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51. Organic Photoredox Catalysts Exhibiting Long Excited-State Lifetimes.

Author

Jeong, Dong Yeun and You, Youngmin

Subjects
*CATALYSTS, *RUTHENIUM catalysts, *MOLECULAR structure, *PHOTOEXCITATION, *TRANSITION metals, *PHOTOINDUCED electron transfer, *CATALYSIS
Abstract

Organic photoredox catalysts with a long excited-state lifetime have emerged as promising alternatives to transition-metal-complex photocatalysts. This paper explains the effectiveness of using long-lifetime photoredox catalysts for organic transformations, focusing on the structures and photophysics that enable long excited-state lifetimes. The electrochemical potentials of the reported organic, long-lifetime photocatalysts are compiled and compared with those of the representative Ir(III)- and Ru(II)-based catalysts. This paper closes by providing recent demonstrations of the synthetic utility of the organic catalysts. 1 Introduction 2 Molecular Structure and Photophysics 3 Photoredox Catalysis Performance 4 Catalysis Mediated by Long-Lifetime Organic Photocatalysts 4.1 Photoredox Catalytic Generation of a Radical Species and its Addition to Alkenes 4.2 Photoredox Catalytic Generation of a Radical Species and its Addition to Arenes 4.3 Photoredox Catalytic Generation of a Radical Species and its Addition to Imines 4.4 Photoredox Catalytic Generation of a Radical Species and its Addition to Substrates Having C≡X Bonds (X=C, N) 4.5 Photoredox Catalytic Generation of a Radical Species and its Bond Formation with Transition Metals 4.6 Miscellaneous Reactions of Radical Species Generated by Photoredox Catalysis 5 Conclusions [ABSTRACT FROM AUTHOR]

Published
2022
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55. Amplified circularly polarized phosphorescence from co-assemblies of platinum(ii) complexes† †Electronic supplementary information (ESI) available: Experimental details; Fig. S1–S20, displaying the quantum chemical calculation results, 1H and 13C{1H} NMR spectra, the 1H NMR and the UV-vis absorption spectra obtained with increasing the concentration of PtN, the ECD spectra of the co-assemblies recorded upon rotating the sample, the ECD spectra for the co-assemblies containing increased concentrations of PtBox, steady-state photophysical and chiroptical behaviors of (R)-/(S)-PtBox, phosphorescence and photoluminescence excitation spectra of PtN, phosphorescence decay traces for the self-assemblies of PtN, phosphorescence spectra of the co-assemblies obtained with increasing the concentration of PtBox, temperature-dependent phosphorescence, UV-vis absorption and ECD spectra of the co-assemblies, and the circularly polarized phosphorescence spectra; Tables S1–S3, listing chiroluminescence data reported in literatures, photophysical data of PtN and (R)-/(S)-PtBox, and biexponential decay fit results of the traces shown in Fig. 5a. See DOI: 10.1039/c8sc04509g

Author

Park, Gyurim, Kim, Hyungchae, Yang, Hoichang, Park, Kyung Ryoul, Song, Inho, Oh, Joon Hak, Kim, Changsoon, and You, Youngmin

Subjects
Condensed Matter::Materials Science, Physics::General Physics, Chemistry, Physics::Atomic and Molecular Clusters, Physics::Chemical Physics, Computer Science::Computational Geometry
Abstract

Co-assemblies of platinum(ii) complexes produce amplified circularly polarized phosphorescence emission., Molecules capable of producing zero-field circularly polarized phosphorescence (CPP) are highly valuable for chiroptoelectronic applications that rely on triplet exciton. However, the paucity of tractable molecular design rules for obtaining CPP emission has inhibited full utilization. We report amplification of CPP by the formation of helical co-assemblies consisting of achiral square planar cycloplatinated complexes and small fractions of homochiral cycloplatinated complexes. The latter has a unique Pfeiffer effect during the formation of superhelical co-assemblies, enabling versatile chiroptical control. Large dissymmetry factors in electronic absorption (gabs, 0.020) and phosphorescence emission (glum, 0.064) are observed from the co-assemblies. These values are two orders of magnitude improved relative to those of individual molecules. In addition, photoluminescence quantum yields (PLQY) also increase by a factor of ten. Our structural, photophysical, and quantum chemical investigations reveal that the chiroptical amplification is attributable to utilization of both the magnetically allowed electronic transition and asymmetric coupling of excitons. The strategy overcomes the trade-off between glum and PLQY which has frequently been found for previous molecular emitters of circularly polarized luminescence. It is anticipated that our study will provide new insight into the future research for the exploitation of the full potential of CPP.

Published
2018

60. Organic Light‐Emitting Diodes: Charge Recombination in Polaron Pairs: A Key Factor for Operational Stability of Blue‐Phosphorescent Light‐Emitting Devices (Adv. Theory Simul. 8/2020)

Author

Odinokov, Alexey, primary, Osipov, Alexey, additional, Oh, Juwon, additional, Moon, Yu Kyung, additional, Ihn, Soo‐Ghang, additional, Lee, Hasup, additional, Kim, Inkoo, additional, Son, Won‐Joon, additional, Kim, Sangmo, additional, Kravchuk, Dmitry, additional, Kim, Jong Soo, additional, Kim, Joonghyuk, additional, Choi, Hyeonho, additional, Kim, Sunghan, additional, Kim, Wook, additional, Lee, Namheon, additional, Kang, Seongsoo, additional, Kim, Dongho, additional, You, Youngmin, additional, and Yakubovich, Alexander, additional

Published
2020
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63. Charge Recombination in Polaron Pairs: A Key Factor for Operational Stability of Blue‐Phosphorescent Light‐Emitting Devices

Author

Odinokov, Alexey, primary, Osipov, Alexey, additional, Oh, Juwon, additional, Moon, Yu Kyung, additional, Ihn, Soo‐Ghang, additional, Lee, Hasup, additional, Kim, Inkoo, additional, Son, Won‐Joon, additional, Kim, Sangmo, additional, Kravchuk, Dmitry, additional, Kim, Jong Soo, additional, Kim, Joonghyuk, additional, Choi, Hyeonho, additional, Kim, Sunghan, additional, Kim, Wook, additional, Lee, Namheon, additional, Kang, Seongsoo, additional, Kim, Dongho, additional, You, Youngmin, additional, and Yakubovich, Alexander, additional

Published
2020
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66. A new photoactivable NO‐releasing {Ru−NO}6 ruthenium nitrosyl complex with a tetradentate ligand containing aniline and pyridine moieties.

Author

Cho, Jang‐Hoon, Kim, Minyoung, You, Youngmin, and Lee, Hong‐In

Subjects
NITROSYL compounds, RUTHENIUM compounds, TIME-dependent density functional theory, ANILINE, X-ray crystallography technique, ELECTRON paramagnetic resonance, SCHIFF bases, DIMETHYL sulfoxide
Abstract

A new type of photoactivable NO‐releasing ruthenium nitrosyl complex, [Ru(EPBP)Cl(NO)], with a tetradentate ligand, N,N'‐(ethane‐1,2‐diyldi‐o‐phenylene)‐bis(pyridine‐2‐carboxamide) (= H2EPBP) was synthesized. Single crystal X‐ray crystallography revealed that the complex has a distorted octahedral coordination geometry and NO is positioned at cis to Cl− ion. NO‐photolysis was observed under a white room light. The photodissociation of Ru−NO bond was identified by various techniques including X‐ray crystallography, IR, UV/Vis absorption, electron paramagnetic resonance (EPR), and NMR spectroscopies. Quantum yields for the NO‐photolysis of the complex in CH3OH, CHCl3, DMSO, CH3CN, and CH3NO2 were measured to be 0.19–0.36 with 400 (±5) nm excitation. Density functional theory (DFT) and time‐dependent density functional theory (TDDFT) calculations were performed to understand the details of the photodissociation of the complex. The calculations suggest that the NO photolysis is most likely initiated by the electronic transition from the aniline moiety π MOs (π (aniline)) of the EPBP2− chelating ligand to the π‐antibonding MO of Ru−NO (π*(Ru−NO)). Experimental and theoretical investigations indicate that the EPBP2− ligand provides an effective platform forming ruthenium nitrosyl complexes useful for NO‐photoreleasing. [ABSTRACT FROM AUTHOR]

Published
2022
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67. Green-Light-Driven Fe(III)(btz)3Photocatalysis in the Radical Cationic [4+2] Cycloaddition Reaction

Author

Jang, Yu Jeong, An, Hyeju, Choi, Seunghee, Hong, Jayeon, Lee, Seung Hyun, Ahn, Kwang-Hyun, You, Youngmin, and Kang, Eun Joo

Abstract

Green-light-driven FeIII(btz)3photocatalysis for the radical cationic [4+2] cycloaddition of terminal styrenes and nucleophilic dienes has been investigated. The Fe-MIC (mesoionic carbene) complex forms a ligand-to-metal charge-transfer transition state with relatively high excited-state reduction potentials that can selectively oxidize terminal styrene derivatives. Unique multisubstituted cyclohexenes and structurally complex biorelevant cyclohexenes were constructed, highlighting the usefulness of this mild and practical first-row transition metal complex system.

Published
2022
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78. Mechanisms and applications of cyclometalated Pt(ii) complexes in photoredox catalytic trifluoromethylation† †Electronic supplementary information (ESI) available: Experimental details and the syntheses of the Pt(ii) catalysts; Fig. S1–S55, showing the phosphorescence spectra, femto- and nanosecond laser flash photolysis results, cyclic and differential pulse voltammograms, phosphorescence quenching experiment results, photoinduced ESR spectrum, spectroelectrochemical UV-vis-NIR absorption spectrum, dark-state reaction results, and 1H, 13C, and 19F NMR spectra; Scheme S1, presenting the synthetic routes to the Pt(ii) complexes; Tables S1–S6, listing optimization results for the trifluoromethylation of 1-dodecene, 3-methylindole and N-methylpyrrole, and the Cartesian coordinates for the optimized geometries of one-electron oxidized species of the Pt complexes. See DOI: 10.1039/c4sc02537g Click here for additional data file

Author

Choi, Won Joon, Choi, Sungkyu, Ohkubo, Kei, Fukuzumi, Shunichi, Cho, Eun Jin, and You, Youngmin

Subjects
Chemistry
Abstract

Pt(ii) complexes catalyse the visible light-driven trifluoromethylation of alkenes and heteroarenes with improved quantum yields, due to strict adherence to an oxidative quenching pathway., The incorporation of a trifluoromethyl group into an existing scaffold can provide an effective strategy for designing new drugs and agrochemicals. Among the numerous approaches to trifluoromethylation, radical trifluoromethylation mediated by visible light-driven photoredox catalysis has gathered significant interest as it offers unique opportunities for circumventing the drawbacks encountered in conventional methods. A limited understanding of the mechanism and molecular parameters that control the catalytic actions has hampered the full utilization of photoredox catalysis reactions. To address this challenge, we evaluated and investigated the photoredox catalytic trifluoromethylation reaction using a series of cyclometalated Pt(ii) complexes with systematically varied ligand structures. The Pt(ii) complexes were capable of catalyzing the trifluoromethylation of non-prefunctionalized alkenes and heteroarenes in the presence of CF3I under visible light irradiation. The high excited-state redox potentials of the complexes permitted oxidative quenching during the cycle, whereas reductive quenching was forbidden. Spectroscopic measurements, including time-resolved photoluminescence and laser flash photolysis, were performed to identify the catalytic intermediates and directly monitor their conversions. The mechanistic studies provide compelling evidence that the catalytic cycle selects the oxidative quenching pathway. We also found that electron transfer during each step of the cycle strictly adhered to the Marcus normal region behaviors. The results are fully supported by additional experiments, including photoinduced ESR spectroscopy, spectroelectrochemical measurements, and quantum chemical calculations based on time-dependent density functional theory. Finally, quantum yields exceeding 100% strongly suggest that radical propagation significantly contributes to the catalytic trifluoromethylation reaction. These findings establish molecular strategies for designing trifluoromethyl sources and catalysts in an effort to enhance catalysis performance.

Published
2014

82. Degradation of blue-phosphorescent organic light-emitting devices involves exciton-induced generation of polaron pair within emitting layers

Author

Kim, Sinheui, primary, Bae, Hye Jin, additional, Park, Sangho, additional, Kim, Wook, additional, Kim, Joonghyuk, additional, Kim, Jong Soo, additional, Jung, Yongsik, additional, Sul, Soohwan, additional, Ihn, Soo-Ghang, additional, Noh, Changho, additional, Kim, Sunghan, additional, and You, Youngmin, additional

Published
2018
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92. 62‐1: Invited Paper:Understanding Degradation Processes of Organic Light‐Emitting Devices

Author

You, Youngmin and Moon, Yu Kyung

Abstract

The short operation lifetime of organic light‐emitting devices originates from irreversible degradation of organic materials, but the mechanism by which degradation initiates has been insufficiently understood. We discovered that degradation is triggered by electron‐transfer interactions between a dopant and a host exciton. A numerical model predicting operational stability has been developed.

Published
2020
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93. Layer-Ordered Organooxotin Clusters for Extreme-Ultraviolet Photolithography

Author

Woo, Sihyun, Baek, Ji Hye, Koh, Chawon, Nishi, Tsunehiro, and You, Youngmin

Abstract

Extreme-ultraviolet (EUV) photolithography, which enables the high-throughput production of well-defined patterns with critical dimensions on the scale of several nanometers, is essential for the fabrication of a highly integrated semiconductor. The full exploitation of EUV lithographic techniques necessitates the development of photoresist (PR) materials with both high EUV sensitivity and a long shelf-life. However, despite notable advances, the available library of EUV PR materials remains limited. Here we report EUV PRs capable of forming preorganized layers consisting of ladder-structured tetranuclear stannoxanes. Single-crystal X-ray structure analyses reveal a close interlayer distance of 8.5 Å through interdigitation of the pseudoaxial butyl chains. The developed EUV PR materials exhibit high solubility in organic solvents commonly used in semiconductor processing, enabling the preparation of PR solutions with superior wettability and uniform film-forming ability on Si wafer substrates. These PR solutions also demonstrate notable resistance to hydrolytic decomposition for as long as 1 month, indicating a long shelf-life. Our PR materials enabled negative-tone patterning processes that involved a solubility decrease upon irradiation. The presence of chromophoric ligands makes our PR materials compatible with conventional UV photolithography, through photochemical reactions involving carbonyl units. In addition, e-beam and EUV lithography could produce fine line patterns of our PRs, with critical dimensions of 20 and 15 nm, respectively. Our research showcases the potential of layer-ordered organooxotin clusters for EUV PR applications.

Published
2024
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