The carbon–carbon covalent bond is one of the most basic concept in organic chemistry. Bond length, bond angle, and torsion angle among carbon atoms are nearly constant on the basis of their hybrid orbitals. On the other hand, highly strained hydrocarbons such as sterically-congested and/or curved polycyclic aromatic hydrocarbons as well as cyclic π-conjugated molecules have attracted much attention with regard to their characteristic features. We focused on two types of redox-active molecules with a extremely elongated C-C single bond (Hyper covalent bond with a bond length beyond 1.8 Å) or a strained double bond, for which unique electrochromic behavior was observed upon oxidation to give deeply colored cationic species.