nonplanar geometry between phenyl rings (45
) enforced by the host, which is a
consequence of the dihedral angle between the two monomeric units of the capsules
(Fig. 7). When the complex was elongated by incorporating glycoluril spacers to
form the RH•L 4 •RH, STB was able to adapt a fully coplanar arrangement, and
Squaraine (SQ) dyes
SQ*
SQ*
ANT*
ANT*
Py…Py*
SQ*
Fig. 5 Formation of ternary complex of anthracene (ANT), squaraines (SQ), and
γ-CD. Photoexcitation of ANT transfers energy to SQ co-guest which fluoresces in near
IR. Spectra, (top left) comparison of fluorescence spectra from excitation at 360 nm to excitation
at 620 nm (9 mM γ-CD, 45 μM ANT, and 11 μM SQ) and (top right) fluorescence spectra at
different concentrations of γ-CD (45 μM ANT and 53 μM SQ). (Bottom) Excimer emission
spectrum of pyrene (Py) decreases as SQ fluorescence increases (inset) in ternary complexes with
40 μM Py, SQ, and 9 mM γ-CD. Spectra are used with permission from Taylor and Francis [34]
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M. Pattabiraman and A. Natarajan
) enforced by the host, which is a
consequence of the dihedral angle between the two monomeric units of the capsules
(Fig. 7). When the complex was elongated by incorporating glycoluril spacers to
form the RH•L 4 •RH, STB was able to adapt a fully coplanar arrangement, and
Squaraine (SQ) dyes
SQ*
SQ*
ANT*
ANT*
Py…Py*
SQ*
Fig. 5 Formation of ternary complex of anthracene (ANT), squaraines (SQ), and
γ-CD. Photoexcitation of ANT transfers energy to SQ co-guest which fluoresces in near
IR. Spectra, (top left) comparison of fluorescence spectra from excitation at 360 nm to excitation
at 620 nm (9 mM γ-CD, 45 μM ANT, and 11 μM SQ) and (top right) fluorescence spectra at
different concentrations of γ-CD (45 μM ANT and 53 μM SQ). (Bottom) Excimer emission
spectrum of pyrene (Py) decreases as SQ fluorescence increases (inset) in ternary complexes with
40 μM Py, SQ, and 9 mM γ-CD. Spectra are used with permission from Taylor and Francis [34]
330
M. Pattabiraman and A. Natarajan