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Photoinduced electron-transfer processes involving covalently linked ruthenium and cobalt polypyridyl complexes. Comparison of electronic coupling in bridged and nonbridged ruthenium and cobalt complexes

Journal Article · · Journal of Physical Chemistry; (United States)
DOI:https://doi.org/10.1021/j100115a026· OSTI ID:6259133
; ;  [1]; ; ;  [2];  [3]
  1. Wayne State Univ., Detroit, MI (United States)
  2. Univ. of North Carolina, Charlotte (United States)
  3. Wayne State Univ., Detroit, MI (United States) Univ. of North Carolina, Charlotte (United States)
+ Show Author Affiliations
Photoinduced electron-transfer processes have been examined in a heterobimetallic coordination complex with polypyridyl ligands. Three relaxation processes were observed to follow light absorption by (bpy)[sub 2]Ru(bb)Co(bpy)[sub 2][sup 5+] (where bpy = 2,2'-bipyridine and bb 1,2-bis(2,2'-bipyridyl-4'-yl)ethane) with lifetimes in water at 25[degrees]C of 0.18, 1, and 6 ns determined using picosecond flash photolysis techniques. These nearly solvent independent relaxation rates are ascribed to forward electron transfer from ([sup 3]MLCT)Ru(bpy)[sub 2][sup 2+] to Co(bpy)[sub 2][sup 3+], spin relaxation at the Co(II) center and back electron transfer from ([sup 4]T[sub 1])Co(bpy)[sub 2][sub 2+] to Ru(bpy)[sub 2][sup 3+]. Luminescence decay of ([sup 3]MLCT)Ru(bpy)[sub 2][sup 2+] has also been used to monitor the electron-transfer quenching step from 77-150 K, and the quenching rate extrapolated to 25[degrees]C (activation energy of 2.2 [times] 10[sup 3] cm[sup [minus]1]) was compatible with the 180-ps lifetime. It is inferred that the back electron transfer rate is retarded by poor donor-acceptor electronic coupling (k[sub el] [congruent] 10[sup [minus]3]). A Mulliken type of perturbational model is proposed to describe the weak electronic coupling in this complex. Spectroscopic parameters are combined with the perturbational expressions to give a plausible account of the electronic coupling in the back-electron-transfer process. 84 refs., 9 figs., 5 tabs.
DOE Contract Number:
FG05-84ER13263; FG02-88ER13944
OSTI ID:
6259133
Journal Information:
Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:13; ISSN JPCHAX; ISSN 0022-3654
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AZINES
BIPYRIDINES
CHEMICAL REACTIONS
COBALT COMPLEXES
COMPLEXES
DATA
DECOMPOSITION
ELECTRON TRANSFER
HETEROCYCLIC COMPOUNDS
INFORMATION
MATHEMATICAL MODELS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PERTURBATION THEORY
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PYRIDINES
RELAXATION
RUTHENIUM COMPLEXES
THEORETICAL DATA
TRANSITION ELEMENT COMPLEXES