Suspension In Nematic Liquid Crystal Research Articles

Control of photoluminescence of CdSe/ZnS quantum dots in a nematic liquid crystal by an electric field

Photoluminescence (PL) spectra of a nematic liquid crystal suspension doped with 10 wt % CdSe/ZnS semiconductor quantum dots (QDs) with a core size of 3.5 nm in a 20-µm thick plane-parallel cell have been investigated. The spectrum of a homogeneously oriented suspension layer exhibits a significant shift of the PL peak by ~83 nm to a wavelength of 676 nm as compared with the QD spectrum in toluene. The application of a dc electric field with a strength of 0.25 V/µm to the cell leads to a slight hypsochromic shift of this peak, the position of which does not change with a further increase in the field strength up to 2 V/µm. The PL intensity changes exponentially and decreases by a factor of two at the field strength of 1 V/µm. The mechanism of PL quenching of QDs in a homogeneously oriented layer of nematic liquid crystal is discussed.

L-Valine and L-Proline - Solid-State IR-LD Spectroscopic Study

Spectral investigation including IR-characteristic bands assignment of the amino acids zwitterions (L)-Valine ((L)-Val) and (L)-Proline ((L)-Pro) was carried out by linear-dichroic infrared (IR-LD) spectroscopy of oriented solid sample as a nematic liquid crystal suspension. The obtained experimental IR-LD results (transition moment directions) were compared with known crystal X-ray data for molecules orientation in the unit cells of the studied compounds, confirming the applicability of the used spectral method for structural determination. The influence of the protonation on the IR-spectroscopic patterns of the both amino acids is discussed.

Dipeptide L -Seryl- L -Methionine—Linear Dichroic IR and Theoretical Characterization

ABSTRACT The dipeptide L -seryl- L -methionine is elucidated structurally by means of solid-state linear dichroic infrared spectroscopy of oriented samples as a colloidal suspension in nematic liquid crystal as a part of our systematic study of OH-containing small peptides. Vibrational analysis supports the experimental data as well. Quantum chemical ab initio calculations are performed in order to obtain the electronic structure and vibrational characteristics of the system studied, where a cisoide-configuration of the C=O–NH amide fragment is predicted.

Structural and IR-Spectroscopic Elucidation of Dipeptide L-Threonyl-LMethionine in Solid State

Dipeptide (L)-threonyl-(L)-methionine (Thr-Met) is characterized structurally by means of a solid-state linear polarized IR- spectroscopy (IR-LD) of oriented samples as a colloidal suspension in nematic liquid crystal and quantum chemical ab initio calculations. Vibrational analysis supports the experimental data as well. The role of intermolecular hydrogen bonding on conformational behavior and spectroscopic properties of the compound, studied in solid state is determined.

Structural elucidation, optical, magnetic and nonlinear optical properties of oxystyryl dyes

Structure, magnetic and optical properties of tetraphenylborate salts of 2,5-[1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]piridinium]-propane and butane are performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV–vis and fluorescence methods, HPLC tandem ESI mess spectrometry (MS/MS), 1H, 13C and 1H– 1H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are used for performing of the structures, optical and nonlinear optical properties of the studied compounds.

1,8-Dinitro-4,5-dihydroxyantraquinone—Solid-state linear-polarized IR-spectroscopy of oriented colloid particles as a suspension in nematic liquid crystal

By means of the linear-polarized IR-spectroscopic (IR-LD) tool to study the oriented solids samples as a colloid suspensions in nematic liquid crystal, the influence of the short contacts and π–π interactions in crystalline phase on IR-bands assignment and profile, i.e., relationship structure-spectroscopic properties, is studied in model system 1,8-dinitro-4,5-dihydroxyantraquinone. For a higher accuracy of the spectroscopic assignments a predetermination of the crystal structure in the same crystalline sample used in IR-LD spectroscopic elucidation is done. Some important aspects of π–π interactions and short contacts in solid phase are described. The advantages of the IR-LD method for an orientation of samples are demonstrated.

Monoclinic and triclinic polymorphs of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene}malononitrile—Solid-state linear-polarized IR-spectroscopy, DFT calculations and vibrational analysis

The linear-dichroic infrared (IR-LD) spectroscopy of oriented solid samples as suspension in nematic liquid crystal have been carried out for experimental IR-band assignment and structural information of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene} malononitrile polymorphs. The last data have been compared with known crystallographic ones, thus determining the validity of IR-LD spectral conclusions as well as its possibility to determination of Davydov's splitting effect and separation of pairs of maxima corresponding to non-equivalent molecules included in the unit cell of given compound. The experimental structural and spectroscopic data in our case are supported with theoretical DFT ones, obtaining both the electronic structure and vibrational frequencies in gas phase.

Spectroscopic and structural elucidation of merocyanine dye 2,5-[1-metyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium]-hexane tetraphenylborate: Aggregation processes

Structural and spectroscopic elucidation of merocyanine dye, 2,5-[1-metyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium]-hexane tetraphenylborate, is performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV–vis and fluorescence methods, HPLC MS/MS tandem and ESI mass spectrometry, 1H, 13C and 1H– 1H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are performed for structural optimization and spectroscopic properties prediction.

Oriented solids as a colloid suspension in nematic liquid crystal – New tool for IR-spectroscopic and structural elucidation of inorganic compounds and glasses

Possibilities of the linear-polarized infrared (IR-LD) spectroscopy of oriented colloid suspensions in nematic liquid crystals, for structural and local structural elucidation for first time are demonstrated of inorganic compounds and glasses. The advantages of the method for tellurite and borate glasses are shown. The IR-band assignment of the typical local structural units in the glasses are proposed by a comparison with the IR-characteristics of appropriate crystalline analogues as α-TeO 2, V 2O 5, MoO 3 · H 2O and its high temperature form. The IR-spectroscopic characteristics of BO 3, BO 4 and boroxol ring are elucidated, using crystalline β-BaB 2O 4, SrB 4O 7, H 3BO 3 and B 2O 3 as model systems, where the structural moieties have been refined by single crystal X-ray diffraction.

The aggregation of the merocyanine dyes, depending of the type of the counterions

Counterions affect on the substructures formation in the case of the merocyanine dye, 1-methyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium] hydrogensquarate both in gas and condense phase. Spectroscopically and structural elucidation of these aggregates have been performed, using solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids as a nematic liquid crystal suspension, UV–vis spectroscopy, HPLC tandem ESI mass spectrometry, 1H and 13C NMR, TGV and DSC. Quantum chemical DFT calculations have been carried out as well. Experimental and theoretical data are compared with analogous ones of corresponding iodide salt of dye studied.

Determination of phenacetin and salophen analgetics in solid binary mixtures with caffeine by infrared linear dichroic and Raman spectroscopy

Quantitative infrared (IR) and Raman spectroscopic approach for determination of phenacetin ( Phen) and salophen ( Salo) in binary solid mixtures with caffeine: phenacetin/caffeine ( System 1) and salophen/caffeine ( System 2) is presented. Absorbance ratios of 746 cm −1 or 721 cm −1 peaks (characteristic for each of determined compounds in the Systems 1 and 2) to 1509 cm −1 and 1616 cm −1 (attributed to Phen and Salo, respectively) were used. The IR spectroscopy gives confidence of 98.9% ( System 1) and 98.3% ( System 2), while the Raman spectroscopic data are with slightly higher confidence of 99.1% for both systems. The limits of detection for the compounds studied were 0.013 and 0.012 mole fraction for IR and Raman methods, respectively. Solid-state linear dichroic infrared (IR-LD) spectral analysis of solid mixtures was carried out with a view to obtaining experimental IR spectroscopic assignment of the characteristic IR bands of both determined compounds. The orientation technique as a nematic liquid crystal suspension was used, combined with the so-called reducing-difference procedure for polarized spectra interpretation. The possibility for obtaining supramolecular stereo structural information for Phen and Salo by comparing spectroscopic and crystallographic data has also been shown. An independent high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis was performed for comparison and validation of vibrational spectroscopy data. Applications to 10 tablets of commercial products APC and Sedalgin are given.

1,1,1‐Trichloro‐3‐(1‐phenethylamino‐ethylidene)‐ pentane‐2,4‐dione—synthesis, spectroscopic, theoretical and structural elucidation

Abstract1,1,1‐Trichloro‐3‐(1‐phenethylamino‐ethylidene)‐pentane‐2,4‐dione is spectroscopically and structurally elucidated by means of linear‐polarized IR spectroscopy (IR‐LD) of oriented solids as a colloidal suspension in nematic liquid crystal. Structural information and IR‐spectroscopic assignment are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6‐311++G** basis set. The geometry is characterized with an inramolecular hydrogen bond of NH…OC with length of 2.526 Å and a NHO angle of 140.5(1)°. The NHC(CH3)CCCO(CH3) fragment is nearly flat with a maximal deviation of total planarity of 10.4°. Copyright © 2007 John Wiley & Sons, Ltd.

Aromatic dipeptides and their salts—Solid-state linear-dichroic infrared (IR-LD) spectral analysis and ab initio calculations

Stereo-structural analysis and IR-bands assignment of the aromatic dipeptides l-tryrosyl- l-phenylalanine ( Tyr-Phe), l-phenylalanyl- l-tyrosine ( Phe-Tyr) and their hydrochloride salts have been carried out by means of IR-LD spectroscopy of oriented as nematic liquid crystal suspension solid samples. The experimental data are compared with known crystallographic ones and theoretical predicted geometries at RHF/ and UHF/6-31G**.

Sol–gel materials doped with 3-(3-(4-(dimethylamino)phenyl)propenoyl)-2 H-chromen-2-one: Spectroscopic and structural elucidation

Conventional and linear-polarized IR-spectroscopic tools based on reducing-difference procedures for non-polarized and polarized IR-spectra interpretation as well as orientation technique of solids (colloidal suspension in nematic liquid crystal) and UV/vis spectroscopy are applied for investigation of new sol–gel materials with potential optical application of doped organic dye 3-(3-(4-(dimethylamino)phenyl)propenoyl)-2 H-chromen-2-one (K2) and Sm 3+ ions. The results show that during aging of the monoliths Sm 3+ forms an unstable complex with K2, [Sm(K2) 2(H 2O) 2](NO 3) 3, which transforms to [Sm(H 2O) 6] 3+ one, typical for gel–Sm 3+ system. Quantum chemical ab initio and DFT calculations are reported with a view to support experimental IR-characteristic bands of the system studied.

Synthesis, spectroscopic and structural elucidation of 3-ethylamino-2-(4-nitro-benzoyl)-but-2-enoic acid phenylamide

3-Ethylamino-2-(4-nitro-benzoyl)-but-2-enoic acid phenylamide is synthesized, isolated, spectroscopical and structural characterized by means of linear-polarized IR-spectroscopy (IR-LD) of oriented solids as a colloidal suspension in nematic liquid crystal. The experimental IR-band assignment and structural information are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6-311++G** basis set. The geometry is characterized by two inramolecular hydrogen bonds of NH…O C with bond lengths of 2.589 and 3.449 Å. The NHO angles are 142.1(3)° and 125.8(4)°, respectively. A transoide configuration of amide fragments is predicted with a torsion NH–C O angle of 150.6°. Phenyl fragments are mutually perpendicular oriented closing an angle of 92.6°.

Influence of intermolecular hydrogen bonding on IR-spectroscopic properties of ( R)-(−)-1-phenylglycinium hydrogen squarate monohydrate in solid-state. IR-LD, Raman spectroscopy and theoretical study

Influence of the intermolecular interactions in solid phase on the overlapped IR-spectroscopic pattern of ( R)-(−)-1-phenylglycinium hydrogen squarate monohydrate is studied experimentally by means of a complex approach, including IR-LD spectroscopy of oriented solid-samples as suspension in nematic liquid crystal, reducing difference procedure for polarized spectra interpretation, deconvolution and curve-fitting procedures. Raman ones completes the IR-spectroscopic data. The experimental results are supported with theoretical ones and the calculated frequencies obtained on UHF/6-311++G ∗∗ level of theory and basis and scaled with a factor of 0.8929 correlated well with experimental observed data, giving a standard deviation of 9 cm −1 for so-called non-characteristic bands.

An Au(III) complex of glycyl- S -serine: a linear polarized IR and 1H- and 13C-NMR investigation

The structure of a mononuclear Au(III) complex of the dipeptide glycyl-S-serine (Gly-Ser) has been predicted using solid-state linear dichroic IR (IR-LD) spectroscopy, based on an orientation technique in a nematic liquid crystal suspension. Results are compared with data from 1H- and 13C-NMR, MS, elemental analysis, thermogravimetry and differential scanning calorimetry. The metal ion is coordinated as a tridentate through NH2, N (from deprotonated amide) and O (COO−) groups to form [Au(C5H9N2O4)Cl], with the fourth position of the square-planar coordination sphere being completed by a Cl− ion.

Structural and spectroscopic analysis of dipeptide l-methionyl-glycine and its hydrochloride

AbstractDipeptide l-methionyl-glycine (Met-Gly) hydrochloride was characterized structurally by means of solid-state linear polarized IR (IR-LD) spectroscopy of oriented samples as colloidal suspension in nematic liquid crystal. Quantum chemical ab initio calculations and vibrational analysis support the experimental data. 1H and 13C nuclear magnetic resonance (NMR) data, mass spectrometry (ESI-MS and FAB-MS) techniques, thermogravimetry (TGV), and differential scanning calorimetry (DSC) method were employed as well. The experimental and theoretical data of hydrochloride salt were compared with analogous data of the neutral dipeptide with the aim to explain the role of intermolecular hydrogen bonding on the conformational behavior and spectroscopic properties of the compound studied.

Mononuclear Au(III)-complexes with tryptophan-containing dipeptides: Synthesis, spectroscopic and structural elucidation

The coordination ability of dipeptides l-tryptophyl- l-phenylalanine (H-Trp-Phe-OH) and l-tyrosyl- l-tryptophan (H-Tyr-Trp-OH) with Au(III) have been elucidated both in solid state and in solution by means of series of methods as UV, 1H and 13C NMR, conventional and linear-polarized IR-spectroscopic tool in solid-state, based on orientation technique as suspension in nematic liquid crystal, FAB-MS, TGV, DSC methods and elemental analysis. The structures of the Au(III)-complexes have been predicted theoretically by DFT calculations at B3LYP level of theory and Lanl2DZ (Au)/6-31+G(3df) (Cl, C, H) basis set. The last data are compared with IR-LD spectroscopic ones giving the experimental evidence of the structures of the complexes studied. The dipeptides interact as tridentate ligands in obtained mononuclear complexes via their –NH 2, deprotonated N −-amide and CO 2 - -groups at molar ratio metal to ligand 1:1. One Cl − ion is joined to the Au(III) as terminal ligand, forming [Au III(LH −1)Cl] species. A near to square-planar flat geometry of the chromophores AuN 2OCl is yielded with maximal deviation of total planarity less than 0.9°.

Solid-state linear-polarized IR-spectroscopic characterization of l-methionine

The IR-spectral characteristic bands assignment in 1700–400 cm −1 IR-spectral region of l-methionine in solid-state has been carried out by means of linear-polarized IR-spectral analysis of oriented solid-samples as a suspension in nematic liquid crystal. The later results are supported by the comparison with the known single crystal X-ray data as far as the presented spectroscopic approach give possibilities not only for obtaining of the experimental IR-bands assignment but a receiving a stereo-structural information.