Effect of the coordination sphere of d0 metallocene on triplet-triplet energy transfer |
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Authors: | G. V. Loukova V. A. Smirnov S. Å. Starodubova |
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Affiliation: | (1) Institute of Problems of Chemical Physics, Russian Academy of Sciences, 1 prosp. Akad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation |
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Abstract: | The triplet nature of rare long-lived states of d0 metallocenes formed upon ligand-to-metal energy transfer was confirmed by studies of triplet-triplet charge transfer in biscyclopentadienyl complexes Cp2MCl2 (M = Zr (1), Hf (2)). The interaction between precatalysts and substrates of catalytic polymerization systems, viz., complexes 1 and 2 and unsaturated hydrocarbons (alkenes and dienes), was studied in the region of concentrations close to catalytic values. For organometallic π-complexes, it has been shown for the first time that, in the case of the unsaturated hydrocarbons, the efficiency of energy transfer obeys the Perrin equation. The process occurs at distances R 0 close to the diameter of the interacting molecules and is well described by the exchange-resonant mechanism of interaction. In the case of the cyclopentadiene-Cp2MCl2 (M = Zr, Hf) systems, R 0 = 14.6 Å. A linear relationship between the critical radius of the quenching sphere R 0 and the number of carbon atoms in a linear α-olefin has been revealed for the first time and evidences the formation of a π-complex between the precatalyst and substrate molecules. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–39, January, 2007. |
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Keywords: | energy transfer triplet-triplet quenching of luminescence excited states of organometallic compounds ligand-to-metal charge transfer phosphorescence zirconinum complexes hafnium complexes |
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