J Am Chem Soc, 2002, 124(2):196-204

Dimers of dipyrrometheneboron difluoride (BODIPY) with light spectroscopic applications in chemistry and biology

A ground-state dimer (denoted DI) exhibiting a strong absorption maximum at 477 nm (ε = 97 000 M-1cm-1) can form between adjacent BODIPY groups attached to mutant forms of the protein, plasminogen activator inhibitor type 1 (PAI-1). No fluorescence from excited DIwas detected. A locally high concentration of BODIPY groups was also achieved by doping lipid phases (micelles, vesicles) with BODIPY-labeled lipids. In addition to an absorption band located at about 480 nm, a new weak absorption band is also observed at ca. 570 nm. Both bands are ascribed to the formation of BODIPY dimers of different conformation (DIand DII). Contrary to DIin PAI-1, the DIIaggregates absorbing at 570 nm are emitting light observed as a broad band centered at about 630 nm. The integrated absorption band of DIis about twice that of the monomer, which is compatible with exciton coupling within a dimer. The Förster radius of electronic energy transfer between a BODIPY excited monomer and the ground-state dimer (DI) is 57 ± 2 Å. A simple model of exciton coupling suggests that in DItwo BODIPY groups are stacked on top of each other in a sandwich-like configuration with parallel electronic transition dipoles. For DIIthe model suggests that the So → S1transition dipoles are collinear. An explanation for the previously reported (J. Am. Chem. Soc. 1994, 116, 7801) exceptional light spectroscopic properties of BODIPY is also presented. These are ascribed to the extraordinary electric properties of the BODIPY chromophore. First, changes of the permanent electric dipole moment (Δμ ≅ -0.05 D) and polarizability (-26 x 10-40C m2V-1) between the ground and the first excited states are small. Second, the So↔ S1electronic transition dipole moments are perpendicular to Δμ.

Bergström F, Mikhalyov I, Hägglöf P, Wortmann R, Ny T, Johansson LBA

IBCH: 1539
Ссылка на статью в журнале: http://pubs.acs.org/doi/abs/10.1021/ja010983f
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