Modulated Conjugation as a Means of Improving the Intrinsic Hyperpolarizability

Abstract

A new strategy for optimizing the first hyperpolarizability based on the concept of a modulated conjugated path in linear molecules is investigated. A series of seven novel chromophores with different types of conjugated paths were synthesized and characterized. Hyper-Rayleigh scattering experiments confirmed that modulated conjugation paths that include benzene, thiophene, and/or thiazole rings in combination with azo and/or ethenyl linkages between dihydroxyethylamino donor groups and various acceptor groups result in enhanced intrinsic hyperpolarizabilities that exceed the long-standing apparent limit for two of the chromophores. The experimental results are analyzed and interpreted in the context of quantum limits, which show that conjugation modulation of the bridge in donor/acceptor molecules simultaneously optimizes the transition moments and the energy-level spacing.

Upper limit on shift current generation in extended systems

“…We show that this bound depends on the band gap, band width, and geometrical properties of the material in question. We find that Kuzyk's bound [8] for the maximum SHG of isolated molecules can be exceeded by conjugation or condensation of molecules to form molecular solids, and that strongly coupled systems generally have larger responses than weakly coupled or isolated ones [9][10][11][12]. As a proof of principle, we perform first-principles calculations of the response tensors of a wide variety of materials, finding that the materials in our database do not yet saturate the upper bound.…”

The effect of electron interactions on the universal properties of systems with optimized off-resonant intrinsic hyperpolarizability

“…13 A comparison of the intrinsic hyperpolarizabilties of molecules can be used to determine the properties that are relevant for optimizing the nonlinearoptical response. Past studies have considered the optimization of the intrinsic hyperpolarizability by varying the shape of the potential energy function, 32,33 which lead to the new paradigm of large-β molecules using modulation of conjugation for which there is some experimental evidence; 34,35 studying the effect of geometry by varying the charges and positions of point nuclei 36 and the effect of applying an arbitrary electromagnetic field. 37 All of these studies find that when the hyperpolarizability of a quantum system is near the fundamental limit, certain universal properties result.…”

Synthesis, Spectral Property and Dyeing Assessment of Azo Disperse Dyes Containing Carbonyl and Dicyanovinyl Groups

“…Notably, p-aminobenzaldehyde 2a was prepared by reduction of nitro group according to the literature, 13 and was used for the next step before complete evaporation of solvent because it was easily polymerized by selfcondensation upon concentration. The diazo dyes substituted with aldehyde 3b-3f and acetyl 4a-4f were synthesized by diazotization using hydrochloric acid and sodium nitrite at 0 o C, followed by a coupling reaction in an one-pot process [14][15][16][17] with various commercially important coupling components such as dialkylanilines (a-d), indole (e) and pyridone (f). As anticipated, the coupling reactions occurred selectively at the para-position of anilines a-d, and at the 3-and 5-position of the indole e 18 and pyridone f component respectively.…”