Vibrational analysis of 1,2-dihydroxycyclobuten-3,4-dione (squaric acid) as a nearly-free molecule

FT-IR and polarized Raman spectra of 1,2-dihydroxycyclobuten-3,4-dione (squaric acid, SA) in dimethylsulfoxide (DMSO) solution have been measured. Scaled quantum mechanical force fields have been calculated at the ab initio SCF, 3-21G level for the free SA molecule and with the AM1 hamiltonian for b...

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Bibliographic Details
Published in:Journal of molecular structure 1992-04, Vol.268 (1), p.23-39
Main Authors: Lunelli, Bruno, Giorgini, Maria Grazia, Negri, Fabrizia, Orlandi, Giorgio
Format: Article
Language:English
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Summary:FT-IR and polarized Raman spectra of 1,2-dihydroxycyclobuten-3,4-dione (squaric acid, SA) in dimethylsulfoxide (DMSO) solution have been measured. Scaled quantum mechanical force fields have been calculated at the ab initio SCF, 3-21G level for the free SA molecule and with the AM1 hamiltonian for both the free molecule and its complexes with DMSO. The comparison between the results of calculations for the free SA molecule and its complexes with DMSO indicates that the overall solvent perturbations are weak. The agreement between observed and computed frequencies allows us to assign the IR and Raman spectra and to derive a reliable force field for SA.
ISSN:0022-2860
1872-8014
DOI:10.1016/0022-2860(92)85057-N