Extending the chain

p

z

p

z

Paired

electrons

LUMO

band

HOMO

band

p

*

Interchain

stacking and overlap

(3-D band)

orbitals

Isolated

p

Linear

chain

(1-D band)

sp2 hybridization

C

C

H

H

C

H

A simple picture of the one-dimensional band as the chain lengthens: