https://scholar.dgist.ac.kr/handle/20.500.11750/57 Sat, 04 Apr 2026 17:04:38 GMT 2026-04-04T17:04:38Z https://scholar.dgist.ac.kr/handle/20.500.11750/17202 Title: Challenges of Measuring Soluble Mn(III) Species in Natural Samples Author(s): Kim, Bohee; Lingappa, Usha Farey; Magyar, John; Monteverde, Danielle; Valentine, Joan Selverstone; Cho, Jaeheung; Fischer, Woodward Abstract: Soluble Mn(III)–L complexes appear to constitute a substantial portion of manganese (Mn) in many environments and serve as critical high-potential species for biogeochemical processes. However, the inherent reactivity and lability of these complexes—the same chemical characteristics that make them uniquely important in biogeochemistry—also make them incredibly difficult to measure. Here we present experimental results demonstrating the limits of common analytical methods used to quantify these complexes. The leucoberbelin-blue method is extremely useful for detecting many high-valent Mn species, but it is incompatible with the subset of Mn(III) complexes that rapidly decompose under low-pH conditions—a methodological requirement for the assay. The Cd-porphyrin method works well for measuring Mn(II) species, but it does not work for measuring Mn(III) species, because additional chemistry occurs that is inconsistent with the proposed reaction mechanism. In both cases, the behavior of Mn(III) species in these methods ultimately stems from inter-and intramolecular redox chemistry that curtails the use of these approaches as a reflection of ligand-binding strength. With growing appreciation for the importance of high-valent Mn species and their cycling in the environment, these results underscore the need for additional method development to enable quantifying such species rapidly and accurately in nature. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. Mon, 28 Feb 2022 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/17202 2022-02-28T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/15506 Title: Controlled Regulation of the Nitrile Activation of a Peroxocobalt(III) Complex with Redox-Inactive Lewis Acidic Metals Author(s): Kim, Kyungmin; Cho, Dasol; Noh, Hyeonju; Ohta, Takehiro; Baik, Mu-Hyun; Cho, Jaeheung Abstract: Redox-inactive metal ions play vital roles in biological O-2 activation and oxidation reactions of various substrates. Recently, we showed a distinct reactivity of a peroxocobalt(III) complex bearing a tetradentate macrocyclic ligand, [Co-III(TBDAP)(O-2)](+) (1) (TBDAP = N,N'-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane), toward nitriles that afforded a series of hydroximatocobalt(III) complexes, [Co-III(TBDAP)(R-C(=NO)O)](+) (R = Me (3), Et, and Ph). In this study, we report the effects of redox-inactive metal ions on nitrile activation of 1. In the presence of redox-inactive metal ions such as Zn2+, La3+, Lu3+, and Y3+, the reaction does not form the hydroximatocobalt(III) complex but instead gives peroxyimidatocobalt(III) complexes, [Co-III(TBDAP)(R-C(=NH)O-2)](2+) (R = Me (2) and Ph (2(Ph))). These new intermediates were characterized by various physicochemical methods including X-ray diffraction analysis. The rates of the formation of 2 are found to correlate with the Lewis acidity of the additive metal ions. Moreover, complex 2 was readily converted to 3 by the addition of a base. In the presence of Al3+, Sc3+, or H+, 1 is converted to [Co-III(TBDAP)(O2H)(MeCN)](2+) (4), and further reaction with nitriles did not occur. These results reveal that the reactivity of the peroxocobalt(III) complex 1 in nitrile activation can be regulated by the redox-inactive metal ions and their Lewis acidity. DFT calculations show that the redox-inactive metal ions stabilize the peroxo character of end-on Co-eta(1)-O-2 intermediate through the charge reorganization from a Co-II-superoxo to a Co-III-peroxo intermediate. A complete mechanistic model explaining the role of the Lewis acid is presented. Sat, 31 Jul 2021 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/15506 2021-07-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/15484 Title: Twist to Boost: Circumventing Quantum Yield and Dissymmetry Factor Trade-Off in Circularly Polarized Luminescence Author(s): Lee, Sumin; Lee, Youngmoon; Kim, Kyungmin; Heo, Seunga; Jeong, Dong Yeun; Kim, Sangsub; Cho, Jaeheung; Kim, Changsoon; You, Youngmin Abstract: Circularly polarized luminescence (CPL) enables promising applications in asymmetric photonics. However, the performances of CPL molecules do not yet meet the requirements of these applications. The shortcoming originates from the trade-off in CPL between the photoluminescence quantum yield (PLQY) and the photoluminescence dissymmetry factor (gPL). In this study, we developed a molecular strategy to circumvent this trade-off. Our approach takes advantage of the strong propensity of [Pt(N^C^N)Cl], where the N^C^N ligand is 1-(2-oxazoline)-3-(2-pyridyl)phenylate, to form face-to-face stacks. We introduced chiral substituents, including (S)-methyl, (R)- and (S)-isopropyl, and (S)-indanyl groups, into the ligand framework. This asymmetric control induces torsional displacements that give homohelical stacks of the Pt(II) complexes. X-ray single-crystal structure analyses for the (S)-isopropyl Pt(II) complex reveal the formation of a homohelical dimer with a Pt···Pt distance of 3.48 Å, which is less than the sum of the van der Waals radii of Pt. This helical stack elicits the metal-metal-to-ligand charge-transfer (MMLCT) transition that exhibits strong chiroptical activity due to the electric transition moment making an acute angle to the magnetic transition moment. The PLQY and gPL values of the MMLCT phosphorescence emission of the (S)-isopropyl Pt(II) complex are 0.49 and 8.4 × 10-4, which are improved by factors of ca. 6 and 4, respectively, relative to the values of the unimolecular emission (PLQY, 0.078; gPL, 2.4 × 10-4). Our photophysical measurements for the systematically controlled Pt(II) complexes reveal that the CPL amplifications depend on the chiral substituent. Our investigations also indicate that excimers are not responsible for the enhanced chiroptical activity. To demonstrate the effectiveness of our approach, organic electroluminescence devices were fabricated. The MMLCT emission devices were found to exhibit simultaneous enhancements in the external quantum efficiency (EQE, 9.7%) and the electroluminescence dissymmetry factor (gEL, 1.2 × 10-4) over the unimolecular emission devices (EQE, 5.8%; gEL, 0.3 × 10-4). These results demonstrate the usefulness of using the chiroptically active MMLCT emission for achieving an amplified CPL. © 2021 American Chemical Society. Mon, 31 May 2021 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/15484 2021-05-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/15435 Title: Hydride-Transfer Reaction to a Mononuclear Manganese(III) Iodosylarene Complex Author(s): Jeong, Donghyun; Cho, Jaeheung Abstract: Metal iodosylarene species have received interest because of their potential oxidative power as a catalyst. We present the first example of hydride-transfer reactions to a mononuclear manganese(III) iodosylbenzene complex, [MnIII(TBDAP)(OIPh)(OH)]2+ (1; TBDAP = N,N-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane), with dihydronicotinamide adenine dinucleotide (NADH) analogues. Kinetic studies show that hydride-transfer from the NADH analogues to 1 occurs via a proton-coupled electron transfer, followed by a rapid electron transfer. © 2021 American Chemical Society. Mon, 31 May 2021 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/15435 2021-05-31T15:00:00Z