Electron-transfer (ET) reactions from aromatic amines to excited states of rhenium(I)-based molecular rectangles[{Re(CO)
3(
-b
py)Br}{Re(CO)
3(
-L)Br}]
2 (b
py = 4,4'-bi
pyridine, L = 4,4'-di
pyridylacetylene (d
pa),
I; L =4,4'-di
pyridylbutadiyne (d
pb),
II; and L = 1,4-bis(4'-
pyridylethynyl)benzene (b
peb),
III) were investigatedin a dichloromethane solution using luminescence quenching techniques. Direct evidence for the ET reactionwas obtained from the detection of the amine cation radical in this system using time-resolved transientabsor
ption s
pectrosco
py. The values of the luminescence quenching rate constants,
kq, of the
3MLCT excitedstate of Re(I) rectangles with amines were found to be higher than those for the monomeric Re(I) com
plexesand other Re(I)-based metallacyclo
phanes. The observed
kq values were correlated well with the drivingforce (
G) for the ET reactions. In addition, a semiclassical theory of ET was successfully a
pplied to the
photoluminescence quenching of Re(I) rectangles with amines.