Analogously, mono-radicals such as nitrogen-doped triangulene (TRI(N)), borondoped triangulene (TRI(B)), TAM, TOT, and phenalenyl (PLY) have also been synthesized either in solution or on the surface (Figure ). Among them, TRI, TAM, TOT and PLY have D3h symmetry, while TRI(N) and TRI(B) exhibit lower symmetry of C2v due to Jahn-Teller distortion. The C2v configuration is more energetically favorable than the D3h configuration by 5.63 kJ/mol and 5.58 kJ/mol, resulting in the distorted symmetry for TRI(N) and TRI(B) (Table ). Despite the D3h symmetry of TRI's chemical structure and consequently of its spin density distribution, it is noted that the two degenerate singly occupied molecular orbitals (SOMO), ψ1 and ψ2, only exhibit C2v symmetry, while their overall density, |ψ1| 2 + |ψ2| 2 , has D3h symmetry (Figure ). This explains the reduction of symmetry in both structure and spin density from D3h to C2v in TRI(N) and the consequential Jahn- Using these monomers as building blocks, we constructed 24 dimers that are connected either directly or bridged by -C≡C-(CC), -C≡C-C≡C-(CCCC) and phenyl (Ph) linkages (Figure ). These molecules are fully conjugated non-Kekulé radicals.