  Crystals of 1,3,5-tripyrrolebenzene (TPB) contain closely packed, perfectly
cofacial stacks of benzene rings with large wavefunction overlap, making it an
interesting candidate organic semiconductor. We study TPB using a variety of
ab-initio and band-structure techniques, and find very large $\pi$ overlap in
the benzene stacks, broad bands (especially for electrons), and relatively
small binding energies for polarons of both signs, making TPB a promising
quasi-one dimensional electron-transport agent. We then explore the sources of
the unusual packing in TPB, finding that calculations of intermolecular
interactions using dispersion-corrected density functional theory provide
valuable insights into why the crystals contain perfectly cofacial
$\pi$-networks.
