A network of weak hydrogen bonds in the crystal structure of Tetrazepam.

The crystal structure of tetrazepam, a benzodiazepine derivative formerly used for its muscle relaxant properties, has been solved and found to be monoclinic, space group P21/c, with lattice parameters a=12.7386(7)Å, b=11.3774(7)Å, c=10.3084(7)Å, ß=103.175(5) and Vunit-cell=1454.69(16) Å3 at room temperature (293K) with Z=4 molecules in the unit-cell. A network of weak hydrogen bonds involving aliphatic hydrogen atoms plays an important role in the formation of this structure.

The phenyl vinyl ether-methanol complex: a model system for quantum chemistry benchmarking.

The structure of the isolated aggregate of phenyl vinyl ether and methanol is studied by combining a multi-spectroscopic approach and quantum-chemical calculations in order to investigate the delicate interplay of noncovalent interactions. The complementary results of vibrational and rotational spectroscopy applied in molecular beam experiments reveal the preference of a hydrogen bond of the methanol towards the ether oxygen (OH∙∙∙O) over the π-docking motifs via the phenyl and vinyl moieties, with an additional less populated OH∙∙∙P(phenyl)-bound isomer detected only by microwave spectroscopy. The correct prediction of the energetic order of the isomers using quantum-chemical calculations turns out to be challenging and succeeds with a sophisticated local coupled cluster method. The latter also yields a quantification as well as a visualization of London dispersion, which prove to be valuable tools for understanding the role of dispersion on the docking preferences. Beyond the structural analysis of the electronic ground state (S0), the electronically excited (S1) state is analyzed, in which a destabilization of the OH∙∙∙O structure compared to the S0 state is observed experimentally and theoretically.

Crystal structure of 1-(2-chloro-acet-yl)-2,6-bis-(4-fluoro-phen-yl)-3,3-di-methyl-piperidin-4-one.

In the title mol-ecule, C21H20ClF2NO2, the piperidine ring adopts a slightly distorted boat conformation. The two benzene rings form a dihedral angle of 87.43 (1)°. A weak intra-molecular C-H⋯π inter-action is observed. In the crystal, weak C-H⋯O hydrogen bonds and weak C-H⋯π inter-actions connect the mol-ecules, forming a three-dimensional network.

Crystal structure of 4-(benzo[d]thia-zol-2-yl)-1,2-dimethyl-1H-pyrazol-3(2H)-one.

In the title compound, C12H11N3OS, the inter-planar angle between the pyrazole and benzo-thia-zole rings is 3.31 (7)°. In the three-dimensional mol-ecular packing, the carbonyl oxygen acts as acceptor to four C-H donors (with one H⋯O as short as 2.25 Å), while one methyl hydrogen is part of the three-centre system H⋯(S, O). A double layer structure parallel to (01) can be recognized as a subsection of the packing.

Aqueous Electrolyte With Weak Hydrogen Bonds for Four-Electron Zinc-Iodine Battery Operates in a Wide Temperature Range.

In the pursuit of high-performance energy storage systems, four-electron zinc-iodine aqueous batteries (4eZIBs) with successive I-/I2/I+ redox couples are appealing for their potential to deliver high energy density and resource abundance. However, susceptibility of positive valence I+ to hydrolysis and instability of Zn plating/stripping in conventional aqueous electrolyte pose significant challenges. In response, polyethylene glycol (PEG 200) is introduced as co-solvent in 2 m ZnCl2 aqueous solution to design a wide temperature electrolyte. Through a comprehensive investigation combining spectroscopic characterizations and theoretical simulations, it is elucidated that PEG disrupts the intrinsic strong H-bonds of water by global weak PEG-H2O interaction, which strengthens the O─H covalent bond of water and intensifies the coordination with Zn2+. This synergistic effect substantially reduces water activity to restrain the I+ hydrolysis, facilitating I-/I2/I+ redox kinetics, mitigating I3 - formation and smoothening Zn deposition. The 4eZIBs in the optimized hybrid electrolyte not only deliver superior cyclability with a low fading rate of 0.0009% per cycle over 20 000 cycles and a close-to-unit coulombic efficiency but also exhibit stable performance in a wide temperature range from 40 °C to -40 °C. This study offers valuable insights into the rational design of electrolytes for 4eZIBs.

Synthesis and crystal structures of two racemic 2-heteroaryl-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-ones.

3-Phenyl-2-(thio-phen-3-yl)-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one (C17H12N2OS2, 1) and 2-(1H-indol-3-yl)-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one 0.438-hydrate (C21H15N3OS·0.438H2O, 2) crystallize in space groups P21/n and C2/c, respectively. The asymmetric unit in each case is comprised of two parent mol-ecules, albeit of mixed chirality in the case of 1 and of similar chirality in 2 with the enanti-omers occupying the neighboring asymmetric units. Structure 2 also has water mol-ecules (partial occupancies) that form continuous channels along the b -axis direction. The thia-zine rings in both structures exhibit an envelope conformation. Inter-molecular inter-actions in 1 are defined only by C-H⋯O and C-H⋯N hydrogen bonds between crystallographically independent mol-ecules. In 2, hydrogen bonds of the type N-H⋯O between independent mol-ecules and C-H⋯N(π) type, and π-π stacking inter-actions between the pyridine rings of symmetry-related mol-ecules are observed.

Dibromomethyl- and bromomethyl- or bromo-substituted benzenes and naphthalenes: C-Br...Br interactions.

The structures of six benzene and three naphthalene derivatives involving bromo, bromomethyl and dibromomethyl substituents, namely, 1,3-dibromo-5-(dibromomethyl)benzene, C7H4Br4, 1,4-dibromo-2,5-bis(bromomethyl)benzene, C8H4Br6, 1,4-dibromo-2-(dibromomethyl)benzene, C7H4Br4, 1,2-bis(dibromomethyl)benzene, C8H6Br4, 1-(bromomethyl)-2-(dibromomethyl)benzene, C8H7Br3, 2-(bromomethyl)-3-(dibromomethyl)naphthalene, C12H9Br3, 2,3-bis(dibromomethyl)naphthalene, C12H8Br4, 1-(bromomethyl)-2-(dibromomethyl)naphthalene, C12H9Br3, and 1,3-bis(dibromomethyl)benzene, C8H6Br4, are presented. The packing patterns of these compounds are dominated by Br...Br contacts and C-H...Br hydrogen bonds. The Br...Br contacts, shorter than twice the van der Waals radius of bromine (3.7 Å), seem to play a crucial role in the crystal packing of all these compounds. The occurrence of Type I and Type II interactions is also discussed briefly, considering the effective atomic radius of bromine, as is their impact on the packing of molecules in the individual structures.

Water-Locked Eutectic Electrolyte Enables Long-Cycling Aqueous Sodium-Ion Batteries.

Aqueous sodium batteries are one of the awaited technologies for large-scale energy storage, but remain poorly rechargeable because of the reactivity issues of water. Here, we present a hydrated eutectic electrolyte featuring a water-locked effect, which is exceptional in that the O-H bond of water is essentially strengthened via weak hydrogen bonding (relative to the original H2O-H2O hydrogen bonds) to low-donor-number anions and ligands. Even without interphase protection, both the anodic and cathodic water electrodecomposition reactions are delayed, extending the aqueous potential window to 3.4 V. Combined with the alleviated electrode dissolution, Na2MnFe(CN)6||NaTi2(PO4)3 batteries deliver a high energy density of ∼80 W h kg-1 at 0.5 C and undergo over 1000 cycles with a 74.5% capacity retention and a 99.4% Coulombic efficiency at 4.2 C. This work may offer a general guide to ultimately exploit the water's innate stability for realizing the promise of aqueous battery technologies.

3,4-Bis-O-propargyl-1,2:5,6-di-O-isopropylidene-D-mannitol: a study of multiple weak hydrogen bonds in the solid state.

The title homochiral compound, C18H26O6, 1, was examined by single-crystal X-ray crystallography in order to understand its potential as a synthetic building block, particularly in inter- and intramolecular cyclocondensation reactions. It has also proven to be an excellent model for understanding multiple weak donor-acceptor D-H...A interactions involving terminal acetylenes as donors and as acceptors. The asymmetric unit of 1 comprises three almost identical independent molecules, each with the mannitol 2R,3R,4R,5R configuration and different conformations. Like independent molecules align in strands through acetylenic donor C-H...O contacts with equivalent dioxolanyl acceptor groups. Two of the strands are aligned unidirectionally, in parallel, while the third strand aligns perpendicular to the first two, to give interwoven layers in the supramolecular structure. A detailed study of the interdigitation of the second propargyl group from each independent molecule between strands, and of other short interstrand C-H...O contacts, provides new insight into the application of weak hydrogen-bond theory within the context of a conformationally flexible symmetrical molecule. Analyses of the Cambridge Structural Database using Crystal Packing Features and ConQuest search motifs support the importance of the D...A distance parameter, demonstrate the different influences of donor and acceptor types, and reveal the interplay between H...A and D...A contributions in different contact types.

12-Ethyl-6a,10a-di-hydro-5H-6-oxachrysene.

In the title compound, C19H16O, the pyran ring is in a half-chair conformation. The essentially planar naphthalene ring system (r.m.s. deviation = 0.020 Å) forms a dihedral angle of 14.37 (5)° with the fused benzene ring. In the crystal, pairs of mol-ecules are connected into inversion dimers by weak C-H⋯O hydrogen bonds to generate R 2 2(6) loops.

1,2,3,5-Tetra-hydro-naphtho-[2,1-c]oxepine.

In the title compound, C14H14O, the seven-membered ring is in a pseudo-chair conformation. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds forming layers parallel to (010). In addition, there are weak π-π stacking inter-actions between inversion-related naphthalene ring systems, with a ring centroid-ring centroid distance of 3.518 (5) Å.

Molecular Orientations of Delayed Fluorescent Emitters in a Series of Carbazole-Based Host Materials.

Molecular orientation is one of the most crucial factors to boost the efficiency of organic light-emitting devices. However, active control of molecular orientation of the emitter molecule by the host molecule is rarely realized so far, and the underlying mechanism is under discussion. Here, we systematically investigated the molecular orientations of thermally activated delayed fluorescence (TADF) emitters in a series of carbazole-based host materials. Enhanced horizontal orientation of the TADF emitters was achieved. The degree of enhancement observed was dependent on the host material used. Consequently, our results indicate that π-π stacking, CH/n (n = O, N) weak hydrogen bonds, and multiple CH/π contacts greatly induce horizontal orientation of the TADF emitters in addition to the molecular shape anisotropy. Finally, we fabricated TADF-based organic light-emitting devices with an external quantum efficiency (ηext) of 26% using an emission layer with horizontal orientation ratio (Θ) of 79%, which is higher than that of an almost randomly oriented emission layer with Θ of 62% (ηext = 22%).

Multiple Weak H-Bonds Lead to Highly Sensitive, Stretchable, Self-Adhesive, and Self-Healing Ionic Sensors.

Herein, we demonstrate a ternary ionic hydrogel sensor consisting of tannic acid, sodium alginate, and covalent cross-linked polyacrylamide as skin-mountable and wearable sensors. Based on the multiple weak H-bonds and synergistic effects between the three components, the as-prepared hybrid hydrogel exhibits ultrastretchability with high elasticity, good self-healing, excellent conformability, and high self-adhesiveness to diverse substrates both in air and underwater. More importantly, the ternary hydrogel exhibits high strain sensitivity especially under subtle strains with a gauge factor of 2.0, which is close to the theoretical value of the ionic hydrogel sensors; an extremely large workable range of strain (0.05-2100%); and a low operating voltage 0.07 V. Consequently, the sensor demonstrates superior sensing performance for real-time monitoring of the large and subtle human motions, including limb motions, swallowing, smiling, and wrist pulse. Therefore, it is believed that the STP hydrogel has great potential applications in health monitoring, smart wearable devices, and soft robots.

Different packing motifs of isomeric (E)-N'-(halo-phenyl-methyl-idene)-N-methyl-2-(thio-phen-2-yl)acetohydrazides controlled by C-H⋯O inter-actions.

The crystal structures of three isomeric (E)-N'-(chloro-phenyl-methyl-idene)-N-methyl-2-(thio-phen-2-yl)acetohydrazides (C14H13ClN2OS) are described, with the Cl atom in ortho (I), meta (III) and para (IV) positions in the benzene ring. The ortho-bromo derivative (II) (C14H13BrN2OS), which is isostructural with its chloro congener (I), is also reported. Mol-ecules (I)-(III) have similar conformations, which approximate to l-shapes, as indicated by their N-C-C-Ct (t = thio-phene) torsion angles of -90.1 (3), -91.44 (18) and -90.7 (9)°, respectively. The conformation of (IV) is different, with an equivalent torsion angle of -170.75 (11)° corresponding to a more extended shape for the mol-ecule. The thio-phene ring in each structure features 'flip' rotational disorder. The packing for (I) and (II) features inversion dimers, linked by pairs of C-H⋯O inter-actions, which generate R22(14) loops. In the crystal of (III), [010] C(8) chains arise, with adjacent mol-ecules linked by pairs of C-H⋯O hydrogen bonds. The packing for (IV) features unusually short C-H⋯O inter-actions arising from an H atom attached to the benzene ring (H⋯O = 2.18 Å), which lead to C(9) [301] chains. Hirshfeld fingerprint percentage contact contributions are similar for the four title compounds.

Crystal structures and Hirshfeld surfaces of differently substituted (E)-N'-benzyl-idene-N-methyl-2-(thio-phen-2-yl)acetohydrazides.

The syntheses and crystal structures of (E)-N'-(3-cyano-benzyl-idene)-N-methyl-2-(thio-phen-2-yl)acetohydrazide, C15H13N3OS, (I), and (E)-N'-(4-meth-oxy-benzyl-idene)-N-methyl-2-(thio-phen-2-yl)acetohydrazide, C15H16N2O2S, (II), with different substituents in the meta and para position of the benzene ring are described. Compounds (I) and (II) both crystallize with two mol-ecules in the asymmetric unit, with generally similar conformations [r.m.s. overlay fits for (I) and (II) of 0.334 and 0.280 Å, respectively] that approximate to L-shapes. The thio-phene rings in (I) are well ordered, whereas those in (II) exhibit 'flip' rotational disorder [occupancies 0.662 (2) and 0.338 (2) for mol-ecule 1, and 0.549 (3) and 0.451 (3) for mol-ecule 2]. The packing for (I) features short C-H⋯O inter-actions arising from the C-H grouping adjacent to the cyanide group and C-H⋯Nc (c = cyanide) links arising from the methine groups to generate [110] double chains. Weak C-H⋯π inter-actions inter-link the chains into a three-dimensional network. The packing for (II) features numerous C-H⋯O and C-H⋯π inter-actions arising from different donor groups to generate a three-dimensional network. Hirshfeld fingerprint plots indicate significant differences in the percentage contact surfaces for (I) and (II).

On the competition between weak O-H···F and C-H···F hydrogen bonds, in cooperation with C-H···O contacts, in the difluoromethane - tert-butyl alcohol cluster.

The 1:1 complex of tert-butyl alcohol with difluoromethane has been characterized by means of a joint experimental-computational investigation. Its rotational spectrum has been recorded by using a pulsed-jet Fourier-Transform microwave spectrometer. The experimental work has been guided and supported by accurate quantum-chemical calculations. In particular, the computed potential energy landscape pointed out the formation of three stable isomers. However, the very low interconversion barriers explain why only one isomer, showing one O-H···F and two C-H···O weak hydrogen bonds, has been experimentally characterized. The effect of the H → tert-butyl- group substitution has been analyzed from the comparison to the difluoromethane-water adduct.

Different weak inter-actions in the crystals of three isomeric (E)-N-methyl-N'-(nitro-benzyl-idene)-2-(thio-phen-2-yl)acetohydrazides.

The crystal structures of three isomeric (E)-N-methyl-N'-(nitro-benzyl-idene)-2-(thio-phen-2-yl)acetohydrazides (formula C14H13N3O3S) are described, with the nitro group in ortho, meta and para positions in the benzene ring. In each crystal structure, mol-ecules are linked by various weak inter-actions (C-H⋯O and C-H⋯π bonds, and π-π stacking), leading to three-dimensional networks in each case, but with little similarity between them.

Weak C-H···O and C-H···π hydrogen bonds and π-π stacking interactions in a series of four N'-[(E)-(aryl)methylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazides.

Oxazolidin-2-ones are widely used as protective groups for 1,2-amino alcohols and chiral derivatives are employed as chiral auxiliaries. The crystal structures of four differently substituted oxazolidinecarbohydrazides, namely N'-[(E)-benzylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C12H12N3O3, (I), N'-[(E)-2-chlorobenzylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C12H12ClN3O3, (II), (4S)-N'-[(E)-4-chlorobenzylidene]-N-methyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C12H12ClN3O3, (III), and (4S)-N'-[(E)-2,6-dichlorobenzylidene]-N,3-dimethyl-2-oxo-1,3-oxazolidine-4-carbohydrazide, C13H13Cl2N3O3, (IV), show that an unexpected mild-condition racemization from the chiral starting materials has occurred in (I) and (II). In the extended structures, the centrosymmetric phases, which each crystallize with two molecules (A and B) in the asymmetric unit, form A+B dimers linked by pairs of N-H···O hydrogen bonds, albeit with different O-atom acceptors. One dimer is composed of one molecule with an S configuration for its stereogenic centre and the other with an R configuration, and possesses approximate local inversion symmetry. The other dimer consists of either R,R or S,S pairs and possesses approximate local twofold symmetry. In the chiral structure, N-H···O hydrogen bonds link the molecules into C(5) chains, with adjacent molecules related by a 21 screw axis. A wide variety of weak interactions, including C-H···O, C-H···Cl, C-H···π and π-π stacking interactions, occur in these structures, but there is little conformity between them.

Crystal structure of 2,2-di-chloro-1-(piperidin-1-yl)ethanone.

In the title compound, C7H11Cl2NO, the piperidine ring shows a chair conformation and the bond-angle sum at the N atom is 359.9°. The H atom of the di-chloro-methyl group is in an eclipsed conformation with respect to the carbonyl group (H-C-C=O = -5°). In the crystal, inversion dimers are linked by pairs of C-H⋯O hydrogen bonds between the di-chloro-methyl group and the carbonyl O atom, which generate R 2 (2)(8) loops. The dimers are linked into a ladder-like structure propagating in the [100] direction by short O⋯Cl [3.1084 (9) Å] contacts.