Energies and Potential Surfaces of the Excited Electronic States of Azines



Principal Investigator

Gad Fischer

Department of Chemistry

Faculty of Science


Xiaolin Cao

Fiona Bettens

Department of Chemistry

Faculty of Science

Paul Wormell

Faculty of Science and Technology

University of Western Sydney


u01 - VPP, PC

The research currently being undertaken concerns the diazine, pyridazine. The work is part of a larger
project in which the lowest singlet-triplet and singlet-singlet p* ¨ n transitions are investigated for the family of azabenzenes. It follows on the partly completed work on the triazines. The comparison of the excited state spectroscopies of these molecules provides new insights into the excited state structures, and excited state intramolecular vibronic interactions.




What are the results to date and the future of the work?

The vapour phase singlet-singlet and singlet-triplet electronic absorption spectra of pyridazine have been measured at pathlengths up to 314 m and at temperatures up to 85 oC. This work has been complemented by ab initio molecular orbital calculations on the molecular structures and potential energy surfaces for the lowest excited electronic states, both singlet and triplet. The results of these calculations together with new analyses of the absorption spectra have allowed vibronic coupling calculations to be undertaken. The vibronic coupling calculations have provided realistic explanations for some of the problematic structure seen in the absorption spectra, and have laid to rest the controversy over the existence of one or two separate electronic states in the singlet absorption spectra.

What computational techniques are used?

GAUSSIAN programmes including HF, MP2, DFT and CASSCF have been used.






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