Aggregation Induced Emission in the Tetraphenylthiophene Crystal: The Role of Triplet States

Special Focus ◽

Intersystem Crossing ◽

Triplet States ◽

Aggregation Induced Emission ◽

The Family ◽

Energy Surfaces ◽

Potential Use

Propeller-shaped molecules have received much attention due to their enhanced emission in the condensed phase (Aggregation Induced Emission, AIE) and their potential use in optoelectronic devices. In this contribution, we examine the excited state mechanisms of tetraphenyl-thiophene (TPT), one member of the family which features weaker AIE. We perform a detailed analysis of the potential energy surfaces with special focus on the role of triplet states considering the crystal structure, intermolecular interactions, exciton couplings and reorganisation energies in the vacuum and solid state. In contrast with other members of the propeller-shaped family, nonradiative decay in TPT is driven by bond breaking. Because of the significant spin-orbit couplings along the reaction coordinate, intersystem crossing plays an important role in the mechanism. Our calculations show that aggregation in the solid state hampers the access to internal conversion pathways, however, intersystem crossing is active in the crystal phase, which explains the weak AIE of this molecule. This new understanding of the role of triplet states on the relaxation mechanisms of AIEgens has implications for the design of solid state highly-emissive materials based on TPT.

Emission Quenching in Tetraphenylfuran Crystal: Why This Propeller-Shaped Molecule Does Not Emit in the Condensed Phase?

Molecules ◽

10.3390/molecules27020522 ◽

2022 ◽

Vol 27 (2) ◽

pp. 522

Author(s):

Ljiljana Stojanović ◽

Rachel Crespo-Otero

Keyword(s):

Solid State ◽

Ground State ◽

Light Emission ◽

Quantum Yields ◽

Triplet States ◽

Fluorescence Quantum Yields ◽

The Family ◽

Emission Quenching ◽

Significant Attention

Due to their substantial fluorescence quantum yields in the crystalline phase, propeller-shaped molecules have recently gained significant attention as potential emissive materials for optoelectronic applications. For the family of cyclopentadiene derivatives, light-emission is highly dependent on the nature of heteroatomic substitutions. In this paper, we investigate excited state relaxation pathways in the tetraphenyl-furan molecule (TPF), which in contrast with other molecules in the family, shows emission quenching in the solid-state. For the singlet manifold, our calculations show nonradiative pathways associated with C-O elongation are blocked in both vacuum and the solid state. A fraction of the population can be transferred to the triplet manifold and, subsequently, to the ground state in both phases. This process is expected to be relatively slow due to the small spin-orbit couplings between the relevant singlet-triplet states. Emission quenching in crystalline TPF seems to be in line with more efficient exciton hopping rates. Our simulations help clarify the role of conical intersections, population of the triplet states and crystalline structure in the emissive response of propeller-shaped molecules.

Reaction Dynamics of O(3P) + Propyne: II. Primary Products, Branching Ratios, and Role of Intersystem Crossing from Ab Initio Coupled Triplet/Singlet Potential Energy Surfaces and Statistical Calculations

The Journal of Physical Chemistry A ◽

10.1021/acs.jpca.6b01564 ◽

2016 ◽

Vol 120 (27) ◽

pp. 4619-4633 ◽

Cited By ~ 13

Author(s):

Ilaria Gimondi ◽

Carlo Cavallotti ◽

Gianmarco Vanuzzo ◽

Nadia Balucani ◽

Piergiorgio Casavecchia

Keyword(s):

Potential Energy ◽

Ab Initio ◽

Reaction Dynamics ◽

Branching Ratios ◽

Intersystem Crossing ◽

Primary Products ◽

Decomposition of Anthranil. Single Pulse Shock-Tube Experiments, Potential Energy Surfaces and Multiwell Transition-State Calculations. The Role of Intersystem Crossing†

The Journal of Physical Chemistry A ◽

10.1021/jp056339v ◽

2006 ◽

Vol 110 (27) ◽

pp. 8248-8258 ◽

Cited By ~ 4

Author(s):

Assa Lifshitz ◽

Carmen Tamburu ◽

Aya Suslensky ◽

Faina Dubnikova

Keyword(s):

Potential Energy ◽

Transition State ◽

Shock Tube ◽

Single Pulse ◽

Intersystem Crossing ◽

A QM/MM Study of Acylphosphatase Reveals the Nucleophilic-Attack and Ensuing Carbonyl-Assisted Catalytic Mechanisms

10.26434/chemrxiv.11984448.v1 ◽

2020 ◽

Author(s):

zheng zhao ◽

Phil bourne ◽

Hao Hu ◽

Huanyu Chu

Keyword(s):

Energy Barrier ◽

Catalytic Mechanism ◽

Interaction Networks ◽

Nucleophilic Attack ◽

Reaction Coordinates ◽

Transition State Stabilization ◽

Catalytic Mechanisms ◽

Acylphosphatase is one of the vital enzymes in many organs/tissues to catalyze an acylphosphate molecule into carboxylate and phosphate. Here we use a combined ab initio QM/MM approach to reveal the catalytic mechanism of the benzoylphosphate-bound acylphosphatase system. Using a multi-dimensional reaction-coordinates-driving scheme, we obtained a detailed catalytic process including one nucleophilic-attack and then an ensuing carbonyl-shuttle catalytic mechanism by calculating two-dimensional potential energy surfaces. We also obtained an experiment-agreeable energy barrier and validated the role of the key amino acid Asn38. Additionally, we qualified the transition state stabilization strategy based on the amino acids-contributed interaction networks revealed in the enzymatic environment. This study provided usefule insights into the underlying catalytic mechanism to contribute to disease-involved research.

Photorelaxation Pathways of 4-(N,N-Dimethylamino)-4′-nitrostilbene Upon S1 Excitation Revealed by Conical Intersection and Intersystem Crossing Networks

Molecules ◽

10.3390/molecules25092230 ◽

2020 ◽

Vol 25 (9) ◽

pp. 2230

Author(s):

Ziyue He ◽

Ruidi Xue ◽

Yibo Lei ◽

Le Yu ◽

Chaoyuan Zhu

Keyword(s):

Branching Ratio ◽

The Other ◽

Conical Intersection ◽

Intersystem Crossing ◽

Physical Insight ◽

Quinoid Form ◽

In Trans ◽

Crossing Networks ◽

Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to reveal the photorelaxation pathways of 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS) upon S1 excitation. Within the interwoven networks of five S1/S0 and three T2/T1 conical intersections (CIs), and three S1/T2, one S1/T1 and one S0/T1 intersystem crossings (ISCs), those competing nonadiabatic decay pathways play different roles in trans-to-cis and cis-to-trans processes, respectively. After being excited to the Franck–Condon (FC) region of the S1 state, trans-S1-FC firstly encounters an ultrafast conversion to quinoid form. Subsequently, the relaxation mainly proceeds along the triplet pathway, trans-S1-FC → ISC-S1/T2-trans → CI-T2/T1-trans → ISC-S0/T1-twist → trans- or cis-S0. The singlet relaxation pathway mediated by CI-S1/S0-twist-c is hindered by the prominent energy barrier on S1 surface and by the reason that CI-S1/S0-trans and CI-S1/S0-twist-t are both not energetically accessible upon S1 excitation. On the other hand, the cis-S1-FC lies at the top of steeply decreasing potential energy surfaces (PESs) towards the CI-S1/S0-twist-c and CI-S1/S0-DHP regions; therefore, the initial twisting directions of DN and DAP moieties determine the branching ratio between αC=C twisting (cis-S1-FC → CI-S1/S0-twist-c → trans- or cis-S0) and DHP formation relaxation pathways (cis-S1-FC → CI-S1/S0-DHP → DHP-S0) on the S1 surface. Moreover, the DHP formation could also take place via the triplet relaxation pathway, cis-S1-FC → ISC-S1/T1-cis → DHP-T1 → DHP-S0, however, which may be hindered by insufficient spin-orbit coupling (SOC) strength. The other triplet pathways for cis-S1-FC mediated by ISC-S1/T2-cis are negligible due to the energy or geometry incompatibility of possible consecutive stepwise S1 → T2 → T1 or S1 → T2 → S1 processes. The present study reveals photoisomerization dynamic pathways via conical intersection and intersystem crossing networks and provides nice physical insight into experimental investigation of DANS.