A nitro group is a common fluorescence quencher,but its quenching efficiency can be easily affected by the surrounding environment.To date,there has been no systematic study on the effects of electronwithdrawing group...A nitro group is a common fluorescence quencher,but its quenching efficiency can be easily affected by the surrounding environment.To date,there has been no systematic study on the effects of electronwithdrawing groups on the quenching efficiency of nitro groups.Herein,by virtue of experimental validation and theoretical calculations,we found that strong electron-withdrawing groups,such as pyridinium and dicyanovinyl groups,are detrimental to the quenching effect of nitro groups.Decreasing the electron-withdrawing ability could restore the nitro group’s quenching effect.展开更多
Polynitro compounds play indispensable roles as high-energy oxidizers in solid propellants and space exploration.Generally,the number of nitro groups governs the energy and stability of these oxidizers:the more the pr...Polynitro compounds play indispensable roles as high-energy oxidizers in solid propellants and space exploration.Generally,the number of nitro groups governs the energy and stability of these oxidizers:the more the presence of nitro groups,the higher the energy,and the lower the stability.Maximizing the number of nitro groups while maintaining good stability is,therefore,challenging.Here,we exploited the synergy between the weak repulsion among groups and the uniform charge distribution to design and synthesize a new polynitro compound,2,2′,5,5′-tetra(trinitromethyl)-3,3′-bi-1,2,4-triazole(BITE-202).This compound not only had 12 nitro groups,which were the most among all small molecules but also exhibited exceptional stability(thermal decomposition at 164℃,stability at 70℃,nonhygroscopic in air,and stable in water).BITE-202 had an ultrahigh oxygen balance of+34.96%,which,in combination with a high density of 1.976 g cm−3,allowed formulations thereof to deliver an exceptionally high specific impulse of 275.2 s,far higher than that of the state-of-the-art ammonium dinitramide(ADN)of 271.6 s.Our findings subvert the long-held concept of“more nitro,lower stability,”and offer a practical approach for constructing ultrahigh-energy oxidizers with superior stability,which undoubtedlyprovides a huge impetus for thedevelopment of nitro chemistry.展开更多
Precise control of luminescence in carbon quantum dots(CQDs),from single-color to full-color emission,is crucial for advancing their applications in biomedical imaging and display technologies.While CQDs luminescence ...Precise control of luminescence in carbon quantum dots(CQDs),from single-color to full-color emission,is crucial for advancing their applications in biomedical imaging and display technologies.While CQDs luminescence is primarily influenced by conjugated domains and surface states,the underlying interaction mechanisms remain poorly understood.This study explores a graded nitro-engineering approach to simultaneously regulate surface states and sp^(2)conjugated domains through nitro(-NO_(2))modulation,enabling comprehensive color tuning.Using o-phenylenediamine(o-PD)as the carbon source and adjusting nitric acid(HNO_(3))concentrations,we synthesized tricolor-emitting nitro-functionalized CQDs(NO_(2)-CQDs).At lower-NO_(2) concentrations,luminescence is mainly influenced by surface states,where the electron-withdrawing effect of-NO_(2) enhancesπ-electron delocalization and stabilizes sp^(2)conjugation.With increasing-NO_(2) content,the lowest unoccupied molecular orbital(LUMO)energy level decreases(-2.12 eV to-3.39 eV),resulting in a red-shift in fluorescence.At higher-NO_(2) concentrations,luminescence is primarily affected by the sp^(2)conjugated domain,where steric hindrance reduces molecular planarity and conjugation,leading to a blue-shift in fluorescence as the sp^(2)domain size decreases(4.03 nm to 2.83 nm).Combining experimental results with density functional theory(DFT)calculations,we reveal the dual role of-NO2in modulating CQDs luminescence,an approach rarely achieved through surface functionalization.This work presents a novel strategy for precise tuning of CQDs luminescence across the visible spectrum.展开更多
The intermolecular coupling of a nitro group with a cyano group mediated by a Sm(Hg) amalgam prepared from metal samarium powder and catalytic mercury dichloride was studied.
Nitrodisulfides were reduced by SmI2/HMPA in anhydrous THF at room temperature to produce active intermediates (samarium thiolates and amides), which were 'living' double-anions and reacted smoothly with aldeh...Nitrodisulfides were reduced by SmI2/HMPA in anhydrous THF at room temperature to produce active intermediates (samarium thiolates and amides), which were 'living' double-anions and reacted smoothly with aldehydes or ketones to afford benzothiazolines in good yields under mild and neutral conditions.展开更多
o-Nitrophenylazide was reduced by SmI2 in anhydrous THF at room temperature to produce active intermediate 2 (samarium amide), "living" double-anion in situ which reacted smoothly with α，β-unsaturated ket...o-Nitrophenylazide was reduced by SmI2 in anhydrous THF at room temperature to produce active intermediate 2 (samarium amide), "living" double-anion in situ which reacted smoothly with α，β-unsaturated ketones to afford 2,3-dihydro-1H-1,5-benzodiazepines in good yields under mild and neutral conditions.展开更多
4,4＇-dibromo-2-nitro-biphenyl and 4,4＇-dibromo-2,3＇-dinitro-biphenyl have been synthesized via nitration reaction with 4,4＇-dibromobiphenyl as the raw material. Three novel thiophene derivatives, 4, 4＇-di（4-hexy...4,4＇-dibromo-2-nitro-biphenyl and 4,4＇-dibromo-2,3＇-dinitro-biphenyl have been synthesized via nitration reaction with 4,4＇-dibromobiphenyl as the raw material. Three novel thiophene derivatives, 4, 4＇-di（4-hexyl-thiophen-2-yl）biphenyl, 4,4＇-di（4-hexyl-thiophen-2-yl）-2- nitro-biphenyl and 4,4＇-di（4- hexyl-thiophen-2-yl）-2,3＇-dinitrobiphenyl were synthesized through Stille coupling reaction, followed by polymerization in the presence of FeC13, respectively. UV-vis absorption spectra, fluorescence spectra, photoluminescence spectra and electrochemical properties of the polymers were investigated. And the band-gap （Eg）, HOMO orbital energy （EHCMO）, and LUMO orbital energy （EUJMO） of the polymers were calculated. Among the polymers, polymer PBTN and PBTD show lower band-gap （2.67 and 2.63 eV）, lower HOMO energy level （-5.38 and -5.4 eV） and broader wavelength （432 and 438 nm） than that of polymer PBTB （2.69 eV, -5.36 eV and 424 nm） with incorporation of one nitro group or two nitro groups in the main chain, respectively.展开更多
基金start-up funding from the State Key Laboratory of Bioactive Substance and Function of Natural Medicines,Institute of Materia Medica,Peking Union Medical College,CAMS Innovation Fund for Medical Sciences(CIFMS)(No.2017-I2M-4-005)。
文摘A nitro group is a common fluorescence quencher,but its quenching efficiency can be easily affected by the surrounding environment.To date,there has been no systematic study on the effects of electronwithdrawing groups on the quenching efficiency of nitro groups.Herein,by virtue of experimental validation and theoretical calculations,we found that strong electron-withdrawing groups,such as pyridinium and dicyanovinyl groups,are detrimental to the quenching effect of nitro groups.Decreasing the electron-withdrawing ability could restore the nitro group’s quenching effect.
基金supported by the National Natural Science Foundation of China(grant nos.21875021,22075024,22305020,and 22375022)Beijing Institute of Technology Research Fund Program for Young Scholars,China(grant no.6120230044).
文摘Polynitro compounds play indispensable roles as high-energy oxidizers in solid propellants and space exploration.Generally,the number of nitro groups governs the energy and stability of these oxidizers:the more the presence of nitro groups,the higher the energy,and the lower the stability.Maximizing the number of nitro groups while maintaining good stability is,therefore,challenging.Here,we exploited the synergy between the weak repulsion among groups and the uniform charge distribution to design and synthesize a new polynitro compound,2,2′,5,5′-tetra(trinitromethyl)-3,3′-bi-1,2,4-triazole(BITE-202).This compound not only had 12 nitro groups,which were the most among all small molecules but also exhibited exceptional stability(thermal decomposition at 164℃,stability at 70℃,nonhygroscopic in air,and stable in water).BITE-202 had an ultrahigh oxygen balance of+34.96%,which,in combination with a high density of 1.976 g cm−3,allowed formulations thereof to deliver an exceptionally high specific impulse of 275.2 s,far higher than that of the state-of-the-art ammonium dinitramide(ADN)of 271.6 s.Our findings subvert the long-held concept of“more nitro,lower stability,”and offer a practical approach for constructing ultrahigh-energy oxidizers with superior stability,which undoubtedlyprovides a huge impetus for thedevelopment of nitro chemistry.
基金supported by National Natural Science Foundation of China(No.51873085)Natural Science Foundation of Liaoning Province-Outstanding Youth Foundation(No.2022-YQ-14)+2 种基金Liaoning Revitalization Talents Program(No.XLYC2007056)China Scholarship Council(CSC Scholarship,No.202006800009)the Shenyang Science and Technology Project(No.RC230707)。
文摘Precise control of luminescence in carbon quantum dots(CQDs),from single-color to full-color emission,is crucial for advancing their applications in biomedical imaging and display technologies.While CQDs luminescence is primarily influenced by conjugated domains and surface states,the underlying interaction mechanisms remain poorly understood.This study explores a graded nitro-engineering approach to simultaneously regulate surface states and sp^(2)conjugated domains through nitro(-NO_(2))modulation,enabling comprehensive color tuning.Using o-phenylenediamine(o-PD)as the carbon source and adjusting nitric acid(HNO_(3))concentrations,we synthesized tricolor-emitting nitro-functionalized CQDs(NO_(2)-CQDs).At lower-NO_(2) concentrations,luminescence is mainly influenced by surface states,where the electron-withdrawing effect of-NO_(2) enhancesπ-electron delocalization and stabilizes sp^(2)conjugation.With increasing-NO_(2) content,the lowest unoccupied molecular orbital(LUMO)energy level decreases(-2.12 eV to-3.39 eV),resulting in a red-shift in fluorescence.At higher-NO_(2) concentrations,luminescence is primarily affected by the sp^(2)conjugated domain,where steric hindrance reduces molecular planarity and conjugation,leading to a blue-shift in fluorescence as the sp^(2)domain size decreases(4.03 nm to 2.83 nm).Combining experimental results with density functional theory(DFT)calculations,we reveal the dual role of-NO2in modulating CQDs luminescence,an approach rarely achieved through surface functionalization.This work presents a novel strategy for precise tuning of CQDs luminescence across the visible spectrum.
基金National Natural Science Foundation of China (Project No. 20072033) and Natural Science Foundation of Zhejiang province for financial support.
文摘The intermolecular coupling of a nitro group with a cyano group mediated by a Sm(Hg) amalgam prepared from metal samarium powder and catalytic mercury dichloride was studied.
基金We thank the National Natural Science Foundation of China (Project! No.29872010)the Laboratory of Organometallic Chemistry,
文摘Nitrodisulfides were reduced by SmI2/HMPA in anhydrous THF at room temperature to produce active intermediates (samarium thiolates and amides), which were 'living' double-anions and reacted smoothly with aldehydes or ketones to afford benzothiazolines in good yields under mild and neutral conditions.
基金We thank the National Natural Science Foundation of China (Project No.29872010) NSF of Zhejiang province for financial support.
文摘o-Nitrophenylazide was reduced by SmI2 in anhydrous THF at room temperature to produce active intermediate 2 (samarium amide), "living" double-anion in situ which reacted smoothly with α，β-unsaturated ketones to afford 2,3-dihydro-1H-1,5-benzodiazepines in good yields under mild and neutral conditions.
基金Supported by the National Natural Science Foundation of China(No.21176193)
文摘4,4＇-dibromo-2-nitro-biphenyl and 4,4＇-dibromo-2,3＇-dinitro-biphenyl have been synthesized via nitration reaction with 4,4＇-dibromobiphenyl as the raw material. Three novel thiophene derivatives, 4, 4＇-di（4-hexyl-thiophen-2-yl）biphenyl, 4,4＇-di（4-hexyl-thiophen-2-yl）-2- nitro-biphenyl and 4,4＇-di（4- hexyl-thiophen-2-yl）-2,3＇-dinitrobiphenyl were synthesized through Stille coupling reaction, followed by polymerization in the presence of FeC13, respectively. UV-vis absorption spectra, fluorescence spectra, photoluminescence spectra and electrochemical properties of the polymers were investigated. And the band-gap （Eg）, HOMO orbital energy （EHCMO）, and LUMO orbital energy （EUJMO） of the polymers were calculated. Among the polymers, polymer PBTN and PBTD show lower band-gap （2.67 and 2.63 eV）, lower HOMO energy level （-5.38 and -5.4 eV） and broader wavelength （432 and 438 nm） than that of polymer PBTB （2.69 eV, -5.36 eV and 424 nm） with incorporation of one nitro group or two nitro groups in the main chain, respectively.
