Self-Assemblies, Folding, and Properties of Perylene Monomers, Oligomers, and Polymers - Molecular Self-Assembly: Advances and Applications - page 183

than the dimeric species. Interestingly, all spectra also retain a
significant monomer-like green emission component. However, the
substantial magnitude of green fluorescence does not translate to a
large monomer-like

population, as optical absorption
and NMR studies reveal that cyclic and linear compounds are almost
completely folded before photoexcitation. Because the ground state
exhibits minimal monomer-like characteristics, the substantial
monomer-like emission can only hint that the foldamer excited states
have active and relatively fast dynamics shuffling folded, partially
folded, and unfolded motifs.

ground-state

Figure 5.22 Normalized absorption (left) and emission (right) spectra

of the dimer (top) and tetramer (bottom) oligomers at nM
concentrations in 4:1 CH :MeOH. The free monomer

(dashed line) is shown for comparison. The cyclic dimer
(

Cl

2 2

) in red have
almost identical absorbance spectra as the linear dimer (

2A ) and the concatenated tetramer ( 2 x 2

2A )

and tetramer ( ) in green showing that cyclic and linear

foldamers are folded similarly in the ground state. The linear
foldamers display higher relative monomer-like emission,
which is indicative of photoinduced unfolding.

4A