Raman, infrared and NMR spectral analysis, normal coordinate analysis and theoretical calculations of 5-(methylthio)-1,3,4-thiadiazole-2(3H)-thione and its thiol tautomer

Tarek A. Mohamed, Usama A. Soliman, Ibrahim A. Shaaban, Wajdi M. Zoghaib, Lee D. Wilson

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10 Citations (Scopus)

Abstract

Raman (3400-100 cm 1) and infrared (4000-200 cm 1) spectra of 5-(methylthio)-1,3,4-thiadiazole-2(3 H)-thione (C3H4N2S3; MTT) were measured in the solid state, and the 1H/13C NMR spectra were obtained in DMSO-d6. Initially, twelve structures were proposed as a result of thiol-thione tautomerism and the internal rotation about the C-S bonds. The energies and vibrational frequencies of the optimized structures were calculated using the 6-31G(d) basis set with the methods of MP2 and DFT/B3LYP with Gaussian 98 quantum calculations. Additionally, 1H/13C NMR chemical shifts were predicted for the thiol (structure 5) and thione (structure 9) tautomers by means of B3LYP/6-311+G(d, p) calculations utilizing the GIAO approximation and the PCM solvation model. After complete relaxation of twelve candidate isomers, the thione tautomer (structure 9) was favored owing to its low energy and its predicted real spectral frequencies. These results agree with the recorded infrared and Raman results, in addition to the observed/calculated 1H and 13C NMR spectra. Aided by normal coordinate analysis and potential energy distributions (PEDs), complete vibrational assignments have been proposed for all observed fundamentals for the thione tautomer. With the aid of MP2/6-31G(d) potential surface scans, CH3, CH3S, and SH barriers to internal rotations were estimated with the optimized structural parameters from the MP2 method with the 6-31G(d) basis set. The results are discussed herein and compared with similar model compounds whenever appropriate.

Original languageEnglish
Pages (from-to)339-349
Number of pages11
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume150
Issue number1
DOIs
Publication statusPublished - 2015

Fingerprint

Thiones
tautomers
Sulfhydryl Compounds
thiols
Spectrum analysis
spectrum analysis
Nuclear magnetic resonance
Infrared radiation
nuclear magnetic resonance
Pulse code modulation
Solvation
Chemical shift
Surface potential
Vibrational spectra
Potential energy
Discrete Fourier transforms
Isomers
solvation
chemical equilibrium
energy

Keywords

  • Infrared
  • Internal rotation barrier
  • MP2 and DFT calculations
  • Raman
  • Vibrational assignment

ASJC Scopus subject areas

  • Instrumentation
  • Atomic and Molecular Physics, and Optics
  • Analytical Chemistry
  • Spectroscopy

Cite this

@article{d22c81a479b849f88a396d8dccb53c67,
title = "Raman, infrared and NMR spectral analysis, normal coordinate analysis and theoretical calculations of 5-(methylthio)-1,3,4-thiadiazole-2(3H)-thione and its thiol tautomer",
abstract = "Raman (3400-100 cm 1) and infrared (4000-200 cm 1) spectra of 5-(methylthio)-1,3,4-thiadiazole-2(3 H)-thione (C3H4N2S3; MTT) were measured in the solid state, and the 1H/13C NMR spectra were obtained in DMSO-d6. Initially, twelve structures were proposed as a result of thiol-thione tautomerism and the internal rotation about the C-S bonds. The energies and vibrational frequencies of the optimized structures were calculated using the 6-31G(d) basis set with the methods of MP2 and DFT/B3LYP with Gaussian 98 quantum calculations. Additionally, 1H/13C NMR chemical shifts were predicted for the thiol (structure 5) and thione (structure 9) tautomers by means of B3LYP/6-311+G(d, p) calculations utilizing the GIAO approximation and the PCM solvation model. After complete relaxation of twelve candidate isomers, the thione tautomer (structure 9) was favored owing to its low energy and its predicted real spectral frequencies. These results agree with the recorded infrared and Raman results, in addition to the observed/calculated 1H and 13C NMR spectra. Aided by normal coordinate analysis and potential energy distributions (PEDs), complete vibrational assignments have been proposed for all observed fundamentals for the thione tautomer. With the aid of MP2/6-31G(d) potential surface scans, CH3, CH3S, and SH barriers to internal rotations were estimated with the optimized structural parameters from the MP2 method with the 6-31G(d) basis set. The results are discussed herein and compared with similar model compounds whenever appropriate.",
keywords = "Infrared, Internal rotation barrier, MP2 and DFT calculations, Raman, Vibrational assignment",
author = "Mohamed, {Tarek A.} and Soliman, {Usama A.} and Shaaban, {Ibrahim A.} and Zoghaib, {Wajdi M.} and Wilson, {Lee D.}",
year = "2015",
doi = "10.1016/j.saa.2015.05.039",
language = "English",
volume = "150",
pages = "339--349",
journal = "Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy",
issn = "1386-1425",
publisher = "Elsevier",
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TY - JOUR

T1 - Raman, infrared and NMR spectral analysis, normal coordinate analysis and theoretical calculations of 5-(methylthio)-1,3,4-thiadiazole-2(3H)-thione and its thiol tautomer

AU - Mohamed, Tarek A.

AU - Soliman, Usama A.

AU - Shaaban, Ibrahim A.

AU - Zoghaib, Wajdi M.

AU - Wilson, Lee D.

PY - 2015

Y1 - 2015

N2 - Raman (3400-100 cm 1) and infrared (4000-200 cm 1) spectra of 5-(methylthio)-1,3,4-thiadiazole-2(3 H)-thione (C3H4N2S3; MTT) were measured in the solid state, and the 1H/13C NMR spectra were obtained in DMSO-d6. Initially, twelve structures were proposed as a result of thiol-thione tautomerism and the internal rotation about the C-S bonds. The energies and vibrational frequencies of the optimized structures were calculated using the 6-31G(d) basis set with the methods of MP2 and DFT/B3LYP with Gaussian 98 quantum calculations. Additionally, 1H/13C NMR chemical shifts were predicted for the thiol (structure 5) and thione (structure 9) tautomers by means of B3LYP/6-311+G(d, p) calculations utilizing the GIAO approximation and the PCM solvation model. After complete relaxation of twelve candidate isomers, the thione tautomer (structure 9) was favored owing to its low energy and its predicted real spectral frequencies. These results agree with the recorded infrared and Raman results, in addition to the observed/calculated 1H and 13C NMR spectra. Aided by normal coordinate analysis and potential energy distributions (PEDs), complete vibrational assignments have been proposed for all observed fundamentals for the thione tautomer. With the aid of MP2/6-31G(d) potential surface scans, CH3, CH3S, and SH barriers to internal rotations were estimated with the optimized structural parameters from the MP2 method with the 6-31G(d) basis set. The results are discussed herein and compared with similar model compounds whenever appropriate.

AB - Raman (3400-100 cm 1) and infrared (4000-200 cm 1) spectra of 5-(methylthio)-1,3,4-thiadiazole-2(3 H)-thione (C3H4N2S3; MTT) were measured in the solid state, and the 1H/13C NMR spectra were obtained in DMSO-d6. Initially, twelve structures were proposed as a result of thiol-thione tautomerism and the internal rotation about the C-S bonds. The energies and vibrational frequencies of the optimized structures were calculated using the 6-31G(d) basis set with the methods of MP2 and DFT/B3LYP with Gaussian 98 quantum calculations. Additionally, 1H/13C NMR chemical shifts were predicted for the thiol (structure 5) and thione (structure 9) tautomers by means of B3LYP/6-311+G(d, p) calculations utilizing the GIAO approximation and the PCM solvation model. After complete relaxation of twelve candidate isomers, the thione tautomer (structure 9) was favored owing to its low energy and its predicted real spectral frequencies. These results agree with the recorded infrared and Raman results, in addition to the observed/calculated 1H and 13C NMR spectra. Aided by normal coordinate analysis and potential energy distributions (PEDs), complete vibrational assignments have been proposed for all observed fundamentals for the thione tautomer. With the aid of MP2/6-31G(d) potential surface scans, CH3, CH3S, and SH barriers to internal rotations were estimated with the optimized structural parameters from the MP2 method with the 6-31G(d) basis set. The results are discussed herein and compared with similar model compounds whenever appropriate.

KW - Infrared

KW - Internal rotation barrier

KW - MP2 and DFT calculations

KW - Raman

KW - Vibrational assignment

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U2 - 10.1016/j.saa.2015.05.039

DO - 10.1016/j.saa.2015.05.039

M3 - Article

VL - 150

SP - 339

EP - 349

JO - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

JF - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

SN - 1386-1425

IS - 1

ER -