The capability of platinum, palladium and ruthenium sulfo- phthalocyanines (PtPcS, PdPcS and RuPcS) to act as singlet oxygen [1O2(1Δg)] photosensitizers in ene reactions in aque- ous medium has been investigated by combining time-re- solved and steady-state techniques. Laser flash photolysis experiments with nanosecond time resolution revealed the population of the lowest excited triplet state in the case of PtPcS and PdPcS upon light excitation. In both cases, this transient is effectively quenched by molecular oxygen lead- ing to the formation of 1O2(1Δg) with a quantum yield ΦΔ = 0.24, as unequivocally demonstrated by time-resolved near-infrared luminescence. In contrast, RuPcS did not photosen- sitize 1O2(1Δg), in accordance with the lack of population of the precursor excited triplet state. These metal–sulfophthalo- cyanines (MPcSs) were further tested in the ene reaction. In line with the photophysical results, PtPcS and PdPcS photo- sensitized the formation of hydroperoxide by 1O2(1Δg) ad- dition to the target α,β-unsaturated carboxylic derivatives whereas RuPcS was totally inactive in this respect. Support- ing the MPcSs on Amberlite® apparently made the ene reac- tion more rapid.
Water-soluble transition-metal phthalocyanines as singlet oxygen photosensitizers in ene reactions
D'AMBROSIO, PRIMIANO;TONUCCI, Lucia;D'ALESSANDRO, Nicola;BRESSAN, Mario
2011-01-01
Abstract
The capability of platinum, palladium and ruthenium sulfo- phthalocyanines (PtPcS, PdPcS and RuPcS) to act as singlet oxygen [1O2(1Δg)] photosensitizers in ene reactions in aque- ous medium has been investigated by combining time-re- solved and steady-state techniques. Laser flash photolysis experiments with nanosecond time resolution revealed the population of the lowest excited triplet state in the case of PtPcS and PdPcS upon light excitation. In both cases, this transient is effectively quenched by molecular oxygen lead- ing to the formation of 1O2(1Δg) with a quantum yield ΦΔ = 0.24, as unequivocally demonstrated by time-resolved near-infrared luminescence. In contrast, RuPcS did not photosen- sitize 1O2(1Δg), in accordance with the lack of population of the precursor excited triplet state. These metal–sulfophthalo- cyanines (MPcSs) were further tested in the ene reaction. In line with the photophysical results, PtPcS and PdPcS photo- sensitized the formation of hydroperoxide by 1O2(1Δg) ad- dition to the target α,β-unsaturated carboxylic derivatives whereas RuPcS was totally inactive in this respect. Support- ing the MPcSs on Amberlite® apparently made the ene reac- tion more rapid.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.