Journal of the American Chemical Society 2006-05-10

X-Shaped electro-optic chromophore with remarkably blue-shifted optical absorption. Synthesis, characterization, linear/nonlinear optical properties, self-assembly, and thin film microstructural characteristics.

Hu Kang, Guennadi Evmenenko, Pulak Dutta, Koen Clays, Kai Song, Tobin J Marks

Index: J. Am. Chem. Soc. 128(18) , 6194-6205, (2006)

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Abstract

A novel type of "X-shaped" two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH(2)Cl(2)) while maintaining a very large first hyperpolarizability (beta). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a beta(zzz) value of 1840 x 10(-30) esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response (chi(2)(333) approximately 232 pm/V at 1064 nm; r(33) approximately 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs.