RESUMO
To study the intersystem crossing (ISC) and the spatial confinement of the triplet excited states of organic chromophores, we prepared a series of Bodipy dimers. We found that the connection position of the two units has a significant effect on the absorption and fluorescence. Singlet oxygen quantum yields of 3.8-12.4% were observed for the dimers, which are independent of solvent polarity. Nanosecond transient absorption spectra indicate the population of long-lived triplet excited states with lifetimes (τT) of 45-454 µs. Pulsed laser-excited time-resolved electron paramagnetic resonance (TREPR) spectra show that the T1 triplet states are essentially delocalized, which is different from the case for the previously reported Bodipy dimers. The TREPR spectra of the triplet states imply that the delocalization over the whole dimer essentially depends on the electron density of the carbon atoms at the connection sites. This property may become a universal rule for controlling the T1 state confinement in multichromophore organic molecules.
RESUMO
We report the experimental observation of a spectral manifestation of a magnetic polariton that was theoretically predicted last year. This unprecedented manifestation is demonstrated not only for 15N-enriched peroxylamine disulfonate, a radical that adheres strictly to the assumptions of the theory, but also for a radical, 4-oxo-2,2,6,6-tetramethylpiperidine-d16;1-15N-1-oxyl, that departs somewhat from the assumptions, as well as the Galvinoxyl radical that represents a severe departure. The magnetic polariton is likely to be of interest to physical chemists in other fields because of the intrinsic advantage of a finite basis set in developing theories.