Self-assembly from the gas-phase: design and implementation of small-molecule chromophore precursors with large nonlinear optical responses.
Self-assembly from the gas-phase: design and implementation of small-molecule chromophore precursors with large nonlinear optical responses.
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DOI：
10.1021/ja900131y
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发表时间：
2009-08
影响因子：
15
通讯作者：
David L Frattarelli;Michele Schiavo;A. Facchetti;M. Ratner;T. Marks
中科院分区：
文献类型：
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作者：
David L Frattarelli;Michele Schiavo;A. Facchetti;M. Ratner;T. Marks
有效地组织具有大一阶超极化率（β）的分子非线性光学（NLO）发色团为电光（EO）应用提供了一个重要的材料合成和加工挑战，部分原因是发色团间的偶极相互作用促进了中心对称组织。在这里，我们报告了一系列八种杂芳香有机发色团的计算建模、合成和表征，这些发色团被设计为通过定向氢键网络从气相自组织成偏心薄膜。沿着分子长轴引入α、ω -供体-受体氢键取代基，可调节超极化性、挥发性、热稳定性、成膜性和宏观NLO响应等特性（chi((2))）。dft水平的分子模型、INDO/S光学性质分析和和-overstates计算表明，与典型的无氟发色团相比，分子核氟化和氢键供体结合可以使β (vec)增加40倍。此外，在发色团pi-供体取代基和氢键供体位点之间包含立体诱导的联苯共轭解耦，使β增加了约50%。实验薄膜二次谐波产生（SHG）光谱在计算响应中证实了这些趋势，在发色团核心氟化后chi（(2)）增加了7.5倍，氢键供体取代后chi（(2)）增加了15倍，从而在ω (o) = 1064 nm处实现了高达302 pm/V的宏观响应。除了响应趋势外，聚类计算还揭示了β (vec)的线性可加性，包括所有含苯甲酸的发色团，直到纵向排列的三聚体。在含苯甲酸发色团薄膜厚度达1.0微米的情况下，SHG响应随薄膜厚度呈线性缩放。
Efficiently organizing molecular nonlinear optical (NLO) chromophores having large first-order hyperpolarizabilities (beta) into acentric microstructures for electro-optic (EO) applications represents a significant materials synthesis and processing challenge, in part due to interchromophore dipolar interactions that promote centrosymmetric organization. Here we report the computational modeling, synthesis, and characterization of a series of eight heteroaromatic organic chromophores, designed to self-organize from the vapor phase via directed hydrogen-bond networks, into acentric thin films. Introduction of alpha,omega-donor-acceptor hydrogen-bonding substituents along the molecular long axes tunes properties such as hyperpolarizability, volatility, thermal stability, film-forming properties, and macroscopic NLO response (chi((2))). DFT-level molecular modeling, INDO/S optical property analysis, and sum-overstates computation indicate that molecular-core fluorination and hydrogen-bond donor incorporation can increase beta(vec) up to 40x versus that of typical fluorine-free chromophores. Furthermore, inclusion of sterically induced biphenyl conjugative decoupling between chromophore pi-donor substituents and the hydrogen-bonding donor sites increases beta by approximately 50%. Experimental thin-film second harmonic generation (SHG) spectroscopy confirms these trends in calculated responses, with chi((2)) increasing 7.5x upon chromophore core fluorination and 15x with hydrogen-bonding donor substitution, thereby achieving macroscopic responses as high as 302 pm/V at omega(o) = 1064 nm. In addition to response trends, cluster calculations also reveal linear additivity in beta(vec) with catenation for all benzoic acid-containing chromophores up to longitudinally aligned trimers. Linear scaling of SHG response with film thickness is observed for benzoic acid-containing chromophores up to 1.0 microm film thickness.