Helquat Dyes: Helicene-like Push-Pull Systems with Large Second-Order Nonlinear Optical Responses

J Org Chem. 2016 Mar 4;81(5):1912-20. doi: 10.1021/acs.joc.5b02692. Epub 2016 Feb 19.

Abstract

Helquat dyes combine a cationic hemicyanine with a helicene-like motif to form a new blueprint for chiral systems with large and tunable nonlinear optical (NLO) properties. We report a series of such species with characterization, including determination of static first hyperpolarizabilities β0 via hyper-Rayleigh scattering and Stark spectroscopy. The measured β0 values are similar to or substantially larger than that of the commercial chromophore E-4'-(dimethylamino)-N-methyl-4-stilbazolium. Density functional theory (DFT) and time-dependent DFT calculations on two of the new cations are used to probe their molecular electronic structures and optical properties. Related molecules are expected to show bulk second-order NLO effects in even nonpolar media, overcoming a key challenge in developing useful materials.

Publication types

  • Research Support, Non-U.S. Gov't