Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes

• DOI: 10.1021/ja407052t
• Publication Date: 2013-09-16T22:09:43Z
• Authors: Sabine Richert; Arnulf Rosspeintner; Stephan Landgraf; Günter Grampp; Eric Vauthey; Daniel R. Kattnig
• Keywords: Excimer; Radical ion; Photoinduced electron transfer; Acceptor; Electron acceptor

We describe the experimental investigation of time-resolved magnetic field effects in exciplex-forming organic donor–acceptor systems. In these systems, photoexcited acceptor state is predominantly deactivated by bimolecular electron transfer reactions (yielding radical ion pairs) or direct exciplex formation. The delayed fluorescence emitted magnetosensitive if reaction pathway involves loose pair states. This effect results from coherent interconversion between electronic singlet and triplet states as described mechanism. By monitoring changes luminescence intensity when applying external fields, details mechanism can be elucidated. this work we present obtained with fluorophore-quencher 9,10-dimethylanthracene/N,N-dimethylaniline (DMA) solvents systematically varied permittivity. A simple theoretical model introduced that allows discriminating initial quenching, viz., exciplex, based on effect. approach validated it to isotopologous pairs pyrene/DMA pyrene-d10/DMA. detect both are formed during quenching stage. Upon increasing solvent polarity, relative importance distant increases. However, even comparably polar media, remains remarkably significant. discuss our relation recent findings involvement exciplexes photoinduced reactions.