Effect of bulky substituents on thiopyrylium polymethine aggregation in the solid state: a theoretical evaluation of the implications for all-optical switching applications

R.L. Gieseking, S. Mukhopadhyay, C. Risko, S.R. Marder, J.L. Brédas
Chem. Mater., 26, 6439-6447, (2014)

Effect of bulky substituents on thiopyrylium polymethine aggregation in the solid state: a theoretical evaluation of the implications for all-optical switching applications

Keywords

Thiopyrylium polymethine

Abstract

​Polymethine dyes in dilute solutions display many of the optical properties required for all-optical switching applications. However, in thin films, aggregation and polymethine–counterion interactions can substantially modify their properties and limit their utility. Here, we examine the impact of a series of bulky substituents on the solid-state molecular packing of thiopyrylium polymethines by using a theoretical approach combining molecular-dynamics simulations and quantum-chemical calculations. Importantly, it is found that the positions of the substituents near the center and/or ends of the dye determine the extent to which aggregation is reduced; in particular, substituents near the polymethine center primarily modify the type of aggregation that is observed, while substituents near the polymethine ends reduce aggregation and aid in maintaining solution-like properties in the solid state. Our theoretical study elucidates relationships between molecular structure and bulk optical properties and provides design guidelines for all-optical switching materials.

Code

DOI: 10.1021/cm5028755

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