Self-Assemblies, Folding, and Properties of Perylene Monomers, Oligomers, and Polymers - Molecular Self-Assembly: Advances and Applications - page 179

Figure 5.21 Normal-phase HPLC chromatograph separates the

homochiral cyclic dimer 2B and the heterochiral cyclic dimer

2K first. The fractions collected were immediately

characterized by ESI. Inset: Nearly identical mass spectra
were obtained for

, eluting 2K

(right), closely matching
the calculated isotopic pattern, with the exact

2K (left) and 2B

m / Z for [ 2B +

NH ] + = [ 2K + NH ] + = 1834.1. 4 4

HPLC monitoring was then performed, starting with each purified
compound at RT, to examine if the diastereomers truly interconvert,
or if the conversion proceeds in only one direction. Convincingly, the
reaction proceeds in both directions until reaching a 50/50 mixture
in about 24 h, after which no further change in the ratio occurred.
Noticing the relative slow interconversion rate, we next examined
the isomerization reaction rate temperature dependence. When
a solution of C for 24 h, NMR

proved that no noticeable isomerization occurred. These results
are consistent with previous studies [57] and the recently reported
free-energy barrier of 87 kJ/mol for interconverting chiral twisted
tetrachloroperylene enantiomers [60].

2K in CDCl was maintained at

−

20

°

3