Previous studies observed one-, two-, and three-dimensional H-bonded supramolecular assemblies in crystal structures of primary amides. However, no systematic study of alpha/beta/gamma-alkyl- and alpha/beta/gamma-aryl-substituted primary amides has been undertaken thus far. In this paper, we report molecular and supramolecular structures of six pharmaceutically relevant primary amides. These include four alpha-substituted amides (2-methylpropionamide, 2-propylvaleramide, 2-phenylacetamide, and 2-methyl-2-phenylpropionamide), one beta-substituted amide (3-methylbutyramide), and one gamma-substituted amide (4-phenylbutyramide). Crystal structures of these compounds are stabilized by the N-H & ctdot;O hydrogen bonds. One-dimensional H-bonded ribbons are observed in 2-propylvaleramide, and two-dimensional H-bonded layers are observed in the other five compounds. By comparing our results to the structures of primary amides (substituted acetamides) previously published by our group and other groups, we were able to formulate the following new structural insights: (i) in crystals of substituted primary amides, ribbons and layers are equally common; (ii) 4-phenylbutyramide molecules form an unusual type of layer based on the R24(8) R44(16) synthon; (iii) the preference for either layer or ribbon is determined by the bulkiness of substituents as well as their positions.

With the growing concern over increased carbon dioxide concentrations in our planet’s atmosphere, much research is being devoted to improving the methods of carbon capture and storage. Amine-based carbon capture techniques are advantageous due to amine’s ability to react directly and reversibly with carbon dioxide to form solid products. To better understand the composition of the solid products obtained by reactions of carbon dioxide with amines under different conditions, such as reactions with gaseous and solid CO2 (dry ice), spontaneous areal absorbance of CO2, and others, several such reactions were conducted. Single-crystal X-ray diffraction analysis of the seven previously and newly observed carbamate derivatives was carried out. The synthetic and structural results of solid products have been compared with published data on the same materials obtained by different methods. Peculiarities of hydrogen bonding were described for these materials based on the topological approach.

Liquid crystal elastomers represent a versatile class of polymer materials with potential applications in soft robotics, adhesives, and smart materials. The integration of photoresponsive molecules into LCEs enables spatiotemporal control, wavelength-selective actuation and remote operations, expanding their application space. However, the incorporation of sensitive photoresponsive molecules is often hindered by the chemical methods and processing conditions required for the LCE fabrication. In this work, we introduce a general strategy for covalent incorporation of photoresponsive moieties into LCEs through Diels-Alder chemistry utilizing late-stage functionalization. This approach facilitates the retention of material alignment and thermomechanical properties, while enabling the functionalization of thick, aligned polysiloxane elastomers. A wide range of photoresponsive molecules, including azobenzenes, spiropyrans, cyanine dyes, and donor-acceptor Stenhouse adducts, were successfully integrated, demonstrating this method's versatility. Furthermore, we leverage the reversible nature of Diels-Alder conjugation to achieve on-demand editing and exchange of photoresponsive moieties within a single LCE, allowing for dynamic tuning of material properties. This platform offers a scalable and efficient route for developing multifunctional LCEs, providing new opportunities for advanced stimuli-responsive materials and broadening the scope of applications across various fields.

To increase the number of potential materials for application as MRI contrast agents, several Cu(II) complexes were synthesized. Cu(II) complexes were chosen because they are less expensive in comparison with the presently used Gd(III), Mn(II) and other agents. Pyridine-2-carboximidamide (1), pyrimidine-2-carboximidamide (2) and pyrazole-2-carboximidamide (3) in the form of different salts along with CuCl2 and NaCl or CuBr2 and NaBr were used to obtain four Cu(II) complexes: dichloro-pyrimidine-2-carboximidamide copper(II) (4), dibromo-pyrimidine-2-carboximidamide copper(II) (5), dichloro-pirazole-2-carboximidamide copper(II) (6), and dibromo-pirazole-2-carboximidamide copper(II) (7). X-ray diffraction analysis revealed that molecular complexes 4–7 contain square planar coordinated Cu(II) atoms and their structures are very similar, as well as their packing in crystals, which allows us to consider them isomorphs. The same synthetic approach to complex preparation where NaCl or NaBr was not used brought us to the formation of dimeric complexes μ-chloro{chloro(pyridine-2-carboximidamide)copper(II)} (8) and μ-chloro{chloro(pyrimidine-2-carboximidamide)copper(II)} (9). In the dimeric complexes, two fragments which were the same as in monomeric complexes 4–7 are held together by bridging Cu-Cl bonds making the coordination of Cu equal to 5 (square pyramid). In dimeric complexes, axial Cu-Cl bonds are 2.7360 and 2.854 Å. These values are Cu-Cl bonds on the edge of existence according to statistical data from CSD. Synthesized complexes were characterized by IR spectroscopy, TGA, PXRD, EPR, and quantum chemical calculations. The higher thermal stability of monomer pyrimidine-based complexes with Cl and Br substituents makes them more prospective for further studies.

The crystal structures of two intermediates, 4-amino-3,5-difluorobenzonitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-difluorobenzoate, C9H9F2NO2 (II), along with a visible-light-responsive azobenzene derivative, diethyl 4,4′-(diazene-1,2-diyl)bis(3,5-difluorobenzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The molecules of I and II demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 (ortho) positions. In the crystals of I and II, the molecules are connected by N—H...N, N—H...F and N—H...O hydrogen bonds, C—H...F short contacts, and π-stacking interactions. In crystal of III, only stacking interactions between the molecules are found.

The title compound, systematic name tris(μ2-perfluoro-o-phenylene)(μ2-3-phenyl-4H-chromen-4-one)-triangulo-trimercury, [Hg3(C6F4)3(C15H10O2)], crystallizes in the monoclinic P21/n space group with one flavone (FLA) and one cyclic trimeric perfluoro-o-phenylenemercury (TPPM) molecule per asymmetric unit. The FLA molecule is located on one face of the TPPM acceptor and is linked in an asymmetric coordination of its carbonyl oxygen atom with two Hg centers of the TPPM macrocycle. The angular-shaped complexes pack in zigzag chains where they stack via two alternating TPPM–TPPM and FLA–FLA stacking patterns. The distance between the mean planes of the neighboring TPPM macrocycles in the stack is 3.445 (2) Å, and that between the benzo-γ-pyrone moieties of FLA is 3.328 (2) Å. The neighboring stacks are interdigitated through the shortened F...F, CH...F and CH...π contacts, forming a dense crystal structure.

Two inter­mediates, 4-amino-3,5-di­fluoro­benzo­nitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-di­fluoro­benzoate, C9H9F2NO2 (II), along with a visible-light-responsive azo­benzene derivative, diethyl 4,4′-(diazene-1,2-di­yl)bis­(3,5-di­fluoro­benzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. In the crystals of I and II, the mol­ecules are connected by N—H⋯N, N—H⋯F and N—H⋯O hydrogen bonds, C—H⋯F short contacts, and π-stacking inter­actions. In the crystal of III, only stacking inter­actions between the mol­ecules are found.

A CuII coordination polymer, catena-poly[[[aquacopper(II)]-bis(μ-4-aminobenzoato)-κ2N:O;κ2O:N] monohydrate], {[Cu(pABA)2(H2O)]·H2O}n (pABA = p-aminobenzoate, C7H4NO2−), was synthesized and characterized. It exhibits a one-dimensional chain structure extended into a three-dimensional supramolecular assembly through hydrogen bonds and π–π interactions. While the twinned crystal shows a metrically orthorhombic lattice and an apparent space group Pbcm, the true symmetry is monoclinic (space group P2/c), with disordered Cu atoms and mixed roles of water molecules (aqua ligand/crystallization water). The luminescence spectrum of the complex shows an emission at 345 nm, cf. 349 nm for pABAH.

The crystal structures of two inter-mediates, 4-amino-3,5-di-fluoro-benzo-nitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-di-fluoro-benzoate, C9H9F2NO2 (II), along with a visible-light-responsive azo-benzene derivative, diethyl 4,4'-(diazene-1,2-di-yl)bis-(3,5-di-fluoro-benzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The mol-ecules of I and II demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 (ortho) positions. In the crystals of I and II, the mol-ecules are connected by N-H⋯N, N-H⋯F and N-H⋯O hydrogen bonds, C-H⋯F short contacts, and π-stacking inter-actions. In crystal of III, only stacking inter-actions between the mol-ecules are found.

Three amidine-based ligands were used in the crystal design of a series of mononuclear Zn(II) complexes. Interaction of zinc chloride, ZnCl2, with N-2-pyridylimidoyl-2-pyridylamidine (Py2ImAm) resulted in complexes [Zn(Py2ImAm)2] (1) and [ZnCl2(Py2ImAm)] (2). In [Zn(Py2ImAm)2] (1, monoclinic, P21/c), the metal ion was coordinated with the bidentate pocket of the anionic form of Py2ImAm, while in [ZnCl2(Py2ImAm)] (2, monoclinic, P21/n), the tridentate coordination to a neutral Py2ImAm was completed by two chloride anions. This structural variation was achieved by a pH-controlling strategy using the weak base triethylamine (TEA). Otherwise, three ionic complexes were obtained with 2-amidinopyridine (PyAm) and Zinc(II), [ZnCl(PyAm)2]Cl (3, triclinic, P-1), [ZnCl(PyAm)2]2[ZnCl4]·C2H5OH (4, monoclinic, P21/n), and [ZnCl(PyAm)2]2Cl·CH3OH (5, triclinic, P-1). They comprised the same [ZnCl(PyAm)2]+ monocation with a butterfly-like shape provided by the bidentate chelate coordination of two PyAm neutral entities and a chloride ligand. In a similar butterfly shape, ionic complex [ZnCl(PmAm)2]2[ZnCl4] (6, monoclinic, C2/c) comprised the mononuclear [ZnCl(PmAm)2]+ cations with two bidentate chelate-coordinated 2-amidinopyrimidine (PmAm) as neutral ligands. The Zn(II) pentacoordinated arrangement in 3–6 was variable, from square pyramidal to trigonal bipyramidal. The reported compounds’ synthetic protocols, crystal structures and photoluminescence properties are discussed.

Structures of three cocrystals of nootropic racetams were studied. They included two cocrystals of phenylpiracetam (PPA) with 4-hydroxybenzoic acid (HBA) with different stoichiometries, PPA·HBA and PPA·2HBA, and cocrystal of 2-(4-phenyl-2-oxopyrrolidin-1-yl)-N’-isopropylideneacetohydrazide (PPAH) with 4-hydroxybenzamide (HBD), PPAH·HBD·(acetone solvate). X-ray study of the pure forms of PPA and PPAH was also carried out to identify variations of molecular synthons under the influence of conformers. The cocrystal structures revealed the diversity of supramolecular synthons namely, amide-amide, amide-acid, acid-acid, and hydroxyl-hydroxyl; however, very similar molecular chains were found in PPA and PPA·2HBA, and similar molecular dimers in PPAH and PPAH·HBD. In addition, conformational molecular diversity was observed as disorder in PPA·2HBA as it was observed earlier for rac-PPA that allows for the consideration that cocrystal as an example of partial solid solution. Quantum chemical calculations of PPA and PPAH conformers demonstrated that for most conformers, energy differences do not exceed 2 kcal/mol that suggests the influence of packing conditions (in this case R- and S-enantiomers intend to occupy the same molecular position in crystal) on molecular conformation.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Co-crystals formed by polynuclear aromatic hydrocarbons (PAH) chrysene, benz(a)anthracene, triphenylene(9,10-benzophenanthrene), benzo(a)pyrene, dibenz[a,c]anthracene, and 9H-carbazole as pi-electron-donor (D) molecules, with pi-electron acceptor, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were synthesized, and their crystal structures were determined using single-crystal X-ray diffraction analysis. All co-crystals exhibit 1:1 donor / acceptor ratio and adopt mixed-stacking motifs. The donor(D)-acceptor (DDQ) pi-pi interactions in stacks are complemented by different sets of D center dot center dot center dot D, D center dot center dot center dot DDQ and DDQ center dot center dot center dot DDQ intermolecular interactions between stacks whose diversity originates from different degree of D/DDQ mismatch and manifests in dissimilar crystal packing motifs. The parallel face-to-face stacking was registered in chrysene-DDQ, while benz(a)anthracene-DDQ reveals brickwork crystal packing with significant parallel slippage. The rest four co-crystals show fairly different herringbone-type crystal packing with rearrangement of intermolecular interactions. The distribution of intermolecular contacts and impact of pi-pi interactions were evaluated through Hirshfeld surface analysis. Molecular orbital energies as well as bandgaps were calculated using DFT. Degree of charge-transfer was estimated based on bond length distribution in the acceptor molecule for each of the co-crystals. (c) 2023 Elsevier B.V. All rights reserved.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

For a series of substituted dithieno[3,2- a :2′,3′- c ]phenazine derivatives X-ray diffraction studies have been carried out.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

1,3-Dimethyl-2,3-dihydrobenzo[d]imidazoles, 1H, and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazoles, 12, are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[d]imidazolium (1g–i+, respectively) have been synthesized and reduced with NaBH4 to 1gH, 1hH, and 1iH, and with Na:Hg to 1g2 and 1h2. Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- (1b+) and 2-cyclohexylbenzo[d]imidazolium (1e+) salts. E(1+/1•) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducing E(1+/1•) values, as well as cathodic shifts in E(12•+/12) and E(1H•+/1H) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the 1H species with PC61BM. Because 2-aryl groups stabilize radicals, 1b2 and 1g2 exhibit weaker bonds than 1e2 and 1h2 and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene (VII) via a “cleavage-first” pathway, while 1e2 and 1h2 react only via “electron-transfer-first”. 1h2 exhibits the most cathodic E(12•+/12) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers with VII via “electron-transfer-first”. Crystal structures show rather long central C–C bonds for 1b2 (1.5899(11) and 1.6194(8) Å) and 1h2 (1.6299(13) Å).