Enhanced proton conductivity in amino acid based self-assembled non-porous hydrogen-bonded organic frameworks

β-Alaninium oxalate hemihydrate, glycinium oxalate, and L-leucinium oxalate salt-cocrystals as non-porous self-assembled hydrogen-bonded organic frameworks afforded proton conductivity of 2.43 × 10^-2 S cm^-1 (60 °C, 95% RH), 3.03 × 10^-2 S cm^-1 (60 °C, 95% RH), and 1.19 × 10^-2 S cm^-1 (80 °C, 95% RH), respectively. These materials possess an extensive 3-dimensional network of hydrogen bonds in their crystal structures, making them efficient proton conducting membranes. The reduction in conductivity values over 10^-1 S cm^-1 order upon exposure of the samples to a D₂O atmosphere in extreme conditions ratified the role of humidity for the conduction of protons. This work explores the relationship between structural features and proton conductivity for the design of proton conducting membranes that are easy to synthesize, eco-friendly, and cheap with potential for futuristic applications.

Experimental Insights into the Electronic Nature, Spectral Features, and Role of Entropy in Short CH3···CH3 Hydrophobic Interactions

Hydrophobic interactions are often explored in solution-state aggregation of molecules. However, an experimental electron density description about these interactions is still lacking. Here, we report a systematic study on the electronic nature of methyl···methyl hydrophobic interactions in a series of multicomponent crystals of biologically active molecules. Charge density models based on high-resolution X-ray diffraction allow the visualization of subtle details of electron density features in the interaction region. Our study classifies these interactions as atypical group···group interactions in contrast to σ-hole interactions, which are stabilized by the minimized electrostatic repulsion and maximized dispersion forces. For the first time, we quantified the solid-state entropic contribution from the torsional mode of the methyl groups in stabilizing these interactions by thermal motion analysis based on neutron diffraction as well as variable-temperature crystallography. The carbon atoms in methyl···methyl interactions show a unique upfield chemical shift in the ¹³C solid-state NMR signal.

Crystal structure of 2,4,6-tris(cyclohexyloxy)-1,3,5-triazine

The title compound, is the first tri-substituted cyclo­hex­yloxy triazine to be described. In the crystal, the triazine rings form (C3i-PU) Piedfort units and the mol­ecules are linked by C—H⋯O hydrogen bonds, forming ribbons propagating along [1-10].

The title compound, C₂₁H₃₃N₃O₃, is a tri-substituted cyclo­hex­yloxy triazine. In the crystal, the triazine rings form (C3i-PU) Piedfort units. The inter-centroid distance of the π–π inter­action involving the triazine rings is 3.3914 (10) Å. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming ribbons propagating along [1-10]. There are also weak C—H⋯N and C—H⋯O contacts present, linking inversion-related ribbons, forming a three-dimensional structure.

S⋯O chalcogen bonding in sulfa drugs: insights from multipole charge density and X-ray wavefunction of acetazolamide

Experimental charge density analysis combined with the quantum crystallographic technique of X-ray wavefunction refinement (XWR) provides quantitative insights into the intra- and intermolecular interactions formed by acetazolamide, a diuretic drug.

Organic alloys of room temperature liquids thiophenol and selenophenol

The first examples of organic alloys of two room temperature liquids, obtained and characterizedvia in situcryo-crystallography, are presented. Thiophenol and selenophenol, which exhibit isostructurality and similar modes of S⋯S and Se⋯Se homo-chalcogen interactions along with weak and rare S–H⋯S and Se–H⋯Se hydrogen bonds, are shown to form solid solutions exhibiting Veggard's law-like trends.

Experimental validation of 'pnicogen bonding' in nitrogen by charge density analysis

The participation of a nitrogen atom acting as an electrophile in pnicogen bonding, a hitherto unexplored interaction has been established by experimental charge density analysis. QTAIM and NBO analyses ratify this observation.

Halogen bonding in fluorine: experimental charge density study on intermolecular F···F and F···S donor-acceptor contacts

The enigmatic type II C-F···F-C and C-F···S-C interactions in pentafluorophenyl 2,2'-bithiazole are shown to be realistic "σ-hole" interactions based on high resolution X-ray charge density analysis.

Concomitant nitrene and carbene insertion accompanying ring expansion: spectroscopic, X-ray, and computational studies

Reinvestigation of the thermolysis of azido-meta-hemipinate (I) yielded, in addition to known II, unusual products III and IV. These products are formed via a rare intramolecular nitrene insertion into an adjacent methoxy C-H bond followed by an intermolecular reaction during a ring-expansion and a ring-extrusion reaction followed by a carbene insertion. The structures of the new compounds were confirmed using a battery of techniques, including HRMS (ESI-QTOF) and 2D NMR as well as X-ray crystallography for compound IV. Density functional theory methods were used to support the proposed mechanism of formation of the products.

2,2,2-Trichloro-N-(3-nitrophenyl)acetamide

In the title compound, C₈H₅Cl₃N₂O₃, the dihedral angle between the nitro­phenyl ring and the acetamide group is 5.47 (6)°. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into chains running parallel to the b axis.

4-{[Bis(2-hy-droxy-eth-yl)amino]-meth-yl}-6-meth-oxy-2H-chromen-2-one

In the title compound, C(15)H(19)NO(5), an intra-molecular O-H⋯O hydrogen bond links the hy-droxy-ethyl side chains, forming a seven-membered ring. In the crystal, mol-ecules are linked into chains via O-H⋯O hydrogen bonds along the b axis. Further, mol-ecules are linked by weak inter-molecular C-H⋯O and π-π stacking inter-actions [centroid-centroid distance = 3.707 (4) Å].

(2E)-1-(5-Chloro-thio-phen-2-yl)-3-(2,3-dimeth-oxy-phen-yl)prop-2-en-1-one

In the title compound, C₁₅H₁₃ClO₃S, the chloro­thio­phene and dimeth­oxy­phenyl groups are linked by a prop-2-en-1-one group. The C=C double bond exhibits an E conformation. The mol­ecule is non-planar, with a dihedral angle of 31.12 (5)° between the chloro­thio­phene and dimeth­oxy­phenyl rings. The meth­oxy group at position 3 is coplanar with the benzene ring to which it is attached, with a C—O—C—C torsion angle of −3.8 (3)°. The meth­oxy group attached at position 2 of the benzene ring is in a (+)synclinal conformation, as indicated by the C—O—C—C torsion angle of −73.6 (2)°. In the crystal, two different C—H⋯O inter­molecular inter­actions generate chains of mol­ecules extending along the b axis.

(2E)-1-(5-Chloro-thio-phen-2-yl)-3-(2,4,5-trimeth-oxy-phen-yl)prop-2-en-1-one

In the title mol­ecule, C₁₆H₁₅ClO₄S, the chloro­thio­phene and trimeth­oxy­phenyl rings make a dihedral angle of 31.12 (5)°. The C=C double bond exhibits an E conformation. In the crystal, C—H⋯O inter­actions generate bifurcated bonds, linking the mol­ecules into chains along the b axis.

4-Azido-methyl-7-methyl-2-oxo-2H-chromene-6-sulfonyl azide

In the title compound, C₁₁H₈N₆O₄S, the plane of the coumarin aromatic ring is twisted by 17.2 (2)° with respect to the plane of the azide group bound to the methyl­ene substituent, whereas it is twisted by 83.2 (2)° to the plane of the azide attached to the sulfonyl group. The crystal structure is stabilized by weak C—H⋯O inter­actions, leading to the formation of dimers with R₂²(12) graph-set motifs. These dimers are further linked by weak S—O⋯π and π–π contacts [centroid–centroid distance = 3.765 (2) Å], leading to the formation of a layered structure.

In situ surface modification of molybdenum-doped organic-inorganic hybrid TiO2 nanoparticles under hydrothermal conditions and treatment of pharmaceutical effluent

Molybdenum-doped TiO2 organic-inorganic hybrid nanoparticles were synthesized under mild hydrothermal conditions by in situ surface modification using n-butylamine. This was carried out at 150 degrees C at autogeneous pressure over 18 h. n-Butylamine was selected as a surfactant since it produced nanoparticles of the desired size and shape. The products were characterized using powder X-ray diffraction, Fourier transform infrared spectrometry, dynamic light-scattering spectroscopy, UV-Vis spectroscopy and transmission electron microscopy. Chemical oxygen demand was estimated in order to determine the photodegradation efficiency of the molybdenum-doped TiO2 hybrid nanoparticles in the treatment of pharmaceutical effluents. It was found that molybdenum-doped TiO2 hybrid nanoparticles showed higher photocatalytic efficiency than untreated TiO2 nanoparticles.

N-H...F hydrogen bonds in fluorinated benzanilides: NMR and DFT study

Using (19)F and (1)H-NMR (with (14)N decoupling) spectroscopic techniques together with density functional theoretical (DFT) calculations, we have investigated weak molecular interactions in isomeric fluorinated benzanilides. Simultaneous presence of through space nuclear spin-spin couplings ((1h)J(N-HF)) of diverse strengths and feeble structural fluctuations are detected as a function of site specific substitution of fluorine atoms within the basic identical molecular framework. The transfer of hydrogen bonding interaction energies through space is established by perturbing their strengths and monitoring the effect on NMR parameters. Multiple quantum (MQ) excitation, up to the highest possible MQ orders of coupled protons, is utilized as a tool for accurate (1)H assignments. Results of NMR studies and DFT calculations are compared with the relevant structural parameters taken from single crystal X-ray diffraction studies.

Synthesis, characterization, and crystallographic study of the PbO-Bi2O3-V2O5 system: Pb(3-x)Bi(2x/3)V2O8 (0.20 < or = x < or = 0.50)

A new solid solution Pb(3-x)Bi(2x/3)V(2)O(8) (0.20 < or = x < or = 0.50), stabilizing the high-temperature gamma form of Pb(3)V(2)O(8), has been isolated in the system Pb(3)V(2)O(8)-BiVO(4). The single-crystal structure of the composition x = 0.50 (Pb(2.5)Bi(1/3)V(2)O(8)) was solved using single-crystal X-ray diffraction (XRD) technique. The compound crystallizes in the trigonal crystal system R3m (No. 166) with a palmierite structural type with a = 5.7463(3) A, c = 20.3047(12) A, V = 580.64(5) A(3), and Z = 3. The final R1 value of 0.0406 was achieved for 217 independent reflections during the structure refinement. The variable-temperature powder XRD shows the absence of any phase transition for all of the members of the solid solution in the limit of 398-80 K. The new solid solution has been characterized by neutron powder diffraction, solid-state UV-vis diffuse-reflectance spectra, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). Alternating-current impedance studies indicate conductivity on the order of 10(-4) Omega(-1) cm(-1) for Pb(2.5)Bi(1/3)V(2)O(8). The change in color of the samples from brown to yellow at high temperature was explained by XPS studies, which indicate the plausible formation of the ppm level of Bi(2)O(3) at such elevated temperature ranges.

Thiourea based novel chromogenic sensor for selective detection of fluoride and cyanide anions in organic and aqueous media

Novel chromogenic thiourea based sensors 4,4'-bis-[3-(4-nitrophenyl) thiourea] diphenyl ether 1 and 4,4'-bis-[3-(4-nitrophenyl) thiourea] diphenyl methane 2 having nitrophenyl group as signaling unit have been synthesized and characterized by spectroscopic techniques and X-ray crystallography. The both sensors show visual detection, UV-vis and NMR spectral changes in presence of fluoride and cyanide anions in organic solvent as well as in aqueous medium. The absorption spectra indicated the formation of complex between host and guest is in 1:2 stoichiometric ratios.