band is the same as the sign of the longer wavelength ECD component of the exciton
feature described above (see Fig. 10.7) [48]. Furthermore, there is an important
solvent dependence of the phenomena: (1) the absorption and ECD spectra undergo
a bathochromic shift in going from methanol to dimethyl sulfoxide (DMSO) both in
the neutral and in the basic solution, while fluorescence and CPL spectra of the basic
solutions shift correspondingly by ca. 25 nm. (2) For diesters we have g lum < 10
–3 in
MeOH solution and g lum % 1.5 Â 10
–3 in DMSO solution, while correspondingly
g abs % 0.8 Â 10
–3 in MeOH and in DMSO. Consequently, for cyclohexane diesters
Fig. 10.6 (Top): CPL spectra of the pyrene-o-OPE ether compound (p,p)-(1S,2S) in CH 2 Cl 2
solutions with different amounts of Ag(I): on the right the linearity plot of the ratio
ΔI 410nm /ΔI 520nm of the o-OPE CPL emission to the pyrene CPL emission is reported. (Bottom):
Molecular orbital representation of the principal orbitals involved in bands assigned to pyrene
moieties and conserved upon Ag complexation, in absence (left) or presence (right) of Ag cation
(see Ref. [41])
230
G. Longhi and S. Abbate
feature described above (see Fig. 10.7) [48]. Furthermore, there is an important
solvent dependence of the phenomena: (1) the absorption and ECD spectra undergo
a bathochromic shift in going from methanol to dimethyl sulfoxide (DMSO) both in
the neutral and in the basic solution, while fluorescence and CPL spectra of the basic
solutions shift correspondingly by ca. 25 nm. (2) For diesters we have g lum < 10
–3 in
MeOH solution and g lum % 1.5 Â 10
–3 in DMSO solution, while correspondingly
g abs % 0.8 Â 10
–3 in MeOH and in DMSO. Consequently, for cyclohexane diesters
Fig. 10.6 (Top): CPL spectra of the pyrene-o-OPE ether compound (p,p)-(1S,2S) in CH 2 Cl 2
solutions with different amounts of Ag(I): on the right the linearity plot of the ratio
ΔI 410nm /ΔI 520nm of the o-OPE CPL emission to the pyrene CPL emission is reported. (Bottom):
Molecular orbital representation of the principal orbitals involved in bands assigned to pyrene
moieties and conserved upon Ag complexation, in absence (left) or presence (right) of Ag cation
(see Ref. [41])
230
G. Longhi and S. Abbate