Henry Rzepa's Blog

The annual “molecule of the year” results for 2021 are now available … and the winner is Infinitene.[cite]10.33774/chemrxiv-2021-pcwcc[/cite],[cite]10.1021/jacs.1c10807[/cite] This is a benzocirculene in the form of a figure eight loop (the infinity symbol), a shape which is also called a lemniscate [cite]10.1021/jo801022b[/cite] after the mathematical (2D) function due to Bernoulli. The most common class of molecule which exhibits this (well known) motif are hexaphyrins (hexaporphyrins; porphyrin is a tetraphyrin)[cite]10.1039/b502327k[/cite],[cite]10.1021/ol0521937[/cite],[cite]10.1002/chem.200600158[/cite], many of which exhibit lemniscular topology as determined from a crystal structure. Straightforward annulenes have also been noted to display this[cite]10.1107/S1600536811048604[/cite] (as first suggested here for a [14]annulene[cite]10.1021/ol0518333[/cite]) and other molecules show higher-order Möbius forms such as trefoil knots.[cite]10.1038/NCHEM.1955[/cite],[cite]10.1039/D0CC04190D[/cite] This new example uses twelve benzo groups instead of six porphyrin units to construct the lemniscate. So the motif is not new, but this is the first time it has been constructed purely from benzene rings. (more…)