A CASSCF-CASPT2 study of the excited-state intramolecular proton transfer reaction in 1-amino-3-propenal using different active spaces

Marta Forés, Ludwik Adamowicz

Research output: Contribution to journalArticle

12 Scopus citations


In this work we analyze how the choice of the active space in the CASSCF (the complete-active-space multiconfiguration self-consistent-field method) and CASPT2 (the second-order perturbation theory based on the CASSCF reference wave function) calculations affects the computed potential energy curves (PECs) for the intramolecular proton transfer reaction in the ground state and the two lowest lying singlet excited states of 1-amino-3-propenal. As anticipated, the results revealed that, qualitatively, the proton transfer in the different states can be correctly described even by minimal active spaces, which include the orbitals involved in the electronic excitation of the considered state and the antibonding sigma orbital corresponding to the bond formed by the molecule with the migrating hydrogen atom. However, quantitatively, the relative energies of the two tautomers and the energy barriers computed at the CASSCF level change when the active space is increased, indicating importance of the dynamic electron correlation. Introducing the dynamic correlation effects via CASPT2 makes the calculated energy parameters more uniform among the different active spaces. The analysis suggested certain optimal active spaces for studying proton transfer reactions in systems similar to 1-amino-3-propenal. The PEC calculations for excited states showed that the results are sensitive to the molecular geometries used in the calculations, particularly near the transition point.

Original languageEnglish (US)
Pages (from-to)1422-1431
Number of pages10
JournalJournal of Computational Chemistry
Issue number13
StatePublished - Oct 1999



  • 1-amino-3-propenal
  • Complete-active-space self-consistent-field (CASSCF)
  • Excited-state intramolecular proton transfer (ESIPT)
  • Multiconfigurational second-order perturbation (CASPT2)

ASJC Scopus subject areas

  • Chemistry(all)
  • Computational Mathematics

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