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

1997; American Chemical Society; Volume: 101; Issue: 4 Linguagem: Inglês

10.1021/jp961542z

1520-5215

Hong Cao, Katsuji Miyata, Tomoyuki Tamura, Yoshihisa Fujiwara, Akio Katsuki, Chen‐Ho Tung, Yoshifumi Tanimoto,

Spectroscopy and Quantum Chemical Studies

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-(CH2)nO(CH2)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 Δg 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 Δg value is estimated to be about 0.000 022.