title: Intramolecular charge transfer in pyrromethene laser dyes: photophysical behaviour of PM650.
abstract: Absorption and fluorescence (steady-state and time-correlated) techniques are used to study the photophysical characteristics of the pyrromethene 650 (PM650) dye. The presence of the cyano group at the 8 position considerably shifts the absorption and fluorescence bands to lower energies with respect to other related pyrromethene dyes; this is attributed to the strong electron-acceptor character of the cyano group, as is theoretically confirmed by quantum mechanical methods. The fluorescence properties of PM650 are intensively solvent-dependent. The fluorescence band is shifted to lower energies in polar/protic solutions, and the evolution of the corresponding wavelength with the solvent is analysed by a multicomponent linear regression. The fluorescence quantum yield and the lifetime strongly decrease in polar/protic solvents, which can be ascribed to an extra nonradiative deactivation, via an intramolecular charge-transfer state (ICT state), favoured in polar media.
authors.affiliation: Departamento de Química Física, Universidad del Pais Vasco-EHU, Apartado 644, 48080 Bilbao, Spain. qfploarf@lg.ehu.es
authors.forename: F
authors.initials: F
authors.lastname: López Arbeloa
authors.forename: J
authors.initials: J
authors.lastname: Bañuelos Prieto
authors.forename: V
authors.initials: V
authors.lastname: Martínez Martínez
authors.forename: T
authors.initials: T
authors.lastname: Arbeloa López
authors.forename: I
authors.initials: I
authors.lastname: López Arbeloa
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry* / Q000528:radiation effects; D007834:Lasers; D008968:Molecular Conformation; D010777:Photochemistry; D011162:Porphobilinogen / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000528:radiation effects; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D005456:Fluorescent Dyes; D012997:Solvents; C504196:pyrromethene 546; C504197:pyrromethene 597; C504195:pyrromethene 650; D011162:Porphobilinogen