Control of the Orientational Order and Nonlinear Optical Response of the “Push−Pull” Chromophore RuPZn via Specific Incorporation into Densely Packed Monolayer Ensembles of an Amphip

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• 作者：Grazia Gonella ; Hai-Lung Dai ; H. Christopher Fry ; Michael J. Therien ; Venkata Krishnan ; Andrey Tronin ; J. Kent Blasie
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：July 21, 2010
• 年：2010
• 卷：132
• 期：28
• 页码：9693-9700
• 全文大小：373K
• 年卷期：v.132,no.28(July 21, 2010)
• ISSN：1520-5126

文摘

The macroscopic nonlinear optical response of the “push−pull” chromophore RuPZn incorporated into a single monolayer of the amphiphilic 4-helix bundle peptide (AP0) covalently attached to a solid substrate at high in-plane density has been measured. The second-order susceptibility, χ_zzz, was found to be in the range of 15 × 10⁻⁹ esu, consistent with a coherent sum of the nonlinear contributions from the individual chromophores (β) as previously measured in isotropic solution through hyper-Rayleigh scattering as well as estimated from theoretical calculations. The microscopic hyperpolarizability of the RuPZn chromophore is preserved upon incorporation into the peptide monolayer, suggesting that the chromophore−chromophore interactions in the densely packed ensemble do not substantially affect the first-order molecular hyperpolarizability. The polarization angle dependence of the second harmonic signal reveals that the chromophore is vectorially oriented in the two-dimensional ensemble. Analysis of the order parameter together with information obtained from grazing incidence X-ray diffraction help in determining the chromophore orientation within the AP0−RuPZn monolayer. Taking into account an average pitch angle of 20° characterizing the coiled-coil structure of the peptide bundle, the width of the bundle’s tilt angle distribution should be σ ≤ 20°, resulting in a mean value of the tilt angle 23° ≤ θ₀ ≤ 37°.