Freezing the polarization of CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite films

Thin films of methylammonium lead halides, CH₃NH₃PbI₃ and CH₃NH₃PbI_3-xCl_x, were deposited onto symmetrical microstructured electrode arrays of gold or platinum on Si/SiO₂ wafers. Polarization studies were carried out on perovskite films under vacuum in the dark. For poling, a constant voltage was applied to the samples while the temperature was cycled between 295 K and 4 K. The measured current densities depending on the temperature showed distinct characteristics relating strongly to the crystal phase and the dielectric properties of the perovskite films. Voltage sweeps were carried out at different scan rates at specific temperature intervals after poling. The polarization of the films due to the migration of iodide vacancies in direction of the blocking perovskite/metal interface was frozen almost up to room temperature. Charge carriers were only able to cross the blocking barrier and contribute to the current where the ions have accumulated during poling. All J-V curves showed hysteresis: inverted and regular hysteresis at room temperature and below, respectively. Inverted hysteresis originates from the slow accumulation of ions at the blocking barrier, while regular hysteresis arises from a distortion in the adjacent crystals which will be discussed.     

Synthesis of Purine and Pyrimidine 3'-Amino-3'-deoxy- and 3'-Amino-2',3'-dideoxyxylonucleosides

A general procedure to obtain the 3'-aminoxylonucleosides 13a,b and 17a,b is presented. The synthetic scheme is based on the 5' directed intramolecular nucleophilic substitution at the 3'-activated position of the nucleoside. The approach of the incoming group to this position takes place regio- and stereoselectively from the most hindered face of the nucleoside. The methodology presented is applicable to ribonucleosides and 2'-deoxyribonucleosides, regardless of their nitrogenated base.     

Sorption of microamounts of Ce3+, Pm3+, Eu3+, Gd3+ and Yb3+ on aluminium hydroxide

The sorption of microamounts of trivalent lanthanides (Ln³⁺) on freshly precipitated Al(OH)₃ has been measured in dependence on pH and the time of sorption. Also, the influence of organic complexing ligands and inorganic electrolytes on the sorption process has been investigated. The mechanism of sorption is discussed. Freshly precipitated Al(OH)₃ can be used for the preconcentration of microamounts of trivalent lanthanides. However, the preconcentration is not quantitative in the presence of high concentrations of complexing ligands (citrate and similar) which form strong complexes with Ln³⁺ ions.     

Synthesis and Upconversion Luminescence in LaF3:Yb3+, Ho3+, GdF3: Yb3+, Tm3+ and YF3:Yb3+, Er3+ obtained from Sulfide Precursors

Rare earth fluorides are mainly obtained from aqueous solutions of oxygen‐containing precursors. Probably, this method is simple and efficient, however, oxygen may partially be retained in the fluoride structure. We offer an alternative method: obtaining fluorides and solid solutions based on them from an oxygen‐free precursor. As starting materials, we choose sulfides of rare‐earth elements and solid solutions based on them. The fluorination is carried out by exposure to hydrofluoric acid of various concentrations. The transmission electron microscopy images revealed the different morphologies of the products, which depend on the concentration of the fluorinating component (HF) and the host element. The solid solution particle size varied from 30–35 nm in the case of GdF₃:Yb³⁺, Tm³⁺ (4 % HF) to larger structures with dimensions exceeding 200 nm, such as that for LaF₃:Yb³⁺, Ho³⁺ (40 % HF). The thermal characteristics, such as the temperatures of the transitions and melting and enthalpies, were determined for the solid solutions and simple fluorides. Applicability of the materials obtained as biological luminescent markers was tested on the example of upconversion luminescence, and good upconversion properties were detected.     

Preparation and polymerization of 3-acrylamido-3-methylbutanoic acid

The preparation of 3-acrylamido-3-methylbutanoic acid by a haloform reaction on diacetone acrylamide and by a Ritter reaction between acrylonitrile and β,β-dimethylacrylic acid is reported. The properties of this crystalline monomer and its homopolymer are also reported.     

Transition metal complexes of 3-cyano- and 3-nitroformazans

The synthesis and characterization of six transition metal complexes of 3-cyano- and 3-nitroformazans are described. Three different formazans were reacted with nickel(II) to produce complexes with bidentate formazan ligands. Mononuclear NiL2 (L = deprotonated formazan) or binuclear hydroxo-bridged (LNi)2(mu-OH) 2 species were produced depending on the steric bulk on the formazan N-aromatic substituents. 1,5-Bis(2-methoxyphenyl)-3-cyanoformazan acts as a tetradentate monoanionic ligand in a copper(II) complex, whereas the analogous 1,5-bis(2-hydroxyphenyl)-3-cyanoformazan binds as a trianion in a tetradentate manner to Fe(III) and Co(III). Crystal structures-the first examples of metal complexes of cyano- or nitroformazans-as well as the electronic spectra of the complexes are discussed in relation to each other as well as that of the uncoordinated formazans.     

3-R-Thio- and 3-R-Oxy-substituted metal acetylacetonates

New S- and O-substituted metal acetylacetonates were prepared from phenylthio-, butylthio-, benzenesulfonato-, and 3-acetoxyacetylacetone and appropriate metal salts. The spectral characteristics of the compounds were obtained. The effect of the α-substituent on the stability of the chelates under the conditions of chromatographic separation on silica gel was revealed. The reactivity of the acetate group bonded to the chelate ring is decreased, which does not allow preparation of new substituted complexes by common transformations of esters.     

The conformation of 3-acetyl-Δ3-carene and 3-carene-7-al

Conclusions The conformations of 3-acetyl-³-carene and 3-carene-7-al were established on the basis of the spectral data and molar Kerr constants.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 994–998, May, 1971.     

Convenient synthesis of 3-vinyl and 3-styryl coumarins

A variety of 2-hydroxy aldehydes on reaction with 3-butenoic acid afford in a one-pot reaction the corresponding 3-vinylcoumarins. As expected, extension of the delocalized π-electron system accomplished by Heck coupling reactions with aryl halides results in an increased fluorescence of the compounds whose applicability is yet to be established.     

Palladium-mediated arylation of 3-aminopiperidines and 3-aminopyrrolidines

This paper describes the palladium-catalyzed arylation of 1-substituted 3-aminopyrrolidines or piperidines. Palladium(0) (1-2 mol %) in conjunction with "Buchwald's ligand" [2-(dimethylamino)-2'-(dicyclohexylphosphine)biphenyl] was shown to be the catalyst of choice for the coupling with aryl bromides or chlorides. When bromobenzene was used, a strong temperature effect was noticed. Whereas no reaction occurred at 100 degrees C, yields higher than 85% were obtained at 130 degrees C for each substrate. Such an effect was not observed when diphosphines were used. Whereas Xantphos and, to a lesser extent BINAP, were moderately efficient in the coupling of all diamines, the palladium-mediated arylation in the presence of monophosphines was strongly dependent on the substrate. The results suggest the participation of both nitrogens of the aminoheterocycle in the reactive intermediate. This participation could also account for the highly selective arylation of the endocyclic nitrogen of unsubstituted 3-aminopyrrolidine or piperidine. Optimal conditions were found for the arylation using 2- or 4-substituted electron-poor or enriched aryl halides.     

3-甲基噻吩和3-氯噻吩的电化学共聚

3-甲基噻吩和3-氯噻吩首次三氟化硼乙醚溶液中实现了电化学共聚。共聚物的分子结构通过电化学分析、红外和拉曼光谱得到了证实。实验结果表明：单体投料比对共聚物的结构和电化学性质有很大的影响;共聚物比3-甲基噻吩和3-氯噻吩的均聚物具有更大的充放电电容和更可逆的氧化还原性质。     

3-nitro- and 3-bromo-3-nitroacrylates in reactions with phenyl azide

1,3-Dipolar cycloaddition of alkyl 3-nitro-and 3-bromo-3-nitroacrylates to phenyl azide gives regioisomeric alkyl 5(4)-nitro-1-phenyl-4,5-dihydro-1H-1,2,3-triazole-4(5)-carboxylates, the corresponding triazoles both with and without nitro group, and alkyl 3-nitro-1-phenylaziridine-2-carboxylates. Nitrotriazolecarboxylates were found to lose the ester moiety during chromatographic separation of the products on aluminum oxide. The structure of the products was determined on the basis of IR, ¹H NMR, and X-ray diffraction data.     

Generation of 3-Carbanion Species from 3-Phenylsulfinyl- and 3-Phenylsulfonyl Propionic Acids

During the course of studies on butenolide synthesis¹ we have investigated the utilities of 3-sulfur-functionalized propionic acid derivatives. We report the results with 3-carbanion species obtained from 3-phenylsulfiny1- and 3-phenylsulfonylpropionic acids (1) and (2). These compounds were easily prepared from 3-phenylthiopropionic acid.     

Novel synthesis, reactivity, and stereochemistry of substituted 3-trifluoromethyl- and 3-perfluoroalkyl-3-phenoxyprop-2-enal

Substituted 3-phenoxy-3-perfluoroalkylprop-2-enals 3a-s are synthesized in high yields starting from a gem-iodoacetoxy derivative 1 and phenoxides 2. Then efficient syntheses of push-pull derivatives 4, 5,8a,b, and nonconjugated analogues 6 and 7 illustrate the synthetic potentialities of 3. Stereochemical studies of these perfluoroalkyl-containing trisubstituted olefinic derivatives 3-8b revealed that the (4)J(CF) coupling constant observed in the (13)C NMR spectra was crucial in the determination of their configurations and conformations in solution. The solvent polarity effect on the stereochemistry of push-pull compounds 3-5 and 8a,b was studied. Unusual significant medium polarity effect on the stereochemistry of imino enol ether derivative 4 was observed.     

Magnetic circular dichroism spectra of some 3-arylfervenulins and 3-aryltoxoflavins

The magnetic circular dichroism (MCU) spectra of some 3-arylfervenulins and 3-aryltoxo-flavins were measured. From the dependence of the Faraday B values of 3-arylfervenulins and 3-aryltoxoflavins on the Hammet σpara values, it is concluded that the substituent effects on the Faraday B values of 3-aryltoxoflavins are reverse to the substituent effects on the Faraday B values of 3-arylfervenulins and the reverse property of 3-aryltoxoflavins concerning the substituent effects rises from the contribution of the 1,5-dipolar structure of 3-aryltoxoflavins.     

Light scattering and intrinsic viscosity investigation of polymethyl-3, 3, 3-trifluoropropylsiloxamer

Solution parameters for the polymer poly-γ-trifluoro-propylmethylsiloxamer has been determined in cyclohexyl acetate, methyl hexanoate, and ethyl acetate. Interpretation of data follows the theory of Fox and Flory. In contrast to poly-dimethylsiloxane, an increased steric hindrance to rotation about the siloxane bond occurs as evidenced by the characteristic ratio of root-mean-square end to end dimensions, (r₀² /r_0f² )^1/2, found to be 1.90 and 1.96 at 25.0 and 72.8°C, respectively. This increase is considered to be primarily due to nearest-neighbor interaction of the polar substituent on the silicon atom. The relation, [η]θ ∝ M^1/2, was observed to hold for this polymer system. The hydrodynamic model appropriate for the polymer is a random coil considerably more permeable to solvent flow than is generally reported for linear polymers. The universal parameter ? was determined to be 1.5 × 10²¹. The effect of temperature on polymer configuration is indicated to be negligible.     

On the Side-Chain Bromination of 3-Methylselenophene and 3-Methylthiophene

3-Bromomethylselenophene can be prepared from 3-methyl-selenophene, N-bromosuccinimide and azo-bis-isobutyronitrile in carbon tetrachloride in 25% yield with the reversed addition method described in this paper. The method also gives consistently high yields of 3-bromomethylthiophene (70–75%) when applied on 3-methylthiophene.     

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

The pyrolysis of the simplest azides HN(3) and CH(3)N(3) has been studied computationally. Nitrogen extrusion leads to the production of NH or CH(3)N. The azides have singlet ground states but the nitrenes CH(3)N and NH have triplet ground states. The competition between spin-allowed decomposition to the excited state singlet nitrenes and the spin-forbidden N(2) loss is explored using accurate electronic structure methods (CASSCF/cc-pVTZ and MR-AQCC/cc-pVTZ) as well as statistical rate theories. Nonadiabatic rate theories are used for the dissociation leading to the triplet nitrenes. For HN(3), (3)NH formation is predicted to dominate at low energy, and the calculated rate constant agrees very well with energy-resolved experimental measurements. Under thermal conditions, however, the singlet and triplet pathways are predicted to occur competitively, with the spin-allowed product increasingly favored at higher temperatures. For CH(3)N(3) thermolysis, spin-allowed dissociation to form (1)CH(3)N should largely dominate at all temperatures, with spin-forbidden formation of (3)CH(3)N almost negligible. Singlet methyl nitrene is very unstable and should rearrange to CH(2)NH immediately upon formation, and the latter species may lose H(2) competitively with vibrational cooling, depending on temperature and pressure.     

Aromatisation of 3-carbomethoxy-3-methyl-3h-pyrazol solvent effect and catalysis through acid

At 60° the title compound isomerises quantitatively to aromatic products $\text{3}$ and $\text{4}$. A kinetic study reveals the influence of solvent polarity and of acid on the rate and direction of this reaction.     

Synthesis of 3-acylamino- and 3-carbethoxy-2-benzopyrylium salts

High yields of 3-acylamino-2-benzopyrylium salts are formed in the acylation of 3,4-dimethoxy- and 3,4-methylenedioxyphenylacetonitrile. The salts are converted to 4-isoquinolones on treatment with ammonia. The acylation of ethyl 3,4-dimethoxyphenylglycidate ester also results in heterocyclization to 3-carbethoxy-2-benzopyrylium salts, which are converted to high yields of the corresponding 3-carbethoxyisoquinolines by treatment with ammonium hydroxide. The mechanisms of these transformations are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 730–732, June, 1971.