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An amphiphilic lanthanide complex, ( E )-1-methyl-4-(2-(4-(dihexadecylamino)phenyl)azo)pyridinium tetrakis(1-phenyl-3-methyl-4-benzoyl-5-pyrazolonato)lanthanum(III), has been synthesized. It forms a stable Langmuir monolayer film on a pure water subphase (pH 5.6, 18°C) when spread from a chloroform solution. Langmuir-Blodgett (LB) films were prepared by transferring the monolayers onto hydrophilic substrates of quartz and calcium fluoride with a transfer ratio close to unity. From a second-harmonic generation measurement, the second-order molecular hyperpolarizability β of the complex was estimated to be about 1.4 × 10 −47 C m 3 V −2 , which is one of the largest values for azo-based, second-order non-linear optical materials reported so far. The infrared and variable-temperature ultraviolet spectra of the film are also reported.

The effect of the gas environment on the second harmonic generation of Langmuir-Blodgett films of non-linear material has been studied. It has been found that the gas environment in general had a strong effect on the structure and the non-linear optical property of the films. The phenomenon has a few implications for the applications of the non-linear optical material films.