Density(p)and speed of sound(u)findings on the binary liquid mixtures consisting of cyclohexanol(CH—OH),with aniline(A),ortho-chloroaniline(o-CA),and meta-chloroaniline(m-CA)were gathered at the various temperatures ...Density(p)and speed of sound(u)findings on the binary liquid mixtures consisting of cyclohexanol(CH—OH),with aniline(A),ortho-chloroaniline(o-CA),and meta-chloroaniline(m-CA)were gathered at the various temperatures spanning the entire concentration range.303.15,308.15,313.15 and 318.15 K at atmospheric pressure.The information measured there was utilized to compute excess molar volume(V_(m)^(E)),excess isentropic compressibility(K_(S)^(E)),excess of speed of sound(u^(F)),excess intermolecular free length(L_(f)^(F))and excess acoustic impedance(Z^(F)).Further,the partial molar volumes(^(-)V°_(m,1).^(-)V°_(φ,1).^(-)V°_(m,2).^(-)V°_(φ,2)),partial molar compressibilities(K°_(m,1).^(-)K°_(φ,1).^(-)K°_(m,2).^(-)K°_(φ,2))and their excess values(^(-)V^(E)_(m,1).^(-)V^(°E)_(φ,1).^(-)V^(E)_(m,2).^(-)V^(°E)_(φ,2)),(K^(E)_(m,1).^(-)K^(°E)_(φ,1).^(-)K^(E)_(m,2).^(-)K^(°E)_(φ,2))were also computed to perceive more information on molecular interaction and structural effects in these mixtures.Applying the theory of Prigogine-Flory-Patterson(PFP)as a framework,the V_(m)^(E)data of the current liquid mixtures were examined.The analysis of the experimental data took into consideration the interactions that occur between the individual molecules that make up liquid mixtures.By using density functional theory DFT(B3LYP)of 6-31++G(d,P)to analyze the geometries,bond characteristics,interaction energies,and hydrogen bonded complexes in organic solvent phase,quantum chemical calculations were able to further confirm the hydrogen bonding that predominates between cyclohexanol with aniline and chlorosubstituted anilines.展开更多
The condensation of benzaldehyde, urea, and ethyl acetoacetate according to the procedure described by Biginelli was investigated at the B3LYP/6-31G（d）, B3LYP/6-31 ＋G（d,p）, and B3LYP/6-311＋G（3df,2p）//B3LYP/6-3...The condensation of benzaldehyde, urea, and ethyl acetoacetate according to the procedure described by Biginelli was investigated at the B3LYP/6-31G（d）, B3LYP/6-31 ＋G（d,p）, and B3LYP/6-311＋G（3df,2p）//B3LYP/6-31＋G（d,p） levels to explore the reaction mechanism. According to the mechanism proposed by Kappe, structures of five intermediates were optimized and four transition states were found. The calculation results proved that the mechanism proposed by Kappe is right.展开更多
In molybdenum chemistry,the oxidative addition of o-quinone or 1,2-dicarbonyl compounds to molybdenum has been widely used in Mo-catalyzed C—C bond construction.The carbonyl oxidative addition to Mo(0)or Mo(Ⅱ)is the...In molybdenum chemistry,the oxidative addition of o-quinone or 1,2-dicarbonyl compounds to molybdenum has been widely used in Mo-catalyzed C—C bond construction.The carbonyl oxidative addition to Mo(0)or Mo(Ⅱ)is the critical elementary reaction of molybdenum catalysis.However,the relevant density functional theory(DFT)studies are relatively scarce,especially regarding the rational selection of functionals.In this work,14 functionals were employed to investigate the Mo-catalyzed carbonyl oxidative addition step.A benchmark study was carried out to evaluate their performance in structure optimization and energy calculation.Analyses of mean absolute error(MAE)and mean squared error(MSE)indicated that the B3LYP-D3(BJ),TPSSh,and ωB97X-D functionals exhibited superior performance in structure optimization.Using the DLPNO-CCSD(T)functional as the reference,the M06,M06-L,and MN15-L functionals exhibited good performance for energy calculation based on the structures optimized using the B3LYP-D3(BJ)functional.In particular,MN15-L provided the best performance with the smallest MAE and MSE.展开更多
As a contribution to the development of new ruthenium complexes with pharmacologically interesting properties,two new mononuclear ruthenium(II)complexes of the general formula[Ru(H-Nap-sbdtc)Cl-(CO)(EPh_(3))_(2)](1&am...As a contribution to the development of new ruthenium complexes with pharmacologically interesting properties,two new mononuclear ruthenium(II)complexes of the general formula[Ru(H-Nap-sbdtc)Cl-(CO)(EPh_(3))_(2)](1&2)[H-(Nap-sbdtc)=2-hydroxy-1-naphthaldehyde-S-benzyl-dithiocarbazate;E=P or As]were synthesized.The new ruthenium(II)carbonyl complexes are remarkably stable and were obtained in good yields.Their identities have been established by satisfactory elemental analyses and various spectroscopic techniques(IR,UV/visible,(^(1)H,^(13)C,and ^(31)P)NMR,and ESI-MS).For a better definition,the molecular structure of complexes 1 and 2 has been determined by X-ray crystallography,which confirms the coordination mode of the ligand and reveals a distorted octahedral geometry around the ruthenium ion.The molecular structure of complexes 1 and 2 has been optimized by DFT calculations.展开更多
Li_(3)V_(2)(PO_(4))_(3)(LVP)coated with N and S co-doped carbon(NSC)was investigated by DFT calculation,suggesting that NSC significantly enhances electronic conductivity and lowers the energy barrier to Li+migration ...Li_(3)V_(2)(PO_(4))_(3)(LVP)coated with N and S co-doped carbon(NSC)was investigated by DFT calculation,suggesting that NSC significantly enhances electronic conductivity and lowers the energy barrier to Li+migration in comparison to LVP-embedded in pristine carbon.To experimentally confirm the theoretical prediction,three types of LVP particle embedded in N and S co-doped porous carbon(LVP@NSC)materials with various nitrogen and sulfur molar ratios(N:S=1:1,1:2 and 2:1)were prepared by a facile freeze-drying-assisted wet chemical route associated with a post-annealing process.When used as a cathode for a lithium-ion battery(LIB),the designed LVP@NSC with N:S=1:2 exhibits outstanding high rate capacities of 124.4 and 107.85 mA h g^(−1),respectively,at 2 and 20 C in a voltage window of 3.0–4.3 V,and an ultralong cycling stability of 500 times at 20 C while retaining a reversible capacity of 100.22 mA h g^(−1),possibly due to its smallest charge transfer resistance and highest Li^(+) migration coefficient,which is in good agreement with the theoretical prediction.This work not only reveals the critical role of an interaction mechanism between NSC and LVP,but also offers great potential for high-energy density LIB applications.展开更多
Converting CO2 to carbon-containing fuels is an effective approach to relieving energy shortages.Carbon quantum dots(CQDs) have shown distinct properties and attracted tremendous interest in CO2 reduction.Herein,we re...Converting CO2 to carbon-containing fuels is an effective approach to relieving energy shortages.Carbon quantum dots(CQDs) have shown distinct properties and attracted tremendous interest in CO2 reduction.Herein,we report a joint experimental-computational mechanistic study of photoreduction CO2 to CO on the model catalyst 9-hydroxyphenal-1-one(HPHN) CQDs with known structure.Our theoretical calculations reveal that the rate-determining step is COOH·formation,which is closely related to the proton and electron transfer induced by hydrogen bonding in the excited state.According to the calculated volcano plot,the solution we proposed is addition Zn^(2+) ions.The active center changed from the hydroxyl oxygen atom to the Zn atom and the barrier of the COOH·formation step is noticeably decreased when Zn^(2+) ions are added.It is further confirmed by the experimental data that the activity of CO2 reduction increases 2.9 times when Zn^(2+) ions are added.展开更多
Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-terie...Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co salts.The Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)moiety.Co-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 V.Notably,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/C.According to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR process.This study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.展开更多
The transportation of the proton,the smallest ion in nature,is rudimentary in chemical and biological reactions[1,2],such as photosynthesis[3],enzyme catalysis[4],and Brensted acid/base reactions[5],and currently even...The transportation of the proton,the smallest ion in nature,is rudimentary in chemical and biological reactions[1,2],such as photosynthesis[3],enzyme catalysis[4],and Brensted acid/base reactions[5],and currently even imperative in some devices,namely proton exchange membrane fuel cells(PEMFCs)[6,7].The processes of these elementary reactions,like proton transfer,appear to be astonishingly analogous.展开更多
Combined theoretical and experimental studies have explained the mechanism of Pd-catalyzed δ-C(sp^(3))-H arylation of primary amines. Instead of the monomeric Pd mechanism, our research unveils that all steps includi...Combined theoretical and experimental studies have explained the mechanism of Pd-catalyzed δ-C(sp^(3))-H arylation of primary amines. Instead of the monomeric Pd mechanism, our research unveils that all steps including C–H activation, oxidative addition, and reductive elimination take place via the heterodimeric Pd–Ag intermediates and transition states. Experimentally, the active heterodimeric Pd–Ag species were detected by mass spectrometry, which further confirms the proposed heterodimeric mechanism. Insight gained through this study reveals the synergistic manner of palladium catalysis and silver(Ⅰ)additives in native NH;-directed C–H activation and C–C coupling reactions.展开更多
Synthesis and structure of Ti complex having a pair of chelating aminotropone[O-N]ligand have been reported.Calculations of density functional theory（DFT） studies suggest that bis（aminotropone） Ti complex,when act...Synthesis and structure of Ti complex having a pair of chelating aminotropone[O-N]ligand have been reported.Calculations of density functional theory（DFT） studies suggest that bis（aminotropone） Ti complex,when activated with methylaluminoxane （MAO）,have high potential for the polymerization of olefinic monomers.These theoretical studies also show that the active species derived from bis（aminotropone） Ti catalyst normally possess higher electrophilicity nature compared with those produced using bis（phenoxyimine） Ti complexes（Ti-FI catalysts） which are known as high performance olefin polymerization catalysts. Bis（aminotropone） Ti catalyst generates a catalytically active species that has higher electrophilicity than a Ti-FI catalysts.展开更多
Novel polymeric Cu<sup>2+</sup> complexes derived from the reaction of cyanoacetylhydrazine (<strong>CAH</strong>;<strong>L</strong>) with CuCl<sub>2</sub>•2H<sub>...Novel polymeric Cu<sup>2+</sup> complexes derived from the reaction of cyanoacetylhydrazine (<strong>CAH</strong>;<strong>L</strong>) with CuCl<sub>2</sub>•2H<sub>2</sub>O in different solvents were synthesized and characterized. The isolated solid polymeric complexes were investigated using modern conventional physicochemical and spectral (IR, <sup>1</sup>H-NMR, UV-Vis. ESR, Raman), magnetic and thermal studies. The results revealed that <strong>CAH</strong> behaves in different ways towards the coordination of the Cu<sup>2+</sup> ion. The promotion of solvents to the cyano group was discussed on the basis of the solvent and the Cu<sup>2+</sup> ion used. Magnetic and spectral studies suggest octahedral geometry is proposed for the Cu<sup>2+</sup> complexes. EPR studies indicate the existence of polymeric complexes depending on the results of <i>g</i>-values. The results suggest that the number of copper atoms ranges from three to twelve atoms. The molecular modeling is drawn and some chemical characteristics are calculated such as chemical reactivity and energy components are investigated between the different types of the ligands.展开更多
Photoredox-catalyzed hydrodifluoromethylation of alkenes has become an effective method to introduce difluoromethyl group into organic molecules.As the reported methods involve either photocatalysts or superstoichiome...Photoredox-catalyzed hydrodifluoromethylation of alkenes has become an effective method to introduce difluoromethyl group into organic molecules.As the reported methods involve either photocatalysts or superstoichiometric amounts of additives,we herein describe a simple alternative without using photocatalyst or additive for the hydrodifluoromethylation of alkenes,through photoactivation of difluoromethyltriphenylphosphonium iodide salt.Mechanistic studies shed light on how the transformation takes place.展开更多
We report the Lewis acid catalysis of aryldiazonium salts,and their Lewis acidity applications in photogeneration of aryl radicals under additive-,photocatalyst-and transition metal-free conditions.In this visible lig...We report the Lewis acid catalysis of aryldiazonium salts,and their Lewis acidity applications in photogeneration of aryl radicals under additive-,photocatalyst-and transition metal-free conditions.In this visible light-mediated transformation,the Lewis acidic character of aryldiazonium salts enables access to the photoactive charge transfer complex with dichalcogenides.The usefulness and versatility of this new protocol are demonstrated through the chalcogenation of a variety of aryldiazonium salts.展开更多
The structure of 3-acetyl-8-methoxy-coumarin （AMC） was verified by single-crystal X-ray crystallography. It crystallizes in monoclinic, space group C2/c with a=15.073（3）, b=13.068（3）, c=11.549（2）, β=119.92（3...The structure of 3-acetyl-8-methoxy-coumarin （AMC） was verified by single-crystal X-ray crystallography. It crystallizes in monoclinic, space group C2/c with a=15.073（3）, b=13.068（3）, c=11.549（2）, β=119.92（3）o, V=1971.7（7）3 , Z=8, F（000）=912, D c=1.470 Mg/m3 , Mr=218.20, μ=0.111 mm-1 , the final R=0.0340 and wR=0.0968 for 1446 observed reflections with I 〉 2σ（I）. The UV-vis absorption and fluorescence of AMC were discussed. The compound exhibits strong blue emission under ultraviolet light excitation. The molecular structure of AMC was optimized using density functional theory （DFT） at the B3LYP/6-31G（d） level, showing that the optimized geometer parameters are in good agreement with the experiment data. In addition, the HOMO and LUMO levels of AMC were deduced.展开更多
A feasible synthesis route is devised for realizing direct carboxylation of thiophene and CO_(2) in a relatively mild solvent-free carboxylate-assisted carbonate(semi)molten medium.The effects of reaction factors on p...A feasible synthesis route is devised for realizing direct carboxylation of thiophene and CO_(2) in a relatively mild solvent-free carboxylate-assisted carbonate(semi)molten medium.The effects of reaction factors on product yield are investigated,and the phase behavior analysis of the reaction medium is detected through the thermal characterization techniques.Product yield varies with the alternative carboxylate co-salts,which is attributed to the difference in deprotonation capacity caused by the base effect within the system.Besides,the detailed mechanism of this carbonate-promoted carboxylation reaction is studied,including two consecutive steps of the formation of carbanion through breaking the C-H bond(s)via the carbonate and the nucleophile attacking the weak electrophile CO_(2) to form C-C bond(s).The activation energy barrier in C-H activation step is higher than the following CO_(2) insertion step whether for the formation of the mono-and/or di-carboxylate,which is in good agreement with that of kinetic isotope effect(KIE)experiments,indicating that the C-H deprotonation is slow and the forming presumed carbanion reacts rapidly with CO_(2).Both the activation energy barriers in deprotonation steps are the minimal for the cesium cluster system since there have the weak the cesium Cs-heteroatom S(thiophene)and Cs-the broken proton interactions compared to the K2CO3 system,which is likely to enhance the acidity of C-H bond,lowering the C-H activation barrier.Besides,these mechanistic insights are further assessed by investigating base and C-H substrate effects via replacing Cs2CO3 with K2CO3 and furoate(la)with thiophene monocarboxylate(1b)or benzoate(1c).展开更多
Reaction of zinc acetate, potassium thiocyanate and the ligand 3-ampy gave the discrete tetrahedral complex [Zn(NCS)<sub>2</sub>(3-ampy)<sub>2</sub>] in which 3-ampy chelates in a monodentate f...Reaction of zinc acetate, potassium thiocyanate and the ligand 3-ampy gave the discrete tetrahedral complex [Zn(NCS)<sub>2</sub>(3-ampy)<sub>2</sub>] in which 3-ampy chelates in a monodentate fashion through its pyridine-N atom. It was characterized by single crystal X-ray diffraction, infrared, and elemental analysis. Density Functional Theory calculations were performed in order to gain insights into the role of weak molecular interactions in the complex that influence the self-assembly process and crystal packing. X---H (X = H, C, N and S) inter-actions. S-H interactions (30.2%) were found to be the main interactions that hold the molecules in the crystal structure. Furthermore, the thermolysis of the complex was studied in order to evaluate whether it was suitable as a precursor for zinc sulphide.展开更多
Stereoselective chemical glycosylation reactions are pivotal for preparing manifold biologically and medically important compounds,while mechanisms of chemical glycosylation reactions remain obscure and largely specul...Stereoselective chemical glycosylation reactions are pivotal for preparing manifold biologically and medically important compounds,while mechanisms of chemical glycosylation reactions remain obscure and largely speculative.Herein,we performed DFT calculations to delve into the multifaceted mechanistic details of glycosylation reactions,including the equilibria among reactive glycosyl triflate intermediates in solution,the stereoselectivity imparting protecting groups,solvent effects,base,and the anomeric effect.Our results provided theoretical corroboration to 2-OAc neighbouring group participation(NGP),the arming/disarming effect,the coordination theory of solvent effect on glycosylation stereochemistry,and the influence of solvent polarity on the reaction kinetics spanning the S_(N)1-S_(N)2 continuum.For the first time,the existence of putative contact-ion-pairs(CIP)of glycosyl oxocarbenium and triflate anion in organic solutions was theoretically confirmed with the identification of multiple ground state structures employing an implicit Solvation Model based on Density(SMD).Kinetics of nucleophilic attack of model glucosyl triflates by simple alcohol acceptors ethanol(EtOH)and trifluoroethanol(TFE),complexed with 2,4,6-tri-tert-butylpyrimidine(TTBP)were explored,revealing the essential role of the close accompanying base for rendering glycosidic bond formation thermodynamically favourable.Our work deepens the comprehension of the glycosylation mechanism,paving the way for the rational design and future advancement of efficient and environmentally friendly stereoselective glycosylation reactions.展开更多
The phospha-Wittig(phosphanylphosphinidene titanium(IV)complex)and phospha-Peterson(lithiated diphosphane)reactions were used to obtain phosphanylphosphaalkenes with the general formula XYCvP-PtBu_(2)(X=alkyl or aryl ...The phospha-Wittig(phosphanylphosphinidene titanium(IV)complex)and phospha-Peterson(lithiated diphosphane)reactions were used to obtain phosphanylphosphaalkenes with the general formula XYCvP-PtBu_(2)(X=alkyl or aryl group or H;Y=alkyl or aryl group).Therefore,two series of reactions with different ketones and aldehydes were performed.Examination revealed that the two methods are complementary.For smaller carbonyl compounds,the phospha-Wittig reaction was shown to be a much better method,while for larger substituents(mainly aromatic),the phospha-Peterson reaction was shown to be a reliable method.These studies led to,among other things,the isolation of seven phosphanylphosphaalkenes in crystalline form after the phospha-Peterson reaction:(Ph)_(2)CvP-PtBu_(2)(3a),Z-(Ph)(4-CN-Ph)CvP-PtBu_(2)(3c),(4-CN-Ph)_(2)CvP-PtBu_(2)(3d),(4-MeO-Ph)_(2)CvP-PtBu_(2)(3e),E-tBu(Ph)CvP-PtBu_(2)(3f),E-{(Me)_(2)N-Ph}(H)CvP-PtBu_(2)(4d)and E-PhPh(H)CvP-PtBu_(2)(4e).The corresponding compounds were obtained in high yields under mild conditions,and more importantly,these new species are relatively air-and absolutely moisture-stable,especially those originating from aldehydes.In addition,a comprehensive DFT study helped us to establish not only the key factors crucial for effective phospha-Wittig-based synthesis of CvP-P species but also the consecutive steps along the reaction path leading to the formation of these compounds.展开更多
We report the synthesis,characterization and DFT studies of a transition-metal-encapsulated superatom compound,[K(2,2,2-crypt)]3[Au@Pb_(12)]·2py,which adopts a distorted symmetry instead of the icosahedral struct...We report the synthesis,characterization and DFT studies of a transition-metal-encapsulated superatom compound,[K(2,2,2-crypt)]3[Au@Pb_(12)]·2py,which adopts a distorted symmetry instead of the icosahedral structure due to the second-order Jahn-Teller effect.DFT computations revealed its chemical bonding nature and aromatic character,and assigned the formal electronic structure as[Au^(-)@Pb_(12)^(2-)]^(3-).展开更多
Aryl-substituted sodium 1,2-diphosphacyclopentadienides Na(P_(2)C_(3)R_(3))(R=Ph,4-Me-C_(6)H_(4),4-Cl-C_(6)H_(4))(1a-c)react with[FeCp(η^(6)-C_(6)H_(5)CH_(3))][PF6]to give heteroleptic 3,4,5-triaryl-1,2-diphosphaferr...Aryl-substituted sodium 1,2-diphosphacyclopentadienides Na(P_(2)C_(3)R_(3))(R=Ph,4-Me-C_(6)H_(4),4-Cl-C_(6)H_(4))(1a-c)react with[FeCp(η^(6)-C_(6)H_(5)CH_(3))][PF6]to give heteroleptic 3,4,5-triaryl-1,2-diphosphaferrocenes[FeCp(η^(5)-P_(2)C_(3)R_(3))](2a-c)in 71-78%yield.The structures of 2a-c were confirmed by NMR,UV-Vis spectroscopy and X-ray structure analysis,and supported by DFT calculations.Electrochemical studies of 2a-c in CH3CN demonstrate a pronounced reversible one-electron oxidation,while in the solid state,all 3,4,5-triaryl-1,2-diphosphaferrocenes show fully reversible oxidation and reduction waves,which indicates the stability of the oxidized form.Regardless of the substituent(R=Ph,4-Me-C_(6)H_(4),4-Cl-C_(6)H_(4)),the studied 1,2-diphosphaferrocenes have similar oxidation and reduction potentials.展开更多
文摘Density(p)and speed of sound(u)findings on the binary liquid mixtures consisting of cyclohexanol(CH—OH),with aniline(A),ortho-chloroaniline(o-CA),and meta-chloroaniline(m-CA)were gathered at the various temperatures spanning the entire concentration range.303.15,308.15,313.15 and 318.15 K at atmospheric pressure.The information measured there was utilized to compute excess molar volume(V_(m)^(E)),excess isentropic compressibility(K_(S)^(E)),excess of speed of sound(u^(F)),excess intermolecular free length(L_(f)^(F))and excess acoustic impedance(Z^(F)).Further,the partial molar volumes(^(-)V°_(m,1).^(-)V°_(φ,1).^(-)V°_(m,2).^(-)V°_(φ,2)),partial molar compressibilities(K°_(m,1).^(-)K°_(φ,1).^(-)K°_(m,2).^(-)K°_(φ,2))and their excess values(^(-)V^(E)_(m,1).^(-)V^(°E)_(φ,1).^(-)V^(E)_(m,2).^(-)V^(°E)_(φ,2)),(K^(E)_(m,1).^(-)K^(°E)_(φ,1).^(-)K^(E)_(m,2).^(-)K^(°E)_(φ,2))were also computed to perceive more information on molecular interaction and structural effects in these mixtures.Applying the theory of Prigogine-Flory-Patterson(PFP)as a framework,the V_(m)^(E)data of the current liquid mixtures were examined.The analysis of the experimental data took into consideration the interactions that occur between the individual molecules that make up liquid mixtures.By using density functional theory DFT(B3LYP)of 6-31++G(d,P)to analyze the geometries,bond characteristics,interaction energies,and hydrogen bonded complexes in organic solvent phase,quantum chemical calculations were able to further confirm the hydrogen bonding that predominates between cyclohexanol with aniline and chlorosubstituted anilines.
文摘The condensation of benzaldehyde, urea, and ethyl acetoacetate according to the procedure described by Biginelli was investigated at the B3LYP/6-31G（d）, B3LYP/6-31 ＋G（d,p）, and B3LYP/6-311＋G（3df,2p）//B3LYP/6-31＋G（d,p） levels to explore the reaction mechanism. According to the mechanism proposed by Kappe, structures of five intermediates were optimized and four transition states were found. The calculation results proved that the mechanism proposed by Kappe is right.
基金Project supported by the Fundamental Research Funds for the Central Universities(No.2042025kf0052)。
文摘In molybdenum chemistry,the oxidative addition of o-quinone or 1,2-dicarbonyl compounds to molybdenum has been widely used in Mo-catalyzed C—C bond construction.The carbonyl oxidative addition to Mo(0)or Mo(Ⅱ)is the critical elementary reaction of molybdenum catalysis.However,the relevant density functional theory(DFT)studies are relatively scarce,especially regarding the rational selection of functionals.In this work,14 functionals were employed to investigate the Mo-catalyzed carbonyl oxidative addition step.A benchmark study was carried out to evaluate their performance in structure optimization and energy calculation.Analyses of mean absolute error(MAE)and mean squared error(MSE)indicated that the B3LYP-D3(BJ),TPSSh,and ωB97X-D functionals exhibited superior performance in structure optimization.Using the DLPNO-CCSD(T)functional as the reference,the M06,M06-L,and MN15-L functionals exhibited good performance for energy calculation based on the structures optimized using the B3LYP-D3(BJ)functional.In particular,MN15-L provided the best performance with the smallest MAE and MSE.
基金The authors Dr P.V.and P.V.gratefully acknowledge UGC[F.No.40-66/2011(SR)]for financial supportThe author(R.N.)is thankful to DST for financial assistance(project no.SR/FT/CS-95/2010).
文摘As a contribution to the development of new ruthenium complexes with pharmacologically interesting properties,two new mononuclear ruthenium(II)complexes of the general formula[Ru(H-Nap-sbdtc)Cl-(CO)(EPh_(3))_(2)](1&2)[H-(Nap-sbdtc)=2-hydroxy-1-naphthaldehyde-S-benzyl-dithiocarbazate;E=P or As]were synthesized.The new ruthenium(II)carbonyl complexes are remarkably stable and were obtained in good yields.Their identities have been established by satisfactory elemental analyses and various spectroscopic techniques(IR,UV/visible,(^(1)H,^(13)C,and ^(31)P)NMR,and ESI-MS).For a better definition,the molecular structure of complexes 1 and 2 has been determined by X-ray crystallography,which confirms the coordination mode of the ligand and reveals a distorted octahedral geometry around the ruthenium ion.The molecular structure of complexes 1 and 2 has been optimized by DFT calculations.
基金financially supported by the financial support from the Natural Science Foundation of Hunan Province of China(2021JJ30538)Scientific Research Foundation of Hunan Provincial Education Department(23C0301)Key Projects of Applied Characteristic Disciplines of“Double First-Class”in Materials Science&Engineering of Huaihua University(19CKA006).
文摘Li_(3)V_(2)(PO_(4))_(3)(LVP)coated with N and S co-doped carbon(NSC)was investigated by DFT calculation,suggesting that NSC significantly enhances electronic conductivity and lowers the energy barrier to Li+migration in comparison to LVP-embedded in pristine carbon.To experimentally confirm the theoretical prediction,three types of LVP particle embedded in N and S co-doped porous carbon(LVP@NSC)materials with various nitrogen and sulfur molar ratios(N:S=1:1,1:2 and 2:1)were prepared by a facile freeze-drying-assisted wet chemical route associated with a post-annealing process.When used as a cathode for a lithium-ion battery(LIB),the designed LVP@NSC with N:S=1:2 exhibits outstanding high rate capacities of 124.4 and 107.85 mA h g^(−1),respectively,at 2 and 20 C in a voltage window of 3.0–4.3 V,and an ultralong cycling stability of 500 times at 20 C while retaining a reversible capacity of 100.22 mA h g^(−1),possibly due to its smallest charge transfer resistance and highest Li^(+) migration coefficient,which is in good agreement with the theoretical prediction.This work not only reveals the critical role of an interaction mechanism between NSC and LVP,but also offers great potential for high-energy density LIB applications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 21677029, 21606040)the Fundamental Research Funds for the Central Universities (DUT18LK26)。
文摘Converting CO2 to carbon-containing fuels is an effective approach to relieving energy shortages.Carbon quantum dots(CQDs) have shown distinct properties and attracted tremendous interest in CO2 reduction.Herein,we report a joint experimental-computational mechanistic study of photoreduction CO2 to CO on the model catalyst 9-hydroxyphenal-1-one(HPHN) CQDs with known structure.Our theoretical calculations reveal that the rate-determining step is COOH·formation,which is closely related to the proton and electron transfer induced by hydrogen bonding in the excited state.According to the calculated volcano plot,the solution we proposed is addition Zn^(2+) ions.The active center changed from the hydroxyl oxygen atom to the Zn atom and the barrier of the COOH·formation step is noticeably decreased when Zn^(2+) ions are added.It is further confirmed by the experimental data that the activity of CO2 reduction increases 2.9 times when Zn^(2+) ions are added.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.22078028 and 21978026).
文摘Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co salts.The Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)moiety.Co-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 V.Notably,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/C.According to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR process.This study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.
基金Financial supports from Scientific Research Projects in Colleges and Universities in Hebei Province,China(ZD2020409 and ZD2019307)the National Natural Science Foundation of China(21301048)+1 种基金the Fundamental Research Funds for the Central Universities(3142018010 and 3142019013)the Natural Science Foundation of Hebei Province of China(E2019508214)。
文摘The transportation of the proton,the smallest ion in nature,is rudimentary in chemical and biological reactions[1,2],such as photosynthesis[3],enzyme catalysis[4],and Brensted acid/base reactions[5],and currently even imperative in some devices,namely proton exchange membrane fuel cells(PEMFCs)[6,7].The processes of these elementary reactions,like proton transfer,appear to be astonishingly analogous.
基金supported by the Tianjin University and the National Natural Science Foundation of China (Nos. 22073067 and 21673156)。
文摘Combined theoretical and experimental studies have explained the mechanism of Pd-catalyzed δ-C(sp^(3))-H arylation of primary amines. Instead of the monomeric Pd mechanism, our research unveils that all steps including C–H activation, oxidative addition, and reductive elimination take place via the heterodimeric Pd–Ag intermediates and transition states. Experimentally, the active heterodimeric Pd–Ag species were detected by mass spectrometry, which further confirms the proposed heterodimeric mechanism. Insight gained through this study reveals the synergistic manner of palladium catalysis and silver(Ⅰ)additives in native NH;-directed C–H activation and C–C coupling reactions.
文摘Synthesis and structure of Ti complex having a pair of chelating aminotropone[O-N]ligand have been reported.Calculations of density functional theory（DFT） studies suggest that bis（aminotropone） Ti complex,when activated with methylaluminoxane （MAO）,have high potential for the polymerization of olefinic monomers.These theoretical studies also show that the active species derived from bis（aminotropone） Ti catalyst normally possess higher electrophilicity nature compared with those produced using bis（phenoxyimine） Ti complexes（Ti-FI catalysts） which are known as high performance olefin polymerization catalysts. Bis（aminotropone） Ti catalyst generates a catalytically active species that has higher electrophilicity than a Ti-FI catalysts.
文摘Novel polymeric Cu<sup>2+</sup> complexes derived from the reaction of cyanoacetylhydrazine (<strong>CAH</strong>;<strong>L</strong>) with CuCl<sub>2</sub>•2H<sub>2</sub>O in different solvents were synthesized and characterized. The isolated solid polymeric complexes were investigated using modern conventional physicochemical and spectral (IR, <sup>1</sup>H-NMR, UV-Vis. ESR, Raman), magnetic and thermal studies. The results revealed that <strong>CAH</strong> behaves in different ways towards the coordination of the Cu<sup>2+</sup> ion. The promotion of solvents to the cyano group was discussed on the basis of the solvent and the Cu<sup>2+</sup> ion used. Magnetic and spectral studies suggest octahedral geometry is proposed for the Cu<sup>2+</sup> complexes. EPR studies indicate the existence of polymeric complexes depending on the results of <i>g</i>-values. The results suggest that the number of copper atoms ranges from three to twelve atoms. The molecular modeling is drawn and some chemical characteristics are calculated such as chemical reactivity and energy components are investigated between the different types of the ligands.
基金financial support from the National Natural Science Foundation of China(Nos.22001248 and 22173103)the Fundamental Research Funds for the Central Universities and the University of the Chinese Academy of Sciences。
文摘Photoredox-catalyzed hydrodifluoromethylation of alkenes has become an effective method to introduce difluoromethyl group into organic molecules.As the reported methods involve either photocatalysts or superstoichiometric amounts of additives,we herein describe a simple alternative without using photocatalyst or additive for the hydrodifluoromethylation of alkenes,through photoactivation of difluoromethyltriphenylphosphonium iodide salt.Mechanistic studies shed light on how the transformation takes place.
基金financial support from the National Natural Science Foundation of China(Nos.22001248 and 22173103)the Fundamental Research Funds for the Central Universities and the University of the Chinese Academy of Sciences。
文摘We report the Lewis acid catalysis of aryldiazonium salts,and their Lewis acidity applications in photogeneration of aryl radicals under additive-,photocatalyst-and transition metal-free conditions.In this visible light-mediated transformation,the Lewis acidic character of aryldiazonium salts enables access to the photoactive charge transfer complex with dichalcogenides.The usefulness and versatility of this new protocol are demonstrated through the chalcogenation of a variety of aryldiazonium salts.
基金financially supported by National Natural Science Foundation of China (21176180)
文摘The structure of 3-acetyl-8-methoxy-coumarin （AMC） was verified by single-crystal X-ray crystallography. It crystallizes in monoclinic, space group C2/c with a=15.073（3）, b=13.068（3）, c=11.549（2）, β=119.92（3）o, V=1971.7（7）3 , Z=8, F（000）=912, D c=1.470 Mg/m3 , Mr=218.20, μ=0.111 mm-1 , the final R=0.0340 and wR=0.0968 for 1446 observed reflections with I 〉 2σ（I）. The UV-vis absorption and fluorescence of AMC were discussed. The compound exhibits strong blue emission under ultraviolet light excitation. The molecular structure of AMC was optimized using density functional theory （DFT） at the B3LYP/6-31G（d） level, showing that the optimized geometer parameters are in good agreement with the experiment data. In addition, the HOMO and LUMO levels of AMC were deduced.
文摘A feasible synthesis route is devised for realizing direct carboxylation of thiophene and CO_(2) in a relatively mild solvent-free carboxylate-assisted carbonate(semi)molten medium.The effects of reaction factors on product yield are investigated,and the phase behavior analysis of the reaction medium is detected through the thermal characterization techniques.Product yield varies with the alternative carboxylate co-salts,which is attributed to the difference in deprotonation capacity caused by the base effect within the system.Besides,the detailed mechanism of this carbonate-promoted carboxylation reaction is studied,including two consecutive steps of the formation of carbanion through breaking the C-H bond(s)via the carbonate and the nucleophile attacking the weak electrophile CO_(2) to form C-C bond(s).The activation energy barrier in C-H activation step is higher than the following CO_(2) insertion step whether for the formation of the mono-and/or di-carboxylate,which is in good agreement with that of kinetic isotope effect(KIE)experiments,indicating that the C-H deprotonation is slow and the forming presumed carbanion reacts rapidly with CO_(2).Both the activation energy barriers in deprotonation steps are the minimal for the cesium cluster system since there have the weak the cesium Cs-heteroatom S(thiophene)and Cs-the broken proton interactions compared to the K2CO3 system,which is likely to enhance the acidity of C-H bond,lowering the C-H activation barrier.Besides,these mechanistic insights are further assessed by investigating base and C-H substrate effects via replacing Cs2CO3 with K2CO3 and furoate(la)with thiophene monocarboxylate(1b)or benzoate(1c).
文摘Reaction of zinc acetate, potassium thiocyanate and the ligand 3-ampy gave the discrete tetrahedral complex [Zn(NCS)<sub>2</sub>(3-ampy)<sub>2</sub>] in which 3-ampy chelates in a monodentate fashion through its pyridine-N atom. It was characterized by single crystal X-ray diffraction, infrared, and elemental analysis. Density Functional Theory calculations were performed in order to gain insights into the role of weak molecular interactions in the complex that influence the self-assembly process and crystal packing. X---H (X = H, C, N and S) inter-actions. S-H interactions (30.2%) were found to be the main interactions that hold the molecules in the crystal structure. Furthermore, the thermolysis of the complex was studied in order to evaluate whether it was suitable as a precursor for zinc sulphide.
基金X.W.L.would like to sincerely appreciate Nanyang Technological University(No.MOE Tier 1,RG9/20)Ministry of Education,Singapore(No.MOE-T2EP30120-0007)+1 种基金A*STAR(No.A20E5c0087)for their generous financial supportT.P.L.thanks the Startup Grant(No.21470001)from Henan University of Technology for the financial support.
文摘Stereoselective chemical glycosylation reactions are pivotal for preparing manifold biologically and medically important compounds,while mechanisms of chemical glycosylation reactions remain obscure and largely speculative.Herein,we performed DFT calculations to delve into the multifaceted mechanistic details of glycosylation reactions,including the equilibria among reactive glycosyl triflate intermediates in solution,the stereoselectivity imparting protecting groups,solvent effects,base,and the anomeric effect.Our results provided theoretical corroboration to 2-OAc neighbouring group participation(NGP),the arming/disarming effect,the coordination theory of solvent effect on glycosylation stereochemistry,and the influence of solvent polarity on the reaction kinetics spanning the S_(N)1-S_(N)2 continuum.For the first time,the existence of putative contact-ion-pairs(CIP)of glycosyl oxocarbenium and triflate anion in organic solutions was theoretically confirmed with the identification of multiple ground state structures employing an implicit Solvation Model based on Density(SMD).Kinetics of nucleophilic attack of model glucosyl triflates by simple alcohol acceptors ethanol(EtOH)and trifluoroethanol(TFE),complexed with 2,4,6-tri-tert-butylpyrimidine(TTBP)were explored,revealing the essential role of the close accompanying base for rendering glycosidic bond formation thermodynamically favourable.Our work deepens the comprehension of the glycosylation mechanism,paving the way for the rational design and future advancement of efficient and environmentally friendly stereoselective glycosylation reactions.
基金support for these studies from Gdańsk University of Technology by the DEC-8/2020/IDUB/I.3.3 grant under the Argentum-‘Excellence Initiative-Research University’program is gratefully acknowledged.Ł.P。
文摘The phospha-Wittig(phosphanylphosphinidene titanium(IV)complex)and phospha-Peterson(lithiated diphosphane)reactions were used to obtain phosphanylphosphaalkenes with the general formula XYCvP-PtBu_(2)(X=alkyl or aryl group or H;Y=alkyl or aryl group).Therefore,two series of reactions with different ketones and aldehydes were performed.Examination revealed that the two methods are complementary.For smaller carbonyl compounds,the phospha-Wittig reaction was shown to be a much better method,while for larger substituents(mainly aromatic),the phospha-Peterson reaction was shown to be a reliable method.These studies led to,among other things,the isolation of seven phosphanylphosphaalkenes in crystalline form after the phospha-Peterson reaction:(Ph)_(2)CvP-PtBu_(2)(3a),Z-(Ph)(4-CN-Ph)CvP-PtBu_(2)(3c),(4-CN-Ph)_(2)CvP-PtBu_(2)(3d),(4-MeO-Ph)_(2)CvP-PtBu_(2)(3e),E-tBu(Ph)CvP-PtBu_(2)(3f),E-{(Me)_(2)N-Ph}(H)CvP-PtBu_(2)(4d)and E-PhPh(H)CvP-PtBu_(2)(4e).The corresponding compounds were obtained in high yields under mild conditions,and more importantly,these new species are relatively air-and absolutely moisture-stable,especially those originating from aldehydes.In addition,a comprehensive DFT study helped us to establish not only the key factors crucial for effective phospha-Wittig-based synthesis of CvP-P species but also the consecutive steps along the reaction path leading to the formation of these compounds.
基金support from the National Natural Science Foundation of China(Grant No.51402286 and 21571171)Jilin Province technical innovation talented personal and team foundation(Grant No.20160519004JH).
文摘We report the synthesis,characterization and DFT studies of a transition-metal-encapsulated superatom compound,[K(2,2,2-crypt)]3[Au@Pb_(12)]·2py,which adopts a distorted symmetry instead of the icosahedral structure due to the second-order Jahn-Teller effect.DFT computations revealed its chemical bonding nature and aromatic character,and assigned the formal electronic structure as[Au^(-)@Pb_(12)^(2-)]^(3-).
基金funded by the grant of the Russian Science Foundation,grant number 21-73-10204The authors gratefully acknowledge the Assigned Spectral-Analytical Center of FRC Kazan Scientific Center of RAS(NMR,X-ray,electrochemical measurements)and the scholarship program of the German Academic Exchange Service(DAAD,X-ray structure determination of 2b)Y.S.G.is grateful for the support of the Ministry of Science and Higher Education of the Russia Federation.
文摘Aryl-substituted sodium 1,2-diphosphacyclopentadienides Na(P_(2)C_(3)R_(3))(R=Ph,4-Me-C_(6)H_(4),4-Cl-C_(6)H_(4))(1a-c)react with[FeCp(η^(6)-C_(6)H_(5)CH_(3))][PF6]to give heteroleptic 3,4,5-triaryl-1,2-diphosphaferrocenes[FeCp(η^(5)-P_(2)C_(3)R_(3))](2a-c)in 71-78%yield.The structures of 2a-c were confirmed by NMR,UV-Vis spectroscopy and X-ray structure analysis,and supported by DFT calculations.Electrochemical studies of 2a-c in CH3CN demonstrate a pronounced reversible one-electron oxidation,while in the solid state,all 3,4,5-triaryl-1,2-diphosphaferrocenes show fully reversible oxidation and reduction waves,which indicates the stability of the oxidized form.Regardless of the substituent(R=Ph,4-Me-C_(6)H_(4),4-Cl-C_(6)H_(4)),the studied 1,2-diphosphaferrocenes have similar oxidation and reduction potentials.
