The g CPL values were determined to be about À7.8 Â 10
–4 in CHCl 3 solution and
about +3.6 Â 10
–4 in PMMA film. Hence, both λ CPL and CPL sign of a chiral organic
fluorophore are tunable by changing between fluidic CHCl 3 solution and a glassy
PMMA film. On the other hand, the CD spectra of 7 in PMMA film (Fig. 2.22) are
almost identical to those in CHCl 3 [Fig. 2.16a]; the g CD value of the first Cotton CD
band of (R)-7 is about À3.8 Â 10
–5 at 344 nm in PMMA film (À5.9 Â 10
–5 in CHCl 3
solution).
In CHCl 3 solution, the two photoexcited pyrene moieties in (R)-7 can approach
each other more closely through reorganization. On the other hand, in PMMA film,
although a remote intramolecular pyrene interaction produce chiral environment of
pyrene units, the PMMA glassy solid inhibits the formation of a closer intramolecular pyrene excimer. The intramolecular reoriented mode involving the two pyrene
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
370 420 470 520 570
-60
-50
-40
-30
-20
-10
0
10
20
DC / V
CPL / mdeg
Wavelength / nm
Fig. 2.21 CPL (upper) and
PL (lower) spectra of (R)-7
in CHCl 3 (1.0 Â 10
-3 M)
(red) and in the PMMA filmdispersed state (black)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
-8
-6
-4
-2
0
2
4
310
340
370
400
Absorbance
g
e
d
m
/
D
CD / mdeg
Wavelength / nm
Fig. 2.22 CD (upper) and
UV-Vis (lower) absorption
spectra of (R)-7 (red) and
(S)-7 (black) in the PMMA
film-dispersed state
26
Y. Imai