Self-Assemblies, Folding, and Properties of Perylene Monomers, Oligomers, and Polymers - Molecular Self-Assembly: Advances and Applications - page 163

chemical shifts between 1 and 2A in ppm are ∆

d ε ∼

0.23, ∆

d φ ∼

0.23,

∆ 0.63. Additionally, median

NOE coupling strengths were observed in monocycle

d γ ∼

0.36, ∆

d η ∼

0.63, ∆

d ι ∼

0.65, and ∆

d ϕ ∼

between the
protons adjacent to disulfide linkages and the perylene aromatic
protons in the 1D GOESY experiment, indicating the ”basket”
structure of

1

. However, no NOE exists between the protons adjacent
to disulfide bonds and those on aromatic rings in the dimer-based
cycles (

1

) because the perylene stack forces the flexible chains
far away from the compact aromatic cores.

2A , 2 x 2

has a
monocyclic ring structure and is a monocyclic monomer. For
compound

The aforementioned NMR analysis validates that 1

, eight sets of symmetric ethylene chemical resonances
in the NMR spectrum corroborate that it must be a ring structure
because linear structures will yield more than eight sets of aliphatic
protons (Fig. 5.17). This is in contrast to compound

2A

that does
have NOE; no NOE is observed between aromatic protons and
ethylene units in compound

1

. As a result, the structure cannot be
concatenated rings as shown in compound

2A

1 x 1 . Thus, compound 2A

must be a monocyclic dimer. Similarly, the observation of eight sets
of symmetric ethylene chemical resonances in the NMR spectrum
of indicates that it must be a ring-structured compound. One

such compound containing four perylene units has asymmetric
concatenated rings; this is compound

2 x 2

has more
than eight sets of protons because the two rings are not equivalent,
and therefore NMR has ruled out the possibility of asymmetric rings,
or

1 x 3 . Compound 1 x 3

being the major product. The only other possibility is that
the major product could be the monocyclic tetramer or compound
4

1 x 3

. If the perylene units had no interactions (i.e., no

π

-stacking) in

the monocyclic tetramer , there would be eight sets of ethylene

proton resonances, but the aromatic protons would not shift upfield
and the separation between bay protons and outer protons would
not occur. In the case of

4

-stacking, as indicated by the upfield shift
and separation of the aromatic protons, there will be more than
eight sets of protons for the monocyclic tetramer

π

. Therefore, the
simultaneous observation of the upfield shift and the separation of
outer-bay protons and the eight sets of symmetric ethylene protons
(Fig. 5.17) has ruled out the possibility of compound

4

being the
major product. This leads to the conclusion that compound

4

2 x 2

must have a concatenated dimer

−

dimer ring structure.