Can range-separated functionals be optimally tuned to predict spectra and excited state dynamics in photoactive iron complexes?

Zobel, Patrick; Kruse, Ayla; Baig, Omar; Lochbrunner, Stefan; Bokarev, Sergey I.; Kuehn, Oliver; González, Leticia; Bokareva, Olga S.

doi:10.1039/d2sc05839a

Cited by 13 publications

(15 citation statements)

References 77 publications

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“…(c) It has been shown that tuning to the first IP in a chromophore does not necessarily also improve on other IPs or excitations that involve orbitals with a character differing from that of the HOMO. This can lead, for example, to the wrong order of states in outer-valence spectra (this can be remedied by a judicious amount of short-range EXX admixture ,− ). (d) Environmental effects, e.g., in a solvent, may influence the optimal ω significantly. − This may render OR-RSHs tuned in the gas phase unsuitable for applications in solution, unless one introduces proper screening in the optimization of ω. , Furthermore, for longer conjugated polymers the optimal ω may approach zero, eliminating the advantages of long-range corrections .…”

Section: Introductionmentioning

confidence: 99%

Accurate Ionization Potentials, Electron Affinities, and Band Gaps from the ωLH22t Range-Separated Local Hybrid Functional: No Tuning Required

Fürst

Kaupp

2023

J. Chem. Theory Comput.

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The optimal tuning (OT) of range-separated hybrid (RSH) functionals has been proposed as the currently most accurate DFT-based way to compute the relevant quantities required for charge-transfer processes in organic chromophores used in organic photovoltaics and related fields. The main drawback of OT-RSHs is that the system-specific tuning of the range-separation parameter is not size-consistent. It therefore also lacks transferability, e.g., when considering processes involving orbitals not involved in the tuning or for reactions between different chromophores. Here we show that the recently reported ωLH22t range-separated local hybrid functional provides ionization energies, electron affinities, and fundamental gaps on par with OT-RSH treatments, approaching the quality of GW results, without any need for system-specific tuning. This holds from relevant organic chromophores of varying sizes all the way to atomic electron affinities. ωLH22t also gives excellent outer-valence quasiparticle spectra and is a generally accurate functional for both main-group and transition-metal energetics, as well as for a variety of excitation types. Range-separated local hybrid functionals are suggested as promising new quantum-chemical tools in molecular electronics.

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Section: Introductionmentioning

confidence: 99%

Accurate Ionization Potentials, Electron Affinities, and Band Gaps from the ωLH22t Range-Separated Local Hybrid Functional: No Tuning Required

Fürst

Kaupp

2023

J. Chem. Theory Comput.

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“…For instance, it was shown that predicted spectra and excited state dynamics of photoactive iron complexes obtained by tuning range-separated hybrid parameters to recover exact conditions do not necessarily have improved agreement with experimental data. 77 However, results from range-separated hybrids with parameters tuned based on CASPT2 agree better with both CASPT2 and experiments. 77 There is generally not a widespread agreement about which DFT functionals perform best for SCO properties, even if we restrict ourselves to a fixed metal and oxidation state, such as Fe(II).…”

Section: Introductionmentioning

confidence: 57%

“…77 However, results from range-separated hybrids with parameters tuned based on CASPT2 agree better with both CASPT2 and experiments. 77 There is generally not a widespread agreement about which DFT functionals perform best for SCO properties, even if we restrict ourselves to a fixed metal and oxidation state, such as Fe(II).…”

Section: Introductionmentioning

confidence: 57%

“…A prior study 72 developed accurate benchmarks for spin state ordering of TMCs using CASPT2 which were then used to evaluate optimal DFT functional choice for predicting spin state ordering. Correlated multiconfigurational methods like CASPT2 33,[73][74][75][76][77] and single-reference methods like CCSD(T) [78][79][80] can provide reliable energies and geometries 81 of HS and LS states for Fe(II) complexes. It was also shown 82 that extended multistate (XMS) CASPT2 and DLPNO-CCSD(T) provide a good description of Mn(III) SCO complex geometries because they recover dispersion from first principles.…”

Section: Introductionmentioning

confidence: 99%

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Assessing the Performance of Approximate Density Functional Theory on 95 Experimentally Characterized Fe(II) Spin Crossover Complexes

Vennelakanti

Taylor

Nandy

et al. 2023

Preprint

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Spin crossover (SCO) complexes, which exhibit changes in spin state in response to external stimuli, have applications in molecular electronics and are challenging materials for computational design. We curate a data set of 95 Fe(II) SCO complexes (SCO-95) from the Cambridge Structural Database that have available low- and high-temperature crystal structures and, in most cases, confirmed experimental spin transition temperatures (T1/2). We study these complexes using density functional theory (DFT) with thirty functionals spanning across multiple rungs of “Jacob’s ladder” to understand the effect of exchange-correlation functional on electronic and Gibbs free energies associated with spin crossover. We specifically assess the effect of varying the Hartree–Fock exchange fraction (aHF) in structures and properties within the B3LYP family of functionals. We identify three best-performing functionals, a modified version of B3LYP (aHF = 0.10), M06-L, and TPSSh, that accurately predict SCO behavior for the majority of the complexes. Contrary to observations from prior studies, double-hybrids with higher aHF values are found to strongly stabilize high-spin states and therefore exhibit poor performance in predicting SCO behavior. Computationally predicted T1/2 values are consistent among the three functionals but show limited correlation to experimentally reported T1/2 values. These failures are attributed to the lack of crystal packing effects and counter-anions in the DFT calculations that would be needed to account for phenomena like hysteresis and two-step SCO behavior. The SCO-95 set thus presents opportunities for method development, both in terms of increasing model complexity and method fidelity.

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“…Blank spots denote parts of the trajectory where there was no contribution larger than 80%. This was a larger threshold than we used in previous works on VCl 3 (ddpd) [ 26 ] (60–70%) and [Fe(cpmp) 2 ] 2+ [ 68 ] (40–50%; cpmp = 6,2″-carboxypyridyl-2,2′-methylamine-pyridyl-pyridine), showing that in the excited-state dynamics of [Cr(ddpd) 2 ] 3+ the trajectories stay in electronic states more similar to the states at the Franck–Condon geometry than in the other two examples noted. Note, however, that we collect the almost-degenerate electronic states corresponding to the components of the octahedral electronic term in this analysis, i.e., the contribution of the individual diabatic state components is usually lower.…”

Section: Results and Discussionmentioning

confidence: 99%

Photodynamics of the Molecular Ruby [Cr(ddpd)2]3+

2023

Self Cite

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The introduction of strong-field ligands can enable luminescence in first-row transition-metal complexes. In this way, earth-abundant near-infrared emitters can be obtained using early 3d metals. A prime example is the molecular ruby [Cr(ddpd)2]3+ (ddpd = N,N′-dimethyl-N,N′-dipyridin-2-ylpyridine-2,6-diamine) that can achieve high phosphorescence quantum yields at room temperature in aqueous solution. To understand these remarkable properties, here, we simulate its photodynamics in water using trajectory surface hopping on linear vibronic coupling potentials parametrized from multiconfigurational CASSCF/CASPT2 calculations. We find that after excitation to the second absorption band, a relaxation cascade through metal-centered states occurs. After an initial back-and-forth intersystem crossing with higher-lying doublet states, the complex relaxes through a manifold of quartet metal-centered states to the low-lying doublet metal-centered states which are responsible for the experimentally observed emission. These electronic processes are driven by an elongation of the Cr–ligand bond lengths as well as the twisting motion of the trans-coordinated pyridine units in the ddpd ligands. The low-lying doublet states are reached within 1–2 ps and are close in geometry to the doublet minima, thus explaining the high phosphorescence quantum yield of the molecular ruby [Cr(ddpd)2]3+.

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Can range-separated functionals be optimally tuned to predict spectra and excited state dynamics in photoactive iron complexes?

Abstract: Density functional theory is an efficient computational tool to investigate photophysical and photochemical processes in transition metal complexes, giving invaluable assistance in interpreting spectroscopic and catalytic experiments. Optimally-tuned range-separated functionals...

Cited by 13 publications

References 77 publications

Accurate Ionization Potentials, Electron Affinities, and Band Gaps from the ωLH22t Range-Separated Local Hybrid Functional: No Tuning Required

Accurate Ionization Potentials, Electron Affinities, and Band Gaps from the ωLH22t Range-Separated Local Hybrid Functional: No Tuning Required

Assessing the Performance of Approximate Density Functional Theory on 95 Experimentally Characterized Fe(II) Spin Crossover Complexes

Photodynamics of the Molecular Ruby [Cr(ddpd)2]3+

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