To investigate the non-covalent interaction between cyclodextrins （CD） and lithium ion, a stoichiometry of α-CD, β-CD, heptakis（2,6-di-O-methyl）-β-CD （DM-β-CD）, or heptakis（2,3,6-tri-O-methyl）-β-CD （TM-...To investigate the non-covalent interaction between cyclodextrins （CD） and lithium ion, a stoichiometry of α-CD, β-CD, heptakis（2,6-di-O-methyl）-β-CD （DM-β-CD）, or heptakis（2,3,6-tri-O-methyl）-β-CD （TM-β-CD） was mixed with lithium salt, respectively, and then incubated at room temperature for 10 min to reach the equilibrium. In posi- tive mode, the electrospray ionization mass spectrometry （ESI-MS） results demonstrated that lithium ion can conjugate to α-, β-, DM-β- or TM-β-CD and form 1：1 stoichiometric non-covalent complexes. The binding of the complexes was further confirmed by collision- induced dissociation. The dissociation constants Kdl of four complexes （Li＋α-CD, Li＋β- CD, Li＋DM-β-CD, and Li＋TM-β-CD） were determined by mass spectrometric titration. The results showed Kdl were 18.7, 26.7, 33.6, 30.5 μmol/L for the complexes of Li＋ with α-CD, β-CD, DM-β-CD, and TM-β-CD, respectively. Kdl for the Li＋ complexes of/3-CD is smaller than that of DM-β-CD due to its steric effect of the partial substituted -CH3. The Kdl for the Li＋ complexes of DM-β-CD is nearly in agreement with that of TM-β-CD, indicating Li＋ is more likely to locate in the small rim of DM-β-CD＇s hydrophobic cavity. The DFT results showed through electrostatic interaction, one Li＋ can strongly conjugate to four neighboring oxygen atoms. For the （α-CD＋Li）＋ complex, one Li＋ may also situate the small rim of α-CD＇s hydrophobic cavity to form a non-specific host-vip complex.展开更多
The synthesis of 5-substituted 1H-tetrazoles in n,n-dimethylformamide（DMF） with b-cyclodextrin（β-CD） as catalyst can get an excellent yield in short reaction time.The interaction of β-CD with p-chlorobenzonitril...The synthesis of 5-substituted 1H-tetrazoles in n,n-dimethylformamide（DMF） with b-cyclodextrin（β-CD） as catalyst can get an excellent yield in short reaction time.The interaction of β-CD with p-chlorobenzonitrile plays an important role in this process.This paper studies the complex of β-CD with p-chlorobenzonitrile using density functional theory（DFT） method.The minimum energy structure is investigated in water,DMF and DMSO.Hydrogen bonds are researched on the basis of natural bonding orbital（NBO） analysis.The relative position between p-chlorobenzonitrile and β-CD in DMF is confirmed by 1H nuclear magnetic resonance（1H NMR）.The data from 13 C and 15 N spectra indicate that more positive charges focus on the carbon atom of cyanogroup（C11） and more negative charges concentrate on the nitrogen atom of cyanogroup（N12） upon complexation.The results from frontier molecular orbitals and Mulliken charge reveal that β-CD catalyst improves the reactivity and electrophilicity of p-chlorobenzonitrile.Meanwhile,the functional group of p-chlorobenzonitrile is easier to be attacked by azide ions in the presence of β-CD as catalyst.展开更多
文摘To investigate the non-covalent interaction between cyclodextrins （CD） and lithium ion, a stoichiometry of α-CD, β-CD, heptakis（2,6-di-O-methyl）-β-CD （DM-β-CD）, or heptakis（2,3,6-tri-O-methyl）-β-CD （TM-β-CD） was mixed with lithium salt, respectively, and then incubated at room temperature for 10 min to reach the equilibrium. In posi- tive mode, the electrospray ionization mass spectrometry （ESI-MS） results demonstrated that lithium ion can conjugate to α-, β-, DM-β- or TM-β-CD and form 1：1 stoichiometric non-covalent complexes. The binding of the complexes was further confirmed by collision- induced dissociation. The dissociation constants Kdl of four complexes （Li＋α-CD, Li＋β- CD, Li＋DM-β-CD, and Li＋TM-β-CD） were determined by mass spectrometric titration. The results showed Kdl were 18.7, 26.7, 33.6, 30.5 μmol/L for the complexes of Li＋ with α-CD, β-CD, DM-β-CD, and TM-β-CD, respectively. Kdl for the Li＋ complexes of/3-CD is smaller than that of DM-β-CD due to its steric effect of the partial substituted -CH3. The Kdl for the Li＋ complexes of DM-β-CD is nearly in agreement with that of TM-β-CD, indicating Li＋ is more likely to locate in the small rim of DM-β-CD＇s hydrophobic cavity. The DFT results showed through electrostatic interaction, one Li＋ can strongly conjugate to four neighboring oxygen atoms. For the （α-CD＋Li）＋ complex, one Li＋ may also situate the small rim of α-CD＇s hydrophobic cavity to form a non-specific host-vip complex.
基金supported by the Scientific Research Fund of Hunan Provincial Education Department(No.12A132)
文摘The synthesis of 5-substituted 1H-tetrazoles in n,n-dimethylformamide（DMF） with b-cyclodextrin（β-CD） as catalyst can get an excellent yield in short reaction time.The interaction of β-CD with p-chlorobenzonitrile plays an important role in this process.This paper studies the complex of β-CD with p-chlorobenzonitrile using density functional theory（DFT） method.The minimum energy structure is investigated in water,DMF and DMSO.Hydrogen bonds are researched on the basis of natural bonding orbital（NBO） analysis.The relative position between p-chlorobenzonitrile and β-CD in DMF is confirmed by 1H nuclear magnetic resonance（1H NMR）.The data from 13 C and 15 N spectra indicate that more positive charges focus on the carbon atom of cyanogroup（C11） and more negative charges concentrate on the nitrogen atom of cyanogroup（N12） upon complexation.The results from frontier molecular orbitals and Mulliken charge reveal that β-CD catalyst improves the reactivity and electrophilicity of p-chlorobenzonitrile.Meanwhile,the functional group of p-chlorobenzonitrile is easier to be attacked by azide ions in the presence of β-CD as catalyst.
基金Supported by the Scientific Research Fund of Hunan Provincial Education Department(No.12A132)the financial supports from the Scientific Research Fund of Hunan Provincial Education Department(No.201104)the Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education for the research work~~
