have the same (R)-axial chirality were investigated, namely, (R)-(À)-(3,5-dioxa-4phosphacyclohepta[2,1-a:3,4-a
0 ]dinaphthalen-4-yl)dimethylamine [(R)-5], with a
single binaphthyl unit, and (11bR,11
0 bR)-4,4
0 -(9,9-dimethyl-9H-xanthene-4,5diyl)-bis-di-naphtha[2,1-d:1
0 ,2
0 -f][1,3,2]dioxaphosphepin [(R,R)-6], with two
binaphthyl units (Fig. 2.8).
The CPL and PL properties of (R)-5 and (R,R)-6 were compared in CHCl 3 . (R)-5
and (R,R)-6 exhibited PL maxima (λ PL ) at 361 and 362 nm in CHCl 3 , respectively, as
shown in Fig. 2.9. (R)-5 and (R,R)-6 emitted CPL in CHCl 3 . Surprisingly, although
(R)-5 and (R,R)-6 contain the same axially chiral binaphthyl unit, they exhibited
oppositely signed CPL spectra, with a positive (+) sign observed for (R)-5 and a
negative (À) sign observed for (R,R)-6. The values of g CPL were determined to be
about +3.4 Â 10
–3 for (R)-5 and À1.3 Â 10
–3 for (R,R)-6, where the |g CPL | value of
6 is smaller than that of 5 by a factor of three.
The solution-state CD and UV-Vis absorption spectra of (R)-5 and (R,R)-6 were
acquired (Fig. 2.10). Several characteristic UV-Vis bands arising from π-πÃ
O
O
P
O
O
P
O
O
O
P N
CH 3
CH 3
CH 3
CH 3
(R)-5
(R,R)-6
Fig. 2.8 Chiral binaphthyl
fluorophores (R)-5 and (R,
R)-6
0.0
1.0
2.0
3.0
4.0
5.0
6.0
340 360 380 400 420 440
-80
-60
-40
-20
0
20
40
60
80
100
DC / V
CPL / mdeg
Wavelength / nm
Fig. 2.9 CPL (upper) and
PL (lower) spectra of (R)-5
(black) and (R,R)-6 (red) in
CHCl 3 (1.0 Â 10
À3
M)
2 Circularly Polarized Luminescence of Axially Chiral Binaphthyl Fluorophores
17