Self-Assemblies, Folding, and Properties of Perylene Monomers, Oligomers, and Polymers - Molecular Self-Assembly: Advances and Applications - page 172

In contrast, the heterogeneous mixture between similarly coded
planar compounds resulted in a new cross-assembly

compound, the heterochromophoric cyclic dimer

1I and 1K

(Scheme 5.10).
NMR and absorbance data demonstrate that both planar compounds
independently display strong homogeneous

2J

π

-stacking interactions

while jointly exhibiting strong heterogeneous -stacking interactions.

Even though the monosulfur compound has a larger

π

π

-stack area
and such five-member ring addition enlarges its size and generates
slightly higher

π

-stacking force, the difference is not sufficient to
form a unique code, providing an example of code redundancy.

= 0.02), experimental
results reveal that their reactions proceed as if carried out in
separate flasks and the molecular codes effectively direct their
distinct separate reaction pathways. When two species co-self-
assemble (

When two species hardly mingle (

c

CA

c ≈

1.0), experimental results elucidate that redundant
molecular codes direct them down the same or very similar reaction
pathways. The imprinted twist angle (structural architecture)
determines the thermodynamic parameters and directs solvophobic
interactions, establishing useful molecular codes. The similarity
limits in twist angle for PDI code compatibility,

CA

∆ q °

,
effectively distinguishes unique molecular codes, corresponding to
a

> 15 twist

∆ G ∆ d

of about 1 kcal/mol. Differences in chemical shift ( ) and SA

absorbance ratio ( r ) effectively report the extent of

π

-stacking,

obs

providing metrics for code deciphering.
Understanding the forces directing self-assembly represents a
crucial step forward to mimic the mechanisms nature employs for
efficient and specific macromolecular synthesis. Variably twisting
the PDI cores effectively tunes the

π

-stacking force, imprinting
distinct molecular shapes and providing at least three independent
codes capable of organizing reaction centers and directing separate
reaction outcomes. Thus, a new hypothesis emerges: matching
of molecular size, shape, and charge produces synergistic weak
intermolecular attractive forces, which impart molecular codes;
such molecular codes effectively control chemical reaction pathways
and products.

5.6 Chiral Molecular Codes

While covalent bonds establish the primary molecular structures,
weak intra- and intermolecular forces govern molecular recognition