Restricted access to a conical intersection to explain aggregation induced emission in dimethyl tetraphenylsilole

Abstract

Aggregation-induced emission of dimethyl tetraphenylsilole is due to restricted access to a conical intersection. The intersection allows for radiationless decay in solution but is not reachable in the aggregate phase.

Exploring Potential Energy Surfaces for Aggregation‐Induced Emission—From Solution to Crystal

“…Phenyl‐substituted siloles are the first group of compounds where AIE was identified . The PES obtained for the representative DMTPS molecule (Figure ) from combined TD‐DFT, CASSCF, and CASPT2 calculations (Figure ) shows that it also follows the RACI model . Excited‐state relaxation in solution leads to a FC‐like S 1 minimum at 3.1 eV where the silole ring keeps a nearly planar structure.…”

“…[3,28,64] The PES obtained for the repre-sentativeD MTPS molecule ( Figure 2) from combinedT D-DFT, CASSCF,a nd CASPT2 calculations (Figure 9) shows that it also follows the RACI model. [35] Excited-state relaxation in solution leads to aF C-likeS 1 minimum at 3.1 eV where the silole ring keeps an early planars tructure. The PES has aC Ia t3 .0 eV, which is separated by ab arrier with an estimated energy of 3.54 eV,s maller than the vertical excitation energy of 3.72 eV.…”

Insights into the Photoinduced Isomerization Mechanisms of a N,C–Chelate Organoboron Compound: A Theoretical Study

“…CIs are crossings between the potential energy surfaces of the same multiplicity, which act as efficient decay funnels from excited states to ground state . CIs have proven to play crucial roles in boron cluster chemistry and to be basic mechanistic elements for important photophysical and photochemical processes such as intramolecular electron transfer, photoisomerization, Wolff rearrangement, Curtius rearrangement, and aggregation‐induced emission …”

“…[25][26][27] CIs have proven to play crucial roles in boron cluster chemistry [28][29][30][31] and to be basic mechanistic elements for important photophysical and photochemical processes such as intramolecular electron transfer, [32] photoisomerization, [33] Wolff rearrangement, [34,35] Curtius rearrangement, [36] and aggregationinduced emission. [37,38] Although the above mentioned computational studies have established that the phototransformations of B(ppy)Mes 2 -based compounds can be rationalized by the reaction pathways on the potential energy surface of electronic singlet states, there exist several experimental arguments about the involvement of photoactive triplet states in this class of reactions. [39][40][41] Triplet acceptors including naphthalene, pyrene, and anthracene with various triplet state energies (2.63, 2.05, and 1.73 eV) led the photoisomerization quantum yield (Φ PI ) to 0.12, 0.03, and 0.00, suggesting that the photoisomerization of N,C-chelate dimesitylboranes proceeds via a triplet state.…”

Effective conjugation in conjugated polymers with strongly twisted backbones: a case study on fluorinated MEHPPV

“…The resulting broad double well torsional potentials in the ground and excited states additionally broaden absorption and emission spectra, respectively, 23 and largely increases both reorganization and Stokes shift compared to MEHPPV, all in agreement with experiment, see Finally fluorine-induced distortion has important consequences for the deactivation of the excited state after photoexcitation. 57 Consequently, increasing sterical hindrance within the DSB oligomer series leads to a systematic drop in fluorescence efficiency, see Fig. The reduction of the radiative rate from k F =  F / F = 1.0 ns -1 in MEHPPV to 0.4 ns -1 in F-MEHPPV should be directly correlated with the reduction of the oscillator strength; 55 the reduction in k F is, however, stronger than that of f (vide supra), which we ascribe to some uncertainty in the determination of the low values for  F and  F of F-MEHPPV.…”