TRIPHENYLCARBINOL DERIVATIVES AS MOLECULES FOR 2ND-ORDER NONLINEAR OPTICS

A series of novel tris D-pi-A substituted triphenylcarbinol derivative s have been synthesized and studied for their molecular second-order n onlinear optical properties by electric field induced second harmonic generation (EFISH) and hyper Rayleigh scattering (HRS). Compared to th eir phenyl analogs with only one D-pi-A system, the triphenylcarbinol derivatives 7 and 10-12 exhibit an increased hyperpolarizability ([bet a] HRS) without the undesired red-shift of the charge-transfer band. T he dipole moments and the hyperpolarizabilities are dependent on both the close proximity (3-4 angstrom) and the orientation of the three NL O-phore units. The nature of the acceptor substituent strongly influen ces the magnitude of the [beta]HRS values. The tris(nitrophenyl) deriv ative 7 exhibits a [beta]HRS value of 15 X 10(-31) esu, which is almos t the same as that of its reference compound p-nitroanisole 13, wherea s the tris(nitrostilbene) derivative 12 exhibits a [beta]HRs value of 338 x 10(-30) esu which is more than 3 times larger than that of its r eference compound 4-methoxy-4'-nitrostilbene 16.