Exploring the lowest energy triplet potential energy surface for cyclic C4H4 isomers with the complete basis set ab initio method.: Is the transformation of triafulvene into cyclobutadiene possible in their excited states?

High level computational studies were performed with the aim being to explore the possibility of converting the experimentally available triafulvene into the hard-to-detect cyclobutadiene. The method is based on the simple approach used to excite triafulvene into the triplet state, and then through various reaction channels, come to the aromatic triplet cyclobutadiene. Triplet cyclobutadiene is only a few kcal/mol higher in energy than singlet cyclobutadiene and should be easily relaxed into the latter. Several reaction pathways that include only a concerted mechanism, as well as reaction pathways that include the radical formation-recombination were also explored. Some possible approaches for experimentally obtaining the singlet or triplet cyclobutadiene were suggested. (C) 1999 Elsevier Science B.V. All rights reserved.