Chlorine and singlet oxygen photoelimination from organoplatinum(IV) complexes
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Solar energy is the most promising carbon neutral energy source for the future. Splitting of simple molecules like HX (X = Cl, Br) has become an attractive way to convert and store solar energy. Halogen photoelimination from metal centers is the most challenging step in photochemical HX splitting cycles. We have synthesized Pt(IV) chloro complexes trans -Pt(PEt3)2R(Cl)3 (R = Cl, aryl and PAH fragments), which eliminate chlorine in the presence of halogen traps when irradiated with uv-vis light. The photo-efficiency of Pt--chloride bond activation increases in the presence of Pt(II) complexes trans -Pt(PEt3)2R(Cl) suggesting the absence of molecular chlorine from reductive elimination of Pt(IV) chloro complexes. Also, we propose that the mechanism of halogen photoelimination from Pt(PEt3)2X3R (X = Cl, Br) (R = aryl, Cl, PAH) complexes is cis elimination via radical abstraction. Synthesis, characterization and photochemistry of a new Pt(IV) carbene pincer hydroperoxo hydroxo complex is described. This complex is highly active photochemically showing 1280% quantum yield and eliminates singlet oxygen and water under ultraviolet light. The photoelimination of singlet oxygen in 86% yield from Pt(IV) carbene pincer hydroperoxo hydroxo complex can be considered as a new route to activate ground state oxygen to excited state oxygen which is vital for complex biological studies.