title: Visible absorption and fluorescence spectroscopy of conformationally constrained, annulated BODIPY dyes.
abstract: Six conformationally restricted BODIPY dyes with fused carbocycles were synthesized to study the effect of conformational mobility on their visible electronic absorption and fluorescence properties. The symmetrically disubstituted compounds (2, 6) have bathochromically shifted absorption and fluorescence spectral maxima compared to those of the respective asymmetrically monosubstituted dyes (1, 5). Fusion of conjugation extending rings to the α,β-positions of the BODIPY core is an especially effective method for the construction of boron dipyrromethene dyes absorbing and emitting at longer wavelengths. The fluorescence quantum yields Φ of dyes 1-6 are high (0.7 ≤ Φ ≤ 1.0). The experimental results are backed up by quantum chemical calculations of the lowest electronic excitations in 1, 2, 5, 6, and corresponding dyes of related chemical structure but without conformational restriction. The effect of the molecular structure on the visible absorption and fluorescence emission properties of 1-6 has been examined as a function of solvent by means of the recent, generalized treatment of the solvent effect, proposed by Catalán (J. Phys. Chem. B 2009, 113, 5951-5960). Solvent polarizability is the primary factor responsible for the small solvent-dependent shifts of the visible absorption and fluorescence emission bands of these dyes.
authors.affiliation: Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200f-bus 02404, 3001 Leuven, Belgium. Noel.Boens@chem.kuleuven.be
authors.forename: Noël
authors.initials: N
authors.lastname: Boens
authors.forename: Volker
authors.initials: V
authors.lastname: Leen
authors.forename: Wim
authors.initials: W
authors.lastname: Dehaen
authors.forename: Lina
authors.initials: L
authors.lastname: Wang
authors.forename: Koen
authors.initials: K
authors.lastname: Robeyns
authors.forename: Wenwu
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authors.lastname: Qin
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Tang
authors.forename: David
authors.initials: D
authors.lastname: Beljonne
authors.forename: Claire
authors.initials: C
authors.lastname: Tonnelé
authors.forename: Jose M
authors.initials: JM
authors.lastname: Paredes
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Ruedas-Rama
authors.forename: Angel
authors.initials: A
authors.lastname: Orte
authors.forename: Luis
authors.initials: L
authors.lastname: Crovetto
authors.forename: Eva M
authors.initials: EM
authors.lastname: Talavera
authors.forename: Jose M
authors.initials: JM
authors.lastname: Alvarez-Pez