In order to study the polar substituent effect almost with no steric effect in organophosphorus chemistry,a series of 4-substituted-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane 1-oxides(1)and p-substituted phenylphospho...In order to study the polar substituent effect almost with no steric effect in organophosphorus chemistry,a series of 4-substituted-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane 1-oxides(1)and p-substituted phenylphosphonates(2)and corresponding mono hexyl esters(3)as model were synthesized.^(31)P-NMR chemical shifts of compounds(1)in methanol and deuterioacetone were determined.The Δδ values reflect 4-sbstituent po- lar effect.The ^(31)P-NMR of compounds(2)and(3)and the pKa of compounds(3)were also measured.The results showed that the trend of polar effects of substituents in both carboxylic and organophosphates chemistry are similar,and the change of polar effects in variation with the alkyl groups is not significant.展开更多
The thermodynamic properties of the reaction of amide and formaldehyde were calculated via B3LYP method when substituents chosen included CH3,CH2CH3,CH2CH2CH3,CH2CH2CH2CH3,CH(CH3)2,CH2CH(CH3)2,CH(CH3)CH2CH3 and ...The thermodynamic properties of the reaction of amide and formaldehyde were calculated via B3LYP method when substituents chosen included CH3,CH2CH3,CH2CH2CH3,CH2CH2CH2CH3,CH(CH3)2,CH2CH(CH3)2,CH(CH3)CH2CH3 and C(CH3)3.Based on the optimization of the structures for reactants and products,the thermodynamic functions of all the species for an actual state were obtained.The thermodynamic data and the equilibrium constants were investigated within a temperature range of 300―343.15 K.The calculated results show that the reaction is exothermic and spontaneous.The trends of all thermodynamic properties are consistent with the temperature.The preferential order of the substituent effect is CH2CH(CH3)2CH(CH3)CH2CH3CH2CH2CH2CH3 CH2CH2CH3CH2CH3≈CH(CH3)2C(CH3)3≈CH3.展开更多
Semi-empirical molecular orbital theory AMI method is employed to study the ortho-position substituent impact on intramolecular proton transfer reaction of perylenequinone. The calculation demonstrates that the peryle...Semi-empirical molecular orbital theory AMI method is employed to study the ortho-position substituent impact on intramolecular proton transfer reaction of perylenequinone. The calculation demonstrates that the perylenequinone molecule is of stable structure. and all substituents may cause the decrease of barriers for the hydrogen transfer reaction.展开更多
B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, inclu...B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, including the interaction energies, donor acceptor (host guest) distances, bond lengths, and vibration frequencies, could show well defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non covalent interaction better, but also easily predict the interaction energies and structures of a particular non covalent complex, which might otherwise be very hard or resource consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.展开更多
The present paper covers the 199 Hg NMR chemical shifts of 24 substituted diphenylmercurials and phenyl(2-benzothiazolylthio)mercurials. There is a good linear relationship between the chemical shift and the Hammett c...The present paper covers the 199 Hg NMR chemical shifts of 24 substituted diphenylmercurials and phenyl(2-benzothiazolylthio)mercurials. There is a good linear relationship between the chemical shift and the Hammett constant of the substituents for both series of compounds, and electron donating substituents cause the chemical shift towards downfield.展开更多
Ten 4-substituted bicyclic phosphates were synthesized and their ^(13)C-NMR were also determined.A good relationship was observed between 4-^(13)C chemical shift and Taft σ_X induc- tive paramenters.Substituent effec...Ten 4-substituted bicyclic phosphates were synthesized and their ^(13)C-NMR were also determined.A good relationship was observed between 4-^(13)C chemical shift and Taft σ_X induc- tive paramenters.Substituent effects on ~3J_(P-C) coupling constant were studied.展开更多
In order to better understand the specific substituent effects on the electrochemical oxidation process of β-O-4 bond, a series of methoxyphenyl type β-O-4 dimer model compounds with different localized methoxyl gro...In order to better understand the specific substituent effects on the electrochemical oxidation process of β-O-4 bond, a series of methoxyphenyl type β-O-4 dimer model compounds with different localized methoxyl groups, including 2-(2-methoxyphenoxy)-1-phenylethanone, 2-(2-methoxyphenoxy)-1-phenylethanol, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanol, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanol have been selected and their electrochemical properties have been studied experimentally by cyclic voltammetry, and FT-IR spectroelectrochemistry. Combining with electrolysis products distribution analysis and density functional theory calculations, oxidation mechanisms of all six model dimers have been explored. In particular, a total effect from substituents of both para-methoxy(on the aryl ring closing to Cα) and Cα-OH on the oxidation mechanisms has been clearly observed, showing a significant selectivity on the Cα-Cβbond cleavage induced by electrochemical oxidations.展开更多
Electronic and bonding situations at reaction centers are often detected by the remote substituent effect.For nonorganometallic reactions,this effect is conventionally described by the well-known Hammett-type substitu...Electronic and bonding situations at reaction centers are often detected by the remote substituent effect.For nonorganometallic reactions,this effect is conventionally described by the well-known Hammett-type substituent constants.However,for most transition metal(TM)-involved systems,no analogous numeral descriptors reflecting the intrinsic differences between metallic and nonmetallic bonding have been rigorously established till present.Herein,we report a Pd(II)–O bond heterolysis energyΔG_(het)(Pd–O)study of the archetypal palladium complexes to represent the thermodynamics of the essential bond-breaking step in Pd-mediated transformations.Meanwhile we furnish the new substituent constantsσPd^(+)s and therefrom facilitate linear free-energy relationship(LFER)analysis for Pd-catalyzed reactions.Indeed,this led us to find an unexpected electron-donating ability of Pd(II)cation,which provided a gifted experimental support,with the aid of computation,to attribute the frustrating observation of a much scattered curvature in theΔG_(het)(Pd–O)-σ+correlation to the electrondonating capacity of the cationic palladium through back-donation of its d-electrons.Applications of LFER analysis withσPd^(+)to predict the redox behavior of the palladium complex and in a kinetics vs.thermodynamicsmechanistic study of transmetalation added further credence to their applicability to TM systems.展开更多
Bright emission of organic luminogens at aggregated state has attracted increasing attention for their potential applications in opto-electronic devices and bio-/chemo-sensors.In this article,upon the introduction of ...Bright emission of organic luminogens at aggregated state has attracted increasing attention for their potential applications in opto-electronic devices and bio-/chemo-sensors.In this article,upon the introduction of different substituents(Br,Ph and TPh)to the large conjugated core of 9-methyl-9H-dibenzo[a,c]carbazole(DBC)moiety,the resultant luminogens demonstrated PL quantum yields in solid state ranging from 4.81%to 47.39%.Through the systematic investigation of molecular packing,together with theory calculation,the strong intermolecular electronic coupling in the dimers is proved as the main factor to the bright emission in the solid state.The results afforded a new avenue to investigate the intrinsic relationship among the molecular structures,packing modes and emission properties.展开更多
In the study, the X-H (X=CH2, NH, O) bond dissociation energies (BDE) of para-substituted azulene (Y-C10H8X-H) were predicted theoretically for the first time using Density Functronal Theory (DFT) methods at U...In the study, the X-H (X=CH2, NH, O) bond dissociation energies (BDE) of para-substituted azulene (Y-C10H8X-H) were predicted theoretically for the first time using Density Functronal Theory (DFT) methods at UB3LYP/6-311 + +g(2df,2p)//UB3LYP/6-31 +g(d) level. It was found that the substituents exerted similar effects on the X-H BDE of azulene as those on benzene, except for 6-substituted 2-methylazulene. Owing to the substituent-dipole interaction, the reaction constants (ρ^+) of 2- and 6-Y-CIoHsX-H (X=NH and O only) varied violently. The origin of the substituent effects on the X-H BDE of azulene was found, by both GE/RE and SIE theory, to be directly associated with variation of the radical effects, although the ground effects also played a modest role in determining the net. substituent effects.展开更多
Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by―OCH3, ―CH3―COOCH3 and ―CN, respectively. The polycondensations via direct arylation took place between the four thiophene der...Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by―OCH3, ―CH3―COOCH3 and ―CN, respectively. The polycondensations via direct arylation took place between the four thiophene derivatives and 2,7-dibromo-9,9-dioctylfluorene under six various catalytic conditions to investigate the substituent effects. The substituent can affect the electron cloud density of the active C―H bond, which can be monitored by the NMR chemical shift. The experimental results show that the reactivity decreases with increasing the chemical shift of active C―H bonds in the four thiophene derivatives, and thus can promote the direct arylation polycondensation. This phenomenon is explained by the electrophilic aromatic substitution(SEAr) mechanism. UV-Visible absorption and photoluminescence were studied to investigate the substituent effect on optical properties of the four copolymers. The results show that these alternating fluorene-thiophene copolymers with different substituents are good fluorescent materials and promising in PLED applications.展开更多
New lanthanide(Eu3+ and Gd3+) complexes were successfully synthesized and the effect of the p-phe nyl substituent on the Eu3+luminescent properties was evaluated.In this sense,benzhydrazide,p-toluic hydrazide,4-hydrox...New lanthanide(Eu3+ and Gd3+) complexes were successfully synthesized and the effect of the p-phe nyl substituent on the Eu3+luminescent properties was evaluated.In this sense,benzhydrazide,p-toluic hydrazide,4-hydroxybenzhydrazide and 4-aminobenzoic hydrazide were used as ligands and the complexes were obtained by mixing the lanthanide salts with hydrazides in ethanol at room temperature and keeping the reaction for 2 h under mechanical stirring.Crystal of Gd-amino was obtained and its structure was elucidated by single-crystal X-ray diffraction,revealing that Gd3+centered in a distorted tricapped trigonal-prismatic molecular geometry.IR spectroscopy and the elucidated structure confirm hydrazides acting as bidentate ligands binding to Ln3+ions through the oxygen of carbonyl group and the nitrogen of terminal amine,forming a five-membered ring,CHN analyses confirm the molecular formulas [Gd(amino)4(H2 O)](NO3)3·(C2 H5 OH) and [Eu(toluic)3(H2 O)3](NO3)3.Lower T1 state energies are observed for ligands p-substituted with higher electron donating capacity groups,such as p-NH2 and pOH.In contrast,higher lifetimes and quantum efficiencies are obtained for Eu3+complexes with ligands p-H and p-CH3 substituted,which are not deactivator groups.展开更多
By the cyclization of 4,4-dimethylcyclohexane-1,3-dione with different aromatic aldehydes, the xanthene regio- isomers were obtained. The diversity of xanthene isomers could be determined. The electronic and steric ef...By the cyclization of 4,4-dimethylcyclohexane-1,3-dione with different aromatic aldehydes, the xanthene regio- isomers were obtained. The diversity of xanthene isomers could be determined. The electronic and steric effects on aromatic aldehydes could be observed.展开更多
The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2 oxospiro[diazirine 3,3 indoline] to 3 diazo 2 oxo indoline have been examined. The rate constants of the thermal is...The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2 oxospiro[diazirine 3,3 indoline] to 3 diazo 2 oxo indoline have been examined. The rate constants of the thermal isomerization increased with increasing external pressure and were related to the σ + P substituent constant of Hammett correlation. The results suggest that the thermal isomerization proceeds via a dipolar transition state involving heterolytic bond fission. However, the kinetic solvent effects on the thermal isomerization were not observed. The special solvent effects were discussed on the basis of the linear free energy relationship.展开更多
MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor...MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor distance had good correlations with the substituent Hammettconstants. However, the extent of C―H bond contraction and the blue shift of the C―H stretchingvibration did not show any good correlation with the traditional substituent constants, indicatingthat certain more complicated mechanisms might be involved in the present systems. Nevertheless, itwas found that highly electron-withdrawing susbtituents were not favorable to the C―H bondcontraction, and it was suggested that the attractive interaction between water and the carbon of -CF_2H probably played an important role in the blue shift.展开更多
CBS-Q and G3 methods were used to generate a large number of reliable Si--H, P---H and S--H bond dissociation energies (BDEs) for the first time. It was found that the Si--H BDE displayed dramatically different subs...CBS-Q and G3 methods were used to generate a large number of reliable Si--H, P---H and S--H bond dissociation energies (BDEs) for the first time. It was found that the Si--H BDE displayed dramatically different substituent effects compared with the C--H BDE. On the other hand, the P---H and S--H BDE exhibited patterns of substituent effects similar to those of the N--H and O--H BDE. Further analysis indicated that increasing the positive charge on Si of XSiH3 would strengthen the Si--H bond whereas increasing the positive charge on P and S of XPH2 and XSH would weaken the P---H and S--H bonds. Meanwhile, increasing the positive charge on Si of XSiH2^+ stabilized the silyl radical whereas increasing the positive charge on P and S in XPH" and XS* destabilized P- and S-centered radicals. These behaviors could be reasonalized by the fact that Si is less electronegative than H while P and S are not. Finally, it was demonstrated that the spin-delocalization effect was valid for the Si-, P- and S-centered radicals.展开更多
To investigate the substituent effect on x-electron delocalization of the N-benzylideneaniline (NBA), the vertical resonance energies △E^V(θ) of eleven substituted NBAs were separated into n and a parts at the B...To investigate the substituent effect on x-electron delocalization of the N-benzylideneaniline (NBA), the vertical resonance energies △E^V(θ) of eleven substituted NBAs were separated into n and a parts at the B3LYP/6-311G(d) level of the Density Functional Theory (DFT). When substituted with an electron-releasing group --OH, the calculated △E^V(θ) of NBA was increased, indicative of more resonance destabilization than the mother molecule. However, when substituted with an electron-withdrawing group -NO2, the calculated △E^V(θ) values indicated less resonance destabilization. The most destabilizing effect was observed especially when the -OH group located at the ortho-position of the aromatic ring in the fragment -N=CH-Ar. For most of the substituted NBA molecules, it was the destabilized a framework that determined the destabilizing feature of the vertical resonance energy, instead of the stabilized n system. When the -NO2 substituent at the para-position of the aromatic ring of the -N=CH-Ar group, the π system had the highest stabilizing effect while the σ framework exhibited the highest destabilizing effect. While the -NO2 substituent was at the para-position of the left aromatic ring (At-), the NBA had the least vertical resonance energy value.展开更多
Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room tem...Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room temperature with terahertz time-domain spectroscopy (THz-TDS). These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory (DFT) method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.展开更多
Density function theory UB3LYP/6-31+g(d) calculations were performed to study the hydrogen bonds between para -substituted phenols and HF,H_2O,or NH_3. It revealed that many properties of the non-covalent complexes,su...Density function theory UB3LYP/6-31+g(d) calculations were performed to study the hydrogen bonds between para -substituted phenols and HF,H_2O,or NH_3. It revealed that many properties of the non-covalent complexes,such as the interaction energies,donor-acceptor distances,bond lengths and vibration frequencies,showed well-defined substituent effects. Therefore,from the substituent effects not only the mechanism of a certain non-covalent interaction can be better understood,but also the interaction energies and structures of a certain non-covalent complex,which otherwise might be very hard or resource-consuming to estimate,can be easily predicted.展开更多
To investigate whether the proton-accepting ability of imidazole in Cu,Zn-superoxide dismutase (SOD) was possibly modulated by Zn(Ⅱ) or not, the proton affinity (Ap) of N^3 in imidazole group was calculated by ...To investigate whether the proton-accepting ability of imidazole in Cu,Zn-superoxide dismutase (SOD) was possibly modulated by Zn(Ⅱ) or not, the proton affinity (Ap) of N^3 in imidazole group was calculated by density functional theory (DFT) with B3LYP functional. It was found that Zn(Ⅱ) attenuates the Ap, because of its electron-withdrawing effect, while the three ligands connected with Zn(Ⅱ) (residues of two His and one Asp) exert an opposite effect, owing to their electron-donating ability. This finding suggested that the three ligands should play a role in the normal function of Cu,Zn-SOD and should be taken into consideration in the future study.展开更多
基金Project Supported by National Science Foundation of China.
文摘In order to study the polar substituent effect almost with no steric effect in organophosphorus chemistry,a series of 4-substituted-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane 1-oxides(1)and p-substituted phenylphosphonates(2)and corresponding mono hexyl esters(3)as model were synthesized.^(31)P-NMR chemical shifts of compounds(1)in methanol and deuterioacetone were determined.The Δδ values reflect 4-sbstituent po- lar effect.The ^(31)P-NMR of compounds(2)and(3)and the pKa of compounds(3)were also measured.The results showed that the trend of polar effects of substituents in both carboxylic and organophosphates chemistry are similar,and the change of polar effects in variation with the alkyl groups is not significant.
基金Supported by the Key Project for Explosives of Commission of Science Technology and Industry for National Defense,China(No.2371000415)
文摘The thermodynamic properties of the reaction of amide and formaldehyde were calculated via B3LYP method when substituents chosen included CH3,CH2CH3,CH2CH2CH3,CH2CH2CH2CH3,CH(CH3)2,CH2CH(CH3)2,CH(CH3)CH2CH3 and C(CH3)3.Based on the optimization of the structures for reactants and products,the thermodynamic functions of all the species for an actual state were obtained.The thermodynamic data and the equilibrium constants were investigated within a temperature range of 300―343.15 K.The calculated results show that the reaction is exothermic and spontaneous.The trends of all thermodynamic properties are consistent with the temperature.The preferential order of the substituent effect is CH2CH(CH3)2CH(CH3)CH2CH3CH2CH2CH2CH3 CH2CH2CH3CH2CH3≈CH(CH3)2C(CH3)3≈CH3.
文摘Semi-empirical molecular orbital theory AMI method is employed to study the ortho-position substituent impact on intramolecular proton transfer reaction of perylenequinone. The calculation demonstrates that the perylenequinone molecule is of stable structure. and all substituents may cause the decrease of barriers for the hydrogen transfer reaction.
基金Supported by the National Natural Science Foundation of China(No. 2 9972 0 38)
文摘B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, including the interaction energies, donor acceptor (host guest) distances, bond lengths, and vibration frequencies, could show well defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non covalent interaction better, but also easily predict the interaction energies and structures of a particular non covalent complex, which might otherwise be very hard or resource consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.
文摘The present paper covers the 199 Hg NMR chemical shifts of 24 substituted diphenylmercurials and phenyl(2-benzothiazolylthio)mercurials. There is a good linear relationship between the chemical shift and the Hammett constant of the substituents for both series of compounds, and electron donating substituents cause the chemical shift towards downfield.
基金Project Supported by National Sciences Foundation of China.
文摘Ten 4-substituted bicyclic phosphates were synthesized and their ^(13)C-NMR were also determined.A good relationship was observed between 4-^(13)C chemical shift and Taft σ_X induc- tive paramenters.Substituent effects on ~3J_(P-C) coupling constant were studied.
基金The authors gratefully acknowledge the financial support of the Natural Science Foundation of China,China(Grant No.21975082 and 21736003)the Guangdong Basic and Applied Basic Research Foundation(Grant Number:2019A1515011472 and 2022A1515011341)the Science and Technology Program of Guangzhou(Grant Number:202102080479).
文摘In order to better understand the specific substituent effects on the electrochemical oxidation process of β-O-4 bond, a series of methoxyphenyl type β-O-4 dimer model compounds with different localized methoxyl groups, including 2-(2-methoxyphenoxy)-1-phenylethanone, 2-(2-methoxyphenoxy)-1-phenylethanol, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanol, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanol have been selected and their electrochemical properties have been studied experimentally by cyclic voltammetry, and FT-IR spectroelectrochemistry. Combining with electrolysis products distribution analysis and density functional theory calculations, oxidation mechanisms of all six model dimers have been explored. In particular, a total effect from substituents of both para-methoxy(on the aryl ring closing to Cα) and Cα-OH on the oxidation mechanisms has been clearly observed, showing a significant selectivity on the Cα-Cβbond cleavage induced by electrochemical oxidations.
基金provided by the National Natural Science Foundation of China(nos.21973052,21933008)the Young Elite Scientists Sponsorship Program by CAST(no.2019QNRC001),and the Haihe Laboratory of Sustainable Chemical Transformations.
文摘Electronic and bonding situations at reaction centers are often detected by the remote substituent effect.For nonorganometallic reactions,this effect is conventionally described by the well-known Hammett-type substituent constants.However,for most transition metal(TM)-involved systems,no analogous numeral descriptors reflecting the intrinsic differences between metallic and nonmetallic bonding have been rigorously established till present.Herein,we report a Pd(II)–O bond heterolysis energyΔG_(het)(Pd–O)study of the archetypal palladium complexes to represent the thermodynamics of the essential bond-breaking step in Pd-mediated transformations.Meanwhile we furnish the new substituent constantsσPd^(+)s and therefrom facilitate linear free-energy relationship(LFER)analysis for Pd-catalyzed reactions.Indeed,this led us to find an unexpected electron-donating ability of Pd(II)cation,which provided a gifted experimental support,with the aid of computation,to attribute the frustrating observation of a much scattered curvature in theΔG_(het)(Pd–O)-σ+correlation to the electrondonating capacity of the cationic palladium through back-donation of its d-electrons.Applications of LFER analysis withσPd^(+)to predict the redox behavior of the palladium complex and in a kinetics vs.thermodynamicsmechanistic study of transmetalation added further credence to their applicability to TM systems.
基金supported by the National Natural Science Foundation of China(51673151,51973162,21875174,21734007)the Natural Science Foundation of Hubei Province(2017CFA002)。
文摘Bright emission of organic luminogens at aggregated state has attracted increasing attention for their potential applications in opto-electronic devices and bio-/chemo-sensors.In this article,upon the introduction of different substituents(Br,Ph and TPh)to the large conjugated core of 9-methyl-9H-dibenzo[a,c]carbazole(DBC)moiety,the resultant luminogens demonstrated PL quantum yields in solid state ranging from 4.81%to 47.39%.Through the systematic investigation of molecular packing,together with theory calculation,the strong intermolecular electronic coupling in the dimers is proved as the main factor to the bright emission in the solid state.The results afforded a new avenue to investigate the intrinsic relationship among the molecular structures,packing modes and emission properties.
基金Project supported by the National Natural Science Foundation of China (No. 20472079) and Anhui Provincial Natural Science Faundation (No 070416237).
文摘In the study, the X-H (X=CH2, NH, O) bond dissociation energies (BDE) of para-substituted azulene (Y-C10H8X-H) were predicted theoretically for the first time using Density Functronal Theory (DFT) methods at UB3LYP/6-311 + +g(2df,2p)//UB3LYP/6-31 +g(d) level. It was found that the substituents exerted similar effects on the X-H BDE of azulene as those on benzene, except for 6-substituted 2-methylazulene. Owing to the substituent-dipole interaction, the reaction constants (ρ^+) of 2- and 6-Y-CIoHsX-H (X=NH and O only) varied violently. The origin of the substituent effects on the X-H BDE of azulene was found, by both GE/RE and SIE theory, to be directly associated with variation of the radical effects, although the ground effects also played a modest role in determining the net. substituent effects.
基金financially supported by the National Natural Science Foundation of China(Nos.60976019 and 61250016)Education Department Program(No.JA12069)and Program for Innovative Research Team in Science and Technology in Fujian Province
文摘Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by―OCH3, ―CH3―COOCH3 and ―CN, respectively. The polycondensations via direct arylation took place between the four thiophene derivatives and 2,7-dibromo-9,9-dioctylfluorene under six various catalytic conditions to investigate the substituent effects. The substituent can affect the electron cloud density of the active C―H bond, which can be monitored by the NMR chemical shift. The experimental results show that the reactivity decreases with increasing the chemical shift of active C―H bonds in the four thiophene derivatives, and thus can promote the direct arylation polycondensation. This phenomenon is explained by the electrophilic aromatic substitution(SEAr) mechanism. UV-Visible absorption and photoluminescence were studied to investigate the substituent effect on optical properties of the four copolymers. The results show that these alternating fluorene-thiophene copolymers with different substituents are good fluorescent materials and promising in PLED applications.
基金the FAPESP(Fundacao de Amparo a Pesquisa de Sao Paulo)(2017/11764-2)。
文摘New lanthanide(Eu3+ and Gd3+) complexes were successfully synthesized and the effect of the p-phe nyl substituent on the Eu3+luminescent properties was evaluated.In this sense,benzhydrazide,p-toluic hydrazide,4-hydroxybenzhydrazide and 4-aminobenzoic hydrazide were used as ligands and the complexes were obtained by mixing the lanthanide salts with hydrazides in ethanol at room temperature and keeping the reaction for 2 h under mechanical stirring.Crystal of Gd-amino was obtained and its structure was elucidated by single-crystal X-ray diffraction,revealing that Gd3+centered in a distorted tricapped trigonal-prismatic molecular geometry.IR spectroscopy and the elucidated structure confirm hydrazides acting as bidentate ligands binding to Ln3+ions through the oxygen of carbonyl group and the nitrogen of terminal amine,forming a five-membered ring,CHN analyses confirm the molecular formulas [Gd(amino)4(H2 O)](NO3)3·(C2 H5 OH) and [Eu(toluic)3(H2 O)3](NO3)3.Lower T1 state energies are observed for ligands p-substituted with higher electron donating capacity groups,such as p-NH2 and pOH.In contrast,higher lifetimes and quantum efficiencies are obtained for Eu3+complexes with ligands p-H and p-CH3 substituted,which are not deactivator groups.
文摘By the cyclization of 4,4-dimethylcyclohexane-1,3-dione with different aromatic aldehydes, the xanthene regio- isomers were obtained. The diversity of xanthene isomers could be determined. The electronic and steric effects on aromatic aldehydes could be observed.
文摘The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2 oxospiro[diazirine 3,3 indoline] to 3 diazo 2 oxo indoline have been examined. The rate constants of the thermal isomerization increased with increasing external pressure and were related to the σ + P substituent constant of Hammett correlation. The results suggest that the thermal isomerization proceeds via a dipolar transition state involving heterolytic bond fission. However, the kinetic solvent effects on the thermal isomerization were not observed. The special solvent effects were discussed on the basis of the linear free energy relationship.
文摘MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor distance had good correlations with the substituent Hammettconstants. However, the extent of C―H bond contraction and the blue shift of the C―H stretchingvibration did not show any good correlation with the traditional substituent constants, indicatingthat certain more complicated mechanisms might be involved in the present systems. Nevertheless, itwas found that highly electron-withdrawing susbtituents were not favorable to the C―H bondcontraction, and it was suggested that the attractive interaction between water and the carbon of -CF_2H probably played an important role in the blue shift.
基金Project supported by the National Natural Science Foundation of China (No. 200332020).
文摘CBS-Q and G3 methods were used to generate a large number of reliable Si--H, P---H and S--H bond dissociation energies (BDEs) for the first time. It was found that the Si--H BDE displayed dramatically different substituent effects compared with the C--H BDE. On the other hand, the P---H and S--H BDE exhibited patterns of substituent effects similar to those of the N--H and O--H BDE. Further analysis indicated that increasing the positive charge on Si of XSiH3 would strengthen the Si--H bond whereas increasing the positive charge on P and S of XPH2 and XSH would weaken the P---H and S--H bonds. Meanwhile, increasing the positive charge on Si of XSiH2^+ stabilized the silyl radical whereas increasing the positive charge on P and S in XPH" and XS* destabilized P- and S-centered radicals. These behaviors could be reasonalized by the fact that Si is less electronegative than H while P and S are not. Finally, it was demonstrated that the spin-delocalization effect was valid for the Si-, P- and S-centered radicals.
基金Project supported by the National Natural Science Foundation of China (No. 204720feng88).
文摘To investigate the substituent effect on x-electron delocalization of the N-benzylideneaniline (NBA), the vertical resonance energies △E^V(θ) of eleven substituted NBAs were separated into n and a parts at the B3LYP/6-311G(d) level of the Density Functional Theory (DFT). When substituted with an electron-releasing group --OH, the calculated △E^V(θ) of NBA was increased, indicative of more resonance destabilization than the mother molecule. However, when substituted with an electron-withdrawing group -NO2, the calculated △E^V(θ) values indicated less resonance destabilization. The most destabilizing effect was observed especially when the -OH group located at the ortho-position of the aromatic ring in the fragment -N=CH-Ar. For most of the substituted NBA molecules, it was the destabilized a framework that determined the destabilizing feature of the vertical resonance energy, instead of the stabilized n system. When the -NO2 substituent at the para-position of the aromatic ring of the -N=CH-Ar group, the π system had the highest stabilizing effect while the σ framework exhibited the highest destabilizing effect. While the -NO2 substituent was at the para-position of the left aromatic ring (At-), the NBA had the least vertical resonance energy value.
基金Project supported by the National Natural Science Foundation of China (Nos. 20373086, 10574134) and Research Programs of Chinese Academy of Sciences.
文摘Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room temperature with terahertz time-domain spectroscopy (THz-TDS). These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory (DFT) method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.
基金ProjectsupportedbytheMinistryofScienceandTechnology ,ChineseAcademyofSciencesandtheNationalNaturalFoundationofChina (No .2 0 2 72 0 5 7)
文摘Density function theory UB3LYP/6-31+g(d) calculations were performed to study the hydrogen bonds between para -substituted phenols and HF,H_2O,or NH_3. It revealed that many properties of the non-covalent complexes,such as the interaction energies,donor-acceptor distances,bond lengths and vibration frequencies,showed well-defined substituent effects. Therefore,from the substituent effects not only the mechanism of a certain non-covalent interaction can be better understood,but also the interaction energies and structures of a certain non-covalent complex,which otherwise might be very hard or resource-consuming to estimate,can be easily predicted.
基金Project supported by the National Basic Research Program of China (No.2003CB 114400) and the National Natural Science Foundation of China (Nos. 30100035 and 30570383).
文摘To investigate whether the proton-accepting ability of imidazole in Cu,Zn-superoxide dismutase (SOD) was possibly modulated by Zn(Ⅱ) or not, the proton affinity (Ap) of N^3 in imidazole group was calculated by density functional theory (DFT) with B3LYP functional. It was found that Zn(Ⅱ) attenuates the Ap, because of its electron-withdrawing effect, while the three ligands connected with Zn(Ⅱ) (residues of two His and one Asp) exert an opposite effect, owing to their electron-donating ability. This finding suggested that the three ligands should play a role in the normal function of Cu,Zn-SOD and should be taken into consideration in the future study.