Linear and Third-Order Nonlinear Optical Properties of Chalcogenopyrylium-Terminated Heptamethine Dyes with Rigid, Bulky Substituents

The aggregation of chalcogenopyrylium-terminated heptamethine dyes in high-chromophore density films can be substantially suppressed by attachment of rigid, bulky substituents that project out of the plane of the conjugated π-system of the dye, allowing the retention in the solid state of favorable linear and nonlinear optical properties relevant to all-optical signal processing (AOSP). Dye structures are systematically engineered with a range of out-of-plane substituents to investigate the impacts on the optical properties at 1550 nm in the solid state. Large magnitudes of the third-order susceptibility are obtained for solid films. Very high values of the two-photon figure-of-merit (2PA-FOM), an important parameter for AOSP, are observed in dilute solutions of seleno- and telluropyrylium dyes (in several cases >30). In the case of the telluropyrylium dye, the 2PA-FOM is not measureable for 50 wt% blends with polymers. Blends of the selenopyrylium examples exhibit 2PA-FOM values that, although decreased substantially relative to the solution values, in some cases meet the requirements for AOSP. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim