Benzene is one of the most widely used units in organic opto-electronic materials. Different from six-membered benzene, seven-membered carbon conjugated system has seen much less applications in opto-electronic materials. Until recently, some attention has been paid to this field. Because of its different molecular orbital characteristic from benzene and easiness to be oxidized, seven-membered carbon ring conjugated system may introduce special and interesting properties to organic opto-electronic materials. In this paper, the conjugated seven-membered carbon rings are reviewed from the point of discovery, synthesis and structural investigation. Then, the skeleton types containing seven-membered carbon rings are analyzed and the synthetic methods for these skeleton types are demonstrated. The applications of conjugated molecules containing seven-membered carbon rings in near infrared absorptive materials, organic field effect transistors, organic solar cells and stimuli-responsive systems are introduced. In the end, the future developments of this field are discussed.
Contents
1 Introduction
2 Conjugated frameworks containing 7-membered carbon ring
3 Representative synthetic methods for conjugated molecules containing 7-membered carbon ring
3.1 Cyclo-addition and electro-cyclization reactions
3.2 Friedel-Crafts reaction
3.3 Condensation reaction
3.4 Scholl-type oxidative coupling reaction
3.5 Metal mediated alkene or alkyne cyclization
3.6 Functionalization of 7-membered ring
4 Application of conjugated molecules containing 7-membered carbon ring in near infrared absorption systems
5 Application of conjugated molecules containing 7-membered carbon ring in organic field effect transistors
5.1 Azulene based systems
5.2 Non-azulene based systems
6 Application of conjugated molecules containing 7-membered carbon ring in organic solar cells
7 Application of conjugated molecules containing 7-membered carbon ring in stimuli-responsive systems
7.1 Azulene based systems
7.2 Non-azulene based systems
8 Conclusion and outlook