Molecular Engineering of the Physical Properties of Highly Luminescent π‑Conjugated Phospholes

The
syntheses as well as detailed studies on the thermal, photophysical,
and self-organization properties of a new series of phosphole-based
ladder-type materials with exocyclic 5-alkylthienyl substituents are
reported. The studies also include DFT calculations that provide support
for the experimentally determined photophysics. In contrast to the
related “phosphole-lipids” with fused conjugated head
that exhibit low luminescence in solution but high luminescence in
the solid state, the new system is highly luminescent in both solution
and the solid state. The extensive structure–property study
reported herein revealed that the physical properties of the new species
can significantly be tuned via the size of the conjugated system of
the head group, the functionalization of the phosphorus center, as
well as the length of the thiophene-appended alkyl chain that impacts
the intermolecular interactions via π–π stacking,
ionic, and van der Waals interactions, respectively. This molecular
engineering approach allows to access materials with intriguing properties
that range from highly emissive oils to self-organized one-dimensional
fibers.