Phenanthrene-Tethered Furan-Containing Cyclophenes: Synthesis and Photophysical Properties

Two phenanthrene-fused furan-containing teraryl cyclophenes 5 and 6 are synthesized. These cyclophenes exhibit charge transfer band in the absorption spectra, unusually large Stokes shifts in the emission spectra, and exceptionally high mubeta values in the electric-field-induced second-harmonic generation (EFISH) experiments. The mubeta(1.91) values for 5 and 6 are 438 and 777 x 10(-48) esu, respectively. The bridging double bond in 5 and 6 can serve as either an electron donor or acceptor depending on the nature of the substituent on furan rings. DFT calculations at the B3LYP/6-31G** level indicate that the electron density distributions in HOMO and LUMO are very different. Interaction between the oligoaryl systems and the double bond may account for the significant enhancement in hyperpolarizability.