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 tetrahydronaphthalene framework have been synthesized and characterized. This conformation-locking approach furnishes NLO chromophores possessing an enhanced thermal stability. X-ray crystallographic data indicate that the polyenic chain of these molecules exhibits a near-planar all-trans conformation in the solid state. EFISH measurements show that these conformationally locked tetraenic chromophores exhibit large second-order optical nonlinearities (μ·β ∼4000 × 10^-48 cm⁶ at 1907 nm), although the nonlinearities of the corresponding "unlocked" analogues are slightly larger. © 1999 American Chemical Society.