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

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Terphenylene subunits are known for their unique electronic and structural properties.
• The synthesis of complex polycyclic aromatic hydrocarbons presents significant synthetic challenges.
• Diradical species are of interest due to their unusual bonding and potential applications.

Purpose of the Study:

• To synthesize a novel terphenylene dimer, octalenobisterphenylene 1.
• To investigate the formation and properties of a diradical dianion derived from octalenobisterphenylene 1.
• To explore the structural and electronic characteristics of the cyclodimerized product.

Main Methods:

• Synthesis of octalenobisterphenylene 1 via tert-butyllithium-mediated cyclization and oxidative coupling.
• Generation of the diradical dianion through treatment with sodium metal and crystallization.
• Characterization using X-ray crystallography, DFT computations, 1H NMR, and ESR spectroscopy.

Main Results:

• A one-pot, two-step synthesis yielded octalenobisterphenylene 1, forming multiple fused rings.
• The diradical dianion [(1•−)2]2− was successfully isolated and characterized, featuring four σ bonds connecting molecular halves.
• X-ray crystallography and computational studies confirmed the structure and revealed minimal spin interaction between the two radical centers.

Conclusions:

• The cyclodimerization of the [3]phenylene subunit is driven by inherent reactivity and ring strain.
• The synthesized diradical dianion represents a novel molecular architecture with distinct electronic properties.
• The findings provide insights into the synthesis and behavior of complex polycyclic systems and diradicals.