(see Table 4.4). Similarly to 18 (see Fig. 4.7), Hiroto and coworkers prepared P-(+)
and M-(À) enantiomers of 19 which displayed strong orange fluorescence
(Φ F ¼ 0.66 in dichloromethane) and moderate CPL activity (Æ1.2 Â 10
À3 )
[34]. Note that different emission properties between racemic and pure enantiomers
were obtained for this compound in the solid state but no CPL in the solid state
was reported.
In 2018, Bedekar and coworkers reported the preparation of (P)-(+) and (M )-(À)
enantiomers of two 5,13-dicyano-9-oxa[7]helicene derivatives 37 and 38 and
reported their photophysical and chiroptical properties [35]. These helical
compounds are also active in CPL and mirror-like CPL spectra were measured
with positive sign for (P) enantiomers, and g lum values of 3–5 Â 10
À3 in DMSO
solutions, i.e., falling within the classical range of helicene compounds. In 2014,
Bedekar and coworkers also reported helicene-like bis-oxazines 39 and 40
from atropisomeric 7,7
0 -dihydroxy BINOL derivatives displaying good CPL
activity, with g lum of +0.0015/À0.0009 and + 0.0014/À0.0013 for (P)À/(M)-39
and (P)À/(M)-40, respectively [36].
4.4 CPL-Active Sulfur-Containing Helicene Derivatives
There are few examples of CPL-active sulfur containing helicenes and helicenoids
reported in the literature. First of all, it is worth to compare results obtained for 34
with those reported by Katz and coworkers in 2001 on thia[7]helicene-bisquinone
derivative 41 decorated with four dodecyloxy groups [37]. Indeed, enantiopure [7]
helicene 41 aggregated into columnar structures depending on the solvent type. The
aggregation occurred in dodecane and in pure materials, but not in chloroform.
The specific rotation showed strong enhancement with increasing concentration,
i.e., [α] D ¼ 2800 and 10,400 at 2 Â 10
À5 M and 2 Â 10
À2 M, respectively, in
(P)-(+)-37
O
NC
NC
(P)-(+)-38
O
O
NC
NC
(P)-(+)-39
O
N
O
O
N
O
(P)-(+)-40
O
N
O
O
N
O
Ph
Ph
O
O
CO 2 Me
CO 2 Me
(P)-(+)-36
O
O
N
N
HO
O
H
(P)-34
O
O
CO 2 Me
CO 2 Me
(P)-(+)-35
Fig. 4.11 Chemical structures of oxahelicenic derivatives
66
J. Crassous
and M-(À) enantiomers of 19 which displayed strong orange fluorescence
(Φ F ¼ 0.66 in dichloromethane) and moderate CPL activity (Æ1.2 Â 10
À3 )
[34]. Note that different emission properties between racemic and pure enantiomers
were obtained for this compound in the solid state but no CPL in the solid state
was reported.
In 2018, Bedekar and coworkers reported the preparation of (P)-(+) and (M )-(À)
enantiomers of two 5,13-dicyano-9-oxa[7]helicene derivatives 37 and 38 and
reported their photophysical and chiroptical properties [35]. These helical
compounds are also active in CPL and mirror-like CPL spectra were measured
with positive sign for (P) enantiomers, and g lum values of 3–5 Â 10
À3 in DMSO
solutions, i.e., falling within the classical range of helicene compounds. In 2014,
Bedekar and coworkers also reported helicene-like bis-oxazines 39 and 40
from atropisomeric 7,7
0 -dihydroxy BINOL derivatives displaying good CPL
activity, with g lum of +0.0015/À0.0009 and + 0.0014/À0.0013 for (P)À/(M)-39
and (P)À/(M)-40, respectively [36].
4.4 CPL-Active Sulfur-Containing Helicene Derivatives
There are few examples of CPL-active sulfur containing helicenes and helicenoids
reported in the literature. First of all, it is worth to compare results obtained for 34
with those reported by Katz and coworkers in 2001 on thia[7]helicene-bisquinone
derivative 41 decorated with four dodecyloxy groups [37]. Indeed, enantiopure [7]
helicene 41 aggregated into columnar structures depending on the solvent type. The
aggregation occurred in dodecane and in pure materials, but not in chloroform.
The specific rotation showed strong enhancement with increasing concentration,
i.e., [α] D ¼ 2800 and 10,400 at 2 Â 10
À5 M and 2 Â 10
À2 M, respectively, in
(P)-(+)-37
O
NC
NC
(P)-(+)-38
O
O
NC
NC
(P)-(+)-39
O
N
O
O
N
O
(P)-(+)-40
O
N
O
O
N
O
Ph
Ph
O
O
CO 2 Me
CO 2 Me
(P)-(+)-36
O
O
N
N
HO
O
H
(P)-34
O
O
CO 2 Me
CO 2 Me
(P)-(+)-35
Fig. 4.11 Chemical structures of oxahelicenic derivatives
66
J. Crassous