Effect of bulky substituents on thiopyrylium polymethine aggregation in the solid state: A theoretical evaluation of the implications for all-optical switching applications
KAUST DepartmentKAUST Solar Center (KSC)
Physical Sciences and Engineering (PSE) Division
Materials Science and Engineering Program
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AbstractPolymethine 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.
SponsorsThis work was supported by the AFOSR MURI program (FA9550-10-1-0558) within the Center for Organic Materials for All-Optical Switching (COMAS). We gratefully acknowledge stimulating discussions with Drs. S. Barlow, J.M. Hales, and J.W. Perry.
PublisherAmerican Chemical Society (ACS)
JournalChemistry of Materials