Organic molecules with inverted gaps between first excited singlet and triplet states and appreciable fluorescence rates

•Organic molecules with inverted singlet-triplet gaps and relevant fluorescence rates•High-throughput virtual screening of synthesizable organic emitter candidates•Multiobjective optimization gaps, rates, colors•Inverted gap emitters as next generation light-emitting diodes In recent years, advances in the design enabled their integration modern digital screens. Current rely on thermally activated delayed fluorescence. They minimize energy between lower, non-emissive first excited triplet higher, emissive singlet. Excitons generated upon electric excitation are distributed singlet states a 3:1 ratio due to spin statistics. The small allows thermal upconversion increases quantum efficiency significantly. Herein, we introduce new family that inverts relative making harvesting favorable. Additionally, both appreciable rates. This class has potential population leading higher long-term device stabilities, even for blue emitters. One proposal designing state-of-the-art materials (OLEDs) is principle (TADF). idea enable facile excited-state triplets, which electron-hole recombination, singlets. Minimizing corresponding difference enables devices up 100% internal efficiency. Ideal potentially surpassing TADF other performance parameters should have negative substantial rates maximize reverse intersystem crossing (ISC) from triplets singlets while minimizing ISC state occupation, operational stability. However, extremely rare, none them emissive. this work, based computational studies, describe considerable show they more common than hypothesized previously. Hund's rule1Hund F. Zur deutung verwickelter spektren, insbesondere der Elemente scandium bis nickel.Z. Physik. 1925; 33: 345-371Crossref Scopus (93) Google Scholar predicts closed-shell lower state. prediction holds all but handful known compounds, inorganic.2Koseki S. Nakajima T. Toyota A. 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Due rigid minima (also adiabatic gap) identical at Franck-Condon point vertical 2. decided continue our study latter minima. note ωB2PLYP′ only reproduces 2, not 1. correctable offset like second-order algebraic diagrammatic construction (ADC(2)) or coupled-cluster singles (EOM-CCSD) (vide infra). performed extensive simulations evaluating properties amorphous solid-state thin films mixed mechanics (QM)/molecular (MM) approach S2 S1). found simulated spectroscopic changed significantly; strengths largely unaffected. suggests least intrinsically affected environment.Table 1Benchmarking differences 21122MethodΔE(S0-S1) [eV]ΔE(S1-T1) [eV]ΔE(S0-S1) [eV]ADC(3)/cc-pVDZ0.777−0.0922.665−0.109ADC(2)/cc-pVDZ1.038−0.1602.578−0.278ADC(2)/cc-pVDZ/IEFPCM(S0)1.029−0.1612.657−0.281ADC(2)/aug-cc-pVDZ1.006−0.1442.614−0.263EOM-CCSD/cc-pVDZ1.092−0.0992.791−0.180FNO-EOM-CCSD/cc-pVDZ1.126−0.1043.418−0.214FNO-EOM-CCSD/aug-cc-pVDZ1.178−0.0863.040−0.167DLPNO-NEVPT2(6,6)/def2-SV(P)1.112−0.1892.552−0.344ωB2PLYP′/def2-SVP1.3160.0423.028−0.218ωB2PLYP′/def2-SVP/C-PCM1.3030.0363.165−0.236ωB2PLYP′/def2-SV(P) (vertical)1.3470.0463.089−0.198ωB2PLYP′/def2-SV(P) (adiabatic)1.2960.0553.045−0.188SA-SF-PBE50/def2-SVP1.095−0.1092.909−0.181Both TD-DFAs reproduce Open table tab Both Compounds isoelectronic differ C–H N. explore structures resulting permutations substitutions 2). 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United States Patent: 3886157 - 5,6,8,8B,9-Pentaazanaphth[3,2,1-d,e]Anthracene Derivatives. 3886157, May 27, 1975.Google 56Product cyclazines.Category Hetarenes Related Ring Systems. Thieme Verlag, 2004Google State differences, estimated rate constants 1–6 summarized 2.Scheme 3Azaphenalenes best rateView Large Image ViewerDownload Hi-res image Download (PPT)Table 2Excited-state transition, 1–6EOM-CCSD/cc-pVDZΔE(S0-S1) [eV]Oscillator f12Fluorescence kF [106 s−1]11.092−0.0990.00000.0019222.791−0.1800.00000.010531.659−0.0680.00350.41642.012−0.0290.00500.87252.251−0.0780.00340.74162.209−0.0710.00581.22All data points EOM-CCSD/cc-pVDZ theory. All Although obtained, optically bright, significantly smaller 107 s−1. look impact substituents properties, well probing mesomeric inductive effects. 18 monosubstituted analogs 1–6, 4. map, single change tenths electronvolts one magnitude. already These observations suggest extent feasible. Notably, studied literature investigated supplemental information S8 S4).Figure 2Map 1–6Show full captionAll theory.View (PPT) To optimize keeping negative, needed establish robust protocol trends property, efficiently applied larger molecules. results, compiled dataset. 3 compares dataset computationally less expensive methods. ADC(2)/cc-pVDZ ADC(2)/aug-cc-pVDZ generally closest agreement EOM-CCSD/cc-pVDZ, too cost saw timing reduction roughly 10% ADC(2) basis. diffuse functions neither nor frozen natural (FNO)-EOM-CCSD ωB2PLYP′/Ahlrich's (def2-SVP) offers accuracy. observed 200-fold still faithfully reproducing strengths. Furthermore, solvent corrections ωB2PLYP′/def2-SVP did changes. calculations good S4 correct shift observed, calculation Gaussian process regression S6). 0.15 ± 0.05 eV 0 eV. below eV, maximizing simultaneously. outliers diagrams 3B) likely errors correlating does outliers. addition, discrepancies S1 solvatochromic solution, UV-visible azaphenalene solution used linear correction. wavelengths provided way. underlying S7, S1, Tables