The Impact of Twisting on the Intersystem Crossing in Acenes: An Experimental and Computational Study

Due to their unique excited state dynamics, acenes play a dominant role in optoelectronic and light-harvesting applications. Their optical and electronic properties are typically tailored by side-group engineering, which often...

Reverse Intersystem Crossing Managing Assistant Dopant for High External Quantum Efficiency Red Organic Light-Emitting Diode

Thermally activated delayed fluorescence (TADF) materials working as an assistant dopant with reduced Dexter energy transfer rate was designed by replacing the donor moiety of 2,3,5,6-tetra(9H-carbazol-9-yl) terephthalonitrile (4CzTPN) with 5H-benzo[4,5]thieno[3,2-c]carbazole...

Modeling TADF: the role of the medium polarizability

A novel approch to estimate intersystem and reverse intersystem crossing rates (ISC and RISC rates, respectively) is proposed. We build on an essential state model recently parametrized {\it ab initio}...

Mechanism of H+ dissociation–induced O–O bond formation via intramolecular coupling of vicinal hydroxo ligands on low-valent Ru(III) centers

The understanding of O–O bond formation is of great importance for revealing the mechanism of water oxidation in photosynthesis and for developing efficient catalysts for water oxidation in artificial photosynthesis. The chemical oxidation of the RuII2(OH)(OH2) core with the vicinal OH and OH2 ligands was spectroscopically and theoretically investigated to provide a mechanistic insight into the O–O bond formation in the core. We demonstrate O–O bond formation at the low-valent RuIII2(OH) core with the vicinal OH ligands to form the RuII2(μ-OOH) core with a μ-OOH bridge. The O–O bond formation is induced by deprotonation of one of the OH ligands of RuIII2(OH)2 via intramolecular coupling of the OH and deprotonated O− ligands, conjugated with two-electron transfer from two RuIII centers to their ligands. The intersystem crossing between singlet and triple states of RuII2(μ-OOH) is easily switched by exchange of H+ between the μ-OOH bridge and the auxiliary backbone ligand.

Experimental and Computational Analysis of Para-Hydroxy Methylcinnamate Following Photoexcitation

Para-hydroxy methylcinnamate is part of the cinnamate family of molecules. Experimental and computational studies have suggested conflicting non-radiative decay routes after photoexcitation to its S1(ππ*) state. One non-radiative decay route involves intersystem crossing mediated by an optically dark singlet state, whilst the other involves direct intersystem crossing to a triplet state. Furthermore, irrespective of the decay mechanism, the lifetime of the initially populated S1(ππ*) state is yet to be accurately measured. In this study, we use time-resolved ion-yield and photoelectron spectroscopies to precisely determine the S1(ππ*) lifetime for the s-cis conformer of para-hydroxy methylcinnamate, combined with time-dependent density functional theory to determine the major non-radiative decay route. We find the S1(ππ*) state lifetime of s-cis para-hydroxy methylcinnamate to be ∼2.5 picoseconds, and the major non-radiative decay route to follow the [1ππ*→1nπ*→3ππ*→S0] pathway. These results also concur with previous photodynamical studies on structurally similar molecules, such as para-coumaric acid and methylcinnamate.