title: Mechanical Forces Alter Conical Intersections Topology.
abstract: Photoreactivity can be influenced by mechanical forces acting over a reacting chromophore. Nevertheless, the specific effect of the external forces in the photoreaction mechanism remains essentially unknown. Conical intersections are key structures in photochemistry, as they constitute the funnels connecting excited and ground states. These crossing points are well known to provide valuable information on molecular photoreactivity, including crucial aspects as potential photoproducts which may be predicted by just inspection of the branching plane vectors. Here, we outline a general framework for understanding the effect of mechanical forces on conical intersections and their implications on photoreactivity. Benzene S1/S0 conical intersection topology can be dramatically altered by applying less than 1 nN force, making the peaked pattern of the intersection become a sloped one, also provoking the transition state in the excited state to disappear. Both effects can be related to an increase in the photostability as the conical intersection becomes more accessible, and its topology in this case favors the recovery of the initial reactant. The results indicate that the presence of external forces acting over a chromophore have to be considered as a potential method for photochemical reactivity control.
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rivero
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.|Department of Biotechnology, Chemistry and Pharmacy, University of Siena , Siena, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Valentini
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: Fernández-González
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Felipe
authors.initials: F
authors.lastname: Zapata
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.|Departamento de Química, Centro de Investigación en Síntesis Química (CISQ) , Madre de Dios, 51, E-26006, Logroño, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: García-Iriepa
authors.affiliation: Departamento de Química, Centro de Investigación en Síntesis Química (CISQ) , Madre de Dios, 51, E-26006, Logroño, Spain.
authors.forename: Diego
authors.initials: D
authors.lastname: Sampedro
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Palmeiro
authors.affiliation: Química Física, Universidad de Alcalá , E- 28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Luis Manuel
authors.initials: LM
authors.lastname: Frutos
mesh_terms: D001554:Benzene / Q000737:chemistry*; D011789:Quantum Theory; D013314:Stress, Mechanical; D013816:Thermodynamics
chemical_list: D001554:Benzene