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Thermally-Activated, Delayed Fluorescence in O,B,O- and N,B,O-Strapped Boron Dipyrromethene Derivatives

Lookup NU author(s): Patrycja Stachelek, Abdulrahman Alsimaree, Rua Alnoman, Emeritus Professor Anthony Harriman, Dr Julian Knight

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Abstract

A small series of boron dipyrromethene (BODIPY) dyes has been synthesized whereby the boron atom is constrained in a five-membered ring formed from either o-dihydroxypyridine or o-aminophenol. In the latter case, the amino group has been converted into the corresponding amide derivative so as to curtail the possibility for light-induced charge transfer from strap to BODIPY. These compounds are weakly emissive in fluid solution but cleavage of the strap, by treatment with a photoacid generator, restores strong fluorescence. Surprisingly, the same compounds remain weakly fluorescent in a rigid glass at 80 K where light-induced charge transfer is most unlikely. In fluid solution, the fluorescence quantum yield increases with increasing temperature due to a thermally activated step but does not correlate with the thermodynamics for intramolecular charge transfer. It is proposed that the strap causes rupture of the potential energy surface for the excited state, creating traps that provide new routes by which the wave packet can return to the ground state. Access to the trap from the excited state is reversible, leading to the delayed emission. Analysis of the temperature dependent emission intensities allows estimation of the kinetic parameters associated with entering and leaving the trap.

Publication metadata

Author(s): Stachelek P, Alsimaree AA, Alnoman RB, Harriman A, Knight JG

Publication type: Article

Publication status: Published

Journal: The Journal of Physical Chemistry

Year: 2017

Volume: 121

Issue: 10

Pages: 2096-2107

Print publication date: 28/02/2017

Online publication date: 28/02/2017

Acceptance date: 28/02/2017

ISSN (print): 1089-5639

ISSN (electronic): 1520-5215

Publisher: American Chemical Society

URL: https://doi.org/10.1021/acs.jpca.6b11131

DOI: 10.1021/acs.jpca.6b11131

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