Gas phase protonated nicotine is a mixture of pyridine- and pyrrolidine-protonated conformers: implications for its native structure in the nicotinic acetyl-choline receptor

The infrared (IR) spectra of gas phase protonated nicotine has been measured in the never-before probed N-H “fingerprint region” (3,200–3,500 cm−1). The protonated molecules generated by an electrospray source are...

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Two-Dimensional Correlation Spectroscopy (2D-COS) of Gas-Phase Pyrrole Clusters in a Supersonic Jet: Treatment of Sharp Bands on a Broad Background

Applied Spectroscopy ◽

10.1177/0003702819892030 ◽

2020 ◽

Vol 74 (4) ◽

pp. 408-416

Author(s):

Yoshiteru Matsumoto ◽

Souichi Tezuka

Keyword(s):

Ir Spectra ◽

Gas Phase ◽

Supersonic Jet ◽

Correlation Spectroscopy ◽

Cavity Ringdown Spectroscopy ◽

Two Dimensional ◽

Cavity Ringdown ◽

Correlation Spectrum ◽

Large Clusters ◽

Small Clusters

Two-dimensional correlation spectroscopy (2D-COS) is a useful technique to analyze any intensity behavior of optical spectra that exhibit a complicated feature with overlapped bands. In this study, we apply 2D-COS to the infrared (IR) spectra of gas-phase pyrrole (Py) clusters. The NH stretching vibrations of the Py clusters are measured by cavity ringdown spectroscopy. The observed IR spectra of the Py clusters consist of sharp bands, full width half-maximum (FWHM) ∼1 cm−1, and a broad background (FWHM >50 cm−1). The 2D asynchronous correlation spectra reveal that the sharp bands and a broad background are assigned to small clusters of dimer to pentamer and large clusters with bulk-like structures, respectively, which support the results of our previous study. The sharp bands are also analyzed using another 2D asynchronous correlation spectrum, which is obtained by decomposing the observed IR spectra into sharp and broad components. Because the asynchronous signals are consistent with those obtained from the IR spectra without decomposition, the result would suggest that we need not to decompose the IR spectra into sharp and broad components before applying 2D-COS. However, our model simulations of 2D-COS showed a counterexample that gives an incorrect result without removing a broad background component from the IR spectra. This study strongly suggests that we need to undertake a careful treatment of the complicated IR spectrum with various widths of bands.

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Effect of additional side groups on the vibrational frequencies of benzoquinone molecules

BIBECHANA ◽

10.3126/bibechana.v14i0.15860 ◽

2016 ◽

Vol 14 ◽

pp. 66-76

Author(s):

Nabin Kumar Raut ◽

Hari Prasad Lamichhane

Keyword(s):

Ir Spectra ◽

Gas Phase ◽

Vibrational Frequencies ◽

The Other ◽

Methyl Groups ◽

Computational Investigation ◽

Strongly Coupled ◽

Solvent Phase ◽

Other Hand

The present work enumerates detailed computational investigation into the IR spectra in gas phase and in solvent of 1, 4- Benzoquinone family (benzoquinone (BQ), duroquinone (DQ), plastoquinone (PQ), ubiquinone (UQ), and dimethoxy dimethyl benzoquinone (MQo)). In the spectra of BQ, PQ, and DQ, we observed separate intense carbonyl (C=O) and C=C bands respectively around 1730 cm-1 (intense), 1645 cm-1 (weak). On the other hand, for UQ and MQo, three prominent bands around 1652, 1703, and 1733 cm-1 were observed, where two C=O modes were uncoupled but one of the carbonyl is strongly coupled with C=C vibrations. The additional methyl groups downshift the intense carbonyl bands and upshift C=C mode frequencies. The carbonyl modes further downshifted in the solvent phase calculation.BIBECHANA 14 (2017) 66-76

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Cycloalkylidenselenoketene durch Pyrolyse von 1,2,3-Selenadiazolen — Untersuchungen mit der temperaturabhängigen PE-Spektroskopie und Matrix-IR-Spektroskopie [1]

Zeitschrift für Naturforschung B ◽

10.1515/znb-1984-1113 ◽

1984 ◽

Vol 39 (11) ◽

pp. 1536-1540 ◽

Cited By ~ 11

Author(s):

Reinhard Schulz ◽

Armin Schweig

Keyword(s):

Liquid Phase ◽

Ir Spectroscopy ◽

Ir Spectra ◽

Gas Phase ◽

Photoelectron Spectroscopy ◽

Variable Temperature ◽

Matrix Ir Spectroscopy

Abstract The gas-phase pyrolysis of cyclohexeno-1,2,3-selenadiazole and cycloocteno-1,2,3-selenadiazole has been investigated by variable temperature photoelectron spectroscopy and matrix IR spectroscopy. The ring contracted, highly reactive products cyclopentylidenselenoketene (cyclopentylidenmethanselone) and cycloheptylidenselenoketene (cycloheptylidenmethanselone) - which had not been found in liquid phase thermolysis experiments - have been detected. Additionally HeI photoelectron and IR spectra of analogous ketenes and thioketenes are presented for comparative reasons.

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Ices in star forming regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900009232 ◽

1997 ◽

Vol 178 ◽

pp. 45-60 ◽

Cited By ~ 11

Author(s):

A.G.G.M. Tielens ◽

D.C.B. Whittet

Keyword(s):

Ir Spectra ◽

Gas Phase ◽

Molecular Cloud ◽

Oxidation Reactions ◽

Star Forming ◽

Star Forming Regions ◽

Interstellar Ice ◽

Simple Molecules ◽

Absorption Features ◽

Cloud Material

IR spectra of sources associated with molecular cloud material show a variety of absorption features attributed to simple molecules, such as H2O, CO, CH3OH, CO2, CH4, and OCS in icy grain mantles. These identifications are reviewed. These molecules are formed through accretion and reaction of gas phase species on grain surfaces. The high abundance of CH3OH and CO2 point towards the importance of hydrogenation and oxidation reactions in this process. Observations also show that thermal outgassing is of great importance for the composition of interstellar ice mantles. Both these processes are discussed in some detail.

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