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Intramolecular electron transfer on the vibrational timescale and rate constants estimated by IR absorption band shape analysis
Author(s) -
Ito Tasuku,
Yamaguchi Tadashi,
Kubiak Clifford P.
Publication year - 2000
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200007)156:1<269::aid-masy269>3.0.co;2-7
Subject(s) - intramolecular force , chemistry , pyrazine , electron transfer , octane , reaction rate constant , valence (chemistry) , pyridine , electrochemistry , absorption spectroscopy , crystallography , analytical chemistry (journal) , stereochemistry , medicinal chemistry , kinetics , organic chemistry , physics , electrode , quantum mechanics
From electrochemical studies, the thermodynamic stability of the mixed valence (one electron reduced) state and the electronic coupling between linked Ru 3 units, was studied in the series of the ligand bridged hexaruthenium clusters, [Ru 3 (μ 3 −O)(μ−CH 3 CO 2 ) 6 (CO)(L)(μ−BL)Ru 3 (μ 3 −O)−(μ−CH 3 CO 2 ) 6 (CO)(L)] (BL = pyrazine: L = 4‐dimethyl‐aminopyridine (dmap) ( 1a ), pyridine (py) ( 1b ), 4‐cyanopyridine (cpy) ( 1c ), 1‐azabicyclo[2.2.2]octane ( 1d ); BL = 4,4′‐bipyridine: L = dmap ( 2a ), py ( 2b ), cpy ( 2c ); BL = 2,7‐diazapyrene: L = dmap ( 3a ); BL = 1,4‐diazabicyclo‐[2.2.2]octane: L = dmap ( 4a ), py ( 4b ), cpy ( 4c )). The mixed valence states undergoing the most rapid intramolecular electron transfers were observed by reflectance IR spectroelectrochemistry. By simulating dynamical effects on the observed ν(CO) absorption bandshapes, the rate constants, k e , for electron transfer in the mixed valence states of 1a , 1b , 1c and 1d were estimated to be 9 × 10 11 s −1 (at room temperature (rt)), 5 × 10 11 s −1 (at rt), ca . 1 × 10 11 s −1 (at rt), and 1 × 10 12 s −1 (at −18 °C), respectively. The rate constant for the −1 mixed valence state of 2a is close to the lower limit that can be estimated by this approach, between 1 × 10 10 and 1 × 10 11 s −1 .