Molecular ferroelectrics have attracted much attention because of their excellent piezoelectricity,mechanical workability,and second harmonic effect.Here,we successfully prepared two molecular ferroelectrics[1,5-3.2.2...Molecular ferroelectrics have attracted much attention because of their excellent piezoelectricity,mechanical workability,and second harmonic effect.Here,we successfully prepared two molecular ferroelectrics[1,5-3.2.2-Hdabcn]X(X=ClO_(4)^(-),1;ReO_(4)^(-),2)by reactions of a quasi-spherical amine 1,5-diazabicycle[3.2.2]nonane(1.5-3.2.2-dabcn)with HX aqueous solution.Compounds 1 and 2 undergo hightemperature phase transitions at 381 K(1)and 396 K(2).Before and after the phase transition,they crystallize in the polar point group mm2,and the centrosymmetric point groups mmm and 4/mmm,respectively.According to Aizu rules,these two compounds experience mmm Fmm2 and 4/mmm Fmm2 type ferroelectric phase transitions,respectively.The ferroelectricity of both compounds is well expressed in their polycrystalline film at room temperature with low coercive voltages of 13 V for 1 and 25 V for 2.Using piezoelectric force microscopy(PFM),the 180°anti-parallel ferroelectric domains and the reversible polarization switching can be clearly observed in 1 and 2.This high-temperature molecular ferroelectric material has great application potential in flexible materials,biomechanics,intelligent wearables and other fields.展开更多
The site-selective C-H fluorination of heteroarenes is a straightforward approach to accessing valuable heteroaryl fluorides but remains a formidable challenge.Herein,we report a general strategy for visible-light-ind...The site-selective C-H fluorination of heteroarenes is a straightforward approach to accessing valuable heteroaryl fluorides but remains a formidable challenge.Herein,we report a general strategy for visible-light-induced C-H fluorination of heteroarenes via the merger of N-F fluorinating reagents and silane.Electron paramagnetic resonance experiments provide evidence for the homolytic cleavage of the N-F bond under blue light-emitting diode irradiation,which is the key step in the process.This transformation is metal-free,photocatalysts-free,and site-selective under mild reaction conditions(ambient temperature,visible-light irradiation,tolerant to H2O).The robustness of this protocol has also been highlighted by late-stage modification of complex and medicinally relevant molecules.展开更多
基金supported by the National Natural Science Foundation of China(Nos.21865015,22071094 and 22075123)the Department of Science and Technology in Jiangxi Province(No.20213BCJ22055)。
文摘Molecular ferroelectrics have attracted much attention because of their excellent piezoelectricity,mechanical workability,and second harmonic effect.Here,we successfully prepared two molecular ferroelectrics[1,5-3.2.2-Hdabcn]X(X=ClO_(4)^(-),1;ReO_(4)^(-),2)by reactions of a quasi-spherical amine 1,5-diazabicycle[3.2.2]nonane(1.5-3.2.2-dabcn)with HX aqueous solution.Compounds 1 and 2 undergo hightemperature phase transitions at 381 K(1)and 396 K(2).Before and after the phase transition,they crystallize in the polar point group mm2,and the centrosymmetric point groups mmm and 4/mmm,respectively.According to Aizu rules,these two compounds experience mmm Fmm2 and 4/mmm Fmm2 type ferroelectric phase transitions,respectively.The ferroelectricity of both compounds is well expressed in their polycrystalline film at room temperature with low coercive voltages of 13 V for 1 and 25 V for 2.Using piezoelectric force microscopy(PFM),the 180°anti-parallel ferroelectric domains and the reversible polarization switching can be clearly observed in 1 and 2.This high-temperature molecular ferroelectric material has great application potential in flexible materials,biomechanics,intelligent wearables and other fields.
基金financial support from the National Natural Science Foundation of China (grant no.22201121)Jiangxi Provincial Natural Science Foundation (grant nos.20224BAB213006 and 20232BAB203002).
文摘The site-selective C-H fluorination of heteroarenes is a straightforward approach to accessing valuable heteroaryl fluorides but remains a formidable challenge.Herein,we report a general strategy for visible-light-induced C-H fluorination of heteroarenes via the merger of N-F fluorinating reagents and silane.Electron paramagnetic resonance experiments provide evidence for the homolytic cleavage of the N-F bond under blue light-emitting diode irradiation,which is the key step in the process.This transformation is metal-free,photocatalysts-free,and site-selective under mild reaction conditions(ambient temperature,visible-light irradiation,tolerant to H2O).The robustness of this protocol has also been highlighted by late-stage modification of complex and medicinally relevant molecules.
