Nonlinear optical properties of benzylic amide [2] catenanes: a novel versatile photonic material

Benzylic amide catenanes are a class of synthetically-accessible interlocke d molecular rings which can rotate one through the other depending on the n ature of the local environment. The rings contain four phenyl units each an d interlocking also affords their packing in novel, highly interacting ways that may lead to unexpected properties thus opening up the possibility of developing new materials. Third harmonic generation in benzylic amide caten ane solutions was measured at a wavelength of lambda = 1064 nm, with the fu ndamental and the harmonic wavelengths in the region of transparency of the material. The thoroughly non resonant value of the hyperpolarisability gam ma(-3 omega; omega, omega, omega) was found to be (6.5 +/- 0.7) x 10(-35) e su with a neg ligible imaginary part, in agreement with the value of (6.8 /- 0.9)x 10(-35) esu calculated from a bond-additivity model of hyperpolari sability. The static second order hyperpolarisability predicted by a Molecu lar Orbital model was about a factor four less than the experimental value. Second hyperpolarizability values of several solvents were also measured a t the fundamental wavelength of lambda = 1061 nm.