State of water in various environments: Aliphatic ketones. MIR/NIR spectroscopic, dielectric and theoretical studies.

This work provides new insight into the state of water in a series of aliphatic ketones. For our studies, we selected nine aliphatic ketones of different size and structure to examine the effect of various structural motifs on behavior of water in the mixtures. Our results reveal that conformational flexibility of aliphatic chains in the linear ketones allows for effective shielding of the carbonyl group, and this flexibility is the main reason for poor solubility of water.

Anharmonicity and Spectra-Structure Correlations in MIR and NIR Spectra of Crystalline Menadione (Vitamin K).

Mid-infrared (MIR) and near-infrared (NIR) spectra of crystalline menadione (vitamin K) were measured and analyzed with aid of quantum chemical calculations. The calculations were carried out using the harmonic approach for the periodic model of crystal lattice and the anharmonic DVPT2 calculations applied for the single molecule model. The theoretical spectra accurately reconstructed the experimental ones permitting for reliable assignment of the MIR and NIR bands.

Solvent Effect on Assembling and Interactions in Solutions of Phenol: Infrared Spectroscopic and Density Functional Theory Study.

This work provides new insight into assembling of phenol in various solvents and competition between different kinds of interactions. To examine both weak and strong interactions, we selected a series of non-aromatic and aromatic solvents. Infrared spectra were measured at low (0.

Solvent effect on the competition between weak and strong interactions in phenol solutions studied by near-infrared spectroscopy and DFT calculations.

Near-infrared (NIR) spectra of phenol in a series of non-aromatic and aromatic solvents were recorded to study the competition between various types of solute-solute and solute-solvent interactions. Depending on the phenol concentration, the free OH and OH involved in the OH⋯OH interactions in the dimers and higher associates are present in cyclohexane solutions. On the other hand, free OH does not appear in Cl-containing solvents since at a low phenol content the OH groups participate in the OH⋯Cl interactions.

How much anharmonicity is in vibrational spectra of CHI and CDI?

This work presents new experimental and theoretical insights on vibrational spectra of CHI and CDI in the liquid phase. For the first time, we provided the contributions from different vibrational modes to mid-infrared (MIR) and near-infrared (NIR) spectra and estimated the extent of anharmonicity in the MIR region. Direct comparison of the intensities from ATR-IR and NIR transmission spectra was possible due to normalization of ATR-IR spectra.

Two-Dimensional Correlation Spectroscopy: The Power of Power Spectra.

Power spectra are a powerful tool provided by two-dimensional correlation analysis. However, this tool is seldom used in practice. This work shows selected examples of using of the power spectra for the study of various kinds of samples with the aim to promote more common use of this tool.

Author Correction: Simulated NIR spectra as sensitive markers of the structure and interactions in nucleobases.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Simulated NIR spectra as sensitive markers of the structure and interactions in nucleobases.

Near-infrared (near-IR; NIR) spectroscopy is continuously advancing in biophysical and biochemical fields of investigation. For instance, recent progresses in NIR hyperspectral imaging of biological systems may be noted. However, interpretation of NIR bands for biological samples is difficult and creates a considerable barrier in exploring the full potential of NIR spectroscopy in bioscience.

IR Spectra of Crystalline Nucleobases: Combination of Periodic Harmonic Calculations with Anharmonic Corrections Based on Finite Models.

This work reports a theoretical study of infrared (IR) spectra of four nucleobases (adenine, cytosine, guanine, and thymine) in the crystalline state. The effects responsible for the fine spectral features were revealed, and the nonfundamental bands significantly contributing to the IR fingerprint region were successfully reproduced. Additionally, we compared the fundamental bands simulated for periodic models in harmonic approximation with the results obtained for finite models in anharmonic approximation.

Spectra-Structure Correlations in Isotopomers of Ethanol (CXCXOX; X = H, D): Combined Near-Infrared and Anharmonic Computational Study.

The effect of isotopic substitution on near-infrared (NIR) spectra has not been studied in detail. With an exception of few major bands, it is difficult to follow the spectral changes due to complexity of NIR spectra. Recent progress in anharmonic quantum mechanical calculations allows for accurate reconstruction of NIR spectra.

Overtones of νC≡N Vibration as a Probe of Structure of Liquid CHCN, CDCN, and CClCN: Combined Infrared, Near-Infrared, and Raman Spectroscopic Studies with Anharmonic Density Functional Theory Calculations.

The νCN band (νC≡N) is a sensitive probe of the state of molecules with nitrile groups. Hence, physicochemical properties of acetonitrile and its derivatives have been frequently investigated by means of vibrational (IR and Raman) spectroscopy. Near-infrared (NIR) spectroscopy combined with high-level quantum mechanical calculations offers deeper physical insight into the structure of liquid nitriles not available from the fundamental region.

Spectra-structure correlations in NIR region: Spectroscopic and anharmonic DFT study of n-hexanol, cyclohexanol and phenol.

We investigated near-infrared (7500-4000 cm) spectra of n-hexanol, cyclohexanol and phenol in CCl (0.2 M) by using anharmonic quantum calculations. These molecules represent three major kinds of alcohols; linear and cyclic aliphatic, and aromatic ones.

Microheterogeneity in binary mixtures of water with CHOH and CDOH: ATR-IR spectroscopic, chemometric and DFT studies.

Here we report ATR-IR spectroscopic study on the separation at a molecular level (microheterogeneity) and the degree of deviation of HO/CHOH and HO/CDOH mixtures from the ideal mixture. Of particular interest is the effect of isotopic substitution in methyl group on molecular structure and interactions in both mixtures. To obtain comprehensive information from the multivariate data we applied the excess molar absorptivity spectra together with two-dimensional correlation analysis (2DCOS) and chemometric methods.

The Effect of Chain Length on Mid-Infrared and Near-Infrared Spectra of Aliphatic 1-Alcohols.

Effect of the chain length on mid-infrared (MIR) and near-infrared (NIR) spectra of aliphatic 1-alcohols from methanol to 1-decanol was examined in detail. Of particular interest were the spectra-structure correlations in the NIR region and the correlation between MIR and NIR spectra of 1-alcohols. An application of two-dimensional correlation analysis (2D-COS) and chemometric methods provided comprehensive information on spectral changes in the data set.

Spectroscopic and Quantum Mechanical Calculation Study of the Effect of Isotopic Substitution on NIR Spectra of Methanol.

In this work, we studied methanol and its deuterated derivatives (CHOH, CHOD, CDOH, CDOD) by NIR spectroscopy and anharmonic quantum chemical calculations. Vibrational bands corresponding to up to three quanta transitions (first and second overtones, binary and ternary combination modes) were predicted by the use of the VPT2 route. The accuracy of prediction of NIR modes was evaluated through density functional theory (DFT) with selected density functionals and basis sets.

Microheterogeneity in CHOH/CDOH mixture.

Recently, we demonstrated the presence of microheterogeneity in binary mixtures of unlike alcohols. [RSC Adv. 2016, 6, 37195-37202] The aim of this work was examination if this phenomenon occurs also in the mixture of very similar alcohols like CHOH and CDOH.

MIR and NIR group spectra of n-alkanes and 1-chloroalkanes.

Numerous attempts were undertaken to resolve the absorption originating from different parts of alkanes. The separation of the contributions from the terminal and midchain methylene units was observed only in the spectra of solid alkanes at low temperatures. On the other hand, for liquid alkanes this effect was not reported as yet.

Resolution enhancement in second-derivative spectra.

Derivative spectroscopy is a powerful tool for the resolution enhancement in infrared, near-infrared, Raman, ultraviolet-visible, nuclear magnetic resonance, electron paramagnetic resonance, and fluorescence spectroscopy. Despite its great significance in analytical chemistry, not all aspects of the applications of this method have been explored as yet. This is the first systematic study of the parameters that influence the resolution enhancement in the second derivative spectra.

Combined IR/NIR and density functional theory calculations analysis of the solvent effects on frequencies and intensities of the fundamental and overtones of the C ═ O stretching vibrations of acetone and 2-hexanone.

Vibrational overtone studies primarily focus on X-H stretching overtone transitions, where X is an atom like C, O, N, or S. In contrast, the studies on the C ═ O stretching overtones are very scattered. To advance the research in this field, we measured the fundamental, first, and second overtones of the C ═ O stretching vibration of acetone and 2-hexanone in n-hexane, CCl4, and CHCl3, as well as in the vapor phase using FT-IR/FT-NIR spectroscopy.

Molecular structure and hydrogen bonding in pure liquid ethylene glycol and ethylene glycol-water mixtures studied using NIR spectroscopy.

The molecular structure and hydrogen bonding of ethylene glycol (EG) and EG-water mixtures in the liquid phase were studied by using near-infrared (NIR) spectroscopy. The spectra were evaluated using a two-dimensional (2D) correlation approach, moving-window 2D correlation analysis and chemometric methods. The minor changes for the CH stretching bands indicate that the structures of pure liquid EG and EG-water mixtures are determined by the intermolecular hydrogen bonding through the OH groups.

FT-IR and two-dimensional correlation analysis of the liquid crystalline phase transitions in the 4-Bromobenzylidene-4'-alkyloxyanilines.

The FT-IR spectra of the 4-bromobenzylidene-4'-alkyloxyanilines (nBBAA, for n = 4-12) were studied as a function of temperature. The molten state of the alkyloxy chain in smectic B (SmB), smectic A (SmA), and isotropic phases was analyzed. Generalized two-dimensional (2D) correlation spectroscopy has been applied to study changes in the conformational structure and specific interactions of molecules at phase transition in homologous series of nBBAA.

Determination of relative rate of spectral events by novel modification of two-dimensional correlation spectroscopy.

Sign of two-dimensional (2D) correlation peaks provides information on sequence of spectral events. This information is related to molecular mechanism of changes in a given system. Recently, few papers addressing the problems with interpretation of the sign of 2D correlation peaks have been published.

Molecular structure and hydrogen bonding of 2-aminoethanol, 1-amino-2-propanol, 3-amino-1-propanol, and binary mixtures with water studied by Fourier transform near-infrared spectroscopy and density functional theory calculations.

The effect of temperature and water content on the molecular structure and hydrogen bonding of 2-aminoethanol (2AE), 1-amino-2-propanol (2AP), and 3-amino-1-propanol (3AP) has been examined by Fourier transform near-infrared (FT-NIR) spectroscopy. The experimental spectra were analyzed using the two-dimensional (2D) correlation approach and chemometrics methods. Interpretation of the spectra was guided by density functional theory (DFT) calculations.

Two-dimensional attenuated total reflection infrared and near-infrared correlation study of the structure of butyl alcohol/water mixtures.

The effect of temperature on attenuated total reflection infrared (ATR-IR) and near-infrared (NIR) transmission spectra of pure butan-1-ol, butan-2-ol, 2-methyl-propan-1-ol, 2-methyl-propan-2-ol, and mixtures with a small water content (X(H2O) View Article and Find Full Text PDF