Enhancement of quantum yield and lifetime of photoinduced charge-separation for cyclometallated platinum(II) complex/ferricyanide system via nafion membrane-solution interface

The photoinduced electron transfer from the excited state of cyclometallate d platinum(II) complex PtLL1L22+ (L-1 = 4-methoxyphenyl-6-phenyl-2,2'-bibyr idine, L-2 = pyridine) incorporated into Nafion membranes to Fe(CN)(6)(3-) in the surrounding solution has been examined. N;N'-tetramethylene-2,2'-bip yridinium (DQ(2+)) entrapped in the Nafion membranes is used as an electron relay. Luminescence quenching studies indicate that the quenching reaction of the excited PtL1L22+ With DQ(2+) is static in nature. PtL1L23+ generate d from the luminescence quenching remains in the Nafion matrix, while DQ(+. ) migrates by an electron hopping mechanism to the Nafion-water interface, where transfers an electron to Fe(CN)(6)(3-) to produce Fe(CN)(6)(4-). The negatively charged Fe(CN)(6)(4-) is repelled into the bulk solution by the anionic Nafion surface. The isolation of the photoinduced oxidized species ptL(1)L(2)(3+). in Nafion from the ultimate reduced species Fe(CN)(6)(4-) i n solution prevents them from undergoing back electron transfer. Thus, an e xtremely long-lived charge separation state is achieved in a high quantum y ield.