Spin--spin interaction in a highly stable neutral diradical: σ-boned dimer of trioxotriangulene.

A σ-bonded dimer of 4,8,10-trioxotriangulene (TOT) was newly synthesized and its electronic spin structure was characterized. The neutral diradical had a singlet ground state due to the strong antiferromagnetic interaction through the σ-bond. The strong intramolecular interaction within the σ-dimer caused a near-infrared photoabsorption of around 700-1,000 nm, which is close to that of the π-stacked dimer of TOT monoradical. [ABSTRACT FROM AUTHOR]