In this report, we describe the synthesis
and electronic properties
of small-molecule and polymeric [8]cycloparaphenylenes ([8]CPPs) with
disjointed pi-conjugated substituents. Arylene-ethynylene linkers
were installed on opposite sides of the [8]CPP nanohoop as separated
by three phenyl units on either side such that the monomer systems
have syn (C2 symmetry) and anti (C1 symmetry) conformers with a small energy gap (0.1–0.6
kcal/mol). This disjoined substitution pattern necessarily forces
delocalization through and around the CPP radial structure. We demonstrate
new electronic states from this radial/linear mixing in both the small
molecules and the pi extended polymers. Quantum chemical calculations
reveal that these electronic processes arise from multiple operative
radial/linear conjugation pathways, as the disjoint pattern results
in both ortho and meta connections
to the CPP ring. These results affirm the unique nature of hybrid
radial and linear pi electron delocalization operative in these new
conjugation pathways.
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