Abstract
The design and synthesis of new macrocycles with well-defined cavities represent a
promising avenue for the development of new supramolecular hosts. Moreover, the ability
to diversify a macrocycle through chemical manipulations enables the fine-tuning and
tailoring of properties. In this report, the synthesis and functionalization of thiapillar[6]arene,
a pillar[6]arene analogue in which the bridging methylene groups are replaced by sulfurs,
are described. First, we demonstrate the scalable synthesis of the parent thiapillar[6]arene.
Next, the diversification of thiapillar[6]arene is demonstrated via functionalization
of the phenols and oxidation of the sulfur atoms. The solid-state structures of two
thiapillar[6]arene derivatives are reported, and the effect of sulfur oxidation state
on the macrocyclic conformation is discussed. All sulfone derivatives described were
found to demonstrate high luminescence quantum yields (ΦF = 0.43–0.66) in CH2Cl2 with emission maxima between λ = 404 and 462 nm. Lastly, assessment of the electrochemical
properties of the sulfone derivatives by square-wave voltammetry revealed electron-accepting
ability owing to the oxidation of the sulfur atoms, with four reduction events observed
for the analogues surveyed. Overall, this work implicates thiapillar[6]arene as a
modular scaffold amenable for further applications in host–guest chemistry and sensing.
Key words
pillararene - thiapillararene - macrocycle - fluorescence - sulfur
