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Water‐Soluble Transition‐Metal‐Phthalocyanines as Singlet Oxygen Photosensitizers in Ene Reactions
Author(s) -
D'Ambrosio Primiano,
Tonucci Lucia,
d'Alessandro Nicola,
Morvillo Antonino,
Sortino Salvatore,
Bressan Mario
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201000784
Subject(s) - chemistry , photochemistry , singlet oxygen , flash photolysis , excited state , ruthenium , quantum yield , triplet state , population , quenching (fluorescence) , oxygen , fluorescence , molecule , reaction rate constant , catalysis , kinetics , organic chemistry , physics , demography , quantum mechanics , sociology , nuclear physics
The capability of platinum, palladium and ruthenium sulfophthalocyanines (PtPcS, PdPcS and RuPcS) to act as singlet oxygen [ 1 O 2 ( 1 Δ g )] photosensitizers in ene reactions in aqueous medium has been investigated by combining time‐resolved 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 leading to the formation of 1 O 2 ( 1 Δ g ) with a quantum yield Φ Δ = 0.24, as unequivocally demonstrated by time‐resolved near‐infrared luminescence. In contrast, RuPcS did not photosensitize 1 O 2 ( 1 Δ g ), in accordance with the lack of population of the precursor excited triplet state. These metal–sulfophthalocyanines (MPcSs) were further tested in the ene reaction. In line with the photophysical results, PtPcS and PdPcS photosensitized the formation of hydroperoxide by 1 O 2 ( 1 Δ g ) addition to the target α,β‐unsaturated carboxylic derivatives whereas RuPcS was totally inactive in this respect. Supporting the MPcSs on Amberlite ® apparently made the ene reaction more rapid.