Unexpected photo-initiated oxidation of antimony in (tetra-tert-butyl)phthalocyaninatoantimony(III) complex in the presence of singlet oxygen acceptors

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• 作者：Hiroaki Isago ; Kyoko Miura ; Masatoshi Kanesato
• 关键词：Phthalocyanine ; Antimony ; Singlet oxygen ; Oxidative addition
• 刊名：Journal of Photochemistry and Photobiology A ; Chemistry
• 出版年：2008
• 期刊代码：66_10106030
• 类别：ch
• 出版时间：25 June 2008
• 卷：197
• 期：2-3
• 页码：313-320
• 文件大小：684 K

摘要

The title complex cation, [Sb(tbpc)]⁺ (where tbpc denotes tetra(tert-butyl)phthalocyaninate, C₄₈H₄₈N₈²⁻), was gradually bleached under irradiation with visible light (900 > λ/nm > 600) in aerated nonaqueous solvents, such as CH₂Cl₂, CHCl₃, benzene, chlorobenzene. On the other hand, irradiation under the same conditions but in the presence of 1,3-diphenylisobenzofuran (DPBF) caused slow oxidation of [Sb(tbpc)]⁺ to the corresponding antimony(V) derivatives, [Sb(tbpc)LL′]⁺, (L and L′ denote monoanionic axial ligands containing oxygen as the donor atom), which was monitored by optical absorption and ESI-MS spectra of the photolyzed solutions. Both the photobleaching and oxidation have efficiently been inhibited by preliminary addition of β-carotene in photolyzed solutions, indicating that photosensitization of singlet oxygen (¹O₂) by [Sb(tbpc)]⁺ itself is involved. The use of furans (except dibenzofuran) or oxazoles instead of DPBF gave rise to similar oxidation but not in the case of the other type ¹O₂-acceptors, such as 9,10-diphenylanthracene, tetraphenylcyclopentadienone, or 2,3-dimethyl-2-butene, indicating that formation of ozonide-type endo-peroxide through 1,4-cycloaddition with ¹O₂ is essential. Peroxides, such as EtOOH and H₂O₂, generated through nucleophilic attack to the ozonide by EtOH and H₂O (present in the solvent) respectively, are considered to oxidize [Sb(tbpc)]⁺ to the antimony(V) species. Photochemistry of antimony–phthalocyanine complex has been studied for the first time of pnicogen derivatives of phthalocyanine.