Six-membered ring chelate complexes of Ru(II): structural and photophysical effects.
The structural and photophysical properties of Ru(II)-polypyridyl complexes with five- and six-membered chelate rings were studied for two bis-tridentate and two tris-bidentate complexes. The photophysical effect of introducing a six-membered chelate ring is most pronounced for the tridentate complex, leading to a room-temperature excited-state lifetime of 810 ns, a substantial increase from 180 ns for the five-membered chelate ring model complex. Contrasting this, the effect is the opposite in tris-bidentate complexes, in which the lifetime decreases from 430 ns to around 1 ns in going from a five-membered to six-membered chelate ring. All of the complexes were studied spectroscopically at both 80 K and ambient temperatures, and the temperature dependence of the excited-state lifetime was investigated for both of the bis-tridentate complexes. The main reason for the long excited-state lifetime in the six-membered chelate ring bis-tridentate complex was found to be a strong retardation of the activated decay via metal-centered states, largely due to an increased ligand field splitting due to the complex having a more-octahedral geometry.
Abrahamsson
Maria
M
Chemical Physics, Department of Photochemistry and Molecular Science, The Angström Laboratories, Uppsala University, Box 523, SE-751 20 Uppsala, Sweden.
Becker
Hans-Christian
HC
Hammarström
Leif
L
Bonnefous
Celine
C
Chamchoumis
Charles
C
Thummel
Randolph P
RP