Computational Design of Boron-Free Triangular Molecules with Inverted Singlet-Triplet Energy Gap

Physical Chemistry Chemical Physics, Journal Year: 2024, Volume and Issue: 26(28), P. 19130 - 19137

Published: Jan. 1, 2024

A novel, computationally designed, class of triangular-shape organic molecules with an inverted singlet-triplet (IST) energy gap is investigated

Language: Английский

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Rational Design of Organic Emitters with Inverted Singlet–Triplet Gaps for Enhanced Exciton Management

The Journal of Physical Chemistry A, Journal Year: 2024, Volume and Issue: 128(34), P. 7114 - 7123

Published: Aug. 19, 2024

In organic light-emitting diodes (OLEDs), the pursuit of efficient molecular emitters has led to development thermally activated delayed fluorescence (TADF) molecules. While TADF compounds have promising properties, they face challenges such as energy gap constraints and uphill exciton transfer. Inverted (INVEST) offer a novel solution with an inverted singlet–triplet (ΔEST) gap, enabling utilization excitons. This study examines design computational analysis array molecules, including 23 INVEST remaining positive gaps. Within STEOM-DLPNO–CCSD framework, we explore role various fragments in determining ΔEST. We also assess importance dynamic spin-polarization (DSP) obtained via Pariser–Parr–Pople (PPP) scheme determination. Exciting trends emerged from our results, pentalene-containing consistently manifesting negative ΔEST values while their naphthalene counterparts exhibited contrasting behavior. Moreover, observed DSP correlates Overall, this research advances OLED materials through analysis, offering avenues for optimizing management enhancing device performance.

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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Singlet–Triplet Inversion in Triangular Boron Carbon Nitrides

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: unknown

Published: Sept. 12, 2024

The discovery of singlet-triplet (ST) inversion in some π-conjugated triangle-shaped boron carbon nitrides is a remarkable breakthrough that defies Hund's first rule. Deeply rooted strong electron-electron interactions, ST has garnered significant interest due to its potential revolutionize triplet harvesting organic LEDs. Using the well-established Pariser-Parr-Pople model for correlated electrons systems, we employ combination CISDT and restricted active space configuration interaction calculations investigate photophysics several triangular nitrides. Our findings reveal these systems primarily driven by network alternating electron-donor electron-acceptor groups molecular rim, rather than structure itself.

Language: Английский

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Functionalization of Clar’s Goblet Diradical with Heteroatoms: Tuning the Excited-State Energies to Promote Triplet-to-Singlet Conversion

The Journal of Physical Chemistry A, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 11, 2025

The ground-state spin multiplicity as well the energy difference between lowest-energy spin-singlet (S1) and spin-triplet (T1) excited states of topologically frustrated organic (diradical) molecules can be tuned by doping with a pair heteroatoms (N or B atoms). We have thus systematically studied here set Clar's Goblet derivatives upon controlled substitution at different C sites, to alter electronic structure disclose positions which: (i) becomes closed-shell singlet (ii) S1 T1 is considerably small (i.e., below 0.1-0.2 eV induce triplet exciton recovery thermal effects). This outcome driven strong correlation effects; therefore, we applied variety single-reference [TD-DFT, CIS(D), SCS-CC2] multireference [CASSCF, NEVPT2, RAS-srDFT] methods. For TD-DFT, covered global hybrid (PBE0, M06-2X), range-separated (ωB97X), double-hybrid (PBE-QIDH, SOS1-PBE-QIDH, PBE0-2) functionals ascertain whether results were highly dependent on functional choice. Overall, found that heterosubstitution strategy could largely modify optical properties pristine diradical system, these forms constituting new compounds further optoelectronic applications.

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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The Role of Theoretical Calculations for INVEST Systems: Complementarity Between Theory and Experiments and Rationalization of the Results

Advanced Optical Materials, Journal Year: 2025, Volume and Issue: unknown

Published: March 5, 2025

Abstract Here, the key role played by theoretical calculations for molecules presenting an inverted singlet‐triplet excited state (e.g. S 1 and T ) energy difference, or Δ E ST < 0, whose interest has steadily raised in recent years fostered experimental advances showing negative values a collection of real‐world systems is reviewed. The evolution computational efforts from pioneering on reduced set prototypical covered, to high‐throughput virtual screenings thousands identify new molecular scaffolds tune properties other than excitation energies, describe necessary benchmarking methods done parallel along years. Overall, complementarity prompted discovery more displaying 0 values, basic design principles are rationalized thus reviewed here too, while allowing at same time find which offer reasonable trade‐off between accuracy cost.

Language: Английский

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The Importance of High-Frequency Modes in the Prediction of RISC Rates for TADF Molecules

The Journal of Physical Chemistry Letters, Journal Year: 2025, Volume and Issue: unknown, P. 3056 - 3062

Published: March 18, 2025

The reverse intersystem crossing (RISC) rate determines the efficiency of dyes displaying thermally activated delayed fluorescence (TADF). Such a can be predicted at full quantum level by considering all vibrational normal modes or adopting an approximated methodology which relies on single classical modes. We evaluated importance degrees freedom in computations for targeting design novel emissive materials from first principles. computed RISC 17 molecules interest TADF comparing mechanics treatment based Fermi's golden rule with Marcus-based semiclassical approaches. results are quantitatively and sometimes qualitatively different two approaches, especially when reorganization energy is small, common occurrence exhibiting TADF. high-frequency varies across set considered, suggesting that their evaluation should become part molecular process.

Language: Английский

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Impact of Structure on Excitation Energies and S₁‐T₁ Energy Gaps of Asymmetrical Systems of Interest for Inverted Singlet‐Triplet Gaps

Journal of Computational Chemistry, Journal Year: 2025, Volume and Issue: 46(8)

Published: March 26, 2025

Computational investigations of Inverted Singlet-Triplet (INVEST) emitters often rely on ADC(2) and TD-DFT excitation energies (EEs) obtained with the vertical approximation. Here, we first considered several cyclazine derivatives examine sensitivity EEs (VEEs) as well singlet-triplet gaps, ΔES1T1 to level at which ground state (S0) structure was optimized. For cyclazine, VEEs gaps from or are spread over a narrow range (< 0.064 eV) whether S0 is optimized various DFT, CCSD, RI-MP2 methods. However, for asymmetric cyclazines, depending protocol optimizing structures, not only substantially wider (up 0.75 but so 0.30 eV), leading cases where, different one obtains positive significantly negative gaps. We relate this behavior introduction significant asymmetry bond-length variations in derivatives, formed by ligand functionalization modification core. On more note, adiabatic (AEEs) display lower (7-30× less) geometry optimization protocols than their analogs. Crucially, M06-HF functional 100% non-local exchange provides closest available CCSD(T) data. show that effect exists also other frameworks (e.g., azulene, pentaazaphenalene, non-alternant polycyclic hydrocarbons) have been INVEST property, broader up 1.19 eV 0.62 eV. emitters, it therefore extremely important judiciously choose computational geometries, computing

Language: Английский

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Enhancing the prediction of TADF emitter properties using Δ-machine learning: A hybrid semi-empirical and deep tensor neural network approach

The Journal of Chemical Physics, Journal Year: 2025, Volume and Issue: 162(14)

Published: April 8, 2025

This study presents a machine learning (ML)-augmented framework for accurately predicting excited-state properties critical to thermally activated delayed fluorescence (TADF) emitters. By integrating the computational efficiency of semi-empirical PPP+CIS theory with Δ-ML approach, model overcomes inherent limitations in key properties, including singlet (S1) and triplet (T1) energies, singlet–triplet gaps (ΔEST), oscillator strength (f). The demonstrated exceptional accuracy across datasets varying sizes diverse molecular features, notably excelling ΔEST values, negative regions relevant TADF molecules inverted S1–T1 gaps. work highlights synergy between physics-inspired models accelerating design efficient emitters, providing foundation future studies on complex systems advanced functional materials.

Language: Английский

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