title: Mechanism of excited state deactivation of indan-1-ylidene and fluoren-9-ylidene malononitriles.
abstract: Herein, we report complementary computational and experimental evidence supporting the existence, for indan-1-ylidene malononitrile and fluoren-9-ylidene malononitrile, of a non-radiative decay channel involving double bond isomerisation motion. The results of UV-Vis transient absorption spectroscopy highlight that the decay takes place within hundreds of picoseconds. In order to understand the related molecular mechanism, photochemical reaction paths were computed by employing multiconfigurational quantum chemistry. The results indicate that the excited state deactivation occurs via concerted double bond twisting of the dicyanovinyl (DCV) unit coupled with a pyramidalisation of its substituted carbon. It is also shown that the observed differences in the excited state lifetimes when passing from indan-1-ylidene malononitrile to fluoren-9-ylidene are associated with the change in the topography of the conical intersection driving the decay from intermediate to sloped, respectively.
authors.affiliation: Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH, USA.
authors.forename: Leandro A
authors.identifier: http://orcid.org/0000-0003-2858-0222
authors.initials: LA
authors.lastname: Estrada
authors.affiliation: Institut de Ciència Molecular, Universitat de València, P.O. Box 22085, ES-46071, Valencia, Spain. Daniel.Roca@uv.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Francés-Monerris
authors.affiliation: Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH, USA.
authors.forename: Igor
authors.identifier: http://orcid.org/0000-0001-8536-6869
authors.initials: I
authors.lastname: Schapiro
authors.affiliation: Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH, USA and Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, via A. Moro 2, I-53100 Siena, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
authors.affiliation: Institut de Ciència Molecular, Universitat de València, P.O. Box 22085, ES-46071, Valencia, Spain. Daniel.Roca@uv.es.
authors.forename: Daniel
authors.identifier: http://orcid.org/0000-0001-6495-2770
authors.initials: D
authors.lastname: Roca-Sanjuán