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Phthalocyanines and related macrocycles for multi‐electron transfer in catalysis, photochemistry and photoelectrochemistry
Author(s) -
Wöhrle Dieter,
Schlettwein Derck,
Schnurpfeil Günter,
Schneider Gerhard,
Karmann Elfriede,
Yoshida Tsukasa,
Kaneko Masao
Publication year - 1995
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1995.220060305
Subject(s) - phthalocyanine , photochemistry , electron transfer , singlet oxygen , photoelectrochemistry , chemistry , catalysis , redox , zinc sulfide , singlet state , sulfide , zinc , materials science , inorganic chemistry , oxygen , electrochemistry , organic chemistry , excited state , electrode , physics , nuclear physics
At different phthalocyanines and related macrocycles it is shown that one‐step, multi‐electron transfer and one‐step, multi‐change of oxidation states occur. At first, the catalytic oxidations of thiols and sulfide in the presence of different Co(II)phthalocyanines are discussed. Thiolates are oxidized to disulfides via a two‐electron transfer whereas the reduction of O 2 occurs via a two‐ or four‐electron transfer to H 2 O 2 or H 2 O. Zn(II) and Al(III)phthalocyanines are efficient sensitizers for the conversion of triplet to singlet dioxygen under illumination with visible light. In the presence of thiolates or sulfides an efficient photo‐oxidation to sulfonic acids or sulfate is observed. The oxidation state of sulfur changes from −2 to +4 or +6, respectively. This process of singlet oxygen reactions finds application in the photodynamic therapy of cancer. The unsubstituted zinc(II)‐phthalocyanine as p‐type molecular semiconductor can efficienfly reduce O 2 in photoelectrochemical experiments whereas zinc(II)phthalocyanines with electronwithdrawing groups as n‐type conductors are active in the photoelectrochemical oxidation of thiols. All processes include multi‐electron transfer. The electrocatalytic reduction of CO 2 is investigated at electrodes modified with Co(II)phthalocyanine. In particular, the phthalocyanine in a polyvinylpyridine membrane is active, so the CO 2 is reduced to CO by multi‐electron transfer. In addition, two photon excitations of a Mg(II)phthalocyanine are presented and some examples are reviewed.