The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtained via asymmetrically stereoselective polymerization have been studied by using **1H NMR spectra, UV spectra, DSC analysis and GPC. The steric micro...The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtained via asymmetrically stereoselective polymerization have been studied by using **1H NMR spectra, UV spectra, DSC analysis and GPC. The steric microstructure i.e. the content of isotactic sequences was found to be increased by using AIBN to ( minus )Sp***** plus ( plus )CSA***** minus as the initiators or catalysts and the mole extinction coefficient to be decreased. Bimodal molecular weight distribution (MWD)s of the obtained PVCZs were caused by two propagating species of the free ions and the ion-pairs associated with the organic salts during polymerization. (Author abstract) 19 Refs.展开更多
In this paper, (-)menthyl methacrylate((-)MnMA) was polymerized at 78C in toluene with three types of anionic catalysts, which were complexes of fluorenyllithium with (-)sparteine - ((-)-Sp) , (S, S)-(+)-2, 3-dimethox...In this paper, (-)menthyl methacrylate((-)MnMA) was polymerized at 78C in toluene with three types of anionic catalysts, which were complexes of fluorenyllithium with (-)sparteine - ((-)-Sp) , (S, S)-(+)-2, 3-dimethoxy-1, 4-bis(dimethylamino)butane((+)DDB) and N,N,N,N-tetra- methylethylenediamine(TMEDA), and the chiral optical property of the obtained polymer was studied. The circular dichroism (CD) spectrum of the polymer showed negative Cotton effect.展开更多
The fluorescence spectra of the poly (N-vinylcarbazole) in solution obtained with chirally organic salts or acid as catalyst or initiator [ (-)Sp: (-)-Sparteine, (+)CSA: D- (+)Camphor-10-sulfonic acid)], respectively,...The fluorescence spectra of the poly (N-vinylcarbazole) in solution obtained with chirally organic salts or acid as catalyst or initiator [ (-)Sp: (-)-Sparteine, (+)CSA: D- (+)Camphor-10-sulfonic acid)], respectively, have been investigated. It is found that the two emission peaks at the longer wavelength (lambda max, ca, 415nm) and the shorter wavelength (lambda max, ca, 370nm) are assigned to the sandwich excimer and second excimer (partial overlap) fluorescence, respectively. The sandwich excimer and partially overlapped excimer are attributed to a fully overlapped structure of neighbouring carbazole chromophores in a totally elipsed conformation of the isotactic sequence, and partially overlapped structure of the syndiotactic sequence. The estimated values of I-415/I-370 and isotactic sequence content by using the fluorescence spectra are in the order: (-)Sp(+) (+)CSA(-)> (+)CSA(-)> (-)Sp(+)ClO(4)(-) (no peak at 415nm for AIBN).展开更多
Asymmetric kinetic resolution polymerization(AKRP)provides an ideal way to obtain highly isotactic polymers and optically pure monomers.However,highly enantioselective AKRP process is still rarely reported to date.And...Asymmetric kinetic resolution polymerization(AKRP)provides an ideal way to obtain highly isotactic polymers and optically pure monomers.However,highly enantioselective AKRP process is still rarely reported to date.And the AKRP of racemic lactide(rac-LA)remains a challenge.Here,in this paper,the AKRP of rac-LA was achieved by means of an enhanced enantiomorphic site control,delivering isotactic polylactide(PLA)and enantiomeric enriched lactide(LA)with the highest kinetic resolution coefficients(k_(rel))to date.Different from common(Salen)Al complex,a series of new chiral(BisSalen)Al complexes were designed and synthesized to form a more confined chiral microenvironment and further improve specific discrimination of rac-LA.The NMR analysis,kinetic studies,the activation parameters and thermal properties of the resulting PLAs provided strong evidence for enhanced enantiomorphic site control.This work enables highly enantioselective AKRP of rac-LA.展开更多
A novel unsymmetrical(S,S,S)-salen ligand bearing a derived chiral-BINOL was synthesized by the reaction of the condensation product of(1S,2S)-1,2-diaminocyclohexane mono(hydrogen chloride)with 3-adamanyl-5-tert-butyl...A novel unsymmetrical(S,S,S)-salen ligand bearing a derived chiral-BINOL was synthesized by the reaction of the condensation product of(1S,2S)-1,2-diaminocyclohexane mono(hydrogen chloride)with 3-adamanyl-5-tert-butyl-2-hydroxybenzalde-hyde and 3-formoyl-2-hydroxy-2'-alkyloxy-1,1'-binaphthyl,which originated from(S)-1,1'-bi-2-naphthol via a four-step reaction.The cobalt complexes of this ligand,in conjunction with a nucleophilic cocatalyst,exhibited excellent activity in catalyzing asymmetric,regio-and stereo-selective copolymerization of CO_(2) and racemic propylene oxide.The highest record of kinetic resolution coefficient(Krel)was obtained with the use of binary catalyst system consisting of(S,S,S)-salenCo(III)complex 1c and bulky bis(triphenylphosphine)-iminium chloride(PPNCl).The resulting poly(propylene carbonate)s have more than 99%carbonate linkages and more than 98%head-to-tail content.展开更多
Chiral-polymers with metal-coordination ability showgreat potential formediating asymmetric reactions.However,the synthesis of structurally diverse chiral polymers remains a great challenge,especially doing so efficie...Chiral-polymers with metal-coordination ability showgreat potential formediating asymmetric reactions.However,the synthesis of structurally diverse chiral polymers remains a great challenge,especially doing so efficiently.Herein,four types of Cucatalyzed multicomponent asymmetric polymerizationswere developed using a flexible combination of OBoc-alkyne.展开更多
基金Project 29774039 was supported by the National Natural Science Foundation of China
文摘The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtained via asymmetrically stereoselective polymerization have been studied by using **1H NMR spectra, UV spectra, DSC analysis and GPC. The steric microstructure i.e. the content of isotactic sequences was found to be increased by using AIBN to ( minus )Sp***** plus ( plus )CSA***** minus as the initiators or catalysts and the mole extinction coefficient to be decreased. Bimodal molecular weight distribution (MWD)s of the obtained PVCZs were caused by two propagating species of the free ions and the ion-pairs associated with the organic salts during polymerization. (Author abstract) 19 Refs.
基金the National Natural Science Foundation of China for financial support
文摘In this paper, (-)menthyl methacrylate((-)MnMA) was polymerized at 78C in toluene with three types of anionic catalysts, which were complexes of fluorenyllithium with (-)sparteine - ((-)-Sp) , (S, S)-(+)-2, 3-dimethoxy-1, 4-bis(dimethylamino)butane((+)DDB) and N,N,N,N-tetra- methylethylenediamine(TMEDA), and the chiral optical property of the obtained polymer was studied. The circular dichroism (CD) spectrum of the polymer showed negative Cotton effect.
文摘The fluorescence spectra of the poly (N-vinylcarbazole) in solution obtained with chirally organic salts or acid as catalyst or initiator [ (-)Sp: (-)-Sparteine, (+)CSA: D- (+)Camphor-10-sulfonic acid)], respectively, have been investigated. It is found that the two emission peaks at the longer wavelength (lambda max, ca, 415nm) and the shorter wavelength (lambda max, ca, 370nm) are assigned to the sandwich excimer and second excimer (partial overlap) fluorescence, respectively. The sandwich excimer and partially overlapped excimer are attributed to a fully overlapped structure of neighbouring carbazole chromophores in a totally elipsed conformation of the isotactic sequence, and partially overlapped structure of the syndiotactic sequence. The estimated values of I-415/I-370 and isotactic sequence content by using the fluorescence spectra are in the order: (-)Sp(+) (+)CSA(-)> (+)CSA(-)> (-)Sp(+)ClO(4)(-) (no peak at 415nm for AIBN).
基金supported by the National Natural Science Foundation of China(21901249)Taishan Scholars Program of Shandong Province(tsqn201812112)+1 种基金the Major Science and Technology Innovation Program of Shandong Province(2022CXGC020604)the Natural Science Foundation of Shandong Province(ZR2023ME008)。
文摘Asymmetric kinetic resolution polymerization(AKRP)provides an ideal way to obtain highly isotactic polymers and optically pure monomers.However,highly enantioselective AKRP process is still rarely reported to date.And the AKRP of racemic lactide(rac-LA)remains a challenge.Here,in this paper,the AKRP of rac-LA was achieved by means of an enhanced enantiomorphic site control,delivering isotactic polylactide(PLA)and enantiomeric enriched lactide(LA)with the highest kinetic resolution coefficients(k_(rel))to date.Different from common(Salen)Al complex,a series of new chiral(BisSalen)Al complexes were designed and synthesized to form a more confined chiral microenvironment and further improve specific discrimination of rac-LA.The NMR analysis,kinetic studies,the activation parameters and thermal properties of the resulting PLAs provided strong evidence for enhanced enantiomorphic site control.This work enables highly enantioselective AKRP of rac-LA.
基金supported by the National Natural Science Foundation of China(20634040)National Basic Research Program of China(973 Program)(2009CB825300)the Outstanding Young Scientist Foundation of the National Natural Science Foundation of China(20625414)
文摘A novel unsymmetrical(S,S,S)-salen ligand bearing a derived chiral-BINOL was synthesized by the reaction of the condensation product of(1S,2S)-1,2-diaminocyclohexane mono(hydrogen chloride)with 3-adamanyl-5-tert-butyl-2-hydroxybenzalde-hyde and 3-formoyl-2-hydroxy-2'-alkyloxy-1,1'-binaphthyl,which originated from(S)-1,1'-bi-2-naphthol via a four-step reaction.The cobalt complexes of this ligand,in conjunction with a nucleophilic cocatalyst,exhibited excellent activity in catalyzing asymmetric,regio-and stereo-selective copolymerization of CO_(2) and racemic propylene oxide.The highest record of kinetic resolution coefficient(Krel)was obtained with the use of binary catalyst system consisting of(S,S,S)-salenCo(III)complex 1c and bulky bis(triphenylphosphine)-iminium chloride(PPNCl).The resulting poly(propylene carbonate)s have more than 99%carbonate linkages and more than 98%head-to-tail content.
基金supported by the National Science Foundation of China(No.21978039)Special Funds of the Central Government Guiding Local Science and Technology Development(Nos.2021JH6/10500148 and 2021JH6/10500146)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20211100)and the Fundamental Research Funds for the Central Universities(Nos.DUT20YG120 and DUT21YG133).
文摘Chiral-polymers with metal-coordination ability showgreat potential formediating asymmetric reactions.However,the synthesis of structurally diverse chiral polymers remains a great challenge,especially doing so efficiently.Herein,four types of Cucatalyzed multicomponent asymmetric polymerizationswere developed using a flexible combination of OBoc-alkyne.
