: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

We provide a simple explanation for X-H bond contraction and the associated blue shift and decrease of intensity in IR spectrum of the so-called improper hydrogen bonds This explanation organizes hydrogen bonds (HBs) with a seemingly random relationship between the X-H bond length (and IR frequency and its intensity) to its interaction energy The factors which affect the X-H bond in all X-H [midline ellipsis] Y HBs can be divided into two parts: (a) The electron affinity of X causes a net gain of electron density at the X-H bond region in the presence of Y and encourages an X-H bond contraction (b) The well understood attractive interaction between the positive H and electron rich Y forces an X-H bond elongation For electron rich, highly polar X-H bonds (proper HB donors) the latter almost always dominates and results in X-H bond elongation, whereas for less polar, electron poor X-H bonds (pro-improper HB donors) the effect of the former is noticeable if Y is not a very strong HB acceptor Although both the above factors increase with increasing HB acceptor ability of Y, the shortening effect dominates over a range of Ys for suitable pro-improper X-Hs resulting in a surprising trend of decreasing X-H bond length with increasing HB acceptor ability The observed frequency and intensity variations follow naturally The possibility of HBs which do not show any IR frequency change in the X-H stretching mode also directly follows from this explanation

Red-, blue-, or no-shift in hydrogen bonds: a unified explanation.

Ordinary differential equations of the first order linear differential equations complex numbers and linear algebra simultaneous linear differential equations numerical methods the descriptive theory of nonlinear differential equations mechanical systems and electric circuits Fourier series Fourier integrals and Fourier transforms the Laplace transformation partial differential equations Bessel functions and Legendre polynomials applications and further properties of matrices vector analysis the calculus of variations analytic functions of a complex variable infinite series in the complex plane the theory of residues conformal mapping.

Advanced Engineering Mathematics. By C. R. Wylie. Pp. xiv, 813. 1966. (McGraw-Hill.)

Pancě Naumov,*,† Stanislav Chizhik,‡,§ Manas K. Panda,† Naba K. Nath,† and Elena Boldyreva*,‡,§ †New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates ‡Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, ul. Kutateladze, 18, Novosibirsk 630128, Russia Novosibirsk State University, ul. Pirogova, 2, Novosibirsk 630090, Russia

Mechanically Responsive Molecular Crystals

Hydrophobic hydration is considered to have a key role in biological processes ranging from membrane formation to protein folding and ligand binding. Historically, hydrophobic hydration shells were thought to resemble solid clathrate hydrates, with solutes surrounded by polyhedral cages composed of tetrahedrally hydrogen-bonded water molecules. But more recent experimental and theoretical studies have challenged this view and emphasized the importance of the length scales involved. Here we report combined polarized, isotopic and temperature-dependent Raman scattering measurements with multivariate curve resolution (Raman-MCR) that explore hydrophobic hydration by mapping the vibrational spectroscopic features arising from the hydrophobic hydration shells of linear alcohols ranging from methanol to heptanol. Our data, covering the entire 0-100 °C temperature range, show clear evidence that at low temperatures the hydration shells have a hydrophobically enhanced water structure with greater tetrahedral order and fewer weak hydrogen bonds than the surrounding bulk water. This structure disappears with increasing temperature and is then, for hydrophobic chains longer than ~1 nm, replaced by a more disordered structure with weaker hydrogen bonds than bulk water. These observations support our current understanding of hydrophobic hydration, including the thermally induced water structural transformation that is suggestive of the hydrophobic crossover predicted to occur at lengths of ~1 nm (refs 5, 9, 10, 14).

Water structural transformation at molecular hydrophobic interfaces

The influence of inherent pseudo Jahn-Teller instability on the stretching vibrations of water molecules in the isomorphous metal(II) saccharinate hexahydrates

The main aim of this topical review is to provide a concise but yet complete overview of the research that has been done in the field of low-lying crystalline water bending vibrations. Both theoretical and experimental work in the field is reviewed, and the most important dilemmas and obstacles hampering a direct explanation of the phenomenon are outlined. The present status in this field is also overviewed and clarified. While this topical review has mostly been focused on crystalline water molecules in crystalline hydrates and their vibrational properties, also some other interest-ing and exciting systems that have recently attracted the attention of the scientific community are covered. These in-cluded water absorbed on surfaces as well as water at the air-water interfaces.

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Low bending vibrations of crystalline water molecules: an ongoing quest or a final word – topical review – a tribute to academician bojan šoptrajanov

Vibrational states of tetrahedral molecular species in electric fields. A theoretical model for quantitative description of the latent symmetry effects in vibrational spectroscopy of matrix isolated tetrahedral species.

The phonon-assisted proton transfer between hydrazinium cations in (N2H5)2HMF6·2H2O (M∈{Ga, Al, Fe}) type compounds. FT IR and quantum theoretical study

/pdf/dynamic-versus-static-approach-to-theoretical-anharmonic-4pavd88jil.pdf

Dynamic versus Static Approach to Theoretical Anharmonic Vibrational Spectroscopy of Molecular Species Elevant to Atmospheric Chemistry: A Case Study of Formic Acid

Ljupčo Pejov

Papers

The influence of inherent pseudo Jahn-Teller instability on the stretching vibrations of water molecules in the isomorphous metal(II) saccharinate hexahydrates

Low bending vibrations of crystalline water molecules: an ongoing quest or a final word – topical review – a tribute to academician bojan šoptrajanov

Vibrational states of tetrahedral molecular species in electric fields. A theoretical model for quantitative description of the latent symmetry effects in vibrational spectroscopy of matrix isolated tetrahedral species.

The phonon-assisted proton transfer between hydrazinium cations in (N2H5)2HMF6·2H2O (M∈{Ga, Al, Fe}) type compounds. FT IR and quantum theoretical study

Dynamic versus Static Approach to Theoretical Anharmonic Vibrational Spectroscopy of Molecular Species Elevant to Atmospheric Chemistry: A Case Study of Formic Acid