Spectroscopic Study of Charge Transfer Complexes of Biphenyl

Biphenyl is a well-known photoconductor with a band gap of 0.16eV lying in the infrared range. In the present work, the charge transfer complexes of biphenyl with the acceptors such as 7,7,8,8-tetracyano-p-quinodimethane, N,N,N,N-tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), Chloranil, and iodine have been studied with ultraviolet-visible near infrared and infrared spectroscopy. Biphenyl-TCNE and biphenyl-DDQ show spin-orbit splitting of valence band and consequently show three optical transitions. Biphenyl-iodine and biphenyl-chloranil show nondegenerate semiconducting nature. The charge transfer complexes (CTCs) show an asymmetric Gaussian band associated with small polaron model. Many of the CTCs also show a scattering of charge carriers by light particles as expected in photoconductors.