Octalenobisterphenylene and Its Diradical Dianionic Cyclodimer: Synthesis, Structural Analysis, and Properties

Abstract Octalenobisterphenylene 1 (also known as terphenylene dimer) was synthesized from 3,3′,5,5′‐tetraaryl‐substituted biaryl by tert ‐butyllithium‐mediated cyclization followed by oxidative coupling. This one‐pot two‐step protocol facilitated the successive formation of four four‐membered and two eight‐membered rings. Treatment of 1 with sodium metal, followed by crystallization from THF, yielded the remarkable diradical dianion [( 1 •– ) 2 ] 2− , where the two molecular halves are connected by four σ bonds. The cyclodimerization is driven by the pronounced reactivity and strain of the central six‐membered ring within the [3]phenylene subunit. The structure and diradical nature of [(Na + ) 2 ( 1 •– ) 2 ] were confirmed through X‐ray crystallography, DFT computations, and 1 H NMR and ESR spectra. These investigations revealed that the two spins, one on each molecular half, exhibit minimal mutual interaction.