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1H-pyrrolo[3,2-h]Quinoline: A Benchmark Molecule for Reliable Calculations of Vibrational Frequencies, IR Intensities, and Raman Activities.
MedLine Citation:
PMID:  23134592     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Reliable assignment of 55 out of 57 vibrational modes has been achieved for 1H-pyrrolo[3,2-h]quinoline using IR, Raman, and fluorescence spectroscopy combined with quantum-chemical calculations. The experiments provided a data set for assessing the performance of different models/basis sets for predicting the vibrational frequencies, as well as IR and Raman intensities for a molecule with 13 heavy atoms. Among six different tested DFT functionals, the hybrid B3LYP used with Pople's split-valence basis sets is suggested as the best choice for accurate and cost-effective IR/Raman spectral simulations. Neither HF nor MP2 methods can satisfactorily describe the vibrational structure. Increasing the basis set size from double to triple zeta and by adding polarization and diffuse functions does not necessarily improve the results, especially regarding the predictions of vibrational frequencies. With respect to the intensities, extending the basis set helps, with the accuracy increasing systematically for the Raman spectra, and in a less regular fashion for the IR. A large difference in accuracy is observed while comparing the spectral parameters predicted for in-plane and out-of-plane normal modes. The former are reliably computed with modest basis sets, whereas for the out-of-plane vibrations, larger basis sets are necessary, but even in this case the out-of-plane vibrations are reproduced with much less accuracy than in-plane modes. This effect is general, as it has been observed using different functional and basis sets.
Authors:
Alexandr Gorski; Sylwester Gawinkowski; Jerzy Jurek Herbich; Oliver Krauss; Bernhard Brutschy; Randolph Paul Thummel; Jacek Waluk
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-7
Journal Detail:
Title:  The journal of physical chemistry. A     Volume:  -     ISSN:  1520-5215     ISO Abbreviation:  J Phys Chem A     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9890903     Medline TA:  J Phys Chem A     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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