Evidence of dual channel electron transfer induced negative magnetic field effect on exciplex emission at very high permittivity of medium

Magnetic field induced change in the pyrene-N,N-dimethylaniline exciplex fluorescence has been studied in condensed phase with very high permittivity. In contrast to the commonly observed enhancement of exciplex fluorescence in presence of magnetic field (for 7 < ε < 33), the effect shows a complete reversal at low DMA concentration in DMSO which is observed only at the blue end of fluorescence. At high DMA concentration the negative MFE at blue end slowly reverts back to the normal. At the red end of the emission the MFE retains its normal character for all donor concentrations even at very high permittivity.

Graphical abstractKinetic model of the exciplex system at very high permittivity (ε ≈ 47). A-Py; D-DMA;[ASD]FC∗-accepter, donor and solvent molecule assembly undergoing super-exchange.Download high-res image (89KB)Download full-size imageHighlights► Dual channel electron transfer. ► Negative magnetic field effect. ► Relaxed and un-relaxed exciplex.