Excited-state dynamics of 5,10,15,20-tetraphenyl-21H, 23H-porphine manganese(III) chloride encapsulated in TiMCM-41 and MCM-41; Proved by fs-diffuse reflectance laser photolysis

5,10,15,20-Tetraphenyl-21H,23H-porphine manganese(III) chloride (Mn^IIITPP(Cl)) was encapsulated into MCM-41 and TiMCM-41, and its photoinduced electron transfer had been studied by using femtosecond diffuse reflectance photolysis. Two different transient species (c.a. 10 ps and c.a. 80 ps) were observed. The shorter-lived species should be originated from relaxation of a "tripmultiplet" state and the longer-lived species should be attributed to the spin-forbidden relaxation (slower than the spin-allowed decay of triptquintet) via a quintet CT state. After irradiation, MnTPPCl^+. radicals are detected in MCM-41 or TiMCM-41, indicating that the mesoporous silicate framework plays a good electron acceptor. Furthermore, it has been found that the formation MnTPPCl^+. is easier in TiMCM-41 than in MCM-41, indicating that framework modification by incorporating the Ti⁴⁺ into the MCM-41 enhances the electron-accepting ability of the MCM-41 framework.