The relationships of catalytic activity of metal Schiff base catalysts and the Hammett constants of their anion–cationic substituents on ligand

For quaternary ammonium, pyridinium, or imidazolium anion–cationic substituents, a linear relationship can be established between the reactivity of metal Schiff base catalysts and the Hammett constants of their anion–cationic substituents with multi‐atomic anions on ligand based on the theoretical and experimental works. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular properties of selenomaltols: new interesting ligands for bioactive metal complexes

Properties of numerous selenium derivatives of maltol (3‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one), which is an important ligand in medicinal chemistry, were studied. Selenium derivatives were obtained using consecutive in silico replacements of maltol oxygen atoms, which produced three mono‐substituted, three di‐substituted and one tri‐substituted derivatives. The geometry optimisations for these compounds in neutral, anionic and cationic forms were performed at the B1LYP/6‐311++G** level of theory. The aromatic properties of the considered selenium compounds were studied in their heterocyclic rings using several indices of aromaticity: harmonic oscillator model of aromaticity, nucleus independent chemical shift(0), nucleus independent chemical shift(1), aromatic stabilisation energy, H index, para delocalisation index and multicentre index. The methods cover all of the main types of aromaticity indices: geometric, magnetic, energetic and electronic. The calculated data show the identical aromaticity order (cation > neutral molecule > anion) for maltol and its thio and seleno derivatives. The predicted aromaticity levels of selenomaltols were compared with the previously studied maltol and various thiomaltols. Copyright © 2015 John Wiley & Sons, Ltd.     

UV, 1H NMR Studies and a Semiempirical Mo Calculations of Some Substituted Phenylthiomethyl Benzoic Acid Derivatives

The effect of substituents on the spectral behavior of some arylthiomethyl benzoic acid derivatives, the corresponding sulfoxides and sulfones were studied. The chemical shifts of ortho hydrogen of benzyl moieties gave linear correlations with Hammett constants for acid sulfides and concave curves for sulfide esters. The effect of substituents on the conformation of sulfides were discussed.     

Ionic conductivity of ZrF4BaF2MX (M = Li,Na;X = F,Cl) glasses

Glasses were prepared in a wide range of compositions for the two systems oof mixed-cation, ZrF₄BaF₂LiFNaF, and mixed-anion, ZrF₄BaF₂LiFLiCl. Ionic conductivities were measured for these glasses and it was found that these glasses were not only cationic but also anionic conductors depending on the total alkali halide content. Four types of mixed-cation and mixed-anion effects on ionic conductivity were demonstrated for the cation-conducting and anion-conducting glasses. In cation conduction, the cation mixing caused the conductivity decline, whereas the anion mixing led to the conductivity enhancement. In anion conduction, on the other hand, the cation mixing led to the conductivity enhancement, whereas the anion mixing caused the conductivity decline.     

离子团簇YSin±(n=7-16)的几何结构和电子性质的相对论密度泛函研究

运用广义梯度近似的相对论密度泛函理论方法对YSi_n^±(n=7-16)离子团簇的几何结构、稳定性和电子特性进行了系统地数值模拟研究.与中性YSi_n团簇比较可得到以下结论：除YSi₁₀⁺和YSi₁₃⁺阳离子团簇外,YSi_n^±团簇基本都保持了中性YSi_n团簇的结构框架,这与垂直和绝热电离能的结果本质上是一致的;大多数离子团簇的原子平均束缚能都相对中性团簇有明显增大,表明离子团簇的结构稳定性都有增强,其中阳离子团簇YSi_n+(n=8, 11和14)和阴离子团簇YSi_n^-(n=9,12和14)比其相邻团簇的稳定性更强.电荷布居分析表明所有团簇中Y原子的HC电荷都在n=15处由正值变为负值,即当Y原子从Si_n框架表面位点落入硅笼中形成内嵌结构团簇时,电荷转移方向发生反转.阴离子团簇中电荷转移量普...     

Effective ionic charges and chemical bonding in GaSe and GaTe from chemical shifts of X-ray K absorption discontinuities

Chemical shifts in the X-ray K absorption edges of gallium and selenium in some of their binary compounds have been studied using a bent crystal X-ray spectrograph. The shifts are found to be governed by the effective charges on the absorbing ions, which have been calculated using Suchet's theory. For the compounds GaSe and GaTe, however, the effective ionic charges cannot be calculated for want of data on the divalent radius of gallium. The plot of the chemical shift, δE, against the theoretically calculated effective ionic charge, q, has been used to determine the charges on the ions in these two compounds. The effective charges, thus determined, provide information about the chemical bonding in the compounds.     

Probing the interaction of ionic liquids with graphene using surface‐enhanced Raman spectroscopy

We report an in situ measurement of the interaction of an imidazolium‐based room temperature ionic liquid with both pure silver and a graphene‐over‐silver electrode under an applied electrochemical potential. At a negative applied potential, overall signal intensity increased indicating enhanced ionic liquid concentration at both silver and graphene electrodes. Vibrational modes associated with the imidazolium ring exhibited greater intensity enhancements and larger peak shifts compared with the anion indicating that the cation adsorbs with the ring and alkyl chain parallel to the electrode surface for both silver and graphene. In contrast to the silver, the surface enhanced Raman spectra of the ionic liquid near graphene showed shifts in the cation peaks even at no applied potential because of the strong π–π interaction between the ionic liquid and the graphene. Furthermore, the intensity of the graphene peak decreased in the presence of ionic liquid possibly due to the interaction between the ionic liquid and graphene. These results illustrate the effectiveness of surface‐enhanced Raman spectroscopy to investigate electrolyte interactions with graphene at the liquid/electrode interface. Copyright © 2015 John Wiley & Sons, Ltd.     

What can the geometry tell about the charge distribution in the mesoionic heterocycles? A DFT study on the SCN4R2 system

This computational organic chemistry study was performed using the hybrid functional B3LYP. Many basis sets were evaluated and the basis set 6‐31G(d) was found to be the most practical in terms of time and accuracy. The study presents the first method in the chemical literature that allows estimation of submolecular charges in mesoionic compounds. The theory was built on a reference model structure for which the absolute value of charge of the aromatic p‐orbitals is known. This is the cornerstone, and by employing the harmonic oscillator model of aromaticity (HOMA) many parameters can be quantified. The electronic structure of the title compound was the subject of this approach. The study addressed the following points: geometries, infrared frequencies, NMR chemical shifts, calculated charges, a chemical reactivity, and the frontier orbitals. The calculations illustrate that the π‐system of the CN₄ segment includes considerable aromatic character and carries a positive charge while the overall charge is negative. This allows classifying it as a σ‐acceptor/π‐donor while the exocyclic counter anion, the sulfur atom, is a σ‐donor/π‐acceptor. The substituents (R groups) in this case are only σ‐donors. The approach may be applied to other mesoionic and mesoaromatic systems. Copyright © 2009 John Wiley & Sons, Ltd.     

N-丁基吡啶四氟硼酸盐/水二元体系的分子动力学模拟研究

利用分子动力学模拟方法研究了离子液体N-丁基吡啶四氟硼酸盐([BPy]BF₄)与Tip4p模型水分子的二元体系的微观结构.比较了各组分间的径向分布函数,结果表明随着离子液体比例的增加,水与阴离子、水与阳离子头部吡啶环、阳离子头部与阴离子上相关原子间的径向分布函数峰值都呈现递增的趋势,而阳离子上丁基链末端碳原子间的径向分布函数没有明显变化;空间分布函数则直观地反映出阴离子主要分布在阳离子的吡啶环周围,水分子在阴离子周围近似呈均等分布,且几率随离子液体比例增大而增加;另外还探讨了不同离子液体比例下的二元体系中氢键的数目和寿命,结果均呈现一定规律的变化.     

甲醛缩氨基脲及其有关化合物的15N和13C核磁共振研究

本文测定了12个甲醛缩氨基脲类化合物的¹⁵N和¹³C NMR谱,研究并对比了不同取代基对¹⁵N和¹³C化学位移的影响,结果表明:¹⁵N化学位移对分子结构和取代基的电子效应更加敏感,变化范围更大.对N-苯甲醛缩氨基脲¹⁵N化学位移与Hammatt取代常数σ的相关性进行了研究,并与苯胺的取代效应作了对比.     

Spectroscopic (FT‐IR,FT‐Raman,UV, 1H,and 13C NMR) and theoretical studies of m‐anisic acid and lithium,sodium, potassium,rubidium, and caesium m‐anisates

In order to understand the nature of the interactions of biologically important ligands, it is necessary to carry out the physico‐chemical studies of these compounds with their biological targets (e.g., receptors in the cell or important cell components). Results of this study make it possible to predict some properties of a molecule, such as its reactivity, durability of complex compounds, and kinship to enzymes. In this paper the effect of alkali metal cations (Li, Na, K, Rb, and Cs) on the electronic structure of m‐methoxybenzoic acid (m‐anisic acid) was studied. The experimental IR (in solid state and solution), Raman, UV (in solid state and solution), ¹H, and ¹³C NMR spectra of m‐methoxybenzoic acid, and its salts were registered, assigned, and analyzed. Some of the obtained results were compared with published data for o‐anisic acid and o‐anisates. The structures of anisic acid and Li, Na, and K m‐anisates were optimized at the B3LYP/6‐311++G** level. The IR, ¹H, and ¹³C NMR spectra and NPA, ChelpG, and MK atomic charges were calculated. The change of metal along with the series: Li → Na → K → Rb → Cs caused: (1) the change in the electronic charge distribution in anisate anion that is seen via the occurrence of the systematic shifts of several bands in the experimental and theoretical IR and Raman spectra of anisates; (2) systematic ¹H and ¹³C NMR chemical shifts; (3) hypsochromic shifts in UV spectra of salts as compared to ligands. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectra of acetonitrile in imidazolium ionic liquids

Raman spectra of dilute solutions of acetonitrile in ionic liquids reveal the characteristic features of ionic liquids' polarity. This is accomplished by investigating the Raman bandshape of the ν (CN) band, corresponding to the CN stretching mode of CH₃CN, which is a very sensitive probe of the local environment. The amphiphilic nature of the CH₃CN molecule allows us to observe the effect of electron pair acceptor and electron pair donor characteristics on ionic liquids. It has been found that the overall polarity of nine different ionic liquids based on 1‐alkyl‐3‐methylimidazolium cations is more dependent on the anion than cation. The observed wavenumber shift of the ν (CN) band of CH₃CN in ionic liquids containing alkylsulfate anions agrees with the significant different values previously measured for the dielectric constant of these ionic liquids. The conclusions obtained from the analysis of the ν (CN) band were corroborated by the analysis of the symmetric ν₁ (CD₃ ) stretching mode of deuterated acetonitrile in different ionic liquids. Copyright © 2010 John Wiley & Sons, Ltd.     

Exploring anionic emission of 2-benzoyl benzimidazole in micellar environments

In this paper, an interesting transformation of the emission of anionic conformer of 2-benzoyl bezimidazole in ionic and non-ionic micelles is reported. Deprotonation is hindered in cationic and non-ionic micelles owing to probe molecule's passage deep inside positive ion-rich Stern-layer in contrast with anionic micelle. The orientation of probe molecule in the two ionic micelles, as determined from the spectral properties is opposite in nature. Micellar environment shields the formation of mono- and di-cationic species at very low pH. Three decay times of the probe in different time domains were attributed to three possible anionic species and they are modified differently in ionic and neutral micelles. Quantum chemical calculations also predict the existence of three different possible anionic species.     

The electrochemistry of arylated anthraquinones in room temperature ionic liquids

Arylated anthraquinone derivatives of different sizes and different π‐basicities have been prepared, and the electrochemical behaviour of these substances has been studied on screen printed graphite electrodes in the three room temperature ionic liquids (RTILs), 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), 1‐hexyl‐3‐methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) and 1‐octyl‐3‐methylimidazolium hexafluorophosphate ([C₈MIM][PF₆]). Half redox potentials for the first and second one electron reduction waves were identified, and the diffusion coefficient values were estimated from cyclic voltammetry measurements. The influence of the nature of the RTIL and of the substitution pattern of the anthraquinone on the solvodynamic radii were studied. A correlation of the reductive potentials with the corresponding Hammett constants of the substituents was tested. Copyright © 2013 John Wiley & Sons, Ltd.     

Grafting of polymers onto graphene oxide by cationic and anionic polymerization initiated by the surface-initiating groups

The grafting of polymers onto graphene oxide (GO) was achieved by two process: (1) cationic polymerization initiated by carboxyl (COOH) groups on GO and (2) anionic alternating copolymerization of epoxides with cyclic acid anhydrides initiated by potassium carboxylate (COOK) groups on GO. The cationic polymerizations of isobutyl vinyl ether and N-vinylcarbazole were successfully initiated by COOH groups on GO to give the corresponding polymer-grafted GO. The cationic polymerization was considered to be initiated by proton addition from COOH groups to monomer and propagation of polymer cation proceeds with carboxylate anion as a counter ion. It was found that the corresponding polymer was successfully grafted onto GO based on the termination reaction of growing polymer cation and surface counter carboxylate anion. On the other hand, the anionic ring-opening alternating copolymerization of epoxide and cyclic acid anhydrides were also initiated by COOK groups on GO, which were previously introduced onto GO by the neutralization of COOH groups with KOH. During the anionic ring-opening copolymerization of styrene oxide (SO) with phthalic anhydride (PAn) and maleic anhydride (MAn), the corresponding polyesters, poly(SO-alt-PAn) and poly(SO-alt-MAn), were successfully grafted onto GO, based on the propagation of the polyesters from COOK groups. The grafting of polymers onto GO during the above cationic and anionic polymerizations was confirmed by thermal decomposition gas chromatogram/mass spectrum. The untreated GO in THF was immediately precipitated within 15 min. On the contrary, these polymer-grafted GOs gave stable dispersions in THF and no precipitation of polymer-grafted GOs was observed even after one week.     

溴代1-己基-3-甲基咪唑离子液体与丙酮的相互作用

运用核磁共振氢谱和碳谱手段,研究了室温离了液体溴代1-己基-3-甲基咪唑([C6mim]Br)在不同浓度的离子液体/丙酮混合体系中的1H和13C化学位移．实验结果表明,离了液体[C6mim]Br的阴离子与丙酮甲基上的氢原子相互作用并形成了氢键．量子化学计算结果与核磁共振实验结果一致．     

Effects of neutral and charged substituents on the infrared carbonyl stretching frequencies in phenyl and alkyl benzoates in DMSO

The carbonyl infrared stretching frequencies for 57 meta‐, para‐ and ortho‐substituted phenyl benzoates, C₆H₅CO₂C₆H₄‐X and alkylbenzoates, C₆H₅CO₂R, containing besides neutral substituents the charged substituents in phenoxy and alkoxy part in dimethyl sulfoxide (DMSO) have been recorded. The carbonyl stretching frequencies, ν_CO, for meta‐ and para‐substituted phenyl esters of benzoic acids in the case of neutral substituents were found to correlate well with the substituent constants, σ°. The ν_CO values for ortho derivatives correlated with the inductive substituent constants, σ_I, only. The values of constants for charged substituents, σ°_±, calculated on the basis of the ν_CO and the ¹³C NMR chemical shifts, δ_CO, in DMSO agree well with the σ°_± values for the corresponding ion pairs reported by Hoefnagel and Wepster and those determined from the log k values of the alkaline hydrolysis in 4.4 M NaCl solution at 50 °C. Thus, the values of substituent constants for ion pairs of charged substituents estimated on the basis of aqueous data could be successfully used in non‐aqueous solution (DMSO) simultaneously with neutral substituents in case the charged substituents were not completely ionized and are in ion pair form. Copyright © 2016 John Wiley & Sons, Ltd.     

碱土氟化物中离子间相互作用势经验参数的确定

描述离子间非Coulomb短程互作用势的函数形式确定后，即可据此讨论离子晶体的一系列物理性质，势函数中出现的参数通过与实验数据的拟合而确定．基于电子壳模型对CaF₂，SrF₂，BaF₂离子晶体的讨论中，强调电子壳电量应一律取负值的基本前提，以经验参数化方法拟合势参数时注意引用近期实验数据．将F离子电量调整为0.97e之后，重新获得的模型参数集与上述碱土氟化物晶格形成能、弹性常数、长光学横波频率、Raman频率，以及极化率实验数据，有较满意的对应关系．     

Synthesis and electrochemical evaluation of 2‐substituted imidazolium salts

Herein, we report the synthesis, electrochemical, and computational evaluation of six 2‐substituted imidazolium bromides and six 2‐substituted imidazolium triflates. All final compounds were obtained in 2 or fewer synthetic steps from inexpensive starting materials and display a single, irreversible electrochemical reduction. The reduction potentials span a range greater than 1 V depending on the electron withdrawing power of the 2‐substituent. Imidazolium bromides such as Bn₂(H)ImBr reduce with E_1/2 = ?2.70 V vs Fc/Fc⁺, whereas the electron‐withdrawing Br‐containing analog Bn₂(Br)ImBr reduces at only ?1.58 V vs Fc/Fc⁺. The reduction potential of imidazolium bromides obeys a linear free energy relationship to σ_m Hammett constants, whereas imidazolium triflates correlate better with the σ_p Hammett constants. These results indicate that the stabilizing effect of the 2‐substituent is anion‐sensitive, changing from induction to resonance upon exchanging bromide for triflate. Predicted electron affinities from density functional theory–optimized structures of imidazolium cations and reduced species more closely match experimental data for the triflates, suggesting that a triflate anion does not electronically perturb the imidazolium core as much as a bromide. Taken together, these data highlight the dual modularity of imidazolium salts by changing both 2‐substituent and anion.     

Mössbauer study of the substituent effect in mixed ligand complexes of europium (III)

A series of europium (III) mixed ligand complexes containing phenanthroline, benzoic acid and their derivatives, respectively, as ligands, were investigated by Mössbauer spectroscopy. The substituents changed the electron density on the donor atoms of the ligands by their electrophilic or nucleophilic nature and changed the stereochemistry of the coordination sphere by their different space requirement. Both effects were reflected in the isomer shift values. The basicity changes on the donor atoms due to the substituents were characterized by the Hammett 6 values of latters. The correlation betweenEu isomer shifts and the Hammett 6 values of the corresponding substituents on the ligands of otherwise analogous europium (III) compounds indicated the binding mode in the complexes /1/.