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The gas-phase structure, stability, spectra, and electron density topography of H-Wn clusters (where n = 1-8) have been calculated using coupled-cluster CCSD(T) and Mo\ller-Plesset second-order perturbation (MP2) theory combined with complete basis set (CBS) approaches. The performance of various density functional theory (DFT) based methods such as B3LYP, M05-2X, M06, M06-L, and M06-2X using 6-311++G(d,p), and aug-cc-pVXZ (aVXZ, where X = D, T, and Q) basis sets has also been assessed by considering values calculated using CCSD(T)/CBS limit as reference. The performance of the functionals has been ranked based on the mean signed/unsigned error. The comparison of geometrical parameters elicits that the geometrical parameters predicted by B3LYP/aVTZ method are in good agreement with those values obtained at MP2/aVTZ level of theory. Results show that M05-2X functional outperform other functionals in predicting the energetics when compared to CCSD(T)/CBS value. On the other hand, values predicted by M06-2X, and M06 methods, are closer to those values obtained from MP2/CBS approach. It is evident from the calculations that H-Wn (where n = 5-8) clusters adopt several interesting structural motifs such as pyramidal, prism, book, Clessidra, cubic, cage, and bag. The important role played by ion-water (O-H···H-) and water-water (O-H···O) interactions in determining the stability of the clusters has also been observed. Analysis of the results indicates that the most stable cluster is made up of minimum number of O-H···H- interaction in conjugation with the maximum number of O-H···O interactions. The Bader theory of atoms in molecules (AIM) and natural bond orbital (NBO) analyses has also been carried out to characterize the nature of interactions between hydride ion and water molecules. It can be observed from the vibrational spectra of H-Wn clusters, the stretching frequencies involving ion-water interaction always exhibit larger redshift and intensities than that of water-water (inter solvent) interactions. [ABSTRACT FROM AUTHOR]

Abstract: A new organic nonlinear optical single crystal, l-phenylalanine-4-nitrophenol (LPAPN) belonging to the amino acid group has been successfully grown by slow evaporation technique. The lattice parameters of the grown crystal have been determined by X-ray diffraction studies. FT-IR spectrum was recorded to identify the presence of functional group and molecular structure was confirmed by NMR spectrum. Thermal strength of the grown crystal has been studied using TG–DTA analyses. The grown crystals were found to be transparent in the entire visible region. The existence of second harmonic generation signals was observed using Nd:YAG laser with fundamental wavelength of 1064nm. [Copyright &y& Elsevier]

4-Alkoxy benzoic acids belong to an important class ofthermotropicliquid crystals that are structurally simple and often used as startingmaterials for many novel mesogens. 4-Hexyloxybenzoic acid (HBA) isa homologue of the same series and exhibits an enantiotropic nematicphase. As this molecule could serve as an ideal model compound, highresolution 13C NMR studies of HBA in solution, solid, andliquid crystalline phases have been undertaken. In the solid state,two-dimensional separation of undistorted powder patterns by effortlessrecoupling (2D SUPER) experiments have been carried out to estimatethe magnitude of the components of the chemical shift anisotropy (CSA)tensor of all the aromatic carbons. These values have been used subsequentlyfor calculating the orientational order parameters in the liquid crystallinephase. The CSA values computed by density functional theory (DFT)calculations showed good agreement with the 2D SUPER values. Additionally, 13C–1H dipolar couplings in the nematic phasehave been determined by separated local field (SLF) spectroscopy atvarious temperatures and were used for computing the order parameters,which compared well with those calculated by using the chemical shifts.It is anticipated that the CSA values determined for HBA would beuseful for the assignment of carbon chemical shifts and for the studyof order and dynamics of structurally similar novel mesogens in theirnematic phases. [ABSTRACT FROM AUTHOR]

Abstract: Good transparent single crystals of l-phenylalanine l-phenylalaninium malonate (LPPMA) have been grown successfully by slow evaporation technique from aqueous solution. Single crystal X-ray diffractometer was utilized to measure unit cell parameter and to confirm the crystal structure. The chemical structure of compound was established by FT-NMR technique. The vibrational modes of the molecules of elucidated from FTIR spectra. Its optical behaviour has been examined by UV–vis spectral analysis, which shows the absence of absorbance in the visible region. Thermal properties of the LPPMA crystal were carried out by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques, which indicate that the material does not decompose before melting. The melting point of grown crystal was observed as 180°C by melting point apparatus. The NLO property was confirmed by the powder technique of Kurtz and Perry. The dielectric behaviour of the sample was also studied for the first time. [Copyright &y& Elsevier]

Abstract: Tris(l-phenylalanine)l-phenylalaninium nitrate, C9H12NO2 +·NO3 −·3C9H11NO2 (TPLPN), a new organic nonlinear optical material was grown from aqueous solution by slow evaporation solution growth at room temperature. The grown crystals were subjected to powder X-ray diffraction and single crystal X-ray diffraction studies to confirm the crystalline nature and crystal structure. The modes of vibration of different molecular groups present in TPLPN have been identified by FTIR spectral analysis. The presence of hydrogen and carbon in the grown crystal were confirmed by using proton and carbon nuclear magnetic resonance (NMR) spectral analyses. The optical transmission spectral study establishes good transmitting ability of the crystal in the entire visible region. The thermogravimetric (TG) and differential thermal analyses (DTA) were carried out to understand the thermal stability of the sample. The nonlinear optical property of the compound observed using Kurtz powder second harmonic generation test assets the suitability of the grown material for the frequency conversion of laser radiation of Nd:YAG. [Copyright &y& Elsevier]

Abstract: Bulk single crystals of l-alanine alaninium nitrate [abbreviated as LAAN], an intriguing material for frequency conversion has been grown from its aqueous solution by both slow solvent evaporation and by slow cooling techniques. The optimized pH value to grow good quality LAAN single crystal was found to be 2.5. The grown crystals were subjected to single crystal X-ray diffraction studies to determine the unit cell dimensions and morphology. Vibrational frequencies of the grown crystals by Fourier transform infrared spectroscopic technique were investigated. Also, the presence of hydrogen and carbon atoms in the grown sample was confirmed using proton and carbon NMR analyses. The dielectric constant and dielectric loss measurements of the as grown crystal at different temperatures and frequencies of the applied field are measured and reported. LAAN has good optical transmission in the entire visible region with cutoff wavelength within the UV region confirms its suitability for device fabrications. The existence of second harmonic generation signals was observed using Nd:YAG laser with fundamental wavelength of 1064nm. Its Laser Damage Threshold (LDT) was measured and also tested by using a Q-switched Nd:YAG laser and the value of LDT of LAAN is 17.76GW/cm2 respectively, is found to be better than certain organic and semiorganic materials. [Copyright &y& Elsevier]

Chiral C2-symmetric bis(amide) molecules, N,N'-bis(4-fluorobenzoyl)-(1R,2R)-diaminocyclohexane (BFBDC), N,N'-bis(4-nitrobenzoyl)-(1R,2R)-diaminocyclohexane (BNBDC), N,N'-bis(4-methoxybenzoyl)-(1R,2R)-diaminocyclohexane (BMBDC), and N,N'-bis(4-aminobenzoyl)-(1R,2R)-diaminocyclohexane (BABDC) are synthesized, and their assembly patterns in the solid state are investigated through single-crystal X-ray analysis. A range of noncovalent interactions give rise to helical superstructures in the crystals. The compounds exhibit good optical transparency and high thermal stability; these may be attributed to the specific molecular structure and extended supramolecular interactions. BMBDC and BABDC molecules possess the largest hyperpolarizabilities in the series owing to the presence of electron-donating groups and exhibit second harmonic generation (SHG) in the solid state. The optical transparency, thermal stability, and SHG capability make these materials potentially interesting candidates for quadratic nonlinear optical applications. [ABSTRACT FROM AUTHOR]

A metal—organic polyhedron of truncated octahedral geometry augmented with a C4-symmetric square-planar CuII paddle-wheel node as a secondary building unit can be prepared using a C3-symmetric ligand that occupies the face of the octahedral cage, where the three phenyl groups containing a m-carboxylate group in the ligand provide the necessary curvature to form the finite octahedral cage. [ABSTRACT FROM AUTHOR]

Biocompatible cholinium-based ionic liquids (ILs) are used extensively in the pharmaceutical and biomedical industries. To enhance structural stability and solubility of drugs, as well as their controlled delivery, IL-based active pharmaceutical ingredients (API) are used widely. In this study, we selected two different sets of biodegradable ILs which also have a direct influence on the structure and stability of insulin. Moreover, we used DFT-based electronic structure calculations with molecular dynamics (MD) simulations to study the effect of a mixture of two different anions in the IL medium and the role of water molecules on the stability of insulin. Microhydration and molecular-level DFT calculations suggest that ILs based on choline geranate [Cho][Ger] and choline taurine [Cho][Tau] differ in their hydration patterns, and thus the stability of the clusters varies significantly. This finding is important for exploring the role of water molecules within these mixtures (i.e., on the interactions between [Ger] and [Tau]). From our calculations it is found that the [Cho][Ger] IL stabilizes the insulin dimer structure strongly through water-mediated H-bonding interactions, whereas the [Cho][Ger][Tau] ternary complex destabilizes insulin. This indicates that IL mixtures over a wide range of concentrations and water molecules at the interface may influence the structural stability and enable suitable combinations of oral formulations to be predicted for drug-delivery applications. From the MD simulations, we conclude that [Cho][Ger] stabilizes the insulin dimer. Our combined DFT and MD simulations will provide valuable information for experimentalists to design and develop novel oral insulin formulations. [ABSTRACT FROM AUTHOR]

Structural characterizations usingXRD and 13C NMR spectroscopyof two rodlike mesogens consisting of (i) three phenyl ring core witha polar cyano terminal and (ii) four phenyl ring core with flexibledodecyl terminal chain are presented. The three-ring-core mesogenwith cyano terminal exhibits enantiotropic smectic A phase while thefour-ring mesogen reveals polymesomorphism and shows enantiotropicnematic, smectic C, and tilted hexatic phases. The molecular organizationin the three-ring mesogen is found to be partial bilayer smectic Adtype, and the interdigitation of the molecules in the neighboringlayers is attributed to the presence of the polar terminal group.For the four-ring mesogen, the XRD results confirm the existence ofthe smectic C and the tilted hexatic mesophases. A thermal variationof the layer spacing across the smectic C phase followed by a discretejump at the transition to the tilted hexatic phase is also observed.The tilt angles have been estimated to be about 45° in the smecticC phase and about 40° in tilted hexatic phase. 13CNMR results indicate that in the mesophase the molecules are alignedparallel to the magnetic field. From the 13C–1H dipolar couplings determined from the 2D experiments, theoverall order parameter for the three-ring mesogen in its smecticA phase has been estimated to be 0.72 while values ranging from 0.88to 0.44 have been obtained for the four-ring mesogen as it passesfrom the tilted hexatic to the nematic phase. The orientations ofthe different rings of the core unit with respect to each other andalso with respect to the long axis of the molecule have also beenobtained. [ABSTRACT FROM AUTHOR]