Red,orange and yellow crystals of 4,5‐­bis(4‐methoxy­phenyl)‐2‐(3‐nitro­phenyl)‐1H‐imidazole

Red non‐solvate crystals of the title compound from ethanol, C₂₃H₁₉N₃O₄, orange solvate crystals from tert‐butanol, C₂₃H₁₉N₃O₄·C₄H₁₀O, yellow solvate crystals from dioxane–water, C₂₃H₁₉N₃O₄·0.5C₄H₈O₂, and intense yellow solvate crystals from benzene–N,N′‐dimethylformamide, C₂₃H₁₉N₃O₄·C₆H₆, differ from each other in their molecular conformation and hydrogen‐bonding scheme. The bathochromic shifts of the crystal color are explained by the molecular planarity and charge‐transfer effect among the imidazole mol­ecules.     

rac‐3‐Benzoyl‐2‐methylpropionic acid and its organic salts: possibilities of Yang photocyclization in crystals

The analysis of the crystal structures of rac‐3‐benzoyl‐2‐methylpropionic acid, C₁₁H₁₂O₃, (I), morpholinium rac‐3‐benzoyl‐2‐methylpropionate monohydrate, C₄H₁₀NO⁺·C₁₁H₁₁O₃⁻·H₂O, (II), pyridinium [hydrogen bis(rac‐3‐benzoyl‐2‐methylpropionate)], C₅H₆N⁺·(H⁺·2C₁₁H₁₁O₃⁻), (III), and pyrrolidinium rac‐3‐benzoyl‐2‐methylpropionate rac‐3‐benzoyl‐2‐methylpropionic acid, C₄H₁₀N⁺·C₁₁H₁₁O₃⁻·C₁₁H₁₂O₃, (IV), has enabled us to predict and understand the behaviour of these compounds in Yang photocyclization. Molecules containing the Ar—CO—C—C—CH fragment can undergo Yang photocyclization in solvents but they can be photoinert in the crystalline state. In the case of the compounds studied here, the long distances between the O atom of the carbonyl group and the γ‐H atom, and between the C atom of the carbonyl group and the γ‐C atom preclude Yang photocyclization in the crystals. Molecules of (I) are deprotonated in a different manner depending on the kind of organic base used. In the crystal structure of (III), strong centrosymmetric O...H...O hydrogen bonds are observed.     

The crystal and molecular structure of sodium 4‐(2,4,6‐triisopropylbenzoyl)benzoate in terms of the photochemical behaviour of the anion

Contrary to the known 4‐(2,4,6‐triisopropylbenzoyl)benzoate salts, di‐μ‐aqua‐bis[tetraaquasodium(I)] bis[4‐(2,4,6‐triisopropylbenzoyl)benzoate] dihydrate, [Na₂(H₂O)₁₀](C₂₃H₂₇O₃)₂·2H₂O, (1), does not undergo a photochemical Norrish–Yang reaction in the crystalline state. In order to explain this photochemical inactivity, the intermolecular interactions were analyzed by means of the Hirshfeld surface and intramolecular geometrical parameters describing the possibility of a Norrish–Yang reaction were calculated. The reasons for the behaviour of the title salt are similar crystalline environments for both the o‐isopropyl groups in the anion, resulting in similar geometrical parameters and orientations, and that these interaction distances differ significantly from those found in salts where the photochemical reaction occurs.     

Influence of 1,4‐dioxane solvent inclusion on the crystal structure of 5,5′‐diphenyl‐2,2′‐(p‐phenylene)di‐1,3‐oxazole (POPOP)

Crystallization of 5,5′‐diphenyl‐2,2′‐(p‐phenylene)di‐1,3‐oxazole (POPOP), C₂₄H₁₆N₂O₂, from chloroform or 1,4‐dioxane yielded crystals in pure and solvated forms, respectively. The solvated crystals of POPOP were found to contain 1,4‐dioxane in a strict 1:2 compound–solvent stoichiometry, C₂₄H₁₆N₂O₂·C₄H₈O₂, thus being a defined solvent‐inclusion compound. The crystal system is monoclinic in both cases and the asymmetric unit of the cell contains only half of the molecule (plus one dioxane molecule in the case of the solvated structure), owing to the centrosymmetry of the di‐1,3‐oxazole molecule.     

2‐Oxo‐2‐phenyl‐N‐[(R)‐1‐phenylethyl]acetamide and N,N‐dimethyl‐2‐(1‐naphthyl)‐2‐oxoacetamide: possibility of Yang photocyclization in a crystal

The crystal structures of 2‐oxo‐2‐phenyl‐N‐[(R)‐1‐phenylethyl]acetamide, C₁₆H₁₅NO₂, (I), and N,N‐dimethyl‐2‐(1‐naphthyl)‐2‐oxoacetamide, C₁₄H₁₃NO₂, (II), were determined in an attempt to understand the reason for the lack of Yang photocyclization in their respective crystals. In the case of (I), the long distance between the O atom of the carbonyl group and the γ‐H atom, and between the C atom of the carbonyl group and the γ‐C atom, preclude Yang photocyclization. For (II), the deviation of the γ‐H atom from the plane of the carbonyl group and interactions between the naphthalene rings are regarded as possible reasons for the chemical inertia. The two independent molecules of (I) differ in their conformation. N—H...O hydrogen bonds link molecules of (I) into chains extended along the b axis.     

(E,E)‐2,5‐Di­methoxy‐1,4‐bis­[2‐(3,4,5‐tri­methoxy­phenyl)­ethenyl]­benzene

In the title compound, C₃₀H₃₄O₈, molecular symmetry is coincident with crystallographic inversion symmetry. A three‐dimensional network is generated containing both C—H·π and C—H·n(O) interactions. A comparison of the geometry of this mol­ecule and the structure of a number of 2,4,6‐tri­methoxy‐substituted analogues is provided.     

Monitoring photo‐induced transformations in crystals of 2,6‐difluorocinnamic acid under ambient conditions

Several conditions need to be fulfilled for a photochemical reaction to proceed in crystals. Some of these conditions, for example, geometrical conditions, depend on the particular type of photochemical reaction, but the rest are common for all reactions. The mutual directionality of two neighbouring molecules determines the kind of product obtained. The influence of temperature on the probability of a photochemical reaction occurring varies for different types of photochemical reaction and different compounds. High pressure imposed on crystals also has a big influence on the free space and the reaction cavity. The wavelength of the applied UV light is another factor which can initiate a reaction and sometimes determine the structure of a product. It is possible, to a certain degree, to control the packing of molecules in stacks by using fluoro substituents on benzene rings. The crystal and molecular structure of 2,6‐difluorocinnamic acid [systematic name: 3‐(2,6‐difluorophenyl)prop‐2‐enoic acid], C₉H₆F₂O₂, (I), was determined and analysed in terms of a photochemical [2 + 2] dimerization. The molecules are arranged in stacks along the a axis and the values of the intermolecular geometrical parameters indicate that they may undergo this photochemical reaction. The reaction was carried out in situ and the changes of the unit‐cell parameters during crystal irradiation by a UV beam were monitored. The values of the unit‐cell parameters change in a different manner, viz. cell length a after an initial increase starts to decrease, b after a decrease starts to increase, c increases and the unit‐cell volume V after a certain increase starts to decrease. The structure of a partially reacted crystal, i.e. containing both the reactant and the product, namely 2,6‐difluorocinnamic acid–3,4‐bis(2,6‐difluorophenyl)cyclobutane‐1,2‐dicarboxylic acid (0.858/0.071), 0.858C₉H₆F₂O₂·0.071C₁₈H₁₂F₄O₄, obtained in situ, is also presented. The powder of compound (I) was irradiated with UV light and afterwards crystallized [as 3,4‐bis(2,6‐difluorophenyl)cyclobutane‐1,2‐dicarboxylic acid toluene hemisolvate, C₁₈H₁₂F₄O₄·0.5C₇H₈] in a space group different from that of the crystal containing the in‐situ dimer.     

2,3‐Dimethoxy‐10‐oxostrychnidinium 2‐(2,4,6‐trinitroanilino)benzoate monohydrate: a 1:1 proton‐transfer salt of brucine with o‐picraminobenzoic acid

In the structure of the title 1:1 proton‐transfer compound of brucine with 2‐(2,4,6‐trinitroanilino)benzoic acid, C₂₃H₂₇N₂O₄⁺·C₁₃H₇N₄O₈⁻·H₂O, the brucinium cations form classic undulating ribbon substructures through overlapping head‐to‐tail interactions, while the anions and the three related partial solvent water molecules (having occupancies of 0.73, 0.17 and 0.10) occupy the interstitial regions of the structure. The cations are linked to the anions directly through N—H...O_COO− hydrogen bonds and indirectly by the three water molecules, which form similar conjoint cyclic bridging units [graph set R²₄(8)] through O—H...O_C=O and O—H...O_COO− hydrogen bonds, giving a two‐dimensional layered structure. Within the anion, intramolecular N—H...O_COO− and N—H...O_nitro hydrogen bonds result in the benzoate and picrate rings being rotated slightly out of coplanarity [inter‐ring dihedral angle = 32.50 (14)°]. This work provides another example of the molecular selectivity of brucine in forming stable crystal structures, and also represents the first reported structure of any form of the guest compound 2‐(2,4,6‐trinitroanilino)benzoic acid.     

(E,E)‐2,5‐Diprop­oxy‐1,4‐bis­[2‐(2,4,6‐trimethoxy­phen­yl)ethen­yl]benzene

The title compound, C₃₀H₃₄O₈, crystallizes in the space group P with one‐half of a mol­ecule in the asymmetric unit. A three‐dimensional network is generated by OCH₃⋯π and CH⋯π inter­actions. The conformation of the C—C bond exocyclic to the central benzene ring is different from that of every other known derivative. A comparison of the geometry of the title mol­ecule and of its solid‐state structure with other 2,4,6‐trimeth­oxy‐substituted PPV [i.e. poly(p‐phenylenevinylene)] oligomers, in particular the isoprop­oxy‐substituted compound, is provided.     

Tris(2‐cyanoethyl) isocyanurate

The title compound, 1,3,5‐tris(2‐cyano­ethyl)‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione, C₁₂H₁₂N₆O₃, forms a layered structure stabilized by C—H?O and C—H?N hydrogen bonds.     

(Z)‐2‐[(1‐Phenylsulfonyl‐1H‐indol‐3‐yl)methylene]‐1‐azabicyclo[2.2.2]octan‐3‐one semicarbazone

In crystals of the title compound, C₂₃H₂₃N₅O₃S, the indole system is planar and the phenyl ring of the phenylsulfonyl group makes a dihedral angle with the best plane of the indole system of 77.18 (4)°. The olefinic bond connecting the azabicyclic and indole systems has Z geometry. The geometry adopted by the C=O bond with respect to the N—N bond is trans. The O atom of the carbonyl group of each molecule is hydrogen bonded to the hydrazidic H atom of an adjacent molecule to form an eight‐membered‐ring dimeric structure.     

1,2‐Bis[5‐(1,3‐dioxolan‐2‐yl)‐2‐ethyl‐3‐thien­yl]‐3,3,4,4,5,5‐hexa­fluoro­cyclo­pent‐1‐ene,a photochromic dithienylethene

The title compound, C₂₃H₂₂F₆O₄S₂, a photochromic dithienyl­ethene, is a promising material for optical storage and other optoelectrical devices. The mol­ecule adopts a photoactive antiparallel conformation in the crystalline state. The distance between the two reactive C atoms which are involved in potential ring closure is 3.829 (4) Å. The dihedral angles between the central cyclo­pentene ring and the adjacent thio­phene rings are 55.38 (7) and 54.81 (9)°. The colourless crystals turn magenta when exposed to UV radiation and the process is reversible.     

A synchrotron study of (2R,5′S)‐5′‐benzyl‐5‐bromo‐6‐methoxyspiro[indane‐2,2′‐piperazine]‐3′,6′‐dione dimethylformamide solvate

Synchrotron radiation was used to study the structure of the title compound, C₂₀H₁₉BrN₂O₃·C₃H₇NO, which was obtained as fine fragile needle‐shaped crystals by recrystallization from dimethylformamide (DMF), one molecule of which is incorporated per asymmetric unit into the crystal. The compound adopts a compact closed conformation with the orientation of the benzyl group such that the aryl ring is positioned over the piperazinedione ring, resulting in a C_spiro...C_trans—C—C_Ph pseudo‐torsion angle of −3.3 (3)°. The five‐membered ring is present in an expected envelope conformation and the six‐membered piperazinedione ring adopts a less puckered boat‐like conformation. Reciprocal amide‐to‐amide hydrogen bonding between adjacent piperazinedione rings and C—H...O interactions involving DMF molecules propagate in the crystal as a thick ribbon in the a‐axis direction.     

Alkyl levulinates as `green chemistry' precursors: butane‐1,4‐diyl bis(4‐oxopentanoate) and hexane‐1,6‐diyl bis(4‐oxopentanoate)

Levulinic acid derivatives are potential `green chemistry' renewably sourced molecules with utility in industrial coatings applications. Suitable single crystals of the centrosymmetric title compounds, C₁₄H₂₂O₆ and C₁₆H₂₆O₆, respectively, were obtained with difficulty. The data for the latter hexane‐1,6‐diyl compound were extracted from the major fragment of a three‐component twinned crystal. Both compounds crystallize in similar‐sized unit cells with identical symmetry, utilizing the same weak nonconventional attractive C—H...O(ketone) hydrogen bonds via C(4) and C(5) motifs, which expand to R²₂(30) ring and C²₂(14) chain motifs. Their different packing orientations in similar‐sized unit cells suggest that crystal growth involving packing mixes could lead to intergrowths or twins.     

Aqua­(thio­sulfato‐κ2O,S)[2,4,6‐tri‐2‐pyridyl‐1,3,5‐triazine‐κ3N2,N1,N6]zinc(II) hemihydrate

The title compound, [Zn(S₂O₃)(C₁₈H₁₂N₆)(H₂O)]·0.5H₂O, contains two almost identical independent monomeric moieties composed of an octa­hedral Zn centre coordinated by a tridentate 2,4,6‐tri‐­2‐pyridyl‐1,3,5‐triazine (tpt) ligand, one aqua ligand and an O,S‐chelating thio­sulfate anion. The structure is stabilized by a solvent water mol­ecule. Multiple strong hydrogen bonds with additional weaker π–π inter­actions between tpt groups define a multiple column spatial organization.     

Four N7‐benzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones as ethanol hemisolvates: similar molecular constitutions but different crystal structures

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, C₃₀H₃₄ClN₃O₂·0.5C₂H₆O, (I), its 7‐(4‐bromobenzyl)‐ analogue, C₃₀H₃₄BrN₃O₂·0.5C₂H₆O, (II), and its 7‐(4‐methylbenzyl)‐ analogue, C₃₁H₃₇N₃O₂·0.5C₂H₆O, (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, C₃₁H₃₄F₃N₃O₂·0.5C₂H₆O, (IV), the ethanol component is disordered across a centre of inversion in the space group P. 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...π interaction, with the half‐occupancy ethanol component linked to the dimer by a combination of C—H...O and O—H...π(arene) hydrogen bonds. The heterocyclic molecules in (IV) are linked into chains of centrosymmetric rings by C—H...O and C—H...π 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).     

Dimeric copper(II) 3,3‐dimethyl­butyrate adducts with ethanol, 2‐methylpyridine, 3‐methylpyridine, 4‐methylpyridine and 3,3‐dimethylbutyric acid

In the crystals of the five title compounds, tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(ethanol‐O)dicopper(II)–ethanol (1/2), [Cu₂(C₆H₁₁O₂)₄(C₂H₆O)₂]·2C₂H₆O, (I), tetrakis(μ‐3,3‐dimethylbutyrato‐O:O′)bis(2‐methylpyridine‐N)di­copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (II), tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(3‐methylpyridine‐N)di‐copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (III), tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(4‐methylpyridine‐N)di‐copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (IV), and tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(3,3‐dimethylbutyric acid‐O)dicopper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₁₂O₂)₂], (V), the di­nuclear Cu^II complexes all have centrosymmetric cage structures and (IV) has two independent molecules. The Cu?Cu separations are: (I) 2.602 (3) Å, (II) 2.666 (3) Å, (III) 2.640 (2) Å, (IV) 2.638 (4) Å and (V) 2.599 (1) Å.     

4‐(2‐Hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine and the 2‐(2,3‐dimethoxyphenyl)‐, 2‐(3,4‐dimethoxyphenyl)‐ and 2‐(2,5‐dimethoxyphenyl)‐substituted derivatives

The 1,5‐benzodiazepine ring system exhibits a puckered boat‐like conformation for all four title compounds [4‐(2‐hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₁H₁₈N₂O, (I), 2‐(2,3‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (II), 2‐(3,4‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (III), and 2‐(2,5‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (IV)]. The stereochemical correlation of the two C₆ aromatic groups with respect to the benzodiazepine ring system is pseudo‐equatorial–equatorial for compounds (I) (the phenyl group), (II) (the 2,3‐dimethoxyphenyl group) and (III) (the 3,4‐dimethoxyphenyl group), while for (IV) (the 2,5‐dimethoxyphenyl group) the system is pseudo‐axial–equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six‐membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O—H...O, N—H...O, N—H...π(arene) or C—H...π(arene).     

Brucine salts of l‐α‐hydr­oxy acids: brucinium hydrogen (S)‐malate penta­hydrate and anhydrous brucinium hydrogen (2R,3R)‐tartrate at 130 K

The structures of two brucinium (2,3‐dimeth­oxy‐10‐oxostrychnidinium) salts of the α‐hydr­oxy acids l ‐malic acid and l ‐tartaric acid, namely brucinium hydrogen (S)‐malate penta­hydrate, C₂₃H₂₇N₂O₄⁺·C₄H₅O₅⁻·5H₂O, (I), and anhydrous brucinium hydrogen (2R,3R)‐tartrate, C₂₃H₂₇N₂O₄⁺·C₄H₅O₆⁻,(II), have been determined at 130 K. Compound (I) has two brucinium cations, two hydrogen malate anions and ten water mol­ecules of solvation in the asymmetric unit, and forms an extensively hydrogen‐bonded three‐dimensional framework structure. In compound (II), the brucinium cations form the common undulating brucine sheet substructures, which accommodate parallel chains of head‐to‐tail hydrogen‐bonded tartrate anion species in the inter­stitial cavities.     

Éthyl 5‐méthylthio‐3‐(4‐nitrophényl)‐3a‐phényl‐3a,4‐dihydro‐3H‐[1,2,4]­triazolo[4,3‐a][1,5]benzodiazépine‐1‐carboxylate

Condensation of N‐p‐nitrophenyl‐C‐ethoxycarbonylnitril­im­ine with 2‐methylthio‐4‐phenyl‐3H‐1,5‐benzodiazepine leads to the title compound, C₂₆H₂₃N₅O₄S. It has been established that 1,3‐dipolar cycloaddition occurs on the C4 =N5 double bond of the 1,5‐benzodiazepine.