Dimerization of delocalized polycyclic
hydrocarbon radicals is
a simple and versatile method to create diradicals with tailored electronic
structures and accessible high-spin states. However, the synthesis
is challenging, and the stability issue of the diradicals remains
a concern. In this study, we present the synthesis of a stable non-Kekulé
1,1′-biolympicenyl diradical 1 using a protection–oxidation–protection
strategy. Diradical 1 demonstrated exceptional stability,
with a solution half-life time exceeding 3.5 years and a solid state
thermal decomposition temperature above 300 °C. X-ray crystallographic
analysis revealed its intersected molecular structure and tightly
bound dimer configuration. A singlet ground state with a small singlet–triplet
energy gap is consistently identified using electron paramagnetic
resonance (EPR) and a superconducting quantum interference device
(SQUID) in a rigid matrix, and the triplet state is thermally accessible
at room temperature. The solution phase properties were systematically
examined through EPR, absorption spectroscopy, and cyclic voltammetry,
revealing a rotational motion in the slow-motion regime and multistage
redox characteristics. This study presents an efficient synthetic
and stabilization strategy for organic diradicals, enabling the development
of various high-spin functional materials.