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
Two diiron dithiolate complexes [Fe2（CO）6（1,8-S2-2-CH2OOCPhC（10）H5）] 1 and[Fe2（CO）6（1,8-S2-2-CH2OOCPh-4-NO2C（10）H5）]2 were synthesized in high yield. The complexes have been confirmed by single-crystal X-r...Two diiron dithiolate complexes [Fe2（CO）6（1,8-S2-2-CH2OOCPhC（10）H5）] 1 and[Fe2（CO）6（1,8-S2-2-CH2OOCPh-4-NO2C（10）H5）]2 were synthesized in high yield. The complexes have been confirmed by single-crystal X-ray diffraction and characterized by IR, UV-Vis, ^1H NMR spectroscopy and cyclic voltammetry. They contain a butterfly Fe2S2 core with the Fe1–Fe2 distances of 2.5237（7）A in 1 and 2.5125（12）A in 2, falling in the normal range of Fe–Fe bond length（2.49 - 2.57 A）. The cyclic voltammetry has been used to investigate the electrochemical properties and the electrocatalytic proton reduction for 1 and 2. The complexes display reduction peaks at –1.074 V, –1.535 V（1） and –0.869 V, –1.247 V（2） vs. Fc/Fc^＋, respectively. With using p-Ts OH acid of different concentration, the reduction peak of complex 2 grows non-linear; on the contrary, that of complex 1 is linear with the addition of the acid. Cyclic voltammetry revealed the two complexes are good catalysts in the CH3CN/NBu4PF6 solution.展开更多
A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coeffici...A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coefficient was 0.9805, and the standard deviation was only 672.27 cm^-1. The results imply that the excited-state substituent constant can be used productively for research on UV energy of 1,4-disubstituted benzenes. The present method provides a new avenue to study the UV absorption spectra of aromatic systems with the excited-state substituent constant, and it is helpful to understand the effect of substituent electrostatic effects on the chemical and physical properties of conjugated compounds with multiple substituents in excited state.展开更多
Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical...Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical shifts （δH（CH=N）） and 13C NMR chemical shifts （δc（CH=N）） of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show thatthe substituent specific cross-interaction effect parameter （△（∑σ）2） plays an important role in quantifying the δc（CH=N） values of XBAYs, but it is negligible for quantifying the δH （CH=N） values; the other substituent parameters also present different influences on the δc （CH=N） and （δH （CH=N）. On the whole, the contributions of X and Y to the δc （CH=N） of XBAYs are balanced, but the δH（CH=N） values of XBAYs mainly rely on the contributions of X.展开更多
Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synth...Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.展开更多
The synthesis and phosphorescence properties of two novel Ir(Ⅲ)complexes bearing tert-butyl substituents,bis(4-tert-butyl-2- phenylbenzothiozolato-N,C^(2′))iridium(Ⅲ)(acetylacetonate)[(tbt)_2Ir(acac)]and bis(4-tert...The synthesis and phosphorescence properties of two novel Ir(Ⅲ)complexes bearing tert-butyl substituents,bis(4-tert-butyl-2- phenylbenzothiozolato-N,C^(2′))iridium(Ⅲ)(acetylacetonate)[(tbt)_2Ir(acac)]and bis(4-tert-butyl-1-phenyl-1H-benzimidazolato- N,C^(2′))iridium(Ⅲ)(acetylacetonate)[(tpbi)_2Ir(acac)],are reported,their molecular structures are confirmed by^1H NMR,ESI-MS and elementary analysis.Photoluminescence(PL)studies revealed that they can emit strong green and orange phosphorescence in high quantum yields.Compared to their prototypes lacking of tert-butyl substituents,the two novel iridium(Ⅲ)complexes both have shorter lifetimes and improved or nearly similar PL quantum efficiencies,implying that the exciton quenching is inhibited effectively when molecular steric hindrance increases.The two chelates have great potential to be used as electrophosphorescent materials.展开更多
Calix[4]arene derivatives have been reported to possess high selectivity for metal ions.In order to analyze the extraction effect of substituents on Hg^(2+)and Pb^(2+),calix[4]arene derivatives containing hydroxyl,bro...Calix[4]arene derivatives have been reported to possess high selectivity for metal ions.In order to analyze the extraction effect of substituents on Hg^(2+)and Pb^(2+),calix[4]arene derivatives containing hydroxyl,bromoethoxy and 1,11-dioxa-4,8-dithiahendecene were successfully synthesized,with their extraction effectiveness towards Hg^(2+)and Pb^(2+)were evaluated respectively.The results indicated that the phenolic hydroxyl in calix[4]arene improved the extraction ability on Hg^(2+)by promoting the formation of the negative oxygen ions that could bind with Hg^(2+)by coordination and ionic bonds.The extraction ability of 5,17-dinitro-26,28-(1’,11’-dioxa-4’,8’-dithiahendecene)-calix[4]arene(calix[4]arene thia derivative)was improved slightly due to the better coordination capacity for metal ions after introduction of 1,11-dioxa-4,8-dithiahendecene,which was a chelate-binding centre.Regarding to Pb^(2+),only 1,11-dioxa-4,8-dithiahendecene on molecule contributed to extraction due to the coordination bond.Since the metal ion with higher charge-to-radius ratio could coordinate with one ligand more stably,Pb^(2+)with higher charge-to-radius ratio than Hg^(2+)was coordinated and extracted by the calix[4]arene thia derivative more easily.Furthermore,extraction rates of the calix[4]arene thia derivative on both ions(Hg^(2+)and Pb^(2+))increased with the increase of pH value in acidic aqueous system(pH<7).展开更多
A comprehensive exploration of the aminolysis mechanism for methyl indole-3-acetate with ammonia is carried out by employing the B3 LYP/6-311++G(d,p), M06-2 X/6-311++G(d,p) and MP2/6-311++G(d,p)//M06-2 X/6-311++G(d,p)...A comprehensive exploration of the aminolysis mechanism for methyl indole-3-acetate with ammonia is carried out by employing the B3 LYP/6-311++G(d,p), M06-2 X/6-311++G(d,p) and MP2/6-311++G(d,p)//M06-2 X/6-311++G(d,p) levels. Two alterative reaction channels of the concerted and addition/elimination stepwise processes including the uncatalyzed, base-catalyzed reactions are taken into consideration. Subsequently, the substituent effects and solvent effects in methanol are also evaluated at the M06-2 X/6-311++G(d,p) level. The calculated results indicate that the calculated values of M06-2 X level are quite close to those of MP2, the stepwise pathway has more advantages to the concerted one for all of the reaction processes and the catalyst facilitates the proton migration and decreases the energy barriers as well. It is shown that the most preferred mechanism is the based-catalyzed stepwise process, the substituent of NH2 group slightly accelerates all the aminolysis reaction processes, and the solvent effect does not remarkably change the mechanism of the reaction.展开更多
The photophysics and photochemistry of pefloxacin(PEF),a 1-ethyl-substituted fluoroquinolone(FQ)antibiotic,were studied using transient,steady-state experimental methods and computational methods.The fundamental photo...The photophysics and photochemistry of pefloxacin(PEF),a 1-ethyl-substituted fluoroquinolone(FQ)antibiotic,were studied using transient,steady-state experimental methods and computational methods.The fundamental photoproperties of PEF and its phototoxicity toward lysozyme,a single-chain protein,were compared with those of a 1-fluorophenyl-substituted FQ antibiotic,difloxacin(DIF).The results showed that the phototoxicity was significantly decreased by the insertion of the bulky1-fluorophenyl substituent(the phototoxicity of DIF was approximately one-quarter of that observed for PEF).This trend was attributed to the lowest lying singlet state with sizeable oscillator strength(f C 0.1)being shifted from319 nm in PEF to 266 nm in DIF upon the insertion of the bulky substituent at the 1-position,as investigated by using computational methods.In addition,95%of the solar UV irradiation that reaches the earth’s surface has wavelength[315 nm.Therefore,reducing the most effective excitation wavelength by optimizing the substituent at the1-position may be a promising strategy to alleviate the phototoxicity of FQ antibiotics.These findings may be applied to other FQ antibiotics because a large number of phototoxicity studies on FQ antibiotics with different substituents at the 1-position can prove these finding’s effectiveness.Delafloxacin,an FQ antibiotic bearing a chlorine and bulky substituent at the 8-and 1-positions,respectively,exhibits no phototoxicity is the most recent example reported to date.To the best of our knowledge,this is the first transient and steady-state study of the effect of the N-1 substituent on the photochemistry and phototoxicity of FQ antibiotics.These findings will be beneficial to the development of novel FQ antibiotics without phototoxicity.展开更多
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
Two new macrocyclic complexes with C-methyl substituents on the framework, namely, [CuL]（ClO4）2 （L = 5,12-dimethyl-1,8-dihydroxyethyl-1,3,6,8,10,13-hexaazacyclotetradecane） 1 and [NiL]（ClO4）2 2, have been synthe...Two new macrocyclic complexes with C-methyl substituents on the framework, namely, [CuL]（ClO4）2 （L = 5,12-dimethyl-1,8-dihydroxyethyl-1,3,6,8,10,13-hexaazacyclotetradecane） 1 and [NiL]（ClO4）2 2, have been synthesized and structurally characterized through X-ray diffraction analysis. Also, crystal structure of [CuL^1]（ClO4）2 （L^1 = 1,8-dimethyl- 1,3,6,8, [ 0,13- hexaazacyclotetradecane） 3 has been determined. Crystal data for 1： C14H32C12CuN6O10, Mr = 578.90, monoclinic, P2 1/n, α = 8.3529（11）, b = 10.8105（17）, c = 13.3709（17） ,A, β = 105.189（10）°, V= 1165.2（3） A3, Z = 2, Dc = 1.650 g/cm^3, F（000） = 602, λ（MoKct） = 0.71073 A,μ = 1.229 mm ^-1, R = 0.0474 and wR = 0.0895 for 2771 observed reflections （I 〉 2σ（Ⅰ））. Crystal data for 2： C14H32C12N6NiO10, Mr = 574.07, monoclinic, P2 1/c, a = 8.3636（12）, b = 12.997（2）, c = 10.764（2） A, β = 99.31（2）°, V = 1154.7（3） A^3, Z = 2, DC = 1.651 g/cm^3, F（000） = 600, λ（MoKa） = 0.71073 A,μ = 1. 134 mm^-1, R = 0.0380 and wR = 0.0796 for 2670 observed reflections （i 〉 2σ（Ⅰ））. Crystal data for 3： C 10H26Cl2CuN6O8, Mr = 492.81, monoclinic, P2 1/n, a = 8.4860（17）, b = 8.6320（17）, c = 12.662（3） ,A,β = 103.40（3）°, V = 902.2（3）A^3, Z = 2, Dc = 1.814 g/cm^3, F（000） = 510, λ（MoKa） = 0.71073A, μ = 1.562 mm^-1, R = 0.0505 and wR = 0.1061 for 1967 observed reflections （I〉 2σ（Ⅰ））. Complexes 1 and 2 are isostructural with the metal ions situated at the inversion center/Hydrogen bonds between O atoms of pendant and perchlorate anion give rise to a two-dimensional supramolecular layer. The Cu（Ⅱ） ions of compounds 1 and 3 adopt distorted axially-elongated octahedral coordinate geometry, and the nickel（Ⅱ） ion in complex 2 is four-coordinated with a square-planar configuration.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
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
Based on the property that carboxymethylcellulose (CMC ) can be de-graded to anhydroglucose residues by cellulase, the rate constant (K) of enzymatic degra-dation of CMC synthesized in the benzene-ethanol medium has b...Based on the property that carboxymethylcellulose (CMC ) can be de-graded to anhydroglucose residues by cellulase, the rate constant (K) of enzymatic degra-dation of CMC synthesized in the benzene-ethanol medium has been determined. Further-morel experimental equation K = 2.71× 10^(-2)(DS)^(-1.2) reflecting the relationship betweenK and the degree of substitution (DS) is correlated and used to describe chemical mi-crostructure uniformity of the distribution of substituents along chains effectively. Chainstructure parameters of enzymatic degradation products of CMC-the number of chainbreaks and the percentage of glucose released have been also measured. Average length ofsubstituted and unsubstituted chain segments are calculated simultaneously. Through thestudy of static and dynamic procedures of enzymatic degradation, the method to charac-terize the distribution of substituents of CMC along the chain has been improved.展开更多
Three series of polythiophenes containing fluoroalkoxy and fluoroether substituents were prepared by electrochemical polymerization. The effect of substituents with fluoroalkoxy or ether functional groups on the elect...Three series of polythiophenes containing fluoroalkoxy and fluoroether substituents were prepared by electrochemical polymerization. The effect of substituents with fluoroalkoxy or ether functional groups on the electrochemical polymerization of thiophene monomers and properties of the obtained polymers were analyzed. The introduction of a fluoroether functional group at the 3-position of the thiophene ring leads to an increase of the oxidation potential of the monomer and to a decrease of the conductivity of the resulting polymers, even with the use of a CH2 group as spacer. Conversely, the presence of an oxygen atom directly at the 3-position of the thiophene ring, which offsets the negative withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conducting polythiophenes.展开更多
The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on ...The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on proton transfer.The mechanism of hydrogen bond enhancement is qualitatively elucidated by comparing the infrared spectra, the reduced density gradient, and the frontier molecular orbitals.The calculated electronic spectra are consistent with the experimental results.To quantify the proton transfer, the potential energy curves(PECs) of the four derivatives in S0 and S1 states are scanned.It is concluded that the ability of proton transfer follows the order: FM > BFM > BFBC > CCM.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
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
Three ethylene-vinyl alcohol copolymers were studied by means of the substituent chemical shift (SCS) method. The SCS parameters of hydroxy (-OH) in two different solvents were obtained: in deuterium oxide/phenol (20/...Three ethylene-vinyl alcohol copolymers were studied by means of the substituent chemical shift (SCS) method. The SCS parameters of hydroxy (-OH) in two different solvents were obtained: in deuterium oxide/phenol (20/80 W/W ) the parameters are S_1 = 42.77±0.08ppm, S_2 = 7.15±0.06 ppm, S_3 (s)= -4.08±0.02ppm, S_3 (t) =-3.09±0.20ppm,S_4 = 0.48±0.03ppm, S_5 = 0.26±0.05ppm. In o-dichloro-benzen-d_4 S_1(s)=44.79±0.61ppm, S_2=7.40±0.00ppm, S_3(s)=-4.51±0.17ppm, S_3(t)=-3.13 ±0.00 ppm, S_4 =0.63±0.04ppm, S_5=0.36±0.00ppm.Simultaneously the ^(13)CNMR spectra of EVA copolymers were assigned by using the SCS parameters obtained.展开更多
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supported by the National Natural Science Foundation of China(Nos.21231003 and 21203195)
文摘Two diiron dithiolate complexes [Fe2（CO）6（1,8-S2-2-CH2OOCPhC（10）H5）] 1 and[Fe2（CO）6（1,8-S2-2-CH2OOCPh-4-NO2C（10）H5）]2 were synthesized in high yield. The complexes have been confirmed by single-crystal X-ray diffraction and characterized by IR, UV-Vis, ^1H NMR spectroscopy and cyclic voltammetry. They contain a butterfly Fe2S2 core with the Fe1–Fe2 distances of 2.5237（7）A in 1 and 2.5125（12）A in 2, falling in the normal range of Fe–Fe bond length（2.49 - 2.57 A）. The cyclic voltammetry has been used to investigate the electrochemical properties and the electrocatalytic proton reduction for 1 and 2. The complexes display reduction peaks at –1.074 V, –1.535 V（1） and –0.869 V, –1.247 V（2） vs. Fc/Fc^＋, respectively. With using p-Ts OH acid of different concentration, the reduction peak of complex 2 grows non-linear; on the contrary, that of complex 1 is linear with the addition of the acid. Cyclic voltammetry revealed the two complexes are good catalysts in the CH3CN/NBu4PF6 solution.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20772028 and No.20472019）, the Natural Science Foundation of Hunan Province （No.06JJ2002）, and the Scientific Research Fund of Hunan Provincial Education Commission.
文摘A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coefficient was 0.9805, and the standard deviation was only 672.27 cm^-1. The results imply that the excited-state substituent constant can be used productively for research on UV energy of 1,4-disubstituted benzenes. The present method provides a new avenue to study the UV absorption spectra of aromatic systems with the excited-state substituent constant, and it is helpful to understand the effect of substituent electrostatic effects on the chemical and physical properties of conjugated compounds with multiple substituents in excited state.
基金supported by the National Natural Science Foundation of China(No.21672058 and No.21272063)
文摘Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical shifts （δH（CH=N）） and 13C NMR chemical shifts （δc（CH=N）） of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show thatthe substituent specific cross-interaction effect parameter （△（∑σ）2） plays an important role in quantifying the δc（CH=N） values of XBAYs, but it is negligible for quantifying the δH （CH=N） values; the other substituent parameters also present different influences on the δc （CH=N） and （δH （CH=N）. On the whole, the contributions of X and Y to the δc （CH=N） of XBAYs are balanced, but the δH（CH=N） values of XBAYs mainly rely on the contributions of X.
文摘Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.
文摘The synthesis and phosphorescence properties of two novel Ir(Ⅲ)complexes bearing tert-butyl substituents,bis(4-tert-butyl-2- phenylbenzothiozolato-N,C^(2′))iridium(Ⅲ)(acetylacetonate)[(tbt)_2Ir(acac)]and bis(4-tert-butyl-1-phenyl-1H-benzimidazolato- N,C^(2′))iridium(Ⅲ)(acetylacetonate)[(tpbi)_2Ir(acac)],are reported,their molecular structures are confirmed by^1H NMR,ESI-MS and elementary analysis.Photoluminescence(PL)studies revealed that they can emit strong green and orange phosphorescence in high quantum yields.Compared to their prototypes lacking of tert-butyl substituents,the two novel iridium(Ⅲ)complexes both have shorter lifetimes and improved or nearly similar PL quantum efficiencies,implying that the exciton quenching is inhibited effectively when molecular steric hindrance increases.The two chelates have great potential to be used as electrophosphorescent materials.
基金Natural Science Foundation of Education Department of Anhui Province,China(No.KJ2013B028)Textile Science and Technology Key Discipline in Anhui Polytechnic University,China
文摘Calix[4]arene derivatives have been reported to possess high selectivity for metal ions.In order to analyze the extraction effect of substituents on Hg^(2+)and Pb^(2+),calix[4]arene derivatives containing hydroxyl,bromoethoxy and 1,11-dioxa-4,8-dithiahendecene were successfully synthesized,with their extraction effectiveness towards Hg^(2+)and Pb^(2+)were evaluated respectively.The results indicated that the phenolic hydroxyl in calix[4]arene improved the extraction ability on Hg^(2+)by promoting the formation of the negative oxygen ions that could bind with Hg^(2+)by coordination and ionic bonds.The extraction ability of 5,17-dinitro-26,28-(1’,11’-dioxa-4’,8’-dithiahendecene)-calix[4]arene(calix[4]arene thia derivative)was improved slightly due to the better coordination capacity for metal ions after introduction of 1,11-dioxa-4,8-dithiahendecene,which was a chelate-binding centre.Regarding to Pb^(2+),only 1,11-dioxa-4,8-dithiahendecene on molecule contributed to extraction due to the coordination bond.Since the metal ion with higher charge-to-radius ratio could coordinate with one ligand more stably,Pb^(2+)with higher charge-to-radius ratio than Hg^(2+)was coordinated and extracted by the calix[4]arene thia derivative more easily.Furthermore,extraction rates of the calix[4]arene thia derivative on both ions(Hg^(2+)and Pb^(2+))increased with the increase of pH value in acidic aqueous system(pH<7).
基金supported by the Special Funds of the National Natural Science Foundation of China(No.11347161)
文摘A comprehensive exploration of the aminolysis mechanism for methyl indole-3-acetate with ammonia is carried out by employing the B3 LYP/6-311++G(d,p), M06-2 X/6-311++G(d,p) and MP2/6-311++G(d,p)//M06-2 X/6-311++G(d,p) levels. Two alterative reaction channels of the concerted and addition/elimination stepwise processes including the uncatalyzed, base-catalyzed reactions are taken into consideration. Subsequently, the substituent effects and solvent effects in methanol are also evaluated at the M06-2 X/6-311++G(d,p) level. The calculated results indicate that the calculated values of M06-2 X level are quite close to those of MP2, the stepwise pathway has more advantages to the concerted one for all of the reaction processes and the catalyst facilitates the proton migration and decreases the energy barriers as well. It is shown that the most preferred mechanism is the based-catalyzed stepwise process, the substituent of NH2 group slightly accelerates all the aminolysis reaction processes, and the solvent effect does not remarkably change the mechanism of the reaction.
基金supported by the National Natural Science Foundation of China(No.21173252)。
文摘The photophysics and photochemistry of pefloxacin(PEF),a 1-ethyl-substituted fluoroquinolone(FQ)antibiotic,were studied using transient,steady-state experimental methods and computational methods.The fundamental photoproperties of PEF and its phototoxicity toward lysozyme,a single-chain protein,were compared with those of a 1-fluorophenyl-substituted FQ antibiotic,difloxacin(DIF).The results showed that the phototoxicity was significantly decreased by the insertion of the bulky1-fluorophenyl substituent(the phototoxicity of DIF was approximately one-quarter of that observed for PEF).This trend was attributed to the lowest lying singlet state with sizeable oscillator strength(f C 0.1)being shifted from319 nm in PEF to 266 nm in DIF upon the insertion of the bulky substituent at the 1-position,as investigated by using computational methods.In addition,95%of the solar UV irradiation that reaches the earth’s surface has wavelength[315 nm.Therefore,reducing the most effective excitation wavelength by optimizing the substituent at the1-position may be a promising strategy to alleviate the phototoxicity of FQ antibiotics.These findings may be applied to other FQ antibiotics because a large number of phototoxicity studies on FQ antibiotics with different substituents at the 1-position can prove these finding’s effectiveness.Delafloxacin,an FQ antibiotic bearing a chlorine and bulky substituent at the 8-and 1-positions,respectively,exhibits no phototoxicity is the most recent example reported to date.To the best of our knowledge,this is the first transient and steady-state study of the effect of the N-1 substituent on the photochemistry and phototoxicity of FQ antibiotics.These findings will be beneficial to the development of novel FQ antibiotics without phototoxicity.
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 National Natural Science Foundation of China (20201008)
文摘Two new macrocyclic complexes with C-methyl substituents on the framework, namely, [CuL]（ClO4）2 （L = 5,12-dimethyl-1,8-dihydroxyethyl-1,3,6,8,10,13-hexaazacyclotetradecane） 1 and [NiL]（ClO4）2 2, have been synthesized and structurally characterized through X-ray diffraction analysis. Also, crystal structure of [CuL^1]（ClO4）2 （L^1 = 1,8-dimethyl- 1,3,6,8, [ 0,13- hexaazacyclotetradecane） 3 has been determined. Crystal data for 1： C14H32C12CuN6O10, Mr = 578.90, monoclinic, P2 1/n, α = 8.3529（11）, b = 10.8105（17）, c = 13.3709（17） ,A, β = 105.189（10）°, V= 1165.2（3） A3, Z = 2, Dc = 1.650 g/cm^3, F（000） = 602, λ（MoKct） = 0.71073 A,μ = 1.229 mm ^-1, R = 0.0474 and wR = 0.0895 for 2771 observed reflections （I 〉 2σ（Ⅰ））. Crystal data for 2： C14H32C12N6NiO10, Mr = 574.07, monoclinic, P2 1/c, a = 8.3636（12）, b = 12.997（2）, c = 10.764（2） A, β = 99.31（2）°, V = 1154.7（3） A^3, Z = 2, DC = 1.651 g/cm^3, F（000） = 600, λ（MoKa） = 0.71073 A,μ = 1. 134 mm^-1, R = 0.0380 and wR = 0.0796 for 2670 observed reflections （i 〉 2σ（Ⅰ））. Crystal data for 3： C 10H26Cl2CuN6O8, Mr = 492.81, monoclinic, P2 1/n, a = 8.4860（17）, b = 8.6320（17）, c = 12.662（3） ,A,β = 103.40（3）°, V = 902.2（3）A^3, Z = 2, Dc = 1.814 g/cm^3, F（000） = 510, λ（MoKa） = 0.71073A, μ = 1.562 mm^-1, R = 0.0505 and wR = 0.1061 for 1967 observed reflections （I〉 2σ（Ⅰ））. Complexes 1 and 2 are isostructural with the metal ions situated at the inversion center/Hydrogen bonds between O atoms of pendant and perchlorate anion give rise to a two-dimensional supramolecular layer. The Cu（Ⅱ） ions of compounds 1 and 3 adopt distorted axially-elongated octahedral coordinate geometry, and the nickel（Ⅱ） ion in complex 2 is four-coordinated with a square-planar configuration.
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.
文摘Based on the property that carboxymethylcellulose (CMC ) can be de-graded to anhydroglucose residues by cellulase, the rate constant (K) of enzymatic degra-dation of CMC synthesized in the benzene-ethanol medium has been determined. Further-morel experimental equation K = 2.71× 10^(-2)(DS)^(-1.2) reflecting the relationship betweenK and the degree of substitution (DS) is correlated and used to describe chemical mi-crostructure uniformity of the distribution of substituents along chains effectively. Chainstructure parameters of enzymatic degradation products of CMC-the number of chainbreaks and the percentage of glucose released have been also measured. Average length ofsubstituted and unsubstituted chain segments are calculated simultaneously. Through thestudy of static and dynamic procedures of enzymatic degradation, the method to charac-terize the distribution of substituents of CMC along the chain has been improved.
基金This work was supported by the National Natural Science Foundation of China.
文摘Three series of polythiophenes containing fluoroalkoxy and fluoroether substituents were prepared by electrochemical polymerization. The effect of substituents with fluoroalkoxy or ether functional groups on the electrochemical polymerization of thiophene monomers and properties of the obtained polymers were analyzed. The introduction of a fluoroether functional group at the 3-position of the thiophene ring leads to an increase of the oxidation potential of the monomer and to a decrease of the conductivity of the resulting polymers, even with the use of a CH2 group as spacer. Conversely, the presence of an oxygen atom directly at the 3-position of the thiophene ring, which offsets the negative withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conducting polythiophenes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874241,11847224,and 11804195)the Shandong Province Higher Educational Science and Technology Program,China(Grant No.J15LJ03)+1 种基金the Taishan Scholar Project of Shandong Province,China,China Post-Doctoral Foundation(Grant No.2018M630796)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2018BA034)
文摘The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on proton transfer.The mechanism of hydrogen bond enhancement is qualitatively elucidated by comparing the infrared spectra, the reduced density gradient, and the frontier molecular orbitals.The calculated electronic spectra are consistent with the experimental results.To quantify the proton transfer, the potential energy curves(PECs) of the four derivatives in S0 and S1 states are scanned.It is concluded that the ability of proton transfer follows the order: FM > BFM > BFBC > CCM.
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Three ethylene-vinyl alcohol copolymers were studied by means of the substituent chemical shift (SCS) method. The SCS parameters of hydroxy (-OH) in two different solvents were obtained: in deuterium oxide/phenol (20/80 W/W ) the parameters are S_1 = 42.77±0.08ppm, S_2 = 7.15±0.06 ppm, S_3 (s)= -4.08±0.02ppm, S_3 (t) =-3.09±0.20ppm,S_4 = 0.48±0.03ppm, S_5 = 0.26±0.05ppm. In o-dichloro-benzen-d_4 S_1(s)=44.79±0.61ppm, S_2=7.40±0.00ppm, S_3(s)=-4.51±0.17ppm, S_3(t)=-3.13 ±0.00 ppm, S_4 =0.63±0.04ppm, S_5=0.36±0.00ppm.Simultaneously the ^(13)CNMR spectra of EVA copolymers were assigned by using the SCS parameters obtained.
