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The complexation reaction between anthracene (AN) and perfluoronaphthalene (PFN) has been found to be magnetically sensitive. The various characteristics of magnetic field effect in the radical ion pair system, namely wavelength, field and dielectric constant dependence, were investigated. The mismatch between theoretically estimated and experimentally determined B 1/2 , has been ascribed to the out-of-plane floppy motion of the perfluoranaphthalene radical anion, which bestows a σ character on the latter thereby affecting the hyperfine coupling constant. The low magnetic sensitivity of this exciplex system has been ascribed to a combined effect of static complexation of AN-PFN and an out-of-plane butterfly motion of the PFN radical.

The magnetic response of the radical pair generated by the hydrogen abstraction of the photoexcited benzil triplet from sodium dodecyl sulphate is studied. It is found that radical decay curves, with or without magnetic field, are affected on addition of small amphiphiles such as 1,4-dioxane. The results have been interpreted on the basis of the ability of the latter to change the micellar aggregation number and intramicellar viscosity.

The exciplex formed between diphenyl hexatriene and dimethyl aniline has been found to be magnetic-field sensitive. The effect of the dielectric constant of the medium and of addition of an alcohol on the magnetic-field modulated luminescence of the exciplex has been discussed. Theoretical B 1 2 values have been calculated by the INDO-UHF method. The lack of correspondence between the theoretical and the experimental B 1 2 values has been explained on the basis of electron hopping. In a viscous polymeric medium, anisotropic interactions between the radical partners have been observed. A qualitative explanation of this novel phenomenon, emphasizing the importance of anisotropic dipolar interactions, has been discussed. To the best of our knowledge, this is the first report on magnetic anisotropy of exciplex luminescence.

Emission spectra of p -N,N-dimethylamino benzonitrile (DMABN) in aqueous β-cyclodextrine (β-CD) solutions are reported. In β-CD two distinct kinds of emission are observed, one with enhanced nonpolar emission (at 355 nm) and the other exhibiting enhanced TICT emission (at 480 nm). The former is attributed to those DMABN molecules which are totally inside the β-CD cavity while the latter is due to DMABN molecules only partially enclosed in the cavity.