Relating the Structure of Geminal Amido Esters to their Molecular Hyperpolarizability

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• 作者：Jacqueline M. ColeTze-Chia Lin ; Christopher M. Ashcroft ; Javier Perez-Moreno ; Yizhou Tan ; Perumal Venkatesan ; Andrew P. Higginbotham ; Philip Pattison ; Alison J. Edwards ; Ross O. Piltz ; Koen Clays ; Andivelu Ilangovan
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 29, 2016
• 年：2016
• 卷：120
• 期：51
• 页码：29439-29448
• 全文大小：445K
• ISSN：1932-7455

文摘

Advanced organic nonlinear optical (NLO) materials have attracted increasing attention due to their multitude of applications in modern telecommunication devices. Arguably the most important advantage of organic NLO materials, relative to traditionally used inorganic NLO materials, is their short optical response time. Geminal amido esters with their donor-π-acceptor (D-π-A) architecture exhibit high levels of electron delocalization and substantial intramolecular charge transfer, which should endow these materials with short optical response times and large molecular (hyper)polarizabilities. In order to test this hypothesis, the linear and second-order nonlinear optical properties of five geminal amido esters, (E)-ethyl 3-(X-phenylamino)-2-(Y-phenylcarbamoyl)acrylate (1, X = 4-H, Y = 4-H; 2, X = 4-CH₃, Y = 4-CH₃; 3, X = 4-NO₂, Y = 2,5–OCH₃; 4, X = 2-Cl, Y = 2-Cl; 5, X = 4-Cl, Y = 4-Cl) were synthesized and characterized, whereby NLO structure–function relationships were established including intramolecular charge transfer characteristics, crystal field effects, and molecular first hyperpolarizabilities (β). Given the typically large errors (10–30%) associated with the determination of β coefficients, three independent methods were used: (i) density functional theory, (ii) hyper-Rayleigh scattering, and (iii) high-resolution X-ray diffraction data analysis based on multipolar modeling of electron densities at each atom. These three methods delivered consistent values of β, and based on these results, 3 should hold the most promise for NLO applications. The correlation between the molecular structure of these geminal amido esters and their linear and nonlinear optical properties thus provide molecular design guidelines for organic NLO materials; this leads to the ultimate goal of generating bespoke organic molecules to suit a given NLO device application.