Open Research Europe: Methoxy- and methylthio-substituted paracyclophanetetraenes (PCTs)

In our article []Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs) [version 1; peer review: awaiting peer review] on the new open access platform of the European Commission, we report the synthesis, characterisation, and computational investigation of two substituted paracyclophanetetraenes (PCTs).

In the article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method.

The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles. We believe the study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

M. Pletzer, F. Plasser, M. Rimmele, M. Heeney, F. Glöcklhofer,* []Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p-phenylene vinylene)s (PPVs) [version 1; peer review: awaiting peer review], Open Res. Europe 2021, 1, 111. [Link, open access]