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Intramolecular Excimer Formation for Covalently Linked Boron Dipyrromethene Dyes

Lookup NU author(s): Dr Mohammed Alamiry, Professor Andrew Benniston, Graeme Copley, Emeritus Professor Anthony Harriman


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Photophysical properties have been recorded for a small series of covalently linked, symmetrical dimers formed around boron dipyrromethene (Bodipy) dyes. Within the series, a control dimer is unable to adopt a cofacial arrangement because of steric factors, while a second dimer possesses sufficient internal flexibility to form the cofacial geometry but with little overlap of the Bodipy units. The other three members of the series take up a cofacial arrangement with varying bite angles between the planes of the two Bodipy units. Fluorescence quantum yields and excited-state lifetimes indicate differing extents of electronic interaction between the two Bodipy head-groups, but only the compound with the smallest bite angle exhibits excimer emission in solution under ambient conditions. Time-resolved fluorescence studies show dual-exponential decay kinetics in each case, while temperature-dependent emission studies reveal reversible coupling between monomer and lower-energy excimer states. The latter is weakly fluorescent, at best, and is seen dearly only for dimers having small bite angles. The application of high pressure to dilute solutions of these dimers promotes excimer formation in certain cases and leads to loss of monomer-like fluorescence. Under high pressure, excimer emission is more evident, and the overall results can be discussed in terms of subtle structural rearrangements that favor excimer formation.

Publication metadata

Author(s): Alamiry MAH, Benniston AC, Copley G, Harriman A, Howgego D

Publication type: Article

Publication status: Published

Journal: Journal of Physical Chemistry A

Year: 2011

Volume: 115

Issue: 44

Pages: 12111-12119

Print publication date: 01/11/2011

Online publication date: 27/09/2011

ISSN (print): 1089-5639

ISSN (electronic): 1520-5215

Publisher: American Chemical Society


DOI: 10.1021/jp2070419


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Newcastle University