Organic materials for second-harmonic generation: advances in relating structure to function

Abstract

The relationships between molecular structure and the nonlinear optical phenomenon second-harmonic generation (SHG) are discussed. New-found relationships built up from basic structural axioms that were deduced in the 1970s and 1980s are the particular focus of this article, using structural results from X-ray and neutron-diffraction studies. The molecular and supramolecular manifestations of the SHG effect are borne out, although ways to optimize the effect on the molecular scale feature predominantly, since control of SHG on the supramolecular scale remains difficult given present limitations. The use of a variety of templates to generate head-to-tail oriented host-guest species thereby bypassing such limitations is described. The paper concludes with a look ahead at next generation 'octupolar' SHG-active compounds, the prediction of new series of SHG-active compounds via data-mining computational procedures, and developments in diffraction technology that may enable structural movies of a molecule to be captured during the SHG process. A practical assessment of the viability of organic SHG materials for industrial application is reviewed with a positive outcome, thus indicating a promising future for organic SHG materials.

Concerted Mitigation of O···H and C(π)···H Interactions Prospects Sixfold Gain in Optical Nonlinearity of Ionic Stilbazolium Derivatives

“…This tentatively suggested a weak linear relationship between η inter and the H(2)…C( interaction length (correlation coefficient R 2 = 0.64, Figure S1 in the Supporting Information); c.f. [2,[5][6], [3], [4], [7] and [8], respectively). Part II: e Criteria of acceptance as short contacts: d(H…O)<2.6Å, d(H…π)<3.0Å.…”

“…The total calculated H…C contact-surface coverage for [8] is 12.6%; however, this value is indiscriminate on ion…ion pairing types; classifying them separately reveals that these H…C interactions are essentially associated with weak cationto-cation H…C contacts involving atoms that do not lie in the main charge-transfer path; cationto-anion contributions are null. k The contact area percentages of the H…O (or H…F) hydrogen 9 bonds for [1]- [6] and [8] (or [7]). Associated Fingerprint plots of [1] and [8] are provided in Figure S5 (Supporting Information).…”

Molecular Origins of the High-Performance Nonlinear Optical Susceptibility in a Phenolic Polyene Chromophore: Electron Density Distributions, Hydrogen Bonding, and ab Initio Calculations

“…Inorganic materials rely on suitable geometric perturbations of the key ions within a solid-state crystalline structural framework of the compound, whereas organic materials rely on the transfer of electronic charge across the molecule. 5 The optical response of NLO-active organic compounds is therefore much faster than …”

Growth and characterization of a new organic nonlinear optical crystal: 1-(3-Nitrophenyl)-5-phenylpenta-2,4-dien-1-one

“…The conjugated π-electron moiety provides a pathway for the entire length of conjugation under the perturbation of an external electric field. Fictionalization of both ends of the π-bond systems with appropriate electron donor and acceptor group can increase the asymmetric electronic distribution in either or both the ground and excited states, thus leading to an increased optical nonlinearity [4][5][6][7].…”