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Yield of ions produced in the luminescence quenching of tris (2,2′‐bipyridine)ruthenium(II) by dichlorophenolate ions
Author(s) -
Senz A.,
Gsponer H. E.
Publication year - 1995
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610081103
Subject(s) - chemistry , ruthenium , reaction rate constant , electron transfer , methanol , quenching (fluorescence) , aqueous solution , quantum yield , 2,2' bipyridine , photochemistry , solvent , excited state , yield (engineering) , fluorescence , kinetics , catalysis , crystallography , organic chemistry , crystal structure , quantum mechanics , nuclear physics , materials science , metallurgy , physics
Abstract The electron‐transfer quenching of Ru(bpy) 3 2+(tris(2,2′‐bipyridine)ruthenium(II) excited state by 2,4‐dichlorophenol (2,4‐DCP), 2,5‐dichlorophenol (2,5‐DCP) and 2,6‐dichlorophenol (2,6‐DCP), in their anionic forms, was studied in de‐aerated solutions of neat methanol and 25, 50 and 75% v/v aqueous methanol at 30°C. The quenching rate constants (k q ) were determined and their values range from 1 × 10 7 to 8 × 10 9 M −1 s −1 . In all the mixtures methanol : water the k q values for 2,5‐DCP were lower than for 2,4‐DCP and 2,6‐DCP. This result was discussed in terms of the effect of chloro atom on the quencher oxidation reaction. The photoredox product Ru(bpy) 3 +was observed by laser flash photolysis and its quantum yield (Φ Ru(+) ) calculated by using a comparative method with the formation of zinctetraphenylporphyrin triplet state. The yields of cage escape (Y ce ) for the different methanol/water mixtures were calculated from the obtained values of Φ Ru(+) ). Y ce increases from 0·1–0·2 in 25% v/v aqueous methanol to 0·5–0·6 in neat methanol. This change of Y ce with the solvent composition was discussed in terms of combined effects of viscosity and solvent cage on the rate constant of cage escape (k −d ) and the rate constant for back electron‐transfer to the ground state from geminate pair (k bc ), respectively. The constants k −d were calculated with the Eigen equation. The constants k bc were estimated from Y ce and k ‐d by applying a simplified reaction scheme. The k bc k bc values range from 3·2 × 10 9 to 1·3 × 10 10 s −1 .