Several RYDMR studies on the radical-ion pair formed in the photolysis of TMPD: Photoconductivity, transient-absorption and fluorescence detection methods

Abstract

Three different RYDMR (reaction-yield detected magnetic resonance) techniques, photoconductivity detected magnetic resonance (PCDMR), transient-absorption detected magnetic resonance (ADMR) and detayed fluorescente detected magnetic resonance (DFDMR), are applied to the investigation of the radical-ion pair formed in the photolysis of TMPD in mixed alcohol solution. Here, PCDMR is a newly developed RYDMR method to study the radical-ion pair. PCDMR and ADMR methods show the acceleration of the quenching reaction from the triplet manifold of the radical-ion pair by microwave radiation under electron spin resonance conditions. These spectra of the radicalion pair are significantly broadened probably because of the dynamic behavior of the radical-ion pair interacting strongly. The long lifetime of the radical-ion pair is due to the Coulomb interaction and the special role of the mixed solvent containing 2-propanol that stabilizes the radical-ion pair. Furthermore, the simultaneous observation of the PCDMR and the DFDMR shows different spectra. This indicates that the spectrum observed by the DFDMR is due to the wealdy interacting RIP formed through the pathway different from those observed by the other two methods.

Magnetic field modulation of the delayed fluorescenceyield in the photoionization reaction of N, N, N′, N′‐tetramethyl‐p‐phenylenediamine in water

“…This is contrasting the mechanism proposed in previous papers [5,7] in which recombination is suggested to be more efficient from the triplet RIP. We believe however that all the previous results can be explained by conceiving our proposed mechanism.…”

“…In an earlier work [8], this group reported such effect in benzene/DMSO binary solvent mixture. In contrast to the previous reports [5,7], the MFE on the delayed fluorescence [8] can only be explained if the singlet RIP is more reactive than the triplet one. In the present study we report on the MFE on the delayed fluorescence from TMPPD in water and water/DMSO mixture using modulation technique [9][10].…”

“…by CIDEP [6], and RYDMR [7] techniques. Interestingly, two different RYDMR methods detected two different RIPs.…”

“…Interestingly, two different RYDMR methods detected two different RIPs. Namely, a weakly interacting short-lived RIP is detected through the delayed fluorescence, whereas monitoring the photoconductivity revealed the presence of a strongly interacting RIP formed from monophotonic ionization [7].…”

Developments of magnetic-resonance-related spin chemistry in Japan

“…In general, both the rise and decay of the RIP contribute to the time evolution of the current. Murai and Matsuyama [37,130] succeeded in completing this new technique and applied it to the system of photoionization of TMPD in alcohol. The broad PCDMR spectrum observed in this particular system was almost identical to the ADMR one [125].…”