Strong π-stacking causes unusually large anisotropic thermal expansion and thermochromism
Madushani Dharmarwardana, Brooke M. Otten, Mukunda M. Ghimire, Bhargav S. Arimilli, Christopher M. Williams, Stephen Boateng, Zhou Lü, Gregory T. McCandless, Jeremiah J. Gassensmith, Mohammad A. Omary
Abstract
Significance π-stacking of polynuclear aromatic rings encompasses fundamental scientific phenomena in chemical bonding and photophysics with strong impacts on societal aspects that include electronic devices, DNA/RNA intercalation, and optical sensing of environmental pollutants. This work describes unusually strong π-stacking in a recently synthesized naphthalene-diimide derivative, as well as a prototypical π-stacked molecule, pyrene. The infinite/cooperative π-stacking in the former and dimer stacking in the latter are much stronger than previously thought to be possible for this type of supramolecular interaction, reaching ∼50 and 20 kcal ⋅ mol −1 , respectively. This has led to unusually large anisotropic thermal expansion and multicycle/multicolor thermochromism in BNDI-T, whereas multiple unusual binding and photophysical properties have been discovered for the classical organic chromophore pyrene.