Magnetic field effect and multiplicity of conformation in a polymer-linked exciplex system

The magnetic field sensitivity of the pyrene-dimethylaniline (Py-DMA) system, linked by a polystrene (PS) spacer, was examined. It was found that isodielectric mixtures of tetrahydrofuran (THF) and dimethylformamide (DMF) and benzene and dimethylsulphoxide (DMSO) behave differently, the latter quenching the magnetic field effect more than the former; this is opposite to that found for the unlinked Py-DMA system. These studies demonstrate the importance of the solvent-dependent polymer backbone conformation. It was found that, in both of the above solvent mixture, the normal luminescence (φ) and the magnetic-field-modulated luminescence (δφ) exhibit a shift in wavelength, indicating conformers with different magnetic sensitivities. The spectra taken at different times after excitation also support this conclusion