen bonds.     

1‐[(4‐Chloro­benzoyl)­methyl]‐4‐(N,N‐di­methyl­amino)­pyridinium bromide sesquihydrate and 1‐[(4‐bromo­benzoyl)­methyl]‐4‐(N,N‐di­methyl­amino)­pyridinium bromide sesquihydrate

The title compounds, C₁₅H₁₆ClN₂O⁺·Br⁻·1.5H₂O and C₁₅H₁₆BrN₂O⁺·Br⁻·1.5H₂O, are isomorphous. The benzene ring is oriented nearly normal to the pyridine ring in both compounds. The molecular packing is mainly influenced by intermolecular O—H⋯O and O—H⋯Br interactions, as well as weak intramolecular C—H⋯O interactions. The H₂OBr⁻ units form an extended water–bromide chain, with a bridging water mol­ecule on a twofold axis.     

l‐Isoleucyl‐l‐serine 0.33‐hydrate,l‐phenyl­alanyl‐l‐serine and l‐methionyl‐l‐serine 0.34‐hydrate

The structures of the title dipeptides, C₉H₁₈N₂O₄·0.33H₂O, C₁₂H₁₆N₂O₄ and C₈H₁₆N₂O₄S·0.34H₂O, complete a series of investigations focused on l ‐Xaa‐l ‐serine peptides, where Xaa is a hydro­phobic residue. All three structures are divided into hydro­philic and hydro­phobic layers. The hydro­philic layers are thin for l ‐phenyl­alanyl‐l ‐serine, rendered possible by an unusual peptide conformation, and thick for l ‐isoleucyl‐l ‐serine and l ‐methionyl‐l ‐serine, which include cocrystallized water mol­ecules on the twofold axes.     

2‐Hydro­xy‐1‐naphth­aldehyde 2‐methyl­thio­semicarbazone

The potentially tridentate O,N,S‐donor ligand, 2‐hydroxy‐1‐naphth­aldehyde 2‐methyl­thio­semicarbazone, C₁₃H₁₃N₃OS, has been structurally characterized and the mol­ecule is found to exhibit a distorted planar structure with the thio­semicarbazide moiety being twisted slightly out of the plane defined by the naphthyl ring.     

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].