Reverse Intersystem Crossing Dynamics in Vibronically Modulated Inverted Singlet–Triplet Gap System: A Wigner Phase Space Study

The Journal of Physical Chemistry Letters, Journal Year: 2024, Volume and Issue: 15(30), P. 7603 - 7609

Published: July 19, 2024

We inspect the origin of inverted singlet-triplet gap (INVEST) and slow change in reverse intersystem crossing (rISC) rate with temperature, as recently observed. A Wigner phase space study reveals that, though INVEST is found at equilibrium geometry, variation exchange interaction doubles-excitation for other geometries harmonic region leads to non-INVEST behavior. This highlights importance nuclear degrees freedom phenomenon, this case, geometric puckering studied molecule determines associated rISC dynamics.

Language: Английский

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Benchmark computations of nearly degenerate singlet and triplet states of N-heterocyclic chromophores. II. Density-based methods

The Journal of Chemical Physics, Journal Year: 2025, Volume and Issue: 162(2)

Published: Jan. 8, 2025

In this paper, we demonstrate the performance of several density-based methods in predicting inversion S1 and T1 states a few N-heterocyclic triangulene based fused ring molecules (popularly known as INVEST molecules) with an eye to identify well performing but cost-effective preliminary screening method. Both conventional linear-response time-dependent density functional theory (LR-TDDFT) ΔSCF (namely maximum overlap method, square-gradient minimization restricted open-shell Kohn–Sham) are considered for excited state computations using exchange–correlation (XC) functionals from different rungs Jacob’s ladder. A well-justified systematism is observed when compared against fully internally contracted multireference configuration interaction singles doubles and/or equation motion coupled-cluster (EOM-CCSD), most important feature being capture spin-polarization presence correlation. set least mean absolute error proposed both approaches, LR-TDDFT ΔSCF, which can be more alternatives on synthesizable larger derivatives templates studied here. We have our findings extensive studies three cyclazine-based molecular templates, additional six related templates. Previous benchmark subsets were conducted domain-based local pair natural orbital-similarity transformed EOM-CCSD (STEOM-CCSD), resulted inadequate evaluation due deficiencies theory. The role exact-exchange, spin-contamination, context DFT comes forefront supports numerical XC these applications. Suitable connections drawn two exciton models, minimal physics governing interactions molecules.

Language: Английский

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Design of new first and fifth generation OLED emitters by doping 12,12-dimethyl-7-phenyl-7,12-dihydrobenzo[a]acridine-3-carbonitrile (BACN): DFT study

Synthetic Metals, Journal Year: 2025, Volume and Issue: unknown, P. 117879 - 117879

Published: April 1, 2025

Language: Английский

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Can ΔSCF and ROKS DFT-Based Methods Predict the Inversion of the Singlet–Triplet Gap in Organic Molecules?

Journal of Chemical Theory and Computation, Journal Year: 2025, Volume and Issue: unknown

Published: March 1, 2025

Inverted singlet–triplet gap systems (INVEST) have emerged as an intriguing class of materials with potential applications emitters in Organic Light Emitting Diodes (OLEDs). Indeed, this type material exhibits a negative energy (ΔEST), i.e., inversion the lowest singlet (S1) and triplet (T1) excited states, that goes against Hund's rule. In study, ΔEST set 15 INVEST molecules has been computed within framework Restricted Open-Shell Kohn–Sham (ROKS) Delta Self-Consistent Field (ΔSCF) methods results were benchmarked wavefunction-based calculations performed at EOM-CCSD, NEVPT2, SCS-CC2 levels. We find ROKS always (and wrongly) predicts positive global hybrid, meta-GGA, long-range corrected functionals is almost functional-independent. also show only way to obtain inverted was resort double hybrid functionals. contrast, using above-mentioned functionals, ΔSCF usually gives ΔEST, although are largely functional-dependent. Overall, applying method based on PBE0 functional provides MSD MAD respect EOM-CCSD results. further driven by different degrees orbital relaxation versus state well captured calculations. As matter fact, somehow mimics involvement higher-order excitations which leads difference spatial localization α β spins, thus introduces (local) spin polarization effects sourcing ΔEST. However, care should be taken when screen behavior view their limited quantitative correlation reference molecular data basis used here.

Language: Английский

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Singlet-Triplet Inversion

Annual Review of Physical Chemistry, Journal Year: 2025, Volume and Issue: 76(1), P. 329 - 355

Published: April 21, 2025

The inversion of singlet and triplet states is a rare phenomenon, where, in opposition to Hund's first rule, electronic are stabilized relative their counterparts. recent discovery organic molecules exhibiting this presents exciting new technological opportunities, such as addressing stability issues light-emitting diodes (OLEDs). In review, we describe fundamental molecular properties that can yield singlet-triplet inversion, generally ascribed phenomenon known dynamic spin polarization. We discuss the systems which was theoretically proposed, experimentally verified, implemented an OLED device. highlight key insights from extensive computational work being carried out understand intricacies these systems. Finally, consider outlook for future inverted (IST) emitters.

Language: Английский

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Large Third-Order Optical Nonlinearity for Dipolar Carbene-Metal-Amide Material with Two-Photon Excited Delayed Fluorescence

Research Square (Research Square), Journal Year: 2025, Volume and Issue: unknown

Published: May 6, 2025

Advanced photonic materials showing two-photon absorption (2PA) have been widely explored to develop three-dimensional imaging, micro and nanofabrication, all-optical switching, lithography on a nanoscale many other enabling technologies. These all require nonlinear chromophores with intrinsic high 2PA cross-sections long-term photo- thermal stability. Here, we disclose the very first example of dipolar carbene-metal-amide (CMA) material cross-section up 105 GM. Overall molecular design considerations such as extended π-conjugation (to increase polarizability), minimizing singlet-triplet energy gap (ΔE_ST), using heavy metal atoms are principles obtain bright one- excited thermally activated delayed fluorescence (TADF) material, one highest radiative rate 2.18·10⁶ s^{− 1} across CMA materials. Bright red 2P-TADF shows excellent photostability (LT₅₀ = 3 h) 20 mW femtosecond pulsed laser excitation at 1000 nm, encouraging further exploration for future applications in advanced technologies requiring third-order optical properties.

Language: Английский

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Searching the Best Double-Hybrid Density Functional to Correctly Predict the Singlet–Triplet Excited-State Inversion in Organic Systems

The Journal of Physical Chemistry C, Journal Year: 2024, Volume and Issue: 128(43), P. 18313 - 18327

Published: Oct. 18, 2024

The theoretically disclosed, and experimentally confirmed, energy inversion of the lowest singlet (S1) triplet (T1) excited states organic molecules (i.e., Hund's rule violation) is investigated herein with aid modern nonempirically derived double-hybrid (DH) density functionals, in search best trade-off between accuracy computational cost viable electronic structure methods. For that purpose, we have selected a family parameter-free expressions differing their specific formulation (DFT-0DH, DFT-QIDH, DFT0-2, SOS1-DFT-0DH, SOS1-DFT-QIDH, SOS1-DFT0-2, RSX-DFT-0DH, RSX-DFT-QIDH, SOS1-RSX-DFT-0DH, SOS1-RSX-DFT-QIDH) as well underlying exchange–correlation functional used (PBE vs r2SCAN). sake evaluating which DH can correctly describe singlet–triplet excited-state inversion, second-order approximate singles doubles method spin-component scaling (SCS-CC2) equation-of-motion coupled cluster (EOM-CCSD) calculations are also carried out. results highlight importance delicate balance all terms composing correlation part being particularly significant for achieving most accurate results. We new (PBE-DH-INVEST) exploiting relationship, providing low error metrics expected to yield robust in, e.g., high-throughput studies.

Language: Английский

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Recent Advances in Thermally Activated Delayed Fluorescence‐Based Organic Afterglow Materials

Small Methods, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 25, 2024

Thermally activated delayed fluorescence (TADF)-based materials are attracting widespread attention for different applications owing to their ability of harvesting both singlet and triplet excitons without noble metals in structures. As compared the conventional room-temperature phosphorescence pathways, TADF originates from reverse intersystem crossing process excited state (T

Language: Английский

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Design of Anti-Hund Organic Emitters Based on Heptazine

ACS Applied Materials & Interfaces, Journal Year: 2024, Volume and Issue: 16(44), P. 60648 - 60657

Published: Oct. 25, 2024

Hund's rule, which is powerful in governing the first excited states of closed-shell organic materials, can hardly be violated to get inverted singlet-triplet gap (INVEST) molecules with negative energy gaps (ΔEST), although INVEST materials have shown extraordinary photophysical properties and promising device performance especially light-emitting diodes. Here, we propose a facile strategy construct emissive by introducing different types substituents heptazine various modes, effectively tune ΔEST enlarged oscillator strength (f) for high fluorescence rate derivatives. Systematic computational studies show that double substitution electron-donating units another nonconjugated substituent hybrid mode most favorable way achieving slightly large f values; conjugated will compete make molecule deviate from feature. Especially, series high-performance heptazine-based emitters were constructed, exhibiting low -0.362 eV, up 0.0436, as well wide range emission color 339 716 nm. Also, designed predicted radiative rates 106 s-1, along efficient reverse intersystem crossing reaching 108 s-1. Importantly, figure merit (FM) was proposed parameter wholly evaluate emitters, highest FM 0.198 found triazine amine-substituted heptazine. These results highlight great potential chromophore constructing revealing fundamental structure-property understandings material design anti-Hund improved properties.

Language: Английский

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Enhancing Reverse Intersystem Crossing with Extended Inverted Singlet–Triplet (X−INVEST) Systems

Advanced Optical Materials, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 17, 2024

Abstract The discovery of triangular‐shaped molecules displaying an inverted singlet–triplet (INVEST) energy gap between their lowest singlet (S 1 ) and triplet (T states opened the way for a new strategy to increase internal quantum efficiency (IQE) organic light‐emitting diodes (OLEDs), enhancing reverse intersystem crossing (RISC) thanks downhill process. However, compounds showing negative ΔE ST suffer from both vanishing spin–orbit coupling (SOC) these excited high differences with higher‐lying singlets triplets, therefore limiting involvement in spin conversion Here, we proposed design entailing extension triangulene cores by connecting two INVEST units form Uthrene‐ Zethrene‐like systems, doped N B. inspection resulting molecular orbitals (MOs) distribution allowed rationalizing electronic structure properties obtained wavefunction‐based methods, how Uthrene‐like architecture can lead quasi ‐resonance S T , some cases provoking inversion. By feeding kinetic model non‐radiative rate constants, calculated first principles, showed extended (X−INVEST) open pathways boost process population emissive .

Language: Английский

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