A Concept for Controlling Singlet Oxygen (¹δ_g) Yields Using Nitroxide Radicals: Phthalocyaninatosilicon Covalently Linked to Nitroxide Radicals

In this study, we have investigated the singlet oxygen ( ¹Δ_g) generation mechanism using phthalocyaninatosilicon (SiPc) covalently linked to nitroxide radicals (NRs), and we succeeded in increasing the singlet oxygen quantum yield (Ψ _Δ) by linking the NRs. This originates from both an increase in the triplet quantum yield and excited-state lifetimes long enough to utilize photochemical reactions. Because the electron exchange interactions with paramagnetic species were known to result only in very fast excited-state relaxation, leading to a decrease in photochemical reaction yields, this increase in Ψ_Δ is an unusual and precious example for increasing photochemical reaction yields by electron exchange interactions with paramagnetic species, In addition, our experiments and theoretical analyses show that the spin-selective energy transfer rate constant is not influenced by linking the NRs and can be evaluated by the product of spin-statistical factors and matrix elements between the initial and final states.