Role of dielectric medium on mesogenic compounds (BCHs) at phase transition temperature: A comparative computational analysis

A comparative computational analysis on two liquid crystalline disubstituted biphenylcyclohexanes (BCHs) of general formula R‐C₆H₁₀‐C₆H₄‐X with R: C₃H₇; X: H (BCH30) and R: C₅H₁₁; X: CN (BCH5CN) has been carried out on the basis of quantum mechanics and intermolecular forces. The evaluation of atomic charge and dipole moment at each atomic centre has been carried out through an all‐valence electron (CNDO/2) method. The configurational energy has been computed using the Rayleigh‐Schrodinger perturbation method. The total interaction energy values obtained were used to calculate the probability of each configuration in dielectric medium (i.e. non‐interacting and non‐mesogenic solvent, benzene) at room temperature, transition temperature and above transition temperature using the Maxwell‐Boltzmann's formula. The flexibility of various interacting configurations has been studied in terms of variation of probability due to small departures from the most probable configurations. Further, the various possible geometrical arrangements between a molecular pair during the different modes of interactions have been considered. An attempt has been made to develop a new and interesting model for mesogenic compounds in a dielectric medium. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and Characterization of Nonlinear Optical Crystal Materials: Cadmium Mercury Thiocyanate and its Lewis Base Adducts

Cadmium mercury thiocyanate (CdHg(SCN)₄, CMTC) and its two lewis base adducts: cadmium mercury thiocyanate dimethyl‐sulphoxide (CdHg(SCN)₄(H₆C₂OS)₂, CMTD) and cadmium mercury thiocyanate glycol monomethyl ether (CdHg(SCN)₄(C₃H₈O₂), CMTG) have been discovered as nonlinear optical (NLO) crystal materials. Their structural, optical and physicochemical properties were characterized by X‐ray powder diffraction (XRPD), infrared spectroscopy, vis/UV/NIR spectra and thermal analysis. It is discovered that their transparency cutoffs lie in the UV region and CMTD crystals possess the shortest cutoff wavelength among the three crystal materials.     

UV spectral characterization of a smectic-C liquid crystal: Theoretical support to the experiment

In the present article, UV spectral characterization of a smectic-C liquid crystal 4,4′-bis(n-alkoxy)azoxybenzene (n = 14) (C₄₀H₆₆N₂O₃) has been carried out. Structure of the molecule has been optimized using the Density functional B3LYP with 6-31+G (d) basis set using crystallographic geometry as input. The absorption spectra have been estimated in the UV region by employing the DFT method, semiempirical CNDO/S and INDO/S parameterizations. The oscillator strength (f) and vertical transition energy (E_V) have been reported corresponding to absorption wavelength (λ_max). These values have been compared with the experimental value reported in the literature to offer theoretical support to the experimental value. Further, some electrochemical properties have been reported for the molecule.     

Synthesis,crystal structure and third order nonlinear optical properties of bis(tetra‐n‐propylammonium) bis(2‐thioxo‐1,3‐dithiole‐4,5‐dithiolato)cuprate(II)

A novel bis (dmit) complex of copper (II), [(C₃H₇)₄N]₂[Cu(dmit)₂] ( 1 ), where dmit is 2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate, was prepared and structurally characterized by X‐ray single crystal diffraction. The copper (II) atom is tetracoordinated by four dmit S atoms, forming a nearly square planar arrangement. The [Cu(dmit)₂]^2‐ anions and the [(C₃H₇)₄N]⁺ counter‐cations form a three‐dimensional solid‐state structure by C–H…S hydrogen bonds. The third‐order nonlinear optical properties of the complex were determined by picosecond Z‐scan technique at a wavelength of 1064 nm. The results indicate the compound exhibits reverse saturation absorption and self‐defocusing performance. The molecular second‐order hyperpolarizability γ is calculated to be as high as (1.8±0.2)×10^‐30 esu. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,growth and characterization of L‐histidinium acetate dihydrate single crystals

L‐histidinium acetate dihydrate {abbreviated as LHAc; [C₆H₁₀ N₃O₂⁺ C₂H₃O₂^‐ 2H₂O], a new nonlinear optical (NLO) material has been grown from aqueous solution. The grown crystals were subjected to X‐ray diffraction, Fourier transform infrared (FTIR) and FT‐Raman analyses. Thermal studies have been carried out for its thermal stability. Optical behaviour such as UV‐Vis‐NIR spectrum and second harmonic generation (SHG) were also investigated. Its SHG efficiency was found as d_eff = 2.2 d_eff (KDP). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of radial‐like ZnO structure by hydrothermal method with ZnSO4·7H2O and Zn(CH3COO)2·2H2O as zinc sources

Radial‐like ZnO structures were prepared using zinc sulfate (ZnSO₄·7H₂O) and zinc acetate [Zn(CH₃COO)₂·2H₂O] as zinc sources by a facile template‐free hydrothermal method in this paper. Structural and optical properties of radial‐like ZnO structures are characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV‐vis spectrophotometer and photoluminescence measurement (PL). It has been found that the distinct surface morphologies of radial‐like ZnO structures grown by different zinc sources. Slim radial‐like ZnO with a hexagonal wurtzite structure is grown by using ZnSO₄·7H₂O as zinc sources, whereas coarse radial‐like ZnO with zincite structure is achieved by zinc acetate. The UV‐vis absorption spectra of them both display an obvious and significant absorption in the ultraviolet region. The room temperature PL spectra of ZnO structures grown by two different zinc sources possess a common feature that consists of a strong ultraviolet (UV) peak and visible emission band.     

Correlation of mesogenic properties with intermolecular interaction energy for homologous series of HnCBP

Intermolecular interaction energy between a pair of molecules of homologous series 4, 4′-disubstituted biphenyl of the general formula HO?(CH₂)_n?O?C₆H₄?C₆H₄?CN(n = 3 ? 11) (H_nCBP) has been evaluated under various interacting conditions viz. stacking, in-plane and terminal interaction. Molecular geometry of the studied molecules was fully optimized without any constraint and checked for imaginary frequencies using hybrid density functional B3LYP combined with 6–31 g^** basis set. Electronic structure of the molecules obtained through these calculations has been utilized to calculate electrostatic and polarization energies under Rayleigh-Schrodinger perturbation theory modified with multi-centered multi-pole expansion method. Dispersion and repulsion energies have been evaluated using Kitaigorodskii formula. The identified minimum energy complexes have been further utilized to evaluate interaction energy under super molecular approach by employing M06 and DFT-D methods. A comparative analysis of the results has been reported with a view to examine suitability of different methods to study molecular aggregations in moderately large organic systems.     

Temperature‐tuned band gap energy and oscillator parameters of Tl2InGaSe4 semiconducting layered single crystals

The optical properties of Tl₂InGaSe₄ layered single crystals have been studied through the transmission and reflection measurements in the wavelength range of 500‐1100 nm. The analysis of room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.86 and 2.05 eV, respectively. Transmission measurements carried out in the temperature range of 10‐300 K revealed that the rate of change of the indirect band gap with temperature is γ = – 4.4 × 10^‐4 eV/K. The absolute zero value of the band gap energy was obtained as E_gi(0) = 1.95 eV. The dispersion of the refractive index is discussed in terms of the single oscillator model. The refractive index dispersion parameters: oscillator wavelength and strength were found to be 2.53 × 10^–7 m and 9.64 × 10¹³ m^–2, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of thiourea mixed cadmium – lead chloride – a nonlinear optical crystal

Nonlinear optical (NLO) crystal of thiourea mixed cadmium–lead chloride dihydrate Cd[(PbCl₃)(NH₂CSNH₂)].2H₂O (TCCPC) have been grown in solution by slow evaporation technique at room temperature. The powder X‐ray diffraction pattern has been recorded and indexed. The UV‐Vis‐NIR transmittance and FT‐IR spectrum have been recorded in the range 200‐1090 nm and 400‐4000 cm^‐1, respectively. The lower cut‐off wavelength is 280 nm in the UV region, which is higher than that of pure Cd(PbCl₃) (CCPC) crystal. The presence of functional groups has been confirmed by FT‐IR analysis. The TCCPC crystal was characterized by SEM and EDX spectrum. The second harmonic generation (SHG) of the thiourea mixed cadmium–lead chloride (TCCPC) crystal is demonstrated by the Kurtz Perry method using Nd:YAG laser and the results confirm that the grown crystal is roughly three times more efficient than ADP. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures of N1, N5‐dibenzoyltetrahydro‐4‐methyl‐1, 5‐benzodiazepin‐2‐one (DBTBO) and tetrahydro‐4‐methyl‐1, 5‐benzodiazepin‐2‐one (TBO)

Adducing structural analogies between the two fused systems, N1, N5‐Dibenzoyltetrahydro‐4‐methyl‐1,5‐benzodiazepin‐2‐one, C₂₄H₂₀N₂O₃ (DBTBO CCDC 200341) and Tetrahydro‐4‐methyl‐1,5‐benzodiazepin‐2‐one, C₁₀H₁₂ N₂O (TBO CCDC 200342) helps to find the pharmacological differences from the view point of variant hetero atom substitutions in the hetero cycle. Both the diazepines crystallized in identical monoclinic space group P2₁/n with a = 14.1134(1) Å, b = 9.2444(1) Å, c = 16.3812(1) Å; β = 107.11(1)º, V = 2042.7(3) ų for DBTBO and a = 9.3363(7) Å, b = 10.4895(8) Å, c = 9.9852(7) Å, β = 91.314(1)º, V = 977.62(1) ų for TBO, respectively. The two structures were solved by direct methods and refined by full‐matrix least‐squares procedure to final R‐values of R1 = 0.0575(DBTBO) and R1 = 0.0984(TBO). Structural differences include non‐identical boat conformations of these seven‐membered rings and the different non‐bonding interactions in the benzodiazepine pair.     

Growth and characterization of a new potential second harmonic generation material from the amino acid family: L‐Valinium picrate

L‐Valinium picrate (C₅H₁₂NO₂)⁺. (C₆H₂N₃O₇)^–, a non‐linear optical material from the amino acid family which has large second harmonic generation (SHG) efficiency, was grown by slow evaporation method. Characterization of the crystals was made using single crystal X‐ray diffraction. The functional groups and the modes of vibrations were found by using the Fourier transform infrared (FTIR) spectroscopy. The second harmonic generation (SHG) conversion efficiency was investigated using the Kurtz and Perry method. The SHG conversion efficiency is 60 times higher than that of the standard KDP and 8 times higher than that of the standard Urea and the optical transparency was analyzed using UV‐visible‐NIR absorption spectrum. The structural features of the material leading to the large SHG efficiency are discussed. Microhardness and dielectric studies were also carried out. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Incorporation of hafnium (IV) into KTP framework from phosphate‐fluoride fluxes

Solid solutions KTi_1‐XHf_XOPO₄ (х = 0.008 – 0.107) possessing the KTiOPO₄ structure, have been synthesized in molten system K₂O‐P₂O₅‐TiO₂‐HfF₄. The crystal growth experiment of Hf‐doped KTP crystal has been reported. The X‐ray powder diffraction data and chemical analysis are also presented. It has been shown that KTiOPO₄ crystal structure slightly changes when Hf incorporates into the framework. Transmission/absorption spectra of KTi_0.974Hf_0.026OPO₄ crystals have been recorded. The incorporation of Hf ions shifts the optical absorption edge in the UV‐visible spectrum towards the long‐wavelength region with absorption near 387 nm.     

Estimation of high and low UV intensity profiles of mesogenic oxovanadium (IV) salen complexes: Doubling effect of homologue number

This article estimates the high and low UV intensity profiles of mesomorphic oxovanadium (IV) salen [VO (4-C_nH_2n+1O)₂ salen; nVLC] complexes. Structure of these complexes have been optimized using the Density functional B3LYP with 6–31 + G (d) basis set using crystallographic geometry as input. The UV absorption spectral characteristics have been estimated in the UV region by employing the DFT method. The oscillator strength (f) and vertical transition energy (E_V) have been reported corresponding to absorption wavelength (λ_max). Further, some electrochemical properties have been reported for the molecule. The doubling effect of homologue number on the reported parameters has been discussed.     

Crystal and Molecular Structure of bis[diaaqua(1H‐cyclopenta(2,1‐b:3,4‐b')(dipyridine ‐2,5‐dione))N ickel(II)]dihydrate

The title compound [Ni(CPDD)(H₂O)₂]₂(H ₂O )₂, {]Ni₂(C₄₄H₂₈N₈O₁₂)] (H₂O)₂ }, where CPDD = 1H‐cyclopenta(2,1‐b:3,4‐b')(dipyridine‐2,5‐dione) has been prepared and its crystal structure determined by single crystal X‐ray diffraction at room temperature. The complex crystallizes in the triclinic space group P1 w ith two molecules in the asymmetric unit. The cell dimensions are a=10.452(1),b=14.098(1) & c=16.023 Å; D=110.13(1), E=100.63(1) & J=100.85(1)°. The two independent molecules in the asymmertic unit are related by pseudo two fold symmetry. In both the molecules the coordination environment around the Ni(II) may be best described as a distorted octahedral. Due to some delocalization of charge towards one of the oxygens(O1a) from the O2a atom some degree of bond localization has been observed. The individual diones of both the molecules are almost right angles at the metal atom. A long the y‐axis inversion related molecules are forming pseudo‐dimers through hydrogen bonding.     

Statistical Study of Molecular Ordering in a Nematogenic Compound – A Computational Analysis

A computational Analysis has been carried out to determine the configurational preference of a pair of a nematogen, 4,4′‐azodiphenetole (C₂H₅‐O‐C₆H₄‐N=N‐C₆H₄‐O‐C₂H₅) [AZO] molecules with respect to translatory and orientational motions. The CNDO/2 method has been employed to compute the atomic charge and atomic dipole at each atomic centre. Configurational energy has been computed using modified Rayleigh‐Schrodinger perturbation method. The interaction energy values obtained through these computations were used to calculate the probability of each configuration at phase transition temperature using Maxwell‐Boltzmann formula. Further, the flexibility of various configurations has been studied in terms of variation of probability due to small departures from the most probable configuration. Molecular parameters like total energy, binding energy and total dipole moment have been given. Results have been discussed in the light of experimental as well as other theoretical observations.     

Crystal structure of 4‐(1‐methyl‐1‐mesitylcyclobutane‐3‐yl)‐2‐aminothiazole

The crystal structure of 4‐(1‐methyl‐1‐mesitylcyclobutane‐3‐yl)‐2‐aminothiazole (C₁₇H₂₂N₂S₁) has been determined by X‐ray crystallographic techniques. The compound crystallizes in the triclinic space group P‐1 with Z = 6. The crystal structure was solved by direct methods and refined by full‐matrix least squares to a final R‐value of 0.052 for 2298 observed reflections [I > 2σ ( I ) ]. There are three crystallographically independent molecules, I, II and III. These molecules are held together by intermolecular N‐H...N hydrogen bonds. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Crystallographic Analysis of Acetyl β ‐boswellic acid

The crystal structure of the title compound (3 α ‐acetoxy‐urs‐12‐en‐24‐oic acid, C₃₂H₅₀O₄) has been determined by X‐ray crystallographic techniques. The compound crystallizes into orthorhombic space group P2₁2₁2₁ with unit cell parameters : a = 12.773(2), b=16.381(4), c=27.929(7)Å. The structure has been solved by direct methods and refined to R = 0.054 for 4930 observed reflections. The structure contains two crystallographically independent molecules in the asymmetric unit which are almost identical in geometry. Rings A, B, D and E have chair conformations while ring C assumes a sofa conformation in both the molecules. The molecules in the structure are linked together by intra‐ and intermolecular O‐H…= and C‐H…O hydrogen bonds.     

Crystal Structure of Diethyl 2‐[2,2,2‐ trifluoro‐1‐(indole‐3‐yl)‐ethyl]‐2‐acetamidomalonate

The title compound (C₁₉H₂₁F₃N₂O₅) has been determined from three dimensional X‐ray diffraction data. The crystals are monoclinic, a = 7.626(4)Å, b = 17.515(4)Å, c = 15.066(3)Å, β = 101.02(3)°, V = 1975(1)ų, Z = 4, D_calc = 1.393g cm^‐3, space group P2₁/c. The structure was solved by direct methods and refined by full‐matrix least‐squares method (R = 0.039).     

Synthesis and characterization of a new nonlinear optical single crystal: L‐Lysinium trifluoroacetate

Single crystals of a new L‐Lysine salt: L‐Lysinium trifluoroacetate {abbreviated as LLyTFA; [(NH₂)‐(CH₂)₄‐CH‐(NH₃)‐(COOH)]⁺ CF₃COO^‐} were grown by slow evaporation of an aqueous solution at room temperature. The grown crystals were subjected to single crystal X‐ray diffraction, FTIR and UV‐Vis‐NIR spectrum analyses. The UV‐Vis‐NIR spectrum shows that the absorption is very less in the whole of the region from ultraviolet to near IR. The Kurtz‐Perry powder SHG measurement using a Nd:YAG laser of wavelength 1064nm confirms the frequency doubling of the crystal and its powder SHG efficiency was measured as d_eff = 0.96 d_eff (KDP). (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)