Effects of High Magnetic Field on the Intramolecular Exciplex Fluorescence of Chain-Linked Phenanthrene and Dimethylaniline

The effects of high magnetic field (≤13 T) on the intramolecular exciplex fluorescence generated from a chain-linked phenanthrene (Phen) and dimethylaniline (DMA) system (Phen-(CH 2 ) n O(CH 2 ) 2 -DMA, n = 4−12) were studied in N, N -dimethylformamide by means of photostationary and laser-induced fluorescence. With increasing the magnetic field from 0 to ca. 1 T, the exciplex fluorescence for the molecules with n = 6−12 increases steeply in intensity and then decreases gradually up to ca. 9 T. Their mean lifetimes exhibit similar magnetic field dependence (≤13 T). The reversal of the effects is observed in high magnetic field (>1 T). This is interpreted in terms of the Δ g mechanism in which a high magnetic field enhances the singlet−triplet intersystem crossing in an intramolecular Phen anion and DMA cation radical pair intervening in the reaction. The Δ g value is estimated to be about 0.000 022.