Iodobenzene diacetate (IBD) catalyzed an quick oxidative aromatization of Hantzsch-1,4-dihydropyridines to pyridines under ultrasonic irradiation

This project was undertaken to demonstrate the potential of iodobenzene diacetate for the oxidative aromatization of Hantzch-1,4-dihydropyridines under ultrasonic irradiation. All reactions were carried out under ultrasonic irradiation and results were compared with traditional method. Sonochemical switching was observed in case of oxidative aromatization of 4-n-alkyl substituted 1,4-DHP. Without sonication, dealkylation occurred in case of n-alkyl substituted 1,4-DHP (ionic mechanism) but under ultrasonic irradiation, n-alkyl group was not expelled (radical mechanism). However, secondary alkyl (isopropyl) and benzyl group were expelled under both conditions.     

Reactivity of C4‐indolyl substituted 1,4‐dihydropyridines toward superoxide anion (O2•) in dimethylsulfoxide

Reactivity of two new C4‐indolyl substituted 1,4‐dihydropyridines (1,4‐DHPs) toward superoxide anion (O₂^? ) in dimethylsulfoxide (DMSO) is reported. Reactivity was followed by electrochemical and spectroscopic techniques. Gas chromatography‐mass spectrometry (GC–MS) was used to identify the final products of the reaction. C4 indolyl‐substituted‐1,4‐DHPs reacted toward O₂^? at significant rates, according to the calculated kinetic rate constants. Results are compared with 4‐phenyl‐DHP and the commercial 1,4‐DHPs, nimodipine, nisoldipine, and amlodipine. Indolyl‐substituted 1,4‐DHPs were more reactive than the commercial derivatives. The direct participation of proton of the 1‐position of the secondary amine in the quenching of O₂^? was demonstrated. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis, in vitro antitubercular activity and 3D-QSAR study of 1,4-dihydropyridines

In continuation of our research program on new antitubercular agents, this article is a report of the synthesis of 97 various symmetrical, unsymmetrical, and N-substituted 1,4-dihydropyridines. The synthesized molecules were tested for their activity against M. tuberculosis H ₃₇Rv strain with rifampin as the standard drug. The percentage inhibition was found in the range 3–93%. In an effort to understand the relationship between structure and activity, 3D-QSAR studies were also carried out on a subset that is representative of the molecules synthesized. For the generation of the QSAR models, a training set of 35 diverse molecules representing the synthesized molecules was utilized. The molecules were aligned using the atom-fit technique. The CoMFA and CoMSIA models generated on the molecules aligned by the atom-fit method show a correlation coefficient (r ²) of 0.98 and 0.95 with cross-validated r ²(q ²) of 0.56 and 0.62, respectively. The 3D-QSAR models were externally validated against a test set of 19 molecules (aligned previously with the training set) for which the predictive ${r^{2} (r^{2}_{\rm pred})}$ is recorded as 0.74 and 0.69 for the CoMFA and CoMSIA models, respectively. The models were checked for chance correlation through y-scrambling. The QSAR models revealed the importance of the conformational flexibility of the substituents in antitubercular activity.     

Effect of heat treatments on the luminescence properties of Zn2SiO4:Mn2+ phosphors prepared by glycothermal methods

Manganese-doped Zn₂SiO₄ phosphors with different crystal structures and morphologies were synthesized by glycothermal reactions of zinc acetate dihydrate and manganese(II) acetate tetrahydrate with tetraethyl orthosilicate in various glycols at 315 °C. The reactions in 1,3-propanediol and 1,4-butanediol yielded α-Zn₂SiO₄:Mn²⁺, whereas the reactions in ethylene glycol and 1,5-pentanediol yielded β-Zn₂SiO₄:Mn²⁺ and ZnO, respectively. The samples obtained in 1,4-butanediol and 1,3-propanediol emitted green light (522 nm), and the sample prepared in 1,4-butanediol showed a higher emission intensity. The photoluminescence intensity of the Zn_1.96Mn_0.04SiO₄ phosphor prepared by a glycothermal reaction in 1,4-butanediol and subsequently calcined at 1100 °C was twice as high as that of the sample synthesized by a conventional solid-state reaction. The high emission efficiency was obtained because the highly homogeneous distribution of Mn²⁺ in the α-Zn₂SiO₄ host synthesized by the glycothermal reaction was maintained during calcination treatment in air.     

H3PAuPh与(H3PAu)2(1,4-C6H4)2光谱性质的密度泛函研究

用密度泛函(DFT)方法优化了配合物H₃PAuPh(a),(H₃PAu)₂(1,4-C₆H₄)₂(b)的基态的几何结构,并用含时密度泛函方法计算了它们的吸收光谱.结果表明配合物a与 b的最低能量吸收谱线的波长分别为257.5 nm和307.6 nm,皆具有C(2p)→Au(6p)电荷转移参与下的p_π 关键词： 激发态 光谱 密度泛函 3')" href="#">AuPH₃     

Photoelectron spectroscopic assignment of symmetry to the ground state and first excited state of the 1,4-cyclohexadiene radical cation

The empirical correlation of the photoelectron spectra of 1,4-cyclohexadiene (molecule 4), 1, 4, 5, 8-tetrahydronaphthalene (molecule 5), 1, 4, 5, 6, 9, 1 0-hexahydroanthracene (molecule 6), and 1, 4, 5, 6, 7, 10, 11, 12-octahydronaphthacene (molecules 6) proves that the electronic ground state of these molecules is ²B_1u, assuming that they have D_2h symmetry. In particular this confirms previous predictions for 1,4-cyclohexadiene (molecule 4), for which the “inverted” orbital sequence 2b_1u(π) above lb_3g(π) had been proposed under the assumption that hyperconjugative “through-bond” interaction dominates the “through-space” interaction of the two semi-localized π-orbitals.     

1,4-二氧六环的真空紫外同步辐射光解离电离研究

The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0-15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C₄H₇O₂⁺, C₃H₆O⁺, C₃H₅O⁺, C₂H₅O⁺, C₂H₄O⁺, C₂H₃O⁺, C₃H₅⁺, CH₃O⁺, C₂H₆⁺, C₂H₅⁺/CHO⁺, C₂H₄⁺ and CH₃⁺ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31+G(d,p) level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.     

Same spectral signature in liquid-state and solid-state 1H photo-CIDNP NMR spectra of cyclohexanone

ABSTRACT

For the first time, a ¹H solid-state photo-CIDNP effect is reported. The effect is observed in frozen solution of cyclohexanone in 1,4-dioxane-d₈ under magic-angle spinning and continuous irradiation by the full spectrum of a xenon arc lamp. The spectral features show close similarity with those observed by ¹H liquid-state photo-CIDNP NMR.     

第I种非对称两态叠加多模叠加态光场的任意不等阶Y压缩

利用多模压缩态理论研究了第种非对称两态叠加多模叠加态光场|Ψ_Iab〉_q的任意不等阶N_j次方Y压缩特性.结果发现:对于任意压缩阶数N_j,态|Ψ_Iab〉_q在一定条件下总可呈现出任意不等阶N_j次方Y混合压缩效应,但在某一压缩阶数区域内并不一定呈现压缩效应;压缩阶数N_j满足特定条件(N_mj=4_mj;4_mj+1;4_mj+2;4_mj+3,其中j=1,2,3,…,…q)时的不等阶N_j次方Y压缩效应仅仅是本文的理论结果在N_j在某一特定条件下的特例.     

Effective orientation of water in 1,4-dioxane···water: the rotational spectrum of the H2 17O isotopologue

The measurements of the rotational spectrum of 1,4-dioxane-water complex, performed by pulsed jet Fourier transform microwave spectroscopy, have been extended to the 7–18.5 GHz frequency region and to two additional isotopologues, 1,4-dioxane···H₂ ¹⁷O and 1,4-dioxane···HOD. The effective orientation of water in the complex has been obtained from the ¹⁷O quadrupole coupling constants.     

Synthesis, characterization and luminescent properties of lanthanide complexes with an unsymmetrical tripodal ligand

Solid complexes of lanthanide nitrates with a new unsymmetrical tripodal ligand, bis[(2′-benzylaminoformyl)phenoxyl)ethyl](ethyl)amine (L) have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Sm(III), Eu(III), Tb(III) and Dy(III) nitrate complexes in solid state were also investigated. Under the excitation of UV light, these complexes exhibited characteristic emission of central metal ions.     

Ultrasound-Engineered fabrication of immobilized molybdenum complex on Cross-Linked poly (Ionic Liquid) as a new acidic catalyst for the regioselective synthesis of pharmaceutical polysubstituted spiro compounds

A novel supported molybdenum complex on cross-linked poly (1-Aminopropyl-3-vinylimidazolium bromide) entrapped cobalt oxide nanoparticles has been successfully fabricated through two different procedures, i.e. ultrasound (US) irradiations (100 W, 40 kHz) and reflux. The efficiency of the two different methods was comparatively investigated on the fundamental properties of proposed catalyst using diverse characterization techniques. Based on the obtained results, the ultrasonication method provides controlled polymerization process; as a result, well connected polymeric network is formed. In addition, the use of ultrasound waves turned out to be able to increase the particles uniformity, specific surface area (from 79.19 to 223.83 m²/g), and the onset thermal degradation temperature (T_d) value (from 248 to 400 °C) of the prepared catalyst which intensifies the catalytic efficiency. Besides, US-treated catalyst demonstrated high chemical stability and maintained its cross-linked network after eight cycles recovery, while the cross-linked network of catalyst obtained under silent condition was completely disrupted. Furthermore, the ultrafast multi-step fabrication procedure was performed in less than 6 h under ultrasonic condition while a similar process promoted by a mechanical stirring method came to a conclusion after 5–6 days. Accordingly, the utility of the ultrasound irradiation was proved, and US-treated catalyst was applied for improved synthetic methodology of spiro 1,4-dihydropyridines and spiro pyranopyrazoles through different acidic active sites. Due to the significant synergistic influence between the proposed catalyst and US irradiation, a variety of novel and recognized mono-spiro compounds were fabricated at room temperature in high regioselectivity.     

Characterization of ZnGa2O4:Mn nanophosphor synthesized by the solvothermal method in 1,4-butanediol-water system

We characterized ZnGa₂O₄:Mn²⁺ (ZnGa₂O₄—zinc gallate) nanophosphor synthesized by the solvothermal method in 1,4-butanediol-containing water to increase the amount of Mn²⁺ ions incorporated in the ZnGa₂O₄ matrix without post-heat treatment. We investigated the influence of water content in the solvent on the photoluminescence (PL) intensity and the Mn amount, the latter being measured by X-ray fluorescence analysis and electron paramagnetic resonance spectroscopy. The PL intensity per Mn amount reached the maximum at the 50 wt% water content. The addition of water promotes repeated dissolution and precipitation, resulting in homogeneous Mn²⁺ distribution in the ZnGa₂O₄ matrix. This suggests that the solvothermal method in the 1,4-butanediol-water system is useful for increasing the amount of Mn²⁺ ions incorporated in the ZnGa₂O₄ matrix without post-heat treatment. At the water content >50 wt%, the decrease in PL intensity is attributed to the optical absorption of the by-product, MnOOH.     

Spectral characteristics of heterocyclic compounds with a chain structure, cooled in an ultrasonic jet

We have recorded the fluorescence excitation spectra of three heterocyclic compounds with a chain structure [BPO (2-phenyl-5-(4-diphenylyl)oxazole), POPOP (1,4-di[2-(5-phenyloxazolyl)]benzene, and TOPOT (1,4-di[2-(5-n-tolyloxazolyl)]benzene] and the fluorescence spectra of POPOP, under conditions where the molecules were cooled in an ultrasonic helium jet. A line structure is observed in the spectra of POPOP and TOPOT; for the BPO molecules, whose configuration changes considerably during electronic excitation, vibrational structure is apparent only in the low-frequency region of the excitation spectrum, and a diffuse spectrum is recorded starting from ν ₀ ⁰ + 200 cm⁻¹. For all the compounds, in the spectra we recorded vibrations with frequencies up to 100 cm⁻¹, arising due to the flexibility of the molecular structure. The rotational contours of the lines for the electronic and vibronic transitions of the POPOP molecules (T_rot = 10.5 K) and TOPOT molecules (T_rot = 15 K) are structureless and bell-shaped. The degree of polarization of the fluorescence P_fl for the jet-cooled POPOP molecules for excitation of vibrations along the absorption band up to 2000 cm⁻¹ above ν ₀ ⁰ is practically constant (∼8.4%) and matches P_fl for high-temperature vapors. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 728–734, November–December, 2006.     

Reactivity of the insecticide chlorpyrifos‐methyl toward hydroxyl and perhydroxyl ion. Effect of cyclodextrins

The reactivity of Chlorpyrifos‐Methyl ( 1 ) toward hydroxyl ion and the α‐nucleophile, perhydroxyl ion was investigated in aqueous basic media. The hydrolysis of 1 was studied at 25 °C in water containing 10% ACN or 7% 1,4‐dioxane at NaOH concentrations between 0.01 and 0.6 M ; the second‐order rate constant is 1.88 × 10^?2 M ^?1 s^?1 in 10% ACN and 1.70 × 10^?2 M ^?1 s^?1 in 7% 1,4‐dioxane. The reaction with H₂O₂ was studied in a pH range from 9.14 to 12.40 in 7% 1,4‐dioxane/H₂O; the second‐order rate constant for the reaction of HOO^? ion is 7.9 M ^?1 s^?1 whereas neutral H₂O₂ does not compete as nucleophile. In all cases quantitative formation of 3,5,6‐trichloro‐2‐pyridinol ( 3 ) was observed indicating an S_N2(P) pathway. The hydrolysis reaction is inhibited by α‐, β‐, and γ‐cyclodextrin showing saturation kinetics; the greater inhibition is produced by γ‐cyclodextrin. The reaction with hydrogen peroxide is weakly inhibited by α‐ and β‐cyclodextrin (β‐CD), whereas γ‐cyclodextrin produces a greater inhibition and saturation kinetics. The kinetic data obtained in the presence of β‐ or γ‐cyclodextrin for the reaction with hydroxyl or perhydroxyl ion indicate that the main reaction pathway for the cyclodextrin‐mediated reaction is the reaction of HO^? or HOO^? ion with the substrate complexed with the anion of the cyclodextrin. The inhibition is attributed to the inclusion of the substrate with the reaction center far from the ionized secondary OH groups of the cyclodextrin and protected from external attack of the nucleophile. Sucrose also inhibits the hydrolysis reaction but the effect is independent of its concentration. Copyright © 2008 John Wiley & Sons, Ltd.     

The solvent-free synthesis of 1,4-dihydropyridines under ultrasound irradiation without catalyst

The condensation of aldehydes, ethyl acetoacetate and ammonium acetate result 1,4-dihydropyridines in 82–99% yields under ultrasound irradiation without solvent and catalyst at room temperature. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields.     

Photoluminescence and Coordination Behaviour of Lanthanide Complexes of Tris (Aminomethyl)Ethane-5-Oxine in Aqueous Solution

Photophysical properties of a multidentate tripodal ligand, 5,5′-(2-(((8-hydroxyquinolin-5-yl) methylamino)methyl)-2-methylpropane-1,3-diyl) bis (azanediyl)bis (methylene)diquinolin-8-ol, (TAME5OX), with La³⁺ and Er³⁺ ions have been examined for photonics applications. The change in behavior in electronic spectra of these complexes reveals the use of TAME5OX as a sensitive optical pH based sensor to detect Ln³⁺ ions whereas indication of strong green fluorescence allows simultaneous sensing within the visible region in competitive medium. The intense fluorescence intermittently gets quenched under acidic and basic conditions due to photoinduced intramolecular electron transfer from the excited 8-hydroxyquinoline (8-HQ) moiety to the metal ion. This renders these compounds the OFF-ON-OFF type of pH-dependent fluorescent sensor. The thermodynamic stability and coordination behaviour of the chelator with the said lanthanide ions have also been probed by potentiometric, UV ? visible and fluorescence spectrophotometric method. TAME5OX forms protonated complex [Ln (H₄L)]⁴⁺ below pH ~4.0 which sequentially deprotonates through one proton process with increase of pH. The stability constants of neutral complexes have been determined to be in the range log β₁₁₀ = 32–34 and pLn in the range of 14–20, indicating TAME5OX is a good synthetic lanthanide chelator. Theoretical spectra were also calculated by ZINDO/s methodology at single excitations (CIS) level on PM7 as sparkle energy-minimized geometries.     

Model and calculation of rate constants of nonradiative <Emphasis Type="Italic">T-S</Emphasis> intersystem conversion: Test by example of naphthalene and its chlorine derivatives

For in-plane spin states (s = z, y), the rate constants K _dg ^s of the nonradiative energy degradation T ₁ ⇝ S ₀ of the lowest triplet T ₁ state of naphthalene (NPH) and its dichloro-substituted derivatives at positions 1,4- and 2,3- of the molecule (1,4-NPH and 2,3-NPH) are calculated. A simple model is proposed for calculations that is based on the nonadiabatic approximation and uses all the out-of-plane vibrational modes of the molecule as promoting vibrational modes. As a result of calculations, the dependences of the rate constants K _dg and K _dg ^s on the positions of chlorine atoms in the molecule are obtained, which are consistent with the known data of magnetooptical measurements. The inversion of the ratio K _dg ^z : K _dg ^y in the 1,4-NPH and 2,3-NPH molecules is established.     

Analysis of 1H and 13C{1H} NMR Spectral Parameters and Geometries of Three Isomeric Diphenylbicyclo[2.2.1]Hept-5-Ene-2,3-Dicarboxylic Anhydrides

Diels-Alder adducts of 1,4-diphenyl-1,3-cyclopentadiene and maleic anhydride were investigated by recording the ¹H and ¹³C{¹H} NMR spectra of three isomeric diphenylbicyclo[2.2.1]hept-5-ene endo and exo 2,3-dianhydrides. the spectra were recorded in CD₂Cl₂ and analysed completely. the effect of the endo and exo configuration of the anhydride ring on the chemical shifts of the bridgehead phenyl protons is discussed. the ortho protons of the exo isomers resonate at higher field than those of the endo isomer, and the resonance pattern of the aromatic protons is narrower in the exo than the endo anhydride. the aromatic regions of the spectra are compared with the same regions of the ¹H NMR spectra of the earlier investigated addition products of 1,4-di-p-tolyl-1,3-cyclopentadiene and 1-phenyl-4-p-tolyl-1,3-cyclopentadiene with maleic anhydride. Chemical shifts of the bridge protons are explained on the basis of X-ray data of the compounds and MacroModel calculations on the minimum energy conformations.     

Spin-crossover phenomenon of the assembled iron complexes with 1,2-bis(4-pyridyl)ethane as bridging ligand studied by Mössbauer spectroscopy

The transition temperatures between high- and low-spin states of the assembled spin-crossover complexes, Fe(NCX)₂(bpa)₂(guest) (X = S, Se, BH₃; bpa = 1,2-bis(4-pyridyl)ethane; guest = biphenyl, 2-nitrobiphenyl, diphenylmethane, or 1,4-dichlorobenzene), were compared with the Mössbauer parameters. The transition temperature increases when the QS value of Fe^II high-spin state becomes small. The transition temperature also increases by changing the anion from NCS to NCSe and then to NCBH₃.