Suspension In Nematic Liquid Crystal Research Articles

Solid-state linear polarized IR-spectroscopic and theoretical analysis of methioninamide ester amide of squaric acid diethyl ester

Methioninamide ester amide of squaric acid ( 1 ) has been analyzed structurally and IR-spectroscopically by means of ab initio calculations and solid-state linear-polarized IR-spectroscopy (IR-LD) of oriented solid-samples as suspension in nematic liquid crystal. The obtained data are compared with known single crystal X-ray diffraction ones. The experimental IR-spectroscopic bands assignment in solid-state has been reported as well, using reducing-difference procedure for polarized IR-spectra interpretation.

IR-LD spectral and theoretical analysis of l-tyrosinamide hydrochloride monohydrate

The possibilities of IR-LD spectroscopy of oriented solid samples as nematic liquid crystal suspension are used for detailed IR-band assignment of l-tyrosinamide hydrochloride monohydrate. In addition the theoretical ab initio results of protonated l-tyrosinamide on UHF/6-31++G ∗∗ in gas phase are presented.

Solid-state linear-dichroic IR-spectroscopy of isophorone derivatives with potential non-linear optical application

Possibilities of linear-dichroic infrared (IR-LD) spectroscopy based on oriented solid samples as suspension in nematic liquid crystal have been applied for detailed experimental IR-band assignment and structural information of 2-[5,5-dimethyl-3-(2-phenyl-vinil)-cyclohex-2-enylidene]-malononitrile, 2-[5,5-dimethyl-3-[2-(2-methoxyphenyl)vinyl]cyclo-hex-2-enylidene]malononitrile and 2-[3-[2-(2,4-dimethoxyphenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene]malononitrile. The data of last two compounds have been compared with known crystallographic ones, thus determining the validity of conclusions made.

Linear-dichroic infrared spectroscopy—Validation and experimental design of the new orientation technique of solid samples as suspension in nematic liquid crystal

A validation of the developed new orientation method of solid samples as suspension in nematic liquid crystal (NLC), applied in linear-dichroic infrared (IR-LD) spectroscopy has been carried out using a model system dl-isoleucine ( dl-isoleu). Accuracy, precision and the influence of the liquid crystal medium on peak positions and integral absorbances of guest molecules have been presented. Optimization of experimental conditions has been performed as well. An experimental design for quantitative evaluation of the impact of four input factors: the number of scans, the rubbing-out of KBr-pellets, the amount of studied compounds included in the liquid crystal medium and the ratios of Lorentzian to Gaussian peak functions in the curve fitting procedure on the spectroscopic signal at five different frequencies, indicating important specifities of the system has been studied.

Polymorphs of Aspirin – Solid-state IR-LD spectroscopic and quantitative determination in solid mixtures

Solid-state linear-dichroic infrared (IR-LD) spectroscopy, using an orientation technique as a suspension in nematic liquid crystal, has been carried out of Aspirin polymorphs (forms I and II). Reducing-difference procedure for polarized IR-spectra interpretation has been applied for structural analysis of both modifications and the data have been compared with known crystallographic ones. A vibration assignment of forms I and II has been included and on this basis, a quantitative determination by FT-IR spectra for form I in mixtures with second one has been presented, using intensity ratio of 1606 cm −1 peak (characteristic for both forms) to 599 cm −1 one (attributed to form I). The obtained reliability is 99.78%.

Solid‐state IR–LD spectroscopic and theoretical analysis of arginine‐containing peptides

Structural prediction and IR-characteristic bands assignment of arginine-containing tri- and tetrapeptides glycyl-glycyl-arginine (GGArg) and glycyl-glycyl-arginyl-alanine (GGArgAla) have been carried out, using linear-dichroic infrared (IR-LD) spectroscopy of oriented solid-samples in a nematic liquid crystal suspension. Spectroscopic data have been supported with ab initio analysis (Hartree-Fock level of theory and 6-31++G** basis set). Predicted geometry parameters have been compared with known crystallographic ones of similar peptides, indicating a good correlation.

6-O-acetylcodeine and its hydrogensquarate: Linear-dichroic infrared (IR-LD) spectroscopy

IR-LD spectroscopy of oriented solid-samples as a suspension in nematic liquid crystal has been applied for IR-characteristic bands assignment of 6-acetylcodeine and its hydrogensquarate. A stereo-structural prediction of both compounds has been shown as well, comparing with known single crystal X-ray diffraction results of 6-acetylcodeine.

Solid state linear-dichroic infrared (IR-LD) spectroscopic characterization of α-and β-glycine polymorphs

AbstractIR-LD spectroscopic analysis using nematic liquid crystal suspension as a solid-state orientation technique and the reducing-difference procedure for polarized spectra interpretation are applied to the α-and β-polymorphs of glycine. Both structural analysis and detailed IR band assignments were carried out.

Solid state linear-dichroic infrared spectral and theoretical analysis of methionine-containing tripeptides

Stereo structural characterization of methionine-containing tripeptides glycine-glycine-methionine (Gly-Gly-Met) and methionine-glycine-glycine (Met-Gly-Gly) is carried out by means of linear-dichroic infrared spectral analysis of oriented as nematic liquid crystal suspension solid samples. Thus obtained data are compared with theoretical ones received by ab initio calculations (Hartree-Fock level of theory and 6-31G** basis set). An IR-spectral characterization of both tripeptides is included as well.

Solid-state linear-dichroic infrared spectroscopic analysis of the dipeptide S-Phe–S-Phe and its mononuclear Au(III) complex

Interaction between the S-Phe–S-Phe dipeptide (PP) and Au(III) leads to the formation of a yellow complex, [Au(PP)Cl3]Cl (1), with monodentate coordination of the dipeptide with Au(III) through one O atom of the COO− group. Three Cl− anions bond to the metal center as terminal ligands. The structure of 1 was obtained by comparative solid-state linear-dichroic infrared (LD-IR) spectroscopic analysis of a solid sample and the pure dipeptide S-Phe–S-Phe, both oriented in a nematic liquid crystal suspension.

Monoclinic and orthorhombic polymorphs of paracetamol—solid state linear dichroic infrared spectral analysis

Solid-state linear dichroic infrared (IR-LD) spectral analysis of both monoclinic (form I) and orthorhombic (form II) polymorphs of paracetamol was carried out using an orientation technique as a nematic liquid crystal suspension. The so-called reducing-difference procedure for polarized spectra interpretation was applied and the obtained supramolecular stereo structural data of both modifications were compared with known crystallographic ones. A detailed vibration assignment of characteristic frequencies of forms I and II was also applied. A quantitative FT-IR spectral approach for monoclinic form determination in mixtures by the intensity ratio of 1610 cm −1 peak (characteristic for both forms) to 1666 cm −1 one (attributed to orthorhombic modification) was presented, as well.

Solid state linear dichroic infrared spectral analysis of benzimidazoles and their N 1-protonated salts

A stereo structural characterization of 2,5,6-thrimethylbenzimidazole (MBIZ) and 2-amino-benzimidaziole (2-NH 2-BI) and their N 1 protonation salts was carried out using a polarized solid state linear dichroic infrared spectral (IR-LD) analysis in nematic liquid crystal suspension. All experimental predicted structures were compared with the theoretical ones, obtained by ab initio calculations. The C s to C 2 v * symmetry transformation as a result of protonation processes, with a view of its reflection on the infrared spectral characteristics was described.