Substituent effect investigation of 3‐(2, 4‐dichlorophenyl)‐1‐(4′‐X‐phenyl)‐2‐propen‐1‐one. Part 1. Correlation analysis of 13C NMR chemical shifts

A series of substituted chlorinated chalcones namely, 3‐(2,4‐dichlorophenyl)‐1‐(4′‐X‐phenyl)‐2‐propen‐1‐one, have been synthesized, X being H, NH₂, OMe, Me, F, Cl, CO₂Et, CN, and NO₂. Dual substituent parameter (DSP) models of ¹³C NMR chemical shift (CS) have revealed that π‐polarization concept could be utilized to explain the reverse field effect at CO, the enhanced substituent field effect at CO, C‐2, and C‐5, and the decreased sensitivity of substituent field effect at C‐6. Chlorine atoms dipole direction at the benzylidene ring either enhances or reduces substituent effect depending on how they couple with the substituent dipole at the probe site. The correlation of ¹³C NMR CS of C‐2, C‐5, and C‐6 with σ and σ indicates that chlorine atoms in the benzylidine ring deplete the ring from charges. Both MSP of Hammett and DSP of Taft ¹³C NMR CS models give similar trends of substituent effects at C‐2, C‐5, and C‐6. However, the former fail to give a significant correlation for CO and C‐6 ¹³C NMR CS. MSP of σ_q and DSP of Taft and Reynolds models significantly correlated ¹³C NMR CS of C_β. MSP of σ_q fails to correlate C‐1′ ¹³C NMR CS. Investigation of ¹³C NMR CS of non‐chlorinated chalcones series: 3‐phenyl‐1‐(4′‐X‐phenyl)‐2‐propen‐1‐one has revealed similar trends of substituent effects as in the chlorinated chalcones series for C‐1′, CO, C_α, and C_β. In contrast, the substituent effect of the non‐chlorinated chalcone series at C‐2, C‐5, and C‐6 did not correlate with any substituent constant. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular structure,experimental and theoretical 1H and 13C NMR chemical shift assignment of cyclic and acyclic α,β‐unsaturated esters

The experimental ¹H and ¹³C NMR spectra of 13 phenyl cinnamates and four 4‐methylcoumarins were investigated and their chemical shifts assigned on the basis of the two‐dimensional spectra. For the unsubstituted cinnamic acid phenyl ester, optimized molecular structures were calculated at a B3LYP/6‐311++G(d,p) level of theory. ¹H and ¹³C NMR chemical shifts were also calculated with the GIAO method at the B3LYP/6‐311 + G(2d,p) level of theory. The comparison between experimental and calculated NMR chemical shift suggests that the experimental spectra are formed from the superposition spectra of the two lowest energy conformers of the compound in solution. The most stable s‐cis configuration found in our studies is also the conformation adopted for a related phenyl cinnamate in solid state. The experimental results were analyzed in terms of the substituent effects. Copyright © 2013 John Wiley & Sons, Ltd.     

Solvent‐dependent structural dynamics of 2(1H)‐pyridinone in light absorbing S4(ππ*) state

The B‐band resonance Raman spectra of 2(1H)‐pyridinone (NHP) in water and acetonitrile were obtained, and their intensity patterns were found to be significantly different. To explore the underlying excited state tautomeric reaction mechanisms of NHP in water and acetonitrile, the vibrational analysis was carried out for NHP, 2(1D)‐pyridinone (NDP), NHP–(H₂O)_n (n = 1, 2) clusters, and NDP–(D₂O)_n (n = 1, 2) clusters on the basis of the FT‐Raman experiments, the B3LYP/6‐311++G(d,p) computations using PCM solvent model, and the normal mode analysis. Good agreements between experimental and theoretically predicted frequencies and intensities in different surrounding environments enabled reliable assignments of Raman bands in both the FT‐Raman and the resonance Raman spectra. The results indicated that most of the B‐band resonance Raman spectra in H₂O was assignable to the fundamental, overtones, and combination bands of about ten vibration modes of ring‐type NHP–(H₂O)₂ cluster, while most of the B‐band resonance Raman spectra in CH₃CN was assigned to the fundamental, overtones, and combination bands of about eight vibration modes of linear‐type NHP–CH₃CN. The solvent effect of the excited state enol‐keto tautomeric reaction mechanisms was explored on the basis of the significant difference in the short‐time structural dynamics of NHP in H₂O and CH₃CN. The inter‐molecular and intra‐molecular ESPT reaction mechanisms were proposed respectively to explain the Franck–Condon region structural dynamics of NHP in H₂O and CH₃CN.Copyright © 2015 John Wiley & Sons, Ltd.     

Crystal structures of 3‐methyl‐2(1H)‐quinoxalinone and three substituted derivatives

3‐Methyl‐2(1H)‐quinoxalinone and three derivatives (3,7‐dimethyl‐2(1H)‐quinoxalinone, 3‐methyl‐6,7‐dichloro‐2(1H)‐quinoxalinone and 3‐methyl‐7‐nitro‐2(1H)‐quinoxalinone) have been synthesised and analysed by ¹H NMR and IR spectral spectroscopies. The crystal structures have been determined at room temperature from X‐ray single crystal diffraction data for three of them and from powder diffraction data for the nitro derivative. 3‐Methyl‐2(1H)‐quinoxalinone crystallises in the P2₁/c monoclinic system, 3,7‐dimethyl‐2(1H)‐quinoxalinone in the Pbca orthorhombic system and the two others compounds in the P$\overline {1} $ triclinic system. For the nitro derivative, C? H$\cdots $ N short contacts are established between the carbon of the methyl and the double bounded nitrogen of the ring. For the three other compounds N? H$\cdots $ O hydrogen bonds involve the atoms of the heterocyclic ring. Copyright © 2011 John Wiley & Sons, Ltd.     

Supramolecular encapsulation of 1,3‐bis(1‐adamantyl)imidazolium chloride by β‐cyclodextrins: towards inhibition of C(2)‐H/D exchange

The study of the hydrogen/deuterium exchange reactions of the C(2)‐proton for different carbene precursors has been carried out in the absence and presence of β‐cyclodextrin in D₂O at 25°C. Formation of the inclusion complexes of imidazolium salts with the native β‐cyclodextrin and the β‐dimethylcyclodextrin is demonstrated by 1D and 2D ¹H NMR, ESI/HRMS and a molecular modelling study. Formation of the inclusion complexes of imidazolium salts with the native β‐cyclodextrin and the β‐dimethylcyclodextrin is a simple and efficient method to modify the acidity of the imidazolium H(2) and to modify its environment. Encapsulation of 1,3‐disubstituted imidazolium chloride by β‐cyclodextrins results in the inhibition of the H(2)/D exchange in the complex. Copyright © 2008 John Wiley & Sons, Ltd.     

2,3-二羟基萘钼多酸有机衍生物的合成及1H NMR和IR谱学研究

本文对二种新合成的2，3－二羟基萘二钼和四钼多酸有机衍生物[n-Bu)4N]2[Mo2O5(OC10H6O)2](Ⅰ）和[n-Bu)4N]2[Mo4O10(OC10H6O)2(OCH3)2](Ⅱ)进行了红外光谱与核磁共振波谱研究，发现[Mo2O5]^2 中钼氧多桥键的红外振动频率较[Mo4O10(OCH3)2]^2 中钼氧多桥键的红外振动频率红移，而在配合物Ⅱ中2，3－二羟基中芳环的^1H化学位移较配合物Ⅰ中向低场移动。同时还发现含二钼配位中心[Mo2O5]^2 的[Mo2O5(OC10H6O)2]^2-与含四钼配位中心[Mo4O10(OCH3)2]^2 的[Mo4O10(OC10H6O)2(OCH3)2]^2-生成条件的差异仅仅只在反应体系的pH值的微小变化，说明钼多酸有机衍生物阴离子是对体系酸碱度极为敏感的物质。     

Substituent effects on the 13C NMR chemical shifts of the imine carbon in N‐(4‐X–benzylidene)‐4‐(4‐Y–styryl) anilines

Long‐range electronic substituent effects were targeted using the substituent dependence of δ_C(C═N), and specific cross‐interactions were explored extendedly. A wide set of N‐(4‐X–benzylidene)‐4‐(4‐Y–styryl) anilines, p‐X–C₆H₄CH═NC₆H₄CH═CHC₆H₄–p‐Y (X = NMe₂, OMe, Me, H, Cl, F, CN, or NO₂; Y = NMe₂, OMe, Me, H, Cl, or CN) were prepared for this study, and their ¹³C NMR chemical shifts δ_C(C═N) of C═N bonds were measured. The results show that both the inductive and resonance effects of the substituents Y on the δ_C(C═N) of p‐X–C₆H₄CH═NC₆H₄CH═CHC₆H₄–p‐Y are less than those of the substituents Y in p‐X–C₆H₄CH═NC₆H₄–p‐Y. Moreover, the sensitivity of the electronic character of the C═N function to electron donation/electron withdrawal by the substituent X or Y attenuates as the length of the conjugated chain is elongated. It was confirmed that the substituent cross‐interaction is an important factor influencing δ_C(C═N), not only when both X and Y are varied but also when either X or Y is fixed. The long‐range transmission of the specific cross‐interaction effects on δ_C(C═N) decreases with increasing conjugated distance between X and Y. The results of this study suggest that there is a long‐range transmission of the substituent effects in p‐X–C₆H₄CH═NC₆H₄CH═CHC₆H₄–p‐Y. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermolysis and photolysis of 2‐ethyl‐4‐nitro‐1(2H)‐isoquinolinium hydroperoxide

The thermal and light‐induced O ? O bond breaking of 2‐ethyl‐4‐nitro‐1(2H)‐isoquinolinium hydroperoxide (IQOOH) were studied using ¹H NMR, steady‐state UV/vis spectroscopy, femtosecond UV/vis transient absorption (fs TA) and time‐dependent density functional theory (TD DFT) calculations. Thermal O ? O bond breaking occurs at room temperature to generate water and the corresponding amide. The rate of this reaction, k = 5.4 · 10^?6 s^?1, is higher than the analogous rates of simple alkyl and aryl hydroperoxides; however, the rate significantly decreases in the presence of small amounts of methanol. The calculated structure of the transition state suggests that the thermolysis is facilitated by a 1,2 proton shift. The photochemical process yields the same products, as confirmed using NMR and UV/vis spectroscopy. However, the quantum yield for the photolysis is low (Φ = 0.7%). Fs TA studies provide additional detail of the photochemical process and suggest that the S₁ state of IQOOH undergoes fast internal conversion to the ground state, and this process competes with the excited‐state O ? O bond breaking. This result was supported by the fact that the model compound IQOH exhibits similar excited‐state decay lifetimes as IQOOH, which is assigned to the S₁ → S₀ internal conversion. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural and vibrational study of 2‐(2′‐ furyl)‐4,5‐1H‐dihydroimidazole

In this study 2‐(2′‐furyl)‐4,5‐1H‐dihydroimidazole (1) was prepared and then characterized by infrared, Raman, and multidimensional nuclear magnetic resonance (NMR) spectroscopies. The crystal and molecular structures of 1 were determined by X‐ray diffraction methods. The density functional theory (DFT) and second‐order Møller–Plesset theory (MP2) with Pople's basis set show that there are two conformers for the title molecule that have been theoretically determined in the gas phase, and that only one of them, conformer I, is present in the solid phase. NMR spectra observed for 1 were successfully compared with the calculated chemical shifts at the B3LYP/6‐311++G** level theorized for this conformer. The harmonic vibrational frequencies for the optimized geometry of the latter conformer were calculated at the B3LYP/6‐311++G** level in the approximation of the isolated molecule. For a complete assignment of the IR and Raman spectra in the solid phase of 1 , DFT calculations were combined with Pulay´s scaled quantum mechanics force field (SQMFF) methodology to fit the theoretical frequency values to the experimental ones. Copyright © 2009 John Wiley & Sons, Ltd.     

On the isotope effect of Tc in squaric acid (H2C4O4)

The phase transition mechanism in squaric acid is reviewed from the viewpoint of the pressure dependence of the O—H—O bond length (2R). The two-dimensional pressure effect on T_c is extracted from the hydrostatic pressure behaviour by taking account of the uniaxial stress applied perpendicular to the layer planes. The result shows that if 2R(H₂SQ) is stretched to 2R(D₂SQ) the phase transition temperature 7^H _c of H₂SQ coincides with T^D _c of D₂SQ. This result supports the suggestion that the phase transition mechanism is of the order-disorder type.     

Determination of N and O‐atoms and N2 (A) Metastable Molecule Densities in the Afterglows of N2‐H2, Ar‐N2‐H2 and Ar‐N2‐O2 Microwave Discharges

Early afterglows of N₂‐H₂, Ar‐N₂‐H₂ and Ar‐N₂‐O₂ flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atoms and the N₂ (A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N and O‐atoms and measurements of NO and N₂ band intensities. If an uncertainty of 30% is estimated on N‐atomic density, an inaccuracy of one order of magnitude is obtained on the O and N₂ (A) densities. In N₂‐(0.05‐2.5%)H₂ and Ar‐(1‐50%)N₂‐(0.05‐2.5%) H₂ gas mixtures, the O‐atoms are coming from O₂ impurities in the discharge. Concentrations of N and O‐atoms and of N₂ (A) densities are compared to the ones obtained in Ar‐(5‐50%)N₂‐(0.2‐2.5%) O₂ gas mixtures in which a controlled amount of O₂ is added. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

NMR and DFT calculation study on structures of 2‐[2‐nitro‐4‐(trifluoromethyl)benzoyl]cyclohexane‐1,3‐dione (NTBC) and its two metabolites isolated from urine of patients suffering from tyrosinemia type I

2‐[2‐Nitro‐4‐(trifluoromethyl)benzoyl]cyclohexane‐1,3‐dione (NTBC) is an active component of nitisinone, a medicine against tyrosinemia type I. Using ¹H, ¹³C and ¹⁹F NMR spectroscopy it has been found that in the urine of patients treated with nitisinone two compounds possessing CF₃ group are always present. They have been isolated by using TLC technique and identified as 4‐hydroxy‐2‐[2‐nitro‐4‐(trifluoromethyl)benzoyl]cyclohexane‐1,3‐dione and 5‐hydroxy‐2‐[2‐nitro‐4‐(trifluoromethyl)benzoyl]cyclohexane‐1,3‐dione, the latter being previously unknown. The constitution, tautomerism and stereochemistry of these compounds have been thoroughly investigated using ¹H and ¹³C NMR spectroscopy supported by theoretical calculations. Molecular structures have been optimized using density functional theory (DFT) with PBE1PBE functional and 6‐31G* basis set. In NMR parameter calculations, the larger 6‐311++G(2d,p) basis set has been used. At both calculation stages, the polarizable continuum model of the solvent has been employed. Copyright © 2010 John Wiley & Sons, Ltd.     

The β‐silicon effect. 4: substituent effects on the solvolysis of 1‐alkyl‐2‐(aryldimethylsilyl)ethyl trifluoroacetates

Solvolysis rates of 2‐(aryldimethylsilyl)‐1‐methylethyl and 2‐(aryldimethylsilyl)‐1‐tert‐butylethyl trifluoroacetates were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of aryl substituents at the silicon atom on the solvolysis rates at 50 °C were correlated with parameters of r⁺ = 0.15 with the Yukawa–Tsuno equation, giving ρ values of ?1.5 for both secondary α‐Me and α‐tert‐Bu systems. The ρ values for those secondary systems are less negative than ?1.75 for the 2‐(aryldimethylsilyl)ethyl system that proceeds by the Eaborn (non‐vertical) mechanism, while they are distinctly more negative than ?0.99 for 2‐(aryldimethylsilyl)‐1‐phenylethyl system that should proceed by the Lambert (vertical) mechanism. There was a fairly linear relationship between the reaction constants (ρ) for the β‐silyl substituent effects and the solvolysis reactivities for a series of β‐silyl substrates. The solvolyses of the α‐Me and tert‐Bu substrates proceed through the transition state (TS) with an appreciable degree of the β‐silyl participation, close to the Eaborn (non‐vertical) TS rather than to the Lambert (vertical) TS. Copyright © 2010 John Wiley & Sons, Ltd.     

A 1H NMR Study of Palladium(II) Coordination Compounds with 2-Aminooxypropanoic Acid and Its Methyl Ester

The ¹H NMR spectra of 2-aminooxypropanoic acid, its methyl ester and their hydrochlorides have been inspected. The interaction of these ligands with palladium(II) has been investigated in deuterium oxide and in dimethyl sulfoxide. The metal has been found to form a chelate with the acid, whereas its esters coordinated to the metal through the nitrogen atom of the aminooxy group only. In dimethyl sulfoxide, also the methyl esters and hydrochlorides of 2-aminooxybutanoic, 2-aminooxy-3-methylpentanoic,as well as the ester of 2-aminooxyhexanoic and the hydrochoride of the ester of 2-aminooxy-3-phenylpropanoic acid have been studied.     

Double proton transfer in crystals of 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a] pyrimidine (hppH): 13C and 15N CPMAS NMR study of (hppH)2

In this paper, we report an example of intermolecular solid‐state proton transfer in the bicyclic guanidine, hppH. A combination of X‐ray crystallography, CPMAS NMR (¹³C and ¹⁵N) and theoretical calculations allows us to determine that a double proton transfer takes place in the (hppH)₂ dimer with an activation energy of about 50 kJ mol^?1. According to the B3LYP/6‐311++G(d,p) calculations, the double proton transfer occurs non‐symmetrically through a zwitterion. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental and theoretical FT‐IR and FT‐Raman spectroscopic analysis of N1‐methyl‐2‐chloroaniline

In this work, the experimental and theoretical vibrational spectra of N1‐methyl‐2‐chloroaniline (C₇H₈NCl) were studied. FT‐IR and FT‐Raman spectra of the title molecule in the liquid phase were recorded in the region 4000–400 cm^?1 and 3500–50 cm^?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (B3LYP) with the 6‐311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT‐IR and FT‐Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. ¹³C and ¹H NMR chemical shifts results were compared with the experimental values. The optimized geometric parameters (bond lengths and bond angles) were given and are in agreement with the corresponding experimental values of aniline and p‐methyl aniline. Copyright © 2008 John Wiley & Sons, Ltd.     

用1H NMR法研究[Co (Xacac)2(Me-en)]ClO4的重氢化

应用¹H NMR技术推定了新合成的二(3-取代X基-2,4-戊二酮).N-甲基乙二胺合钴(Ⅲ)配合物:[Co (Xacac)₂(Me-en)]ClO₄(X=CH₃、Cl、NO₂)的△(R)∧(S)和△(S)∧(R)异构体的空间构型,测定了各配合物异构体手性配位氮原子上的重氢化速率常数k_D值(34.0℃).结果表明,取代基X对k_D值有着显著影响。     

Strong visible‐light photovoltaic effect in multiferroic Pb(Fe1/2V1/2)O3 bulk ceramics

The multiferroic Pb(Fe_1/2V_1/2)O₃ (PFV) bulk ceramic was fabricated by a conventional ceramic sintering method. The strong visible‐light photovoltaic effect in Sn‐doped‐In₂O₃(ITO)/PFV/ITO structure capacitor was observed. The open‐circuit voltage was up to ～0.7 V, which was much higher than the value (～0.3 V) in BiFeO₃ film. The photo‐excited electric current is almost proportional to the incident light illumination intensity. The good visible‐light photovoltaic makes PFV ceramic a potential candidate for practical application in solar cell devices.

     

取代基效应对二芳基硝酮CH=N(O)桥基1H NMR化学位移的影响

合成一系列取代二芳基硝酮XArCH=N（O）ArY化合物,测定其核磁共振氢谱（¹H NMR）,指认出桥基CH=N（O）上质子的化学位移δH[CH=N（O）],定量研究取代基效应对δH[CH=N（O）]的影响.得到一个4参数定量方程,标准偏差（S）为0.020,较好地表达了δH[CH=N（O）]的变化规律.结果表明,该类化合物的δH[CH=N（O）]主要受4个因素影响：X基团的场/诱导效应[σ_F（X）];Y基团的共轭效应[σ_R（X）];基团X和Y之间的特殊交叉作用（Δσ²）;以及基团X和O^-之间的特殊交叉作用[Δσ²_（X-O^-）].其中,Δσ²_（X-O^-）对δ_{H[CH=N（O）]}变化的贡献超过70%.通过δH[CH=N（O）]与二芳基希夫碱XArCH=NArY桥基CH=N上质子化学位移的δH（CH=N）比较发现,这两类化合物桥基上质子的化学位移之间没有良好的线性关系.因而,在应用NMR谱图解析有机化合物分子结构时,不能简单地用δH（CH=N）的变化去类比δ_{H[CH=N（O）]}的变化.     

Kinetics and related studies of the formation of 2,3‐dihydroquinazolin‐4(1H)‐ones in the presence of different benzaldehyde derivatives

The kinetics and activation parameters for the reaction between 2‐amino‐benzamide and some benzaldehyde derivatives in the presence of formic acid have been reported and discussed. A linear plot of lnk vs l/T showed that the reactions obey the Arrhenius equation. Both the Arrhenius and the Eyring equations were used to calculate the activation energy. The effect of nitro groups was studied on different positions of benzaldehyde. For all substituents, the reactions followed second‐order kinetics, and the partial orders of reactions were recognized with respect to each reactant. Comparisons between the magnitudes of ΔH^? and TΔS^?showed that the reactions were enthalpy controlled. The validity of the isokinetic relationship and the compensation effect was tested, and the isokinetic temperature (β) was obtained. A linear enthalpy‐entropy plot (ΔH^?versusΔS^?) showed that the compensation effect is established, and this process occurs via a same mechanism across a series of reactions. From the Van't Hoff and Exner's plots, the isokinetic temperature was obtained.