Synthesis and characterization of nonlinear optical chromophores with conformationally locked polyenes possessing enhanced thermal stability

Dipolar NLO chromophores with an interposed conjugated tetraene segment in which all but four of the methine groups are incorporated into a tetrahydro naphthalene framework have been synthesized and characterized. This conform ation-locking approach furnishes NLO chromophores possessing an enhanced th ermal stability. X-ray crystallographic data indicate that the polyenic cha in of these molecules exhibits a near-planar all-trans conformation in the solid state. EFISH measurements show that these conformationally locked tet raenic chromophores exhibit large second-order optical nonlinearities (mu.b eta similar to 4000 x 10(-48) cm(6) at 1907 nm), although the nonlinearitie s of the corresponding "unlocked" analogues are slightly larger.