Phosphorescent Properties of Heteroleptic Ir(III) Complexes: Uncovering Their Emissive Species

The Journal of Physical Chemistry A, Journal Year: 2023, Volume and Issue: 127(34), P. 7241 - 7255

Published: Aug. 19, 2023

In this contribution, we assess the computational machinery to calculate phosphorescence properties of a large pool heteroleptic [Ir(C^N)2(N^N)]+ complexes (where N^N is an ancillary ligand and C^N cyclometalating ligand) including their phosphorescent rates emission spectra. Efficient protocols are next proposed. Specifically, different flavors DFT functionals were benchmarked against DLPNO-CCSD(T) for energies. The transition density matrix decomposition analysis emitting triplet excited state enable us categorize studied into cases, from predominant ligand-centered (3LC) character charge-transfer (3CT) character, either metal-to-ligand charge transfer (3MLCT), ligand-to-ligand (3LLCT), or combination two. We have also calculated vibronically resolved spectra rates. Ir(III) with 3CT characterized by less bands as compared those 3LC character. Furthermore, some close-lying states so that calculation poses additional challenges. these scenarios, it necessary perform geometry optimizations higher-lying (i.e., Tn). demonstrate in latter scenarios all species must be considered recover shape experimental global computed energies, spectra, rates, etc. unambiguously pinpoint first time involved process provide general classification regard properties.

Language: Английский

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Electronic Couplings for Singlet Fission Processes Based on the Fragment Particle-Hole Densities

Journal of Chemical Theory and Computation, Journal Year: 2023, Volume and Issue: 19(13), P. 3900 - 3914

Published: June 9, 2023

A new diabatization scheme is proposed to calculate the electronic couplings for singlet fission process in multichromophoric systems. In this approach, a robust descriptor that treats single and multiple excitations on an equal footing adopted quantify localization degree of particle hole densities states. By maximally localizing particles holes terms predefined molecular fragments, quasi-diabatic states with well-defined characters (locally excited, charge transfer, correlated triplet pair, etc.) can be automatically constructed as linear combinations adiabatic ones, directly obtained. This approach very general it applies various spin multiplicities combined kinds preliminary structure calculations. Due high numerical efficiency, able manipulate more than 100 diabatization. The applications tetracene dimer trimer reveal high-lying multiply excited transfer have significant influences both formation separation pair even enlarge coupling latter by 1 order magnitude.

Language: Английский

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Extended N‐centered ensemble density functional theory of double electronic excitations

Journal of Computational Chemistry, Journal Year: 2024, Volume and Issue: 45(22), P. 1945 - 1962

Published: May 3, 2024

Abstract A recent work (arXiv:2401.04685) has merged N ‐centered ensembles of neutral and charged electronic ground states with excited states, thus providing a general in‐principle exact (so‐called extended ‐centered) ensemble density functional theory excitations. This formalism made it possible to revisit the concept density‐functional derivative discontinuity, in particular case single excitations from highest occupied Kohn–Sham (KS) molecular orbital, without invoking usual “asymptotic behavior density” argument. In this work, we address broader class excitations, focus on double An implementation is presented for two‐electron Hubbard dimer model. thorough comparison true physical ground‐ excited‐state structures that fictitious KS system also presented. Depending choice as well asymmetry correlation strength, an inversion can be observed. some other cases, strong mixture within makes assignment “single excitation” or “double irrelevant.

Language: Английский

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∆DFT predicts inverted singlet-triplet gaps with chemical accuracy at a fraction of the cost of wavefunction-based approaches

Published: June 3, 2024

Efficient OLEDs must quickly convert singlet and triplet excitons into photons. Molecules with an inverted singlet-triplet energy gap (INVEST) are promising candidates for this task. However, typical INVEST molecules have drawbacks like too low oscillator strengths excitation energies. High-throughput screening could identify suitable molecules, but existing methods problematic: The workhorse method TD-DFT cannot reproduce inversion, while wavefunction-based slow. This study proposes a state-specific based on unrestricted Kohn-Sham DFT common hybrid functionals. Tuned the new INVEST15 benchmark set, achieves error of less than 1 kcal/mol, which is traced back to cancellation between spin contamination dynamic correlation. Applied larger structurally diverse NAH159 set in black-box fashion, maintains small (1.2 kcal/mol) accurately predicts signs 83% cases, confirming its robustness suitability workflows.

Language: Английский

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WFOT: A Wave Function Overlap Tool between Single- and Multi-Reference Electronic Structure Methods for Spectroscopy Simulation

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(11), P. 4804 - 4819

Published: June 3, 2024

We report the development of a novel diagnostic tool, named wave function overlap tool (WFOT), designed to evaluate between functions computed at single-reference [i.e., time-dependent density functional theory or configuration interaction singles (CIS)] and multireference (i.e., CASSCF/CASPT2) electronic structure levels theory. It relies on truncating single- WFs CIS-like expansions spanning same configurational space maximizing molecular orbital by means unitary transformation. To demonstrate functionality we calculate transient spectrum acetylacetone evaluating excited state absorption signals with quality top on-the-fly dynamics simulations. Semiautomatic spectra generation is facilitated interfacing COBRAMM package, which also allows one use WFOT several quantum chemistry codes such as Gaussian, NWChem, OpenMolcas. Other exciting possibilities for utilization code beyond simulation spectroscopy are eventually discussed.

Language: Английский

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A Constraint-Based Orbital-Optimized Excited State Method (COOX)

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

Published: Sept. 30, 2024

In this work, we present a novel method to directly calculate targeted electronic excited states within self-consistent field calculation based on constrained density functional theory (cDFT). The constraint is constructed from the static occupied-occupied and virtual-virtual parts of state difference (simplified) linear-response time-dependent calculations (LR-TDDFT). Our new shows stable convergence behavior, provides an accurate adhering Aufbau principle, can be solved restricted SCF for singlet excitations avoid spin contamination. This also allows straightforward application post-SCF electron-correlation methods like MP2 or direct RPA methods. We details our constraint-based orbital-optimized (COOX) compare it similar schemes. accuracy excitation energies will analyzed benchmark systems, while quality resulting densities investigated by evaluating nuclear forces structure optimizations. investigate performance proposed COOX long-range charge transfer conical intersections with ground-state.

Language: Английский

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Quantification of the Ionic Character of Multiconfigurational Wave Functions: The Q_a^t Diagnostic

The Journal of Physical Chemistry A, Journal Year: 2023, Volume and Issue: 127(46), P. 9842 - 9852

Published: Oct. 18, 2023

The complete active space self-consistent field (CASSCF) method is a cornerstone in modern excited-state quantum chemistry providing the starting point for most common multireference computations. However, CASSCF, when used with minimal space, can produce significant errors (>2 eV) even excitation energies of simple hydrocarbons if states interest possess ionic character. After illustrating this problem some detail, we present diagnostic character, denoted as Q at, that readily computed from transition density. A set 11 molecules considered to study vertical energies. State-averaged CASSCF obtains mean absolute error (MAE) 0.87 eV 34 singlet considered. We highlight strong correlation between obtained and at diagnostic, its power predict problematic cases. Conversely, using configuration interaction single double excitations Pople's size extensivity correction (MR-CISD+P), excellent results are an MAE 0.11 eV. Furthermore, correlations disappear. In summary, hope presented will facilitate reliable user-friendly computations on conjugated organic molecules.

Language: Английский

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State-Specific Coupled-Cluster Methods for Excited States

arXiv (Cornell University), Journal Year: 2024, Volume and Issue: unknown

Published: Jan. 1, 2024

We reexamine $\Delta$CCSD, a state-specific coupled-cluster (CC) with single and double excitations (CCSD) approach that targets excited states through the utilization of non-Aufbau determinants. This methodology is particularly efficient when dealing doubly states, domain where standard equation-of-motion CCSD (EOM-CCSD) formalism falls short. Our goal here to evaluate effectiveness $\Delta$CCSD applied other types comparing its consistency accuracy EOM-CCSD. To this end, we report benchmark on excitation energies computed EOM-CCSD methods, for set molecular excited-state encompasses not only but also doublet-doublet transitions (singlet triplet) singly-excited closed-shell systems. In latter case, rely minimalist version multireference CC known as two-determinant method compute states. dataset, consisting 276 stemming from \textsc{quest} database [V\'eril \textit{et al.}, \textit{WIREs Comput. Mol. Sci.} \textbf{2021}, 11, e1517], provides significant base draw general conclusions concerning $\Delta$CCSD. Except doubly-excited found underperforms For transitions, difference between mean absolute errors (MAEs) two methodologies (of \SI{0.10}{\eV} \SI{0.07}{\eV}) less pronounced than obtained systems (MAEs \SI{0.15}{\eV} \SI{0.08}{\eV}). discrepancy largely attributed greater number in exhibiting multiconfigurational characters, which are more challenging

Language: Английский

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Classification and quantitative characterisation of the excited states of π-conjugated diradicals

Faraday Discussions, Journal Year: 2024, Volume and Issue: 254, P. 107 - 129

Published: Jan. 1, 2024

Diradicals are of high current interest as emerging materials for next generation optoelectronic applications. To tune their excited-state properties it would be greatly beneficial to have a detailed understanding the wave functions different states involved but this endeavour is hampered by formal and practical barriers. tackle these challenges, we present analysis well concrete results on diradical excited states. We start with investigation available two-orbital two-electron model viewed from both valence-bond molecular orbital perspectives. highlight presence zwitterionic illustrate connections found in closed-shell molecules. Subsequently, introduce protocols analysing realistic multireference computations applying

Language: Английский

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Exploring Ground and Excited States Via Single Reference Coupled-Cluster Theory and Algebraic Geometry

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

Published: Sept. 17, 2024

The exploration of the root structure coupled cluster (CC) equations holds both foundational and practical significance for computational quantum chemistry. This study provides insight into intricate structures these nonlinear at CCD CCSD level theory. We utilize techniques from algebraic geometry, specifically monodromy parametric homotopy continuation methods, to calculate full solution set. compare computed CC roots against various established theoretical upper bounds, shedding light on accuracy efficiency bounds. hereby focus dissociation processes four-electron systems such as (H

Language: Английский

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