This approach was followed for the first time by Sisido et al. in 1985 [13]. They
synthesized a poly-pyrenylalanine (pyr-2, Scheme 12.1) and studied the CPL in
polar solvents, such as dimethylformamide (DMF) at variable temperature
(6 Â 10
À5 M). The g lum vs. wavelength plot showed a sign inversion upon changing
the temperature (from 3 to 60
C) and even a bisignate profile for intermediate
temperatures. These features suggest the presence of two sources for the excimer
transitions: one stems from an apolar contribution due to exciton resonance (PyrÃ-Pyr $ Pyr-PyrÃ), predominant at lower wavelengths, the second one comes from
charge transfer resonance (Pyr
+
-Pyr
À
$ Pyr
À -Pyr
+
), predominant at longer
Inouye 2014
O
O
O
O
4
4
HOOC
COOH
R =
R
R
pyr-1
Fig. 12.2 Top: adopted strategy for inclusion of pyrene dimers in γ-CDx and CPL/total luminescence spectra measured in H 2 O (pH 9.5, C ¼ 4.5 Â 10
À5 M). Bottom: structure of the compound.
Adapted with permission from reference [12]
n
Sisido 1985
pyr-2
H
N
N
H
O
H
H
N
O
H
N
O
N
H
O
R
H
N
O
O
O
R
n
m
4
O
O
R =
n = 34, m = 0
n = 28, m = 2
pyr-3
pyr-4
Sisido 1990
Scheme 12.1 Structures of pyrene-decorated polypeptides developed by Sisido
12 Circularly Polarized Luminescence from Intramolecular Excimers
277