Chemistry of cyclic cross-conjugated system extended by quinonoid structure.

One of the recent advances in the field of non-benzenoid aromatics would be the chemistry of the extended cyclic cross-conjugated compounds derived by insertion of more complex conjugated π-electron system instead of the exo-double bond in fulvene-, fulvalene-, annulenone-, and oxocarbon-systems. Many physical and chemical properties of remarkable interest have been developed in these newly designed cross-conjugated variations. The present review deals with the chemistry of quinarenes, quinarenones, quinocarbons, and their hetero analogs which are the extended cyclic cross-conjugated π-electron systems comprising one or more quinonoid structures. The fundamental insights mentioned here would provide helpful suggestions for the molecular design of organic dyes, highly polarized compounds, electron acceptors or electron donors having a bright prospect of developing the new field of application to the optoelectronics, organic super conductors, and so on.