N-Heterocyclic nitrogen Lewis acids are important in synthetic chemistry.Stable cyclic(amino)(aryl)nitrenium cations,cyc-1^(+)-cyc-3^(+),were synthesized by chemical oxidation of aryl azo compounds with different subs...N-Heterocyclic nitrogen Lewis acids are important in synthetic chemistry.Stable cyclic(amino)(aryl)nitrenium cations,cyc-1^(+)-cyc-3^(+),were synthesized by chemical oxidation of aryl azo compounds with different substituents,H and I,at the para positions of the phenyl group.The excited triplet states of cyc-1^(+)-cyc-3^(+) abstract H-atoms step by step to generate radical intermediates cyc-1H^(*+-)cyc-3H^(*+)traced by EPR spectroscopy and products cyc-1H^(2+)-cyc-3H^(2+) characterized by single crystal X-ray diffraction.The Lewis acidity of species cyc-1^(+)-cyc-3^(+) are remote substituent-dependent.Cyc-2^(+)-cyc-3^(+) have much higher acidity than those previously reported congeners based on energies of LUMOs.The electrophilicity enables them to form Lewis adducts with neutral Lewis base Me_(3)P,and to gain one-electron to produce neutral radicals cyc-1^(*)-cyc-3^(*).展开更多
Photoredox-mediated reversible-deactivation radical polymerization(RDRP)is an effective approach to synthesize polymers with defined composition and architecture.Current photoinduced RDRP primarily depends on outer-sp...Photoredox-mediated reversible-deactivation radical polymerization(RDRP)is an effective approach to synthesize polymers with defined composition and architecture.Current photoinduced RDRP primarily depends on outer-sphere electron transfer or homolysis mechanisms.Herein,we describe an example of iodine-mediated RDRP facilitated by photoinduced charge transfer complex(CTC)catalysis.The approach uses cheap and easily accessible N^(-)heterocyclic nitrenium salt(NHN^(+)...I^(-))as the photoactive CTC.Upon the irradiation of visible light,NHN^(+)...I^(-)undergoes single electron transfer to generate NHN·and I·radicals.The NHN·radical activates dormant Pn-I polymers via inner-sphere single electron transfer,leading to the propagating Pn·radical for chain growth and the I^(-)anion for recovering the CTC,and the I·radical deactivates the polymerization via coupling with Pn·.展开更多
基金the National Key R&D Program of China(Grants 2016YFA0300404 and 2018YFA0306004,X.W.)the National Natural Science Foundation of China(Grants 21525102 and 21690062,X.W.,and 21901005,W.W.)+1 种基金the Natural Science Foundation of Anhui Province(Grant 1908085QB48,W W.)the China Postdoctoral Science Foundation(Grant 2019M651771,W.W.).
文摘N-Heterocyclic nitrogen Lewis acids are important in synthetic chemistry.Stable cyclic(amino)(aryl)nitrenium cations,cyc-1^(+)-cyc-3^(+),were synthesized by chemical oxidation of aryl azo compounds with different substituents,H and I,at the para positions of the phenyl group.The excited triplet states of cyc-1^(+)-cyc-3^(+) abstract H-atoms step by step to generate radical intermediates cyc-1H^(*+-)cyc-3H^(*+)traced by EPR spectroscopy and products cyc-1H^(2+)-cyc-3H^(2+) characterized by single crystal X-ray diffraction.The Lewis acidity of species cyc-1^(+)-cyc-3^(+) are remote substituent-dependent.Cyc-2^(+)-cyc-3^(+) have much higher acidity than those previously reported congeners based on energies of LUMOs.The electrophilicity enables them to form Lewis adducts with neutral Lewis base Me_(3)P,and to gain one-electron to produce neutral radicals cyc-1^(*)-cyc-3^(*).
基金Supported by the National Natural Science Foundation of China(Nos.21773240 and 22173103)the University of the Chinese Academy of Sciences and Beijing National Laboratory for Molecular Sciences(No.BNLMS2023014)。
文摘Photoredox-mediated reversible-deactivation radical polymerization(RDRP)is an effective approach to synthesize polymers with defined composition and architecture.Current photoinduced RDRP primarily depends on outer-sphere electron transfer or homolysis mechanisms.Herein,we describe an example of iodine-mediated RDRP facilitated by photoinduced charge transfer complex(CTC)catalysis.The approach uses cheap and easily accessible N^(-)heterocyclic nitrenium salt(NHN^(+)...I^(-))as the photoactive CTC.Upon the irradiation of visible light,NHN^(+)...I^(-)undergoes single electron transfer to generate NHN·and I·radicals.The NHN·radical activates dormant Pn-I polymers via inner-sphere single electron transfer,leading to the propagating Pn·radical for chain growth and the I^(-)anion for recovering the CTC,and the I·radical deactivates the polymerization via coupling with Pn·.
