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Mechanisms and applications of cyclometalated Pt(II) complexes in photoredox catalytic trifluoromethylation

Title
Mechanisms and applications of cyclometalated Pt(II) complexes in photoredox catalytic trifluoromethylation
Authors
Choi, Won JoonChoi, SungkyuOhkubo, KeiFukuzumi, ShunichiCho, Eun JinYou, Youngmin
Ewha Authors
유영민Shunichi Fukuzumi
SCOPUS Author ID
유영민scopus; Shunichi Fukuzumiscopus
Issue Date
2015
Journal Title
CHEMICAL SCIENCE
ISSN
2041-6520JCR Link

2041-6539JCR Link
Citation
CHEMICAL SCIENCE vol. 6, no. 2, pp. 1454 - 1464
Publisher
ROYAL SOC CHEMISTRY
Indexed
SCI; SCIE; SCOPUS WOS
Document Type
Article
Abstract
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.
DOI
10.1039/c4sc02537g
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엘텍공과대학 > 화학신소재공학전공 > Journal papers
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