Comparative Studies of Some Novel Cu(II) Polymeric Complexes Derived from Cyanoacetylhydrazine (CAH;L). The Role of Solvents Used on the Structure and Geometry of the Isolated Cu²⁺Complexes

Novel polymeric Cu2+ complexes derived from the reaction of cyanoacetylhydrazine (CAH;L) with CuCl2•2H2O in different solvents were synthesized and characterized. The isolated solid polymeric complexes were investigated using modern conventional physicochemical and spectral (IR, 1H-NMR, UV-Vis. ESR, Raman), magnetic and thermal studies. The results revealed that CAH behaves in different ways towards the coordination of the Cu2+ ion. The promotion of solvents to the cyano group was discussed on the basis of the solvent and the Cu2+ ion used. Magnetic and spectral studies suggest octahedral geometry is proposed for the Cu2+ complexes. EPR studies indicate the existence of polymeric complexes depending on the results of g-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.

Crystal Structure, Photoluminescent, and Theoretical Studies of 3-Acetyl-8-methoxy-coumarin

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.

Crystal Packing Studies, Thermal Properties and Hirshfeld Surface Analysis in the Zn(II) Complex of 3-Aminopyridine with Thiocyanate as Co-Ligand

Reaction of zinc acetate, potassium thiocyanate and the ligand 3-ampy gave the discrete tetrahedral complex [Zn(NCS)2(3-ampy)2] 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.

DFT study on mechanism of the classical Biginelli reaction

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.

Insight into the CO2 photoreduction mechanism over 9-hydroxyphenal-1-one(HPHN) carbon quantum dots

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.

Quasi-Grotthuss mechanism in a nonporous sulphate

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.

Direct carboxylation of thiophene with CO_(2) in the solvent-free carboxylate-carbonate molten medium:Experimental and mechanistic insights

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).

Photocatalytic vinyl radical-mediated multicomponent 1,4-/1,8-carboimination across alkynes and olefins/(hetero)arenes

We developed a highly selective and efficient multicomponent transformation by utilizing alkynes and olefins/(hetero)arenes through photoinduced energy-transfer catalysis.The reaction involves the formation of three distinct chemical bonds,namely C(sp~3)–C(sp~2),C(sp~2)–C(sp~3),and C(sp~3)–N,in a single coordinated manner.The strategy used a vinyl radical-mediated radical relay approach under mild conditions,exhibiting a broad substrate scope(>70 examples),excellent functional-group tolerance,and remarkable regio-and anti-stereoselectivity.Through the utilization of a combination of experimental techniques and density functional theory(DFT),we delved deeper into the mechanistic intricacies of this distinctive system.Results revealed that the selective radical addition to electron-deficient alkynes,rather than olefins,was governed by the inherent reactivity of alkyl radicals.This discovery presented a highly effective approach for the synthesis of stereodefined multisubstituted alkenes.

Fluorescent properties and in vitro studies of new dehydroabietic acid-based diarylamines fluorescent probes

A series of dehydroabietic acid-based diarylamines have been synthesized in order to investigate their fluorescent properties, photostability, cell toxicity and in vitro fluorescence imaging. The geometries as well as their molecular properties were optimized at the B3LYP/6-31G~* level using Gaussian 03. The results indicate that molecular geometry, HOMO and LUMO energies, and energy gaps are important to predict absorption and fluorescent properties. Five of the compounds can be effectively taken up by human cervical carcinoma, human hepatocellular carcinoma SMMC-7721, human gastric cancer SGC-7901 and human lung adenocarcinoma A549 cells and strong blue fluorescent signals are detected in these cells. These compounds are potential candidates for fluorescent probes in biological diagnosis.

Visible-light-induced direct hydrodifluoromethylation of alkenes with difluoromethyltriphenylphosphonium iodide salt

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.

Aryldiazonium salts can serve as nitrogen-based Lewis acid catalysts and their applications in the formation of photoactive charge transfer complexes

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.

Dual ligands relay-promoted transformation of unstrained ketones to polyfluoroarenes and nitriles

C-C bond activation has emerged as a powerful tool for the construction of complex molecules.Herein,we report a dual ligands relay-promoted transformation of unstrained aryl,alkenyl and alkynyl ketones to the corresponding polyfluoroarenes and nitriles via C-C(=O)bond cleavage and subsequent decarboxylative arylation process.Various polyfluoroarene and nitrile products are obtained in one pot under cyanide-free conditions.The protocol features high atom economy,broad functional group tolerance and excellent heterocyclic compatibility.The late-stage functionalization of the drug and natural product demonstrated the synthetic utility of our protocol.Furthermore,the decisive role of the dual ligands was clarified and the mechanistic rationale including theβ-C elimination as the rate-limiting step was supported by detailed density functional theory(DFT)studies.

A pH-universal ORR catalyst with atomic Fe-heteroatom(N,S)sites for high-performance Zn-air batteries

Developing innovative,easy-to-manufacture,and non-Pt-group-metal(non-PGM)electrocatalysts is essential for the highly efficient oxygen reduction reaction(ORR).Herein,we report a self-sacrificing post-synthetic strategy to synthesize highly loaded Fe-isolated single atoms anchored on the hierarchical porous N,S co-doped carbon matrix(Fe-SAs/S,N-C/rGO).The optimized Fe-SAs/S,N-C/rGO exhibits excellent ORR activity in the pH-universal range with half-wave potentials of 0.89,0.80,and 0.60 V in alkaline,acidic,and neutral media,comparable to the commercial Pt/C(0.85,0.81,and 0.64 V,respectively).The homemade liquid Zn-air battery(ZAB)with Fe-SAs/S,N-C/rGO as the cathode catalyst displays an open-circuit voltage(OCV)of~1.61 V,discharging specific capacity of 817.23 mAh·g^(-1),and long-term durability of~1865 cycles,outperforming those of the device with commercial Pt/C+RuO_(2)(1.49 V,657.32 mAh·g^(-1),and~120 cycles,respectively).Intriguingly,the corresponding flexible solidstate ZAB delivers satisfactory OCV,peak power density,foldability,and cycling stability at room temperature,as well as adaptability at a low temperature of -10℃.Besides,density functional theory(DFT)calculation reveals that the atomic FeN_(3)S moieties in Fe-SAs/S,N-C/rGO can cause charge redistribution and lower the binding strength of oxygen-containing intermediates,resulting in accelerated ORR kinetics and optimized catalytic activity.This work provides insights into experimental and theoretical guidance towards non-PGM electrocatalysts for efficient energy conversion.

Synthesis of medium-sized benzo[b]azocines and benzo[b]azonines by photoinduced 8-/9-endo sulfonyl-cyclization

An efficient photochemical radical sulfonyl cyclization of designed dienes to medium-sized benzo[b]azocines and benzo[b]azonines was developed.This chemoselective method provides new highly functionalized eight-and nine-membered N-heterocycles.Radical inhibition experiments,light on/off experiments,and apparent quantum efficiency calculations were used to clarify the radical mechanism.Density functional theory calculations enabled rationalization of the rate-determining step and observed chemoselectivity.Large-scale synthesis and derivatizations via epoxidation and convenient N-Ts deprotection showed the potential utility of this strategy.This photochemical method for synthesizing sulfonylbenzo[b]azocines and sulfonylbenzo[b]azonines with insertion of sulfur dioxide provides new sustainable routes for the synthesis of valuable medium-sized Nheterocycles.

Theoretical insight into the activity and selectivity in palladium/Ming-Phos-catalyzed three-component asymmetric synthesis of gem-diarylmethine silanes

Recently,a three-component coupling reaction for efficient construction of gem-diarylmethine silanes was developed,utilizing a Pd-Ming-Phos catalyst.To explore the underlying mechanism governing this intriguing reaction,we have conducted comprehensive density functional theory(DFT)computations(M06-L/SDD/6-311++G(d,p)/SMD//B3LYP-D3/lanl2dz/6-31G(d,p)).DFT calculations reveal that the oxidative addition of Ar Br to Pd(0)is the rate-determining step,and the carbenation process of Ph CHN_(2)to Pd(Ⅱ)is the enantioselectivity-determining step.Moreover,the Ming-Phos ligand exhibits a self-adaptive nature,allowing it to dynamically adapt its coordination patterns with the metal center in different elementary steps,thereby enhancing the overall reactivity.The enantioselectivity is determined by both the trans effect and the side-arm effect of the ligand.This mechanism nicely explains why TY-Phos with P-tBu_(2)instead of the Ming-Phos with P-Ph2results in poor reactivity and much reduced enantioselectivity.This study not only provides deeper insights into the functioning principles of Sad Phos ligands but also offers valuable guidance for future ligand modifications and optimizations.

Single-atom Co-N_(4)catalytic sites anchored on N-doped ordered mesoporous carbon for excellent Zn-air batteries

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.

Highly efficient bis(aminotropone) Ti catalyst for ethylene polymerization

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.

Theoretical Analysis of the Mechanism of Cationic Pd(Ⅱ)-catalyzed Fujiwara-Moritani Reaction

A systematic theoretical investigation has been studied on Fujiwara-Moritani reaction between 3-methoxyacetanilide with n-butyl acrylate by means of density functional theory(DFT) calculations when two types of Pd(Ⅱ) catalysts are employed. In [Pd(MeCN)_4](BF_4)_2 catalytic cycle, a 1,4-benzoquinone(BQ)-induced C-H activation of trans-(MeCN)_2Pd(BQ)~(2+) with 3-methoxyacetanilide occurs as the first step to give DC-4_(MeCN), facilitating the insertion of n-butyl acrylate and β-hydride elimination, followed by recycling of catalyst through hydrogen abstraction of monocationic BQ fragment. In Pd(OAc)_(2) catalytic cycle, it is proposed that the most favored reaction pathway should proceed in dicationic mechanism involving a BQ-assisted hydrogen transfer for C-H activation by Pd active catalyst(HOAc)_(2)Pd(BQ)^(2+) to generate DC-4_(HOAc), promoting acrylate insertion and β-hydride elimination, followed by the regeneration of catalyst to give the final product. The calculations indicate that the rate-determining step in [Pd(MeCN)_(4)](BF_4)_(2) catalytic system is the acrylate insertion, while it is the regeneration of catalyst in the Pd(OAc)_(2) catalytic system. In particular, the roles of BQ and ligand effects have also been investigated.

Single-atom Fe-N_(5)catalyst for high-performance zinc-air batteries

Developing innovative and efficient non-precious-metal-group(non-PMG)electrocatalysts is crucial for the wide use of zinc-air batteries(ZABs).Herein,a single-atom catalyst(termed as Fe-N-C/rGO SAC)with unique five N-coordinated Fe(Fe-N_(5))centers is prepared by pyrolyzing the composite of zeolitic-imidazolate-frameworks-8(ZIF-8)and graphene oxide(GO).Specifically,the individual Fe site is stabilized by four equatorial and one axial N atoms donated by the N-doped carbon matrix and imidazole ring,respectively,thus forming an asymmetric electron depletion zone over the metal center,which can effectively promote the generation of reactive intermediates and accelerate the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes for ZABs.The rechargeable liquid ZAB with Fe-N-C/rGO catalyst exhibits an extremely high energy density(928.25 Wh·kg^(−1)),a remarkable peak power density(107.12 mW·cm^(−2)),and a long cycle life(400 h).Additionally,the corresponding flexible solid-state ZAB displays superior foldability and remarkable cycling stability.This work provides both experimental and theoretical guidance for rational design of non-PMG electrocatalyst-driven ZABs.

Exploring the pivotal role of silver(Ⅰ) additives in palladium-catalyzed NH_(2)-directed C(sp^(3))–H arylation reactions

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.