Semi-empirical method PM3 was used to study the geometry and vibrational spectrum of N-(2-hydroxy-l-naphthyl-methylene)-l-pyrenamine (NPY) with the intermediate hydrogen bond. Results are comparable to experimentation...Semi-empirical method PM3 was used to study the geometry and vibrational spectrum of N-(2-hydroxy-l-naphthyl-methylene)-l-pyrenamine (NPY) with the intermediate hydrogen bond. Results are comparable to experimentations. Based on results of both NPY and its model, N-(2-hydroxy-l-naphthyl-methylene)aniline, it was found that the N-(2-hydroxy-l-naphthyl-methylene) group is principally responsible for the special hydrogen bonding through conjugation effect.展开更多
This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, （H2O）3 and its pyramid...This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, （H2O）3 and its pyramidal halide complexes, X- （H2O）3 （X= F, Cl, Br, I） with the gradient-corrected density functional theory method at the B3LYP/6- 311＋＋G（2d,2p） and B3LYP/Aug-cc-pVTZ levels. It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors. The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S（＋） （H2O）3 mostly originates from the O-H rocking modes, whereas chirality of S（-）-X-（H2O）3 （X = F, Cl, Br, I） has its important origin in the O-H stretching modes. The calculated optical rotatory power demonstrates that S（＋） （H2O）3 and S（＋）-F-（H2O）3 are positively chiral, whereas S（-）-X-（H2O）3 （X=Cl, Br, I） are negatively chiral. With the polarizable continuum model, calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S（＋）-（H2O）3 is enhanced and the negative chirality of S（-）-X-（H2O）3 （X=Cl, Br, I） and the positive chirality of S（＋）-F-（H2O）3 are reduced with an augmentation of the solvent dielectric constant.展开更多
This paper reports that vibrational spectroscopic analysis on hYdrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water comp...This paper reports that vibrational spectroscopic analysis on hYdrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311＋G（d,p） basis set. Changes in wavenumber position and linewidth （fullwidth at half maximum） have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.展开更多
Semi-empirical AMI method was used to study 1：1 and 1：2 hydrogen bond complexes formed with perylene dianhydride and pyridine derivatives. The weak interaction energy become bigger as the number of hydrogen bonds in...Semi-empirical AMI method was used to study 1：1 and 1：2 hydrogen bond complexes formed with perylene dianhydride and pyridine derivatives. The weak interaction energy become bigger as the number of hydrogen bonds increases. The donor groups on the host and electron-withdrawing groups on the guest molecules favor hydrogen bonding interactions, and the formation of hydrogen bonding leads to electron density flow from the host to the guest molecules. Electronic spectra of these complexes were computed using INDO/SCI method. Blue-shift of the clectronic absorption spectra for the complexes, comparing that of the host, takes place, and the first peaks for different complexes changed slightly. These are in agreement with the experimcntal results. The cause of blue-shift was discussed, and the electronic transitions were assigned based on theoretical calculations. The potential curve of double proton transfer in the complex was calculated, and the transition state and activated energy relative to the N H bond were obtained.展开更多
Comprehensive study on the homologous series of compounds in the form A-R- HHB are synthesized with central rigid core as benzoic acids together with substituent’s alkoxy (A) and alkyl (R) group of equal chain length...Comprehensive study on the homologous series of compounds in the form A-R- HHB are synthesized with central rigid core as benzoic acids together with substituent’s alkoxy (A) and alkyl (R) group of equal chain lengths from 5 to 10 are connected to hexyl-p-hydroxy benzoate (HHB). These complexes form supramolecular structures by self assembling process due to intermolecular hydrogen bonding. The formation is analyzed with techniques involving polarizing optical microscope, infrared spectroscopy, proton NMR spectroscopy and powdered X-ray diffraction. Results suggest that complexes arise from both A and R groups exhibit enantiotropic layered texture of crystal G phase observed by microscopic studies due to flexible nature of mesogenics. The conversion of free to molecular complexes is determined with variations in spectral shifts between its terminal groups COOH and OH of molecules involving inter molecular hydrogen bonding and its bonding index by FTIR spectra. The changes in structure and dynamics due to hydrogen bonding in complexes are convinced by proton NMR spectra with chemical shifts in specified range. The defects in crystal structure responsible for enantiotropic phenomena are analyzed by powdered X ray diffraction.展开更多
The crystal structure of spiro[2.2”]acenaphthene-1”-onespiro[3.3’]-5’-(2,3-dichlorophenylmethylidene)-1’-methylpipe-ridin-4’-one-4-(2,3-dichorophenyl) octahydroindolizine was elucidated by single crystal X ray d...The crystal structure of spiro[2.2”]acenaphthene-1”-onespiro[3.3’]-5’-(2,3-dichlorophenylmethylidene)-1’-methylpipe-ridin-4’-one-4-(2,3-dichorophenyl) octahydroindolizine was elucidated by single crystal X ray diffraction. The title compound C37H30Cl4N2O2, crystallizes in the orthorhombic system, space group P212121 with a = 8.4610(4) , b = 16.0926(6) , c= 23.8997(11) and Z = 4. The central piperidine ring adopts twisted conformation, the piperidine of octahydroindolizine ring is in chair conformation and the pyrrole ring is in slightly twisted envelope conformation. Details of the synthesis, NMR, crystal structure determination and intra- and inter- molecular interactions of the compound are given.展开更多
FT infrared spectrometer was used to obtain a series of infrared spectra at various temperatures of pentaerythritol(PE)、pentaglycerine(PG)、neopentylglycol(NPG) and their binary mixtures.The shifts of -OH absorption ...FT infrared spectrometer was used to obtain a series of infrared spectra at various temperatures of pentaerythritol(PE)、pentaglycerine(PG)、neopentylglycol(NPG) and their binary mixtures.The shifts of -OH absorption peak reveal the solid solid phase transition mechanisms and the connection of wave number shifts with temperature and enthalpies of phase transition.The solid solid phase transitions of the three polyols and their binary mixtures are known to transform from a low symmetric layered crystal structure to a highly symmetric face centered cubic structure.Experimental results support a mechanism which involves reversible breaking of nearest neighbor hydrogen resonance bonds in the molecular crystals at the transformation temperature.Infrared spectra show reversible increase in the wave number of the absorption peak of -OH groups with reversible breaking of the hydrogen bonds.This is in agreement with the experimental results of X ray diffraction and thermal analysis.展开更多
The hydrogen\|bond defect of water in PVA hydrogels was studied by Raman spectral analysis. The PVA hydrogels were prepared from PVA of different DP in different concentrations via freeze/thawed method.It was found th...The hydrogen\|bond defect of water in PVA hydrogels was studied by Raman spectral analysis. The PVA hydrogels were prepared from PVA of different DP in different concentrations via freeze/thawed method.It was found that the hydrogen bond defect of water in PVA hydrogels is affected by their crystallinity which was depended on the molecular weight and concentration of PVA and also the number of freeze/thawed cycles.After swelling in water for 24?h,partial VA units were released from the crystalline regions,this means that more `free’ VA units could bond with water in PVA hydrogels,causing the decrease of C value and the increase of N value.展开更多
文摘Semi-empirical method PM3 was used to study the geometry and vibrational spectrum of N-(2-hydroxy-l-naphthyl-methylene)-l-pyrenamine (NPY) with the intermediate hydrogen bond. Results are comparable to experimentations. Based on results of both NPY and its model, N-(2-hydroxy-l-naphthyl-methylene)aniline, it was found that the N-(2-hydroxy-l-naphthyl-methylene) group is principally responsible for the special hydrogen bonding through conjugation effect.
基金Project supported by the Scientific Foundation of Education Department of Yunnan Province of China (Grant No. 07Z11621)the Innovation Foundation for New Researchers in Dali University (Grant No. KY421040)the National Natural Science Foundation of China (Grant No. 20573114)
文摘This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, （H2O）3 and its pyramidal halide complexes, X- （H2O）3 （X= F, Cl, Br, I） with the gradient-corrected density functional theory method at the B3LYP/6- 311＋＋G（2d,2p） and B3LYP/Aug-cc-pVTZ levels. It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors. The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S（＋） （H2O）3 mostly originates from the O-H rocking modes, whereas chirality of S（-）-X-（H2O）3 （X = F, Cl, Br, I） has its important origin in the O-H stretching modes. The calculated optical rotatory power demonstrates that S（＋） （H2O）3 and S（＋）-F-（H2O）3 are positively chiral, whereas S（-）-X-（H2O）3 （X=Cl, Br, I） are negatively chiral. With the polarizable continuum model, calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S（＋）-（H2O）3 is enhanced and the negative chirality of S（-）-X-（H2O）3 （X=Cl, Br, I） and the positive chirality of S（＋）-F-（H2O）3 are reduced with an augmentation of the solvent dielectric constant.
基金supported by National Natural Science Foundation of China (Grant Nos.10774057 and 10974067)
文摘This paper reports that vibrational spectroscopic analysis on hYdrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311＋G（d,p） basis set. Changes in wavenumber position and linewidth （fullwidth at half maximum） have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.
文摘Semi-empirical AMI method was used to study 1：1 and 1：2 hydrogen bond complexes formed with perylene dianhydride and pyridine derivatives. The weak interaction energy become bigger as the number of hydrogen bonds increases. The donor groups on the host and electron-withdrawing groups on the guest molecules favor hydrogen bonding interactions, and the formation of hydrogen bonding leads to electron density flow from the host to the guest molecules. Electronic spectra of these complexes were computed using INDO/SCI method. Blue-shift of the clectronic absorption spectra for the complexes, comparing that of the host, takes place, and the first peaks for different complexes changed slightly. These are in agreement with the experimcntal results. The cause of blue-shift was discussed, and the electronic transitions were assigned based on theoretical calculations. The potential curve of double proton transfer in the complex was calculated, and the transition state and activated energy relative to the N H bond were obtained.
文摘Comprehensive study on the homologous series of compounds in the form A-R- HHB are synthesized with central rigid core as benzoic acids together with substituent’s alkoxy (A) and alkyl (R) group of equal chain lengths from 5 to 10 are connected to hexyl-p-hydroxy benzoate (HHB). These complexes form supramolecular structures by self assembling process due to intermolecular hydrogen bonding. The formation is analyzed with techniques involving polarizing optical microscope, infrared spectroscopy, proton NMR spectroscopy and powdered X-ray diffraction. Results suggest that complexes arise from both A and R groups exhibit enantiotropic layered texture of crystal G phase observed by microscopic studies due to flexible nature of mesogenics. The conversion of free to molecular complexes is determined with variations in spectral shifts between its terminal groups COOH and OH of molecules involving inter molecular hydrogen bonding and its bonding index by FTIR spectra. The changes in structure and dynamics due to hydrogen bonding in complexes are convinced by proton NMR spectra with chemical shifts in specified range. The defects in crystal structure responsible for enantiotropic phenomena are analyzed by powdered X ray diffraction.
文摘The crystal structure of spiro[2.2”]acenaphthene-1”-onespiro[3.3’]-5’-(2,3-dichlorophenylmethylidene)-1’-methylpipe-ridin-4’-one-4-(2,3-dichorophenyl) octahydroindolizine was elucidated by single crystal X ray diffraction. The title compound C37H30Cl4N2O2, crystallizes in the orthorhombic system, space group P212121 with a = 8.4610(4) , b = 16.0926(6) , c= 23.8997(11) and Z = 4. The central piperidine ring adopts twisted conformation, the piperidine of octahydroindolizine ring is in chair conformation and the pyrrole ring is in slightly twisted envelope conformation. Details of the synthesis, NMR, crystal structure determination and intra- and inter- molecular interactions of the compound are given.
文摘FT infrared spectrometer was used to obtain a series of infrared spectra at various temperatures of pentaerythritol(PE)、pentaglycerine(PG)、neopentylglycol(NPG) and their binary mixtures.The shifts of -OH absorption peak reveal the solid solid phase transition mechanisms and the connection of wave number shifts with temperature and enthalpies of phase transition.The solid solid phase transitions of the three polyols and their binary mixtures are known to transform from a low symmetric layered crystal structure to a highly symmetric face centered cubic structure.Experimental results support a mechanism which involves reversible breaking of nearest neighbor hydrogen resonance bonds in the molecular crystals at the transformation temperature.Infrared spectra show reversible increase in the wave number of the absorption peak of -OH groups with reversible breaking of the hydrogen bonds.This is in agreement with the experimental results of X ray diffraction and thermal analysis.
文摘The hydrogen\|bond defect of water in PVA hydrogels was studied by Raman spectral analysis. The PVA hydrogels were prepared from PVA of different DP in different concentrations via freeze/thawed method.It was found that the hydrogen bond defect of water in PVA hydrogels is affected by their crystallinity which was depended on the molecular weight and concentration of PVA and also the number of freeze/thawed cycles.After swelling in water for 24?h,partial VA units were released from the crystalline regions,this means that more `free’ VA units could bond with water in PVA hydrogels,causing the decrease of C value and the increase of N value.
