Two-electron reductions of 3,3′-bis(2,6-dimesitylpyridin-4-yl)-1,1′-biphenyl 1 with elemental potassium in the absence and presence of 18-c-6 afforded the diradical dianion salts [K⁺]₂˙[trans-1]˙˙²⁻ and [K(18-c-6)]⁺₂˙[cis-1]˙˙²⁻, which exhibit trans and cis configurations, respectively. The transoid conformer could be converted to the cisoid one through reacting with 18-c-6.