Self-Assemblies, Folding, and Properties of Perylene Monomers, Oligomers, and Polymers - Molecular Self-Assembly: Advances and Applications - page 164

Figure 5.17

1

H NMR spectra of (a) dimer

−

dimer catenane 2 x 2 , (b)

macrocyclic dimer 2A , and (c) macrocyclic monomer 1 . Note

the upfield shift of the aromatic protons in catenane 2 x 2 and

macrocyclic dimer due to perylene forming stacks and

spreading of the aliphatic protons on the TEG chain in the
monocyclic monomer

2A

1 .

Perylene folded in a stacking motif shows a remarkable intensity
reversal between the vibronic 0

→

0 band and 0

→

1 band in the

electronic absorption of the

π

-to-

π

*

transition. Accordingly, the

monocyclic perylene monomer 1 should resemble the free perylene

derivative such as 1A as shown in Fig. 5.18a. Similarly, to the linear

folded dimer ( 2A ), the optical absorption spectrum of the cyclic 2A

→ →

confirms the reversal of vibronic 0 1 band intensity (Fig.

5.18b), validating a ring with one perylene unit docking on another.
Optical absorption of catenane

0 and 0

is almost identical to the linear
folded tetramer, proving that the four perylene units are

2 x 2

π

-stacked
(Fig. 5.18c). The results of optical absorption studies of catenane 2 x 2

support the MS and NMR assignment of a concatenated dimer

−

dimer

ring structure.

5.5.3 Definition of Molecular Codes

Perylene diimides (PDIs) are particularly interesting because they
assemble efficiently, often augmented by solvophobic forces. Bay
substitutions twist the perylene dihedrally out of plane, with the
dihedral angle tunable from 0 to 37

° −

57]. Remarkably, differently
twisted monomers preferentially self-assemble into segregated
nanostructures even in the presence of other twisted units, revealing
their unique molecular encryption (Scheme 5.8).

[55