A series of π-conjugated phenyl-pyrenoimidazole
(Py-Im) systems were synthesized through a one-pot condensation
reaction
between 4,5-pyrenedione and various benzaldehyde derivatives. The
single crystal structures of these Py-Im compounds were
determined, and the results showed that Py-Ims can serve
as versatile supramolecular synthons for the formation of diverse
solid-state structures, ranging from linear hydrogen bonded networks
to complex helical hydrogen bonded networks and layered π–π
stacking assemblies. The crystallographic structures exhibit correlation
to the nature of substituent groups attached to the Py-Im systems, while the dominant intermolecular forces that dictate their
solid-state packing can be reasonably accounted for by molecular electrostatic
potential analysis. Photophysical properties of these Py-Im derivatives were examined by UV–vis absorption and fluorescence
spectroscopy. Our studies disclosed that weak-to-moderate electron-donating/withdrawing
groups have insignificant effects, but strongly electron-withdrawing
groups can greatly alter the photophysical properties through enhanced
proton-exchange processes taking place on the imidazolyl moiety.