Chemical Stabilities of the Lowest Triplet State in Aryl Sulfones and Aryl Phosphine Oxides Relevant to OLED Applications
Sears, John S.
Marder, Seth R.
KAUST DepartmentKAUST Solar Center (KSC)
Laboratory for Computational and Theoretical Chemistry of Advanced Materials
Material Science and Engineering Program
Physical Science and Engineering (PSE) Division
Online Publication Date2019-02-14
Print Publication Date2019-03-12
Permanent link to this recordhttp://hdl.handle.net/10754/631111
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AbstractAryl sulfones and phosphine oxides are widely used as molecular building blocks for host materials in the emissive layers of organic light-emitting diodes. In this context, the chemical stability of such molecules in the triplet state is of paramount concern to long-term device performance. Here, we explore the triplet excited-state (T1) chemical stabilities of aryl sulfonyl and aryl phosphoryl molecules by means of UV absorption spectroscopy and density functional theory calculations. Both the sulfur–carbon bonds of the aryl sulfonyl molecules and the phosphorus–carbon bonds of aryl phosphoryl derivatives are significantly more vulnerable to dissociation in the T1 state when compared to the ground (S0) state. Although the vertical S0→T1 transitions correspond to non-bonding→π-orbital transitions, geometry relaxations in the T1 state lead to -* character over the respective sulfur–carbon or phosphorus–carbon bond, a result of significant electronic state mixing, which facilitates bond dissociation. Both the activation energy for bond dissociation and the bond dissociation energy in the T1 state are found to vary linearly with the adiabatic T1-state energy. Specifically as T1 becomes more energetically stable, the activation energy becomes larger, and dissociation becomes less likely, i.e., more endothermic or less exothermic. While substitutions of electron-donating or accepting units onto the aryl sulfones and aryl phosphine oxides have only marginal influence on the dissociation reactions, extension of the -conjugation of the aryl groups leads to a significant reduction in the triplet energy and a considerable enhancement in the T1-state chemical stabilities.
CitationLi H, Hong M, Scarpaci A, He X, Risko C, et al. (2019) Chemical Stabilities of the Lowest Triplet State in Aryl Sulfones and Aryl Phosphine Oxides Relevant to OLED Applications. Chemistry of Materials. Available: http://dx.doi.org/10.1021/acs.chemmater.8b04235.
SponsorsWe thank Solvay SA, the National Natural Science Foundation of China (21403037), and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (2015R1D1A1A01061487) for support. We thank Jean-Pierre Catinat and Véronique Mathieu (Solvay) for measuring the phosphorescence spectrum of PPTSO.
PublisherAmerican Chemical Society (ACS)
JournalChemistry of Materials