Ultrasound-promoted greener synthesis of 2H-chromen-2-ones catalyzed by copper perchlorate in solventless media

Copper perchlorate is found to be a heterogeneous catalyst for an efficient and greener synthesis of 4-substituted 2H-chromen-2-ones via von Pechmann condensation of substituted phenols and β-keto esters in solventless media with excellent yields using ultrasound irradiation. The present methodology offers several advantages such as excellent yields, simple procedure and milder conditions.     

An efficient and green one-pot synthesis of tetrahydrobenzo[a]xanthenes, 1,8-dioxo-octahydroxanthenes and dibenzo[a,j]xanthenes by Fe3O4@Agar-Ag as nanocatalyst

Molecular Diversity - Agar-coated Fe3O4 nanoparticles (Fe3O4@agar) were prepared simply through in situ co-precipitation of Fe2+ and Fe3+ ions via NH4OH in an aqueous solution of Agar. Coating of...     

Ultrasound-promoted synthesis of oximes catalyzed by a basic ionic liquid [bmIm]OH

The basic ionic liquid 1-butyl-3-methylimidazolium hydroxide, [bmIm]OH, efficiently catalyzes the condensation reaction of aldehydes and ketones with hydroxylamine hydrochloride under ultrasound irradiation. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields.     

Ultrasound-promoted greener synthesis of benzoheterocycle derivatives catalyzed by nanocrystalline copper(II) oxide

CuO nanoparticles provide an efficient, economic, and novel method for the synthesis of quinoxaline, benzoxazine, and benzothiazine under ultrasonic irradiation. The protocol offers advantages in terms of higher yields, short reaction times, and mild reaction conditions, with reusability of the catalyst.     

Ultrasound-promoted greener synthesis of 2,4,5-trisubstituted imidazoles catalyzed by Zr(acac)4 under ambient conditions

A simple, efficient and green procedure has been developed for the synthesis of 2,4,5-trisubstituted imidazoles catalyzed by zirconium (IV) acetylacetonate using ultrasonic irradiation. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times and milder conditions.     

Poly(4-vinylpyridinium)hydrogen sulfate: a novel and efficient catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under conventional heating and ultrasound irradiation

A simple and convenient procedure for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes is described through a one-pot condensation of 2-naphthol with aryl aldehydes in the presence of poly(4-vinylpyridinium)hydrogen sulfate as an efficient, cheap, readily synthesized and eco-friendly catalyst in a solvent free media using conventional heating and ultrasound irradiation.     

Ultrasound-promoted regio and chemoselective synthesis of pyridazinones and phthalazinones catalyzed by ionic liquid [bmim]Br/AlCl3

The first ultrasound-promoted multicomponent synthesis of pyridazinones and phthalazinones from arenes, cyclic anhydrides and ArNHNH₂ in the presence of an efficient recyclable catalyst, [bmim]Br/AlCl₃, in high yield and short reaction time is reported.     

Origin of antiferroelectricity in NH4H2PO4 from first principles

The low-temperature antiferroelectric (AFE) phase of NH4H2PO4 corresponds to H ordering in O-H-O bridges leading to H2PO4 group polarizations perpendicular to the tetragonal c axis and alternating in chains. We determine the microscopic origin of such order by means of first-principles calculations in the framework of the density functional theory. The formation of N-Hcdots, three dots, centeredO bridges with correlated charge transfers and NH4+ group distortions turn out to be essential in stabilizing the AFE configuration against a c-polarized ferroelectric (FE) phase, as well as other FE states polarized perpendicular to the c axis. These FE states lie only a few meV above the AFE phase, which explains the observation of FE-AFE phase coexistence near the AFE transition.     

Crystal structure of di-(L-serine) phosphate monohydrate [C3O3NH7]2H3PO4H2O

The crystal structure of di-(L-serine) phosphate monohydrate [C₃O₃NH₇]₂H₃PO₄H₂O is determined by single-crystal x-ray diffraction. The intensities of x-ray reflections are measured at temperatures of 295 and 203 K. The crystal structure is refined using two sets of intensities. It is established that, in the structure, symmetrically nonequivalent molecules of L-serine occur in two forms, namely, the monoprotonated positively charged molecule CH₂(OH)CH(NH₃)⁺COOH and the zwitterion CH₂(OH)CH(NH₃)⁺COO^?, which are linked with each other and with the H₂PO ^?₄ ion through a hydrogen-bond system involving water molecules.

     

Electrical relaxation in proton conductor composites based on (NH4)H2PO4/TiO2

We report on electrical relaxation measurements of (1 − x)NH₄H₂PO₄-xTiO₂ (x = 0.1) composites by admittance spectroscopy, in the 40-Hz–5-MHz frequency range and at temperatures between 303 and 563 K. Simultaneous thermal and electrical measurements on the composites identify a stable crystalline phase between 373 and 463 K. The real part of the conductivity, σ’, shows a power-law frequency dependence below 523 K, which is well described by Jonscher’s expression , where σ ₀ is the dc conductivity, ω _p /2π = f _p is a characteristic relaxation frequency, and n is a fractional exponent between 0 and 1. Both σ ₀ and f _p are thermally activated with nearly the same activation energy in the II region, indicating that the dispersive conductivity originates from the migration of protons. However, activation energies decrease from 0.55 to 0.35 eV and n increases toward 1.0, as the concentration of TiO₂ nanoparticles increases, thus, enhancing cooperative correlation among moving ions. The highest dc conductivity is obtained for the composite x = 0.05 concentration, with values above room temperature about three orders of magnitude higher than that of crystalline NH₄H₂PO₄ (ADP), reaching values on the order of 0.1 (Ω cm)^− 1 above 543 K.     

Ultrasound-promoted a green protocol for the synthesis of 2,4-diarylthiazoles under ambient temperature in [bmim]BF4

A mild, efficient, facile and eco-friendly procedure for the synthesis of 2,4-diarylthiazoles from arylthioamides and α-bromoacetophenones in 1-n-butyl-3-methylimidazolium tetrafluoroborate as a “green” media under ultrasound irradiation at room temperature is described. It is interesting to mention that only one product was obtained when two different α-bromoacetophenones were reacted with 1,3-phenyl dithioamide as the substrate. Work-up is very simple and there is no need to purify the product. A recycling study confirmed that the ionic liquid can be reused multiple times without a significant loss in its activity.     

一种新型钼磷酸盐杂多化合物(NH3CH2CH2NH3)7H2[NaMo12O30(PO4)2(HPO4)5(H2PO4)]·7H2O的合成和光谱研究

本文采用水热反应条件 ,合成得到一种新型的含五价钼原子的杂多化合物 :(NH3CH2 CH2 NH3) 7H2[NaMo1 2 O30 (PO4 ) 2 (HPO4 ) 5(H2 PO4 ) ]·7H2 O ,在晶体结构测定的基础上对其进行红外、拉曼和紫外 可见漫反射光谱研究。结果表明 :较长的Mo(Ⅴ )—O键键长和分子内大量的氢键造成化合物红外光谱特征的红移。     

Organic synthesis in water: a green protocol for the synthesis of 2-(cyclohexylamino)-3- aryl- indeno[1,2-b]furan-4-ones

Aldehydes, 1,3-indandione and cyclohexylisocyanide undergo smooth coupling-cyclization in water to produce the corresponding 2-(cyclohexylamino)-3-aryl- indeno [1,2-b] furan-4-ones in good yields. Water was used as a solvent to avoid the use of other highly toxic and environmentally unfavorable solvents for this synthesis.

---

Graphical Abstract  A simple and efficient synthesis of 2-(cyclohexylamino)-3-aryl- indeno[1,2-b]furan-4-ones was achieved via a one-pot three-component reaction of cyclohexylisocyanide, aldehydes, and 1,3-indandione in water for 5 h in good yields. zFX

     

Ultrasound-promoted synthesis of 1-amidoalkyl-2-naphthols via a three-component condensation of 2-naphthol, ureas/amides, and aldehydes, catalyzed by sulfamic acid under ambient conditions

A three-component one-pot condensation of 2-naphthol, ureas/amides and aldehydes catalyzed by sulfamic acid, under ultrasound irradiation and ambient conditions gives 1-amidoalkyl-2-naphthols in excellent yield and in short time.     

Transient optical absorption of hole polarons in ADP (NH4H2PO4) and KDP (KH2PO4) crystals

A study of transient optical absorption of the ADP (NH₄H₂PO₄) and KDP (KH₂PO₄) nonlinear crystals in the visible and UV spectral regions is reported. Measurements made by absorption optical spectroscopy with nanosecond-time resolution established that the transient optical absorption (TOA) of these crystals originates from optical transitions in the hole A and B radicals and the optical-density relaxation kinetics is rate-controlled by interdefect tunneling recombination, which involves these hole centers and the electronic H⁰ centers representing neutral hydrogen atoms. At 290 K, hole polarons and the H⁰ centers undergo thermally stimulated migration, which is not accompanied by carrier ejection into the conduction or valence band. The slow components of the TOA kinetics with characteristic times from a few tens of milliseconds to a few seconds can be assigned to diffusion-controlled annihilation of hydrogen vacancies associated with impurity or structural defects.     

Thermochromic Phase Transition in [NH2(C2H5)2]2CuCl4 Crystals

The absorption spectra of [NH₂(C₂H₅)₂]₂CuCl₄ crystals in the visible spectral region in the vicinity of the thermochromic phase transition at T ₁ = 311 K are investigated. It is shown that in these crystalline compounds the phenomenon of thermochromism is primarily associated with the change of the plane-quadratic geometry of the coordination environment of Cu²⁺ to the tetrahedral form. The influence of ionizing irradiation on the phase-transition temperature and on the thermochromic properties of this crystal is studied.     

Raman studies of phase transitions in ferroelectric [C2H5NH3]2ZnCl4

The present paper accounted for the synthesis, differential scanning calorimetric and vibrational spectroscopy of [C₂H₅NH₃]₂ZnCl₄grown at room temperature. Differential scanning calorimetric (DSC) disclosed five phase transitions at T₁=231 K, T₂=234 K, T₃=237 K, T₄=247 K and T₅=312 K. The temperature dependence of the dielectric constant at different temperatures proved that this compound is ferroelectric below 238 K. Raman spectra as function temperature have been used to characterize these transitions and their nature, which indicates a change of the some peak near the transitions phase. The analysis of the wavenumber and the line width based on the order–disorder model allowed to obtain information relative to the thermal coefficient and the activation energy near the transitions phase.     

An efficient synthesis of 3,4-dihydropyrimidin-2-ones catalyzed by NH2SO3H under ultrasound irradiation

The condensation of aldehydes, beta-keto esters and urea catalyzed by NH(2)SO(3)H in ethanol results dihydropyrimidinones in high yields under ultrasound irradiation.     

Optical,structural characterization and dielectric relaxation of [C2H5NH3]2ZnCl4 compound

ABSTRACT

The new organic-inorganic compound [C₂H₅NH₃]₂ZnCl₄ has been grown by the slow evaporation at room temperature. The zero-dimensional (0-D) structure for this compound was determined by the single X-ray diffraction. It crystallizes at room temperature in the non-centrosymmetric space group Pna2₁ and consists of ethylammonium cations [C₂H₅NH₃]⁺ and [ZnCl₄]^2? tetrahedra anions. That is interconnected by means of hydrogen bonding contacts N-H···Cl. The molecular geometry and vibrational frequencies of [ZnCl₄]^2? and [C₂H₅NH₃]⁺ in the ground state was calculated using density functional method (B3LYP) with 6–31G(d) and 6–311G (d,p) basis set. The optimized geometric bond lengths and bond angles, obtained by using B3LYP/6–311G (d,p), show the best agreement with the experimental data. The optical absorbance was measured in order to deduce the absorption coefficient α, optical band gap E_g. The optical band gap is determined by extrapolating the plotted graph of (αhυ)^1/2 vs. (hυ). The large value of indirect optical band gap energy indicates the insulating nature of this material. Moreover, the extinction coefficient, refractive index and the dielectric permittivity of [C₂H₅NH₃]₂ZnCl₄ compound were calculated and the results are discussed. The evolution of the dielectric loss as a function of frequency revealed a distribution of relaxation times, probably ascribed to the reorientational dynamics of alkyl chains in this compound, and then analyzed with the Cole–Cole formalism.     

Vibrational Spectra of [Zn(15NH3)4] (ReO4)2 and [Cd(NH3)4] (ReO4)2 With 110Cd/116Cd and H/D Isotopic Substitution

The infrared spectra of the zinc tetraammine with ¹⁵N, and cadmium tetraammine perrhenates with ¹¹⁰Cd/¹¹⁶Cd and H/D isotopic substitution, provides useful data in determining skeletal pseudo - exact force constants. An approximate set of force constants in the F₂ symmetry class for the whole complexes were obtained.