Benzofuran-terminated infrared dyes and their electro-optic properties in guest–host polymers

Molecular first hyperpolarizabilities and dipole moments of new benzo-fused dyes were calculated using quantum–mechanical density functional theory (DFT). Two new infrared dyes were synthesized: each one was terminated with 6-diethylaminobenzo[b]furan on one end, and with CF3-tricyanodihydrofuran on the other end. The midsection of the π-electron framework for one dye contained a morpholino-substituted cyclohexenylene unit, and the other dye contained an ethoxysiloxane-substituted cyclohexenylene unit. Guest–host films were deposited on ITO-glass and contact poled. Electro-optic coefficients (r33) were measured at a wavelength of 1550 nm by the attenuated total reflection method and by a modified simple Teng-Man reflection method. The measured values of r33 were compared with values estimated from a well-known model that employs the molecular properties of the dyes and the film poling parameters. Thermal stability and electronic absorption spectra of the dyes were measured.

► Hyperpolarizabilities of 16 new benzo-fused heterocyclic tetraenic dyes were calculated by DFT. ►All benzo-tetraenic dyes were predicted to outperform the corresponding phenyl-tetraenic dyes. ►Two new benzofuran-tetraenic dyes were synthesized and guest-host films were characterized. ►Electro-optic coefficients (r33) were measured at 1550 nm by ATR and simple Teng-Man methods. ►After poling with a field of about 65 V/m, the highest measured r33 was about 60 pm/V.