The effect of solvent ratio and water on the growth of C60 nanowhiskers

The growth of C₆₀ nanowhiskers (C₆₀NWs) prepared by a modified liquid–liquid interfacial precipitation method is investigated, focusing on the effect of solvent ratio and water content in the C₆₀–toluene–isopropyl alcohol (IPA) solution system. The precipitation of C₆₀NWs was markedly influenced by the solvent ratio of toluene to IPA, and the C₆₀NWs were found to grow longer above a critical diameter (D_c), which depends on the solvent ratio. The addition of a small amount of H₂O to the C₆₀–toluene–IPA solution promoted the growth of C₆₀NWs. This catalytic effect of water on the growth of C₆₀NWs was confirmed also by the experiment using heavy water (D₂O) and by the decrease of growth activation energy of C₆₀NWs with increase of H₂O content in the C₆₀–toluene–IPA solution.     

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)     

Some properties of aqueous solutions of α-NiSO4 · 6H2O

The concentration dependences of the properties of solutions of ??-NiSO₄ · 6H₂O (mineral retgersite) in H₂O and 20% H₂SO₄ have been measured in a wide range of concentrations (up to ??20 solvent molecules per dissolved-salt molecule). It is shown that the solution density, the light absorption coefficient at a wavelength of 394 nm, and the intensity of the Raman scattering peak characteristic of the sulfate ion depend linearly on the bulk salt concentration in the solutions. No shift of the Raman peak as a result of a change in the concentration was observed. These facts indicate that the type of dissolved particles and the character of interactions between them and with the solvent remain the same with an increase in the salt concentration. The data in the literature on the formation of ion pairs in retgersite solutions are discussed.     

Substituent and solvent effects on UV‐visible absorption spectra of liquid crystalline disubstituted biphenylcyclohexane derivatives – a computational approach

A computational approach has been carried out on liquid crystalline disubstituted biphenylcyclohexanes (BCHs) of general formula R‐C₆H₁₀‐C₆H₄‐C₆H₄‐X with R: C₃H₇; X: H (BCH30) and R: C₅H₁₁; X: CN (BCH5CN) using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate and analyze the spectral shifts, and absorbance measurements in UV‐visible range of the systems. The electronic transitions, absorption wavelength, HOMO (Highest Occupied Molecular Orbital), and LUMO (Lowest Unoccupied Molecular Orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters has also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Further, these absorption spectra will provide valuable data base for future computational studies, and the other experimental investigations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Luminescent properties of europium (III) acetate monohydrate in synthetic opal pores

Abstract

This paper presents a systematic photoluminescence spectra study of the (111) growth surface of an opal photonic crystal whose pores were filled with salt Europium (III) acetate monohydrate (C₆H₉EuO₆×H₂O). Ultraviolet excitation was provided by semiconductor laser operating at wavelengths of 405?nm. Emission spectra were measured both for free-form salt samples and for salt in opal pores annealed at various temperatures up to 1000?°C. The influence of changes in the coordination environment of europium ions on the luminescence spectra in the process of dehydration and salt decomposition up to Eu₂O₃ is established. Differences in the spectra of salt in the pores of opal were revealed compared with the spectra in the free state.     

Crystal structures of S-benzylisothiouronium hexachloroplatinate (IV) and tetrachloroaurate (III)

The crystal structures of two S-benzylisothiouronium salts, [C₆H₅. CH₂. S. C (NH₂)₂ ]₂ PtCl₆ and C₆H₅. CH₂ S. C (NH₂)₂AuCl₄, have been determined from three-dimensional X-ray data obtained from integrated Weissenberg photographs. Both structures were refined by full-matrix least squares toR = 0.11. The packing in both structures occurs in alternating sheets representing polar and apolar regions. The ion pairs are held together by ionic forces and a large number of hydrogen bonds.     

Structures and Non-linear Optical Properties of Multi-Sulfur π-Conjugated Compounds 4,5-Vinylenedithio-1,3-dithiole-2-thione (C5H2S5) and 4,5-Vinylenedithio-1,3-dithiole-2-one (C5H2OS4)

Abstract Both the title multi-sulfur molecules C₅H₂S₅ (1) and C₅H₂OS₄ (2) have a chair conformation, while molecule 1 has a higher degree of π-conjugation. Both the crystals are characterized by short S···S intermolecular contacts and by face-to-face column-like packing style, but crystal 1 has been more stabilized which may be the result of its stronger π–π intermolecular interactions. Compound 1 crystallizes in non-centrosymmetric polar space group Pmn2₁ with a = 10.6826(17), b = 9.3633(11), c = 4.0764(6) ?, V = 407.74(10) ?³, and Z = 2. The molecular dipole moment of 1 is ±62.5(1)° away from the macro-polarization direction along the c-axis. Consequently, the crystalline powder of crystal 1 exhibit a second harmonic generating (SHG) intensity 0.5 time strong as that of urea standard powder crystals when irradiated by a 1,080 nm of Nd:YAP laser beam. Compound 2 shows no SHG effect because it crystallizes in centrosymmtric space group Pbca with a = 11.4208(8), b = 7.8843(9), c = 33.587(3) ?, V = 3024.3(5) ?³, and Z = 16. Index Abstract Structures and Non-linear Optical Properties of Multi-Sulfur π-Conjugated Compounds 4,5-Vinylenedithio-1,3-dithiole-2-thione (C₅H₂S₅) and 4,5-Vinylenedithio-1,3-dithiole-2-one (C₅H₂OS₄) Gang Xue, Qi Fang,* Wen-Tao Yu, Xia Chen, and Hong Lei Compound C₅H₂S₅ crystallizes in the polar space group Pmn2₁ and its crystalline powder exhibits a second harmonic generating (SHG) intensity 0.5 times that of urea standard (1080 nm → 540 nm), while the similar compound C₅H₂OS₄ has no SHG effect because of its centrosymmetric space group Pbca.      

Crystal and molecular structure of di-μ-bromobromopentakis(benzimidazole)dicopper(II) monobromide tetrahydrate [Cu2Br3(C7H6N2)5]Br·4H2O

A new complex compound. [Cu₂Br₃(C₇H₆N₂)₅]Br·4H₂O, has been synthesized and its crystal structure investigated by single-crystal X-ray methods. The crystals are isostructural with those of the [Cu₂Cl₃(C₇H₆N₂)₅]Cl·4H₂O salt. They are orthorombic, space group Pnma with 4 formula units in a cell of dimensions:a+19.923(1),b+17.555(2),c+12.0523(4)Å. The structure was refined by full-matrix least-squares to giveR+0.047 andR _w+0.053 for 3569 intensities above 3σ(I). As in the chloride compound, the complex cation consists of pairs of distorted trigonal bipyramidal Cu(II) centers which share an edge by two equatorial bromide ions. The Cu...Cu nonbonding distance in the complex in 3.4894(7)Å. The two Cu?Br?Cu bridges are not equivalent and their geometry is slightly different from that in the chloride complex. Comparison of the investigated structure to other binulear bis(μ-halide) bridged copper(II) complexes of similar structure has been made.     

Crystal structure of the piperazine-1,4-diium (DL-)hydrogen malate (1:2)

The crystalline salt of piperazine-1,4-diium (DL-)hydrogen malate (1:2), (C₄H₁₂N₂)²⁺ (C₄H₅O₅)₂^–, has been prepared and characterized by X-ray crystallography. The title salt crystallizes in monoclinic space group P2₁/n with a = 7.073(1), b = 14.180(2), c = 7.526(1) Å, = 94.66(1), V = 752.33(18) ų and Z = 2. Results indicate that the title salt exists as a racemic compound but a conglomerate. In the structure, axial and equatorial hydrogen atoms of piperiaine-1,4-diium are all involved in different bifurcated hydrogen bonds. The integral structure, formed by the hard hydrogen bonds of N–HsO and O–HsO, is stabilized further by soft hydrogen bond of C–HsO.     

Crystal structure of radical cation salt (BEDT-TTF)4(GaCl4)2 · C6H5CH3

A new radical cation salt based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with the tetrahedral anion GaCl ₄ ^? , namely, (BEDT-TTF)₄(GaCl₄)₂ · C₆H₅CH₃, has been synthesized. The crystal structure of this salt is determined by X-ray diffraction analysis [a = 31.757(2) Å, b = 6.8063(3) Å, c = 34.879(2) Å, β = 90.453(4)°, V = 7538.8(7) ų, space group I2/c, and Z = 4]. In the structure, the radical cation layers alternate with the anion layers along the c-axis. The anion layers consist of the GaCl ₄ ^? tetrahedra and solvent molecules. The packing of BEDT-TTF molecules in the radical cation layer differs from that in the structure of the known salt (BEDT-TTF)₂GaCl₄, even though both compounds exhibit semiconductor properties.     

Crystal growth,crystal structure and pyroelectric properties of the polar hexagonal antimony tartrates MII[Sb2(C4H2O6)2]·2H2O (MII = Ca,Sr, Pb)

Single crystal growth of lead antimony tartrate dihydrate, Pb[Sb₂((+)C₄H₂O₆)₂]·2H₂O, was successfully performed. The determined polar hexagonal crystal structure is isomorphous to the corresponding calcium and strontium antimony tartrates dihydrates. New results of crystal growth and the redetermination of the crystal structures of the nonlinear optical crystal Sr[Sb₂((+)C₄H₂O₆)₂]·2H₂O and its calcium analogue are reported, together with investigations of the thermal stability and the pyroelectric properties of these polar crystals.

     

Role of n-alkoxy terminal end groups on mesomorphism

A homologous series RO-C₆H₄-CH:CH-COO-C₆H₄-CO-CH:CH-C₆H₄-OC₆H₁₃ (n) of novel liquid crystals (LC) has been synthesized and studied with a view to understanding and establishing the relation between molecular structure of a substance and the LC properties or behavior of thermotropic LC materials. Novel series consist of 11 homologues. C₁ and C₂ homologue derivatives are non-LCs and the rest of homologues (C₃ to C₁₆) are nematogenic without exhibition of smectic property. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curve Cr-N/I of a phase diagram behaved in normal manner. N/I transition curve partly deviated at C₆ and C₁₀ homologues from normal descending behavior, and exhibited very narrow and sharp odd-even effects. Textures of nematic phase are threaded or Schlieren. Thermal, analytical, and spectral data confirmed the molecular structures of novel chalconyl ester derivatives. Thermal stability for nematic is 95.77°C and the upper and lower mesophase lengths vary from 35 to 16°C at C₅ and C₈ homologues respectively. Group efficiency order derived for nematic on the basis thermal stability is -OC₁₀H₂₁ (n) > -OC₈H₁₇(n) > -OC₆H₁₃(n).     

The Double Salts Cd(C6H5COO)2 · CdCl2 and Cd(C6H5COO)2 · CdBr2

The systems Cd(C₆H₅COO)₂ CdCl₂ H₂O and Cd(C₆H₅COO) ₂ CdBr₂ H₂O have been studied at 25 °C. Formation of the double salts Cd(C₆H₅COO)₂ · CdCl₂ and Cd(C₆H₅COO)₂ · CdBr₂(1:1:0) has been established and their chemical individuality has been confirmed by chemical, X-ray, and DT-analyses. Proceeding from data on the structure of Cd(C₆H₅COO)₂ · 2 H₂O and the composition of the 1:1:0 double salts as well as using Pauling's rules for the most probable spacial disposition of the ions, the crystal structure type of the double salts obtained are predicted.     

Study of the molecular structure on liquid crystal properties with reference to thermotropic azoester derivatives

An azoester homologues series: RO?C₆H₄?COO?C₁₀H₆?N?N?C₆H₄?OC₅H₁₁ (para) as novel liquid crystalline (LC) materials has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties with reference to laterally substituted phenyl ring and terminally substituted ?OR and ?OC₅H₁₁ (n) groups; including ?COO? and ?N?N? central bridges. Novel homologous series of thermotropic LC variety consists of thirteen homologues (C₁ to C₁₈). C₁ to C₃ derivatives are nonliquid crystal (NLC); C₄ is only nematogenic and C₅ to C₁₈ are smectogenic plus nematogenic. All the mesogenic homologues (C₄ to C₁₈) are enantiotropically nematogenic or/and smectogenic as confirmed by a polarizing optical microscopy (POM) equipped with a heating stage. Transition curves Cr-I/M, Sm?N, and N?I behaved in normal manner in a phase diagram. Odd-even effect is exhibited by Sm?N and N?I transition curves. Analytical, spectral and thermal data confirms the molecular structure of novel homologues. Novel azoester series is predominantly nematogenic and partly smectogenic whose mesogenic temperatures ranges minimum to maximum from 79.0°C to 162.0°C. Thermal stability for smectic and nematic are 128.2°C and 147.7 °C, respectively. Thus, it is a middle ordered melting type of novel series whose total mesophaselength ranges from 20.0°C to 56.0°C. Textures of nematic are threaded or schlieren and that of smectic are smectic A or C.     

Mesomorphism dependence of a terminal or lateral alkoxy group

A novel homologous series of thermotropic mesomorphs has been synthesized and studied with a view to understanding and establishing the effect of molecular structure on mesomorphic properties with reference to rigidity and flexibility of the homologues series: RO-C₆H₄-CH?CH-CO-C₆H₄-OC₁₈H₃₇(n). The novel homologous series comprises 13 novel homologues (C₁ to C₁₈), from which 11 homologues are enantiotropically mesogenic (C₃ to C₁₈). Smectogenic mesophase commences from C₇ homologue, and nematogenic mesophase is exhibited by C₃ to C₁₈ homologues in enantiotropic manner. Thus, C₇ to C₁₈ homologues are enantiotropically smectogenic plus nematogenic. Textures of smectic phase are of the type A or C, and that of nematic phase are threaded or Schlieren as confirmed through an optical polarizing microscope equipped with a heating stage. Transition curve of a phase diagram behaved in a normal manner except N-I transition curve, which shows minor deviating trend (C₁₂ to C₁₈) from expected normal behavior. An odd-even effect is exhibited by N-I and Sm-N transition curves. Analytical, spectral, and thermal data confirm the molecular structures of novel homologues. Thermal stabilities for smectic and nematic are 52.7°C and 66.6°C, respectively, whose total mesophase lengths range from 12.0°C to 28.0°C. Thus, novel series of chalcones is a low melting series whose mesogenic transition temperatures vary between 38.0 and 86.0°C.     

Mesomorphism dependence on halogenated chalconyl esters in terms of molecular flexibility/rigidity

Vinyl carboxy central group containing a novel chalconyl ester homologous series: RO.C₆H₄.CH ? CH.COO.C₆H₄.CH ? CH.CO.C₆H₄.I (para) have been synthesized and studied with a view to understand and establish the relation between thermotropic liquid crystalline (LC) behaviors and the molecular structure. Novel chalconyl ester homologous series consists of thirteen homologs (C₁–C₁₈). C₁–C₃ homologs are nonmesogenic, C₄ homolog is enantiotropic nematogenic and the rest of the homologs (C₅–C₁₈) are enantiotropically smectogenic plus nematogenic. Phase transition temperatures and textures of LC phase were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Cr-M/I, Sm-N, N-I transition curves in a phase diagram behaved in normal manner. Sm-N and N-I transition curves exhibited odd-even effect from C₄–C₁₀ or nearby C₁₀ homolog. Textures of nematic phase are threaded or Schlieren and that of the smectic phase are of the type smectic A or C. Analytical and spectral data confirms the molecular structure of homologs. Thermal stabilities for smectic and nematic mesophases are 155.0 and 180.7, respectively, and their corresponding mesophaselengths are varied from minimum to maximum at 17.0°C–39.0°C as well as 15.0°C–30.0°C. Thus, it is middle ordered melting type series. The group efficiency orders derived on the basis of smectic and nematic thermal stabilities are as under: Sm: -C₆H₄.I > -C₆H₄.Cl > -C₄H₃S and N:- C₆H₄.I > -C₆H₄.Cl > -C₄H₃S from comparative study of structurally similar analogous series     

AES and FTIR characterization of sol–gel alumina films

In this work we obtained sol–gel alumina coatings on AISI 304 stainless steel substrates. Alumina sols were prepared by using aluminum isopropoxide (AI) as precursor, acetic acid (HOAc) as catalyst, ethanol (C₂H₅OH) or isopropanol (C₃H₈O) as solvent, and water. The as-prepared solutions were deposited on stainless steel substrates by means of the dip-coating technique. The obtained composites were characterized by Fourier transform infrared spectroscopy (FTIR) and Auger electron spectroscopy (AES). We observed that the concentration of AlO type bonds in the obtained alumina coatings depends on the solvent type used, temperature and peptization state of the sol, withdrawal speed, and number of dipping cycles. AES experiments showed that the interface formed between the alumina coating and substrate surface is in general formed by several layers of different chemical compositions.     

The salt of l‐prolinium picrate

A crystalline salt of prolinium picrate, C₁₁H₁₂N₄O₉, has been prepared and characterized by X‐ray crystallography. The salt crystallizes in orthorhombic space group P2₁2₁2₁ with a = 6.325(1)Å, b = 9.269(1)Å, c = 24.379(4)Å, V = 1429.4(5)ų, Z = 4. In the title salt, the picrate and prolinium ion are held by different bifurcated hydrogen bonds of N‐H—O type, and stablized by bifurcated hydrogen bonds of CH—O type. There exists a competion between hydrogen bonds and π–π stacking in determining the title crystal. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

Study of mesomorphism dependence on molecular flexibility of an azoester series containing a napthyl unit

A novel azoester homologous series of liquid crystalline (LC) compounds: RO?C₆H₄-COO?C₁₀H₆-N:N-C₆H₄?OC₄H₉(n) without lateral substitution has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on thermotropic LC substances with reference to tailed-end group. The novel homologous series consists of 13 homologs (C₁ to C₁₈) whose nematogenic and smectogenic mesomorphism commences enantiotropically from C₆ and C₁₂ members of the series, respectively. The C₁₂–C₁₈ homologs are smectogenic and C₆–C₁₈ are nematogenic, of which C₁₂–C₁₈ homologs are smectogenic plus nematogenic. The C₁–C₅ homologs are nonmesogenic. Transition temperatures and the textures of the homologs were determined and identified by an optical polarizing microscope (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren and that of the smectic phase are of the type A or C. Transition curves Cr-M/I, Sm-N and N-I of a phase diagram behaved in normal manner except N-I transition temperature of C₁₀ homolog which deviated by 9°C–10°C from normal behavior. N-I transition curve exhibited odd-even effect. Analytical, spectral, and thermal data confirms the molecular structures of homologs. Thermal stability for smectic and nematic are 115.5°C and 138.5°C, respectively whose corresponding mesophaselengths are varied from 10.0°C to 16.0°C and 13.0°C to 24.0°C, respectively. Group efficiency order for smectic and nematic are derived from comparative study of structurally similar analogous series; as smectic: ?OC₄H₉ (n) > ?CH₃ > ?H; Nematic: ?H > ?OC₄H₉ (n) > ?CH₃