title: Excited state proton transfer in 3-methyl-7-azaindole dimer. Symmetry control.
abstract: The concerted double proton transfer undergone by the C(2)(h) dimer of 7-azaindole upon electronic excitation has also been reported to occur in 3-methyl-7-azaindole monocrystals and in dimers of this compound under free-jet conditions. However, the results obtained in this work for the 3-methyl-7-azaindole dimer formed in a 10(-4) M solution of the compound in 2-methylbutane suggest that the dimer produces no fluorescent signal consistent with a double proton transfer in the liquid phase or in a matrix. In this paper, the spectroscopic behavior of the doubly hydrogen bonded dimer of 3-methyl-7-azaindole is shown to provide a prominent example of molecular symmetry control over the spectroscopy of a substance. This interpretation opens up a new, interesting research avenue for exploring the ability of molecular symmetry to switch between proton-transfer mechanisms. It should be noted that symmetry changes in the 3-methyl-7-azaindole dimer are caused by an out-of-phase internal rotation of the two methyl groups.
authors.affiliation: Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. javier.catalan@uam.es
authors.forename: Javier
authors.initials: J
authors.lastname: Catalán
authors.forename: Cristina
authors.initials: C
authors.lastname: Díaz
authors.forename: Pilar
authors.initials: P
authors.lastname: Pérez
authors.forename: José L G
authors.initials: JL
authors.lastname: de Paz