Protonic Acid Research Articles

Substituent-directed ESIPT-coupled Aggregation-induced Emission in Near-infrared-emitting Quinazoline Derivatives.

A series of ESIPT (excited state intramolecular proton transfer) active systems (HQz1-HQz6) derived from quinazoline have been reported. The ESIPT emission for these derivatives gets completely quenched in solvents with diverse polarities which have been restored via aggregation-induced emission (AIE) with large Stokes shift (up to 314 nm). It varied from 450 to 701 nm just by altering substituents at the para position of hydroxy group in the central phenyl ring. As well, HQz1-HQz6 displayed solid state emission [∼455 (blue) to ∼704 nm (red)]. The formyl group on the central hydroxy-phenyl ring of these derivatives induces ESIPT by increasing acidity of the hydroxy proton which has been followed by 1 H NMR studies. Further, it has been clearly shown that emission colour and aggregate morphology can be fine tuned by incorporating apt substituents. The present study offers a simple route to obtain colour tunable ESIPT emission via AIE which is very important for biological imaging and fabrication of optoelectronic devices.

SYNTHESIS, STRUCTURE AND THERMAL PROPERTIES OF RHENIUM CARBONYL CONTAINING HETEROBIMETALLIC DERIVATIVES OF VANADIUM (III)

This paper describes the data on synthesis of bis(cyclopentadienyl)vanadium(III) of pentacarbonyl rhenium bistetrahydrofuranate complex with the reaction between dicyclopentadienylvanadium (III) chloride and rhenium sodiumpentacarbonyl in tetrahydrofurane (THF). Formed in this case the target product was separated from reaction mixture by extracting with hot hexane. Their reactionary ability in relation to protonic and aprotonic acids Lewis had been inverstigated. It is revealed, that at interaction of the above mentioned complexes with HCl there is a splitting Re-V bond with formation (C5H5)2VCl and HRe(CO)5; (C5H5)2VCl and HRe(CO)4PPh3 respectively. At interaction with HgCl2 also occurs having break V-Re bond and it turn out (C5H5)2VCl and (OC)5ReHgCl; (C5H5)2VCl and PPh3(OC)4ReHgCl. The interection of these complexes with ligands of various dentate is investigated. A monodentate liqand-triphenil phosphine (PPh3) substitutes one of carbonyl-groups in Re(CO)5) – fragment. Bidentate ligand- acetylacetone (acac) easily push out from coordination sphere vanadium more donor ligand cyclopentadienyl. The composition and structure of the complexes were characterized by the data of NMR, IR, EPR-spectroscopy and thermal analysis.

Organic Catalysis: Synthesis of Propylene Carbonate by the Carboxylation of Propylene Oxide in the Presence of Phenols and Fluorinated Alcohols

Phenol, polyphenols, as well as fluorinated alcohols actively catalyze the carboxylation of propylene oxide to form propylene carbonate in mild conditions (60°С, 7 at). The highest catalytic activity is characteristic of polyhydric phenols having neighbouring OH groups and alcohols with an enhanced acidity of OH protons. These catalysts in combination with tetrabutyammonium iodide exhibit activity at low concentrations (0.25 mol %) and ensure almost quantitative yields of propylene carbonate. The activity of the catalysts much increases with increasing ammonium salt amount (TOF up to 260), as well as temperature and initial СО2 pressure (TON up to 370).

Platinum and Molybdenum Oxide Supported on Mesostructured Silica Nanoparticles for n-Pentane and Cyclohexane Isomerization

Alkane isomerization into its equivalent branched isomers has gained numerous attention as a reaction to obtain high quality fuel. In this study, platinum and molybdenum oxide supported on mesostructured silica nanoparticles (Pt/MoO3/MSN) was prepared via impregnation method and tested for n-pentane and cyclohexane isomerization. The catalyst was characterized by using X-ray diffraction (XRD), nitrogen (N2) physisorption, and pyridine Fourier-transform infrared (pyridine-FTIR) spectroscopy. The IR result revealed that the addition of Pt and MoO3 into MSN formed different strength of Lewis and Brönsted acid sites. It was observed that the catalyst possessed strong acid sites and several numbers of relatively weak Lewis and Brönsted acid sites. Pt/MoO3/MSN was catalytically active towards n-pentane and cyclohexane isomerization with conversion of 63 and 87%, respectively, at 300 °C. It was proposed that the addition of Pt might assist the generation of active protonic acid sites from molecular hydrogen via the mechanism of hydrogen spillover and hence improve isomerization reaction.

PYRANOCHROMENES, THIOPYRANOCHROMENILIUM SALTS. PERSPECTIVES OF SYNTHESIS

The reactions of propanonilchromenes with protonic and aprotonic acids were investigated. The possibility of aromatisation of thiopyranochromen-2-ones’ 4Н-thiopiranic fragment was demonstrated using NMR 1Н spectroscopy method in time and new chromenothiopyrilium perchlorates (thriftoracetates) were discovered.

Synthesis and Characterizations of meso-Nitrocorroles

5,15-Bis(pentafluorophenyl)-10-nitrocorrole and its pyridinate Ga(III) complex were obtained by nitration of the corresponding meso-free corroles in moderate yields. The acidity of the central NH proton proved to be significantly increased in the freebase form, suggesting the stabilization of 2NH-corrole anionic state due to the resonance effect of the nitro group. Fluorescence quenching was observed for meso-nitrocorrole and its Ga(III) complex.

Sulphosuccinic acid as a novel dopant for solution processable polyaniline

This work reports on the use of sulphosuccinic acid (SSA), as a new organic dopant for polyaniline (PANI). The SSA doped PANI gives good conductivity and forms dispersions in both polar and non-polar solvents. PANI-SSA can also form aqueous dispersion without the use of any dispersion aids or stabilizers. Doping of PANI is carried out through two techniques, viz. (1) aqueous synthesis of emeraldine base of PANI (PANI-EB) from hydrochloric acid doped PANI (PANI-HCl) salt followed by protonic acid doping (in aqueous solution) with SSA and (2) in situ doping during polymerization of aniline in acid solution of SSA. The conductivity studies revealed that PANI-SSA re-doped from method (1) has a conductivity of 4.2 S/cm, which is four times higher than that of PANI-HCl and one order of magnitude higher than that of PANI-SSA synthesized by in situ method (2). The correlation between conductivity, microstructure evolution and crystallinity for the samples prepared using two different methods is also discussed.

Electrochemical performance of interspace-expanded molybdenum disulfide few-layer

Interspace-expanded molybdenum disulfide (IE-MoS2) has been designed as a supercapacitor electrode material to improve the cycling stability. IE-MoS2 was formed through the ultrasound exfoliation of the interspace-compacted molybdenum disulfide (IC-MoS2), which was initially prepared through hydrothermal synthesis using Na2MoO4 as molybdenum source and CH4N2S as sulfur source. As-formed IE-MoS2 shows a few-layer structure with approximate 8–16 monolayer packing and monolayer distance of 0.83 nm. The MoS2 few-layer distance increased from 12 nm of IC-MoS2 to 20 nm for IE-MoS2. The specific capacitance was determined to be 108 F g−1 for IC-MoS2 to 192 F g−1 for IE-MoS2 at 0.5 A g−1. The improved specific capacitance was ascribed to more active sulfur atom exposed at the edges of IE-MoS2 few-layer to conduct the promoted proton attachment reaction. IE-MoS2 showed the capacity retention of 42% when the current density increased from 0.5 to 10 A g−1, presenting the high-rate capability. IE-MoS2 achieved the capacity retention of 116% at 10 A g−1 after 5000 charge-discharge cycles, which was ascribed to the electro-activation of the few-layer expanded MoS2 in proton acid electrolyte solution. IE-MoS2 exhibited the obviously improved cycling stability in comparison with IC-MoS2. All solid-state IE-MoS2 supercapacitor based on two symmetric IE-MoS2 electrodes and H2SO4-PVA gel electrolyte exhibited the energy density of 18.75 Wh kg−1 and power density of 375 W kg−1 at 0.5 A g−1 and high voltage window of 1.5 V. IE-MoS2 supercapacitor also exhibited the improved capacity retention of 110% after 1000 charge-discharge cycles. Such well-designed IE-MoS2 few-layer with highly improved cycling stability performance presented the promising energy storage application.

Frequency independent AC electrical conductivity and dielectric properties of polyaniline-based conductive thermosetting composite

Abstract Electrical impedance characteristics of polyaniline (PANI)-dodecylbenzenesulfonic acid (DBSA)/divinylbenzene (DVB) composite were evaluated as a function of PANI content in the frequency range of 102–108 Hz. Polymer composites were prepared by a one-step thermal process where doping of the PANI and curing of the polymer matrix DVB have occurred simultaneously in the presence of a strong protonic acid, i.e. DBSA. The alternating current (AC) conductivity value with respect to frequency of the PANI-DBSA/DVB composite shows a direct current (DC) plateau up to an extensive frequency range. Almost metal-like behavior is obtained with such highly conductive plastic material. In all frequency regions, composites with higher PANI concentration showed a frequency independent behavior, while in the case of neat composites without PANI, a frequency dependent behavior is observed. A plot of the real part of complex impedance vs. frequency and a plot of AC conductivity of the composites indicate that the high electrical conductivity in high PANI concentration composites is because of the direct contacts between filler PANI particles. In this work, AC conductivity behavior and dielectric properties of very highly conductive thermoset composites are presented, and it is shown that conductivity is frequency independent for a very high frequency range (up to 108 Hz).

Modulation of the Prototropic Exchange Rate in pH‐Responsive Yb‐HPDO3A Derivatives as ParaCEST Agents

AbstractThe aim of this work was to design new pH‐sensitive paramagnetic chemical exchange saturation transfer (paraCEST) agents with a more acidic pH readout window with respect to the Yb complex of the 10‐(2‐hydroxypropyl)‐1,4,7,10‐ tetraazacyclododecane‐1,4,7‐triacetic acid (HPDO3A). In particular, three HPDO3A derivatives have been synthesized by substituting the methyl group on the 2‐hydroxypropyl arm with the electron withdrawing substituents –CF3, –CH2NH2 and –CH2OH. The Yb complexes have been characterized in terms of i) number and relative abundance of isomers present and, ii) pH sensitivity range in CEST applications. The influence of the introduced substituents on the –OH proton acidity and kex has been investigated and the new agents have been compared with the parent Yb‐HPDO3A. All complexes showed an increased acidity and an enhanced exchange rate of the –OH proton. As a consequence, the pH‐CEST sensitivity has been shifted to more acidic values. Eventually, the –CH2OH bearing derivative has been tested to assess the intra‐endosomal pH which is too acidic to be determined with Yb‐HPDO3A.

Green Synthesis of Haloformates from Olefins Using Formic Acid as Reactant, Protonic Acid, and Solvent

Bromoformates and iodoformates are successfully synthesized in high yields with regioselectivity and stereoselectivity by using ZnAl-BrO3 – layered double hydroxides (LDHs) and KX (X = Br, I) in the presence of formic acid (HCOOH). The protocol exploits the versatile function of formic acid as solvent, nucleophilic reagent, and acidic medium simultaneously, simplifying the reaction and separation of the products.

Proton-Controlled Organic Microlaser Switch.

Microscale laser switches have been playing irreplaceable roles in the development of photonic devices with high integration levels. However, it remains a challenge to switch the lasing wavelengths across a wide range due to relatively fixed energy bands in traditional semiconductors. Here, we report a strategy to switch the lasing wavelengths among multiple states based on a proton-controlled intramolecular charge-transfer (ICT) process in organic dye-doped flexible microsphere resonant cavities. The protonic acids can effectively bind onto the ICT molecules, which thus enhance the ICT strength of the dyes and lead to a red-shifted gain behavior. On this basis, the gain region was effectively modulated by using acids with different proton-donating ability, and as a result, laser switching among multiple wavelengths was achieved. The results will provide guidance for the rational design of miniaturized lasers with performances based on the characteristic of organic optoelectronic materials.

N-doped and N/Fe-codoped porous carbon spheres derived from tetrazine-based polypyrrole as efficient electrocatalysts for the oxygen reduction reaction

N-doped and N/Fe-codoped carbon materials are currently recognized as the most efficient electrocatalysts for the oxygen reduction reaction (ORR) because of their high catalytic activity, excellent stability, and superior tolerance to fuel. In this work, a novel kind of tetrazine-based polypyrrole spheres (PTPys) is prepared by protonic acid catalyzed Friedel-Crafts polymerization of bis(N-pyrrolyl)-1,2,4,5-tetrazine (TPy) with dimethoxymethane in dichloroethane. The resultant PTPys with a diameter of 100–300 nm are directly pyrolyzed at 900 °C to give N-doped porous carbon spheres (N/Cs-900 electrocatalyst). The N/Fe-codoped porous carbon spheres (Fe/N-Cs-900 electrocatalyst) are then constructed by mixing PTPys with Fe(OAc)2 followed by pyrolysis at 900 °C. The as-synthesized N/Cs-900 and Fe/N-Cs-900 electrocatalysts both have a well-defined spherical architecture together with a relatively high N content, high surface area and porosity. Owing to the synergistic influences, Fe/N-Cs-900 electrocatalyst exhibits excellent ORR activities in both alkaline and acidic electrolytes together with superior poisons tolerance in acidic media, whereas N/Cs-900 electrocatalyst displays ORR activity primarily in alkaline electrolyte. This approach can synthesize heteroatom-doped porous carbon spheres dispensing with the need for any templates, which is of great explored potentiality and utilized value.

PBI-Blended Membrane Evaluated in High Temperature SO2 Electrolyser

It has been shown that hydrogen, which can be used for energy storage, can be produced efficiently by the membrane based Hybrid Sulfur (HyS) process. During the HyS electrolysis step, SO2 and H2O are converted to H2 and H2SO4. The proton exchange membrane (PEM) used for this process should have both a high proton conductivity and acid stability. Since the widely used perfluorosulfonic type materials are restricted by their humidification requirements, materials such as polybenzimidazole (PBI) has been found to be promising in blends with partially fluorinated polyaromatic polymers at operating temperatures of 80 and 95 °C within the SO2 electrolyser. Operation at higher temperatures (>100 °C) however holds many advantages such as improved reaction kinetics and simplified water management. For this study a cross-linked partially fluorinated polyaromatic PBI blended membrane was evaluated at 120 °C. Humidified SO2 was supplied to the anode to produce sulfuric acid while hydrogen was formed at the cathode. The SO2:H2O feed was managed at the applied current densities until a constant voltage was obtained, and there after increased accordingly with increasing current density. Polarisation curves (Figure 1) recorded for the blended PBI membrane were comparable with reported s-PBI in literature values in the lower current density region (< 0.5 A/cm2). A maximum current density of 1.1 A/cm2 was reached in comparison to the 0.5 A/cm2 for s-PBI at a temperature of 110 °C. Voltage stability was monitored at a current density of 0.3 and 0.6 A/cm2 for a duration of 6 hours or until the maximum voltage had been reached. The lower current density (0.3 A/cm2) was more constant over the course of the measurement, with a standard deviation of 3 mV, when compared to the higher applied current density. These results are promising for further testing and optimization of the blended PBI membranes for higher temperature SO2 electrolysis. Figure 1

Soluble Molecularly Imprinted Nanorods for Homogeneous Molecular Recognition.

Nowadays, it is still difficult for molecularly imprinted polymers (MIPs) to achieve homogeneous recognition since they cannot be easily dissolved in organic or aqueous phase. To address this issue, soluble molecularly imprinted nanorods have been synthesized by using soluble polyaniline doped with a functionalized organic protonic acid as the polymer matrix. By employing 1-naphthoic acid as a model, the proposed imprinted nanorods exhibit an excellent solubility and good homogeneous recognition ability. The imprinting factor for the soluble imprinted nanoroads is 6.8. The equilibrium dissociation constant and the apparent maximum number of the proposed imprinted nanorods are 248.5 μM and 22.1 μmol/g, respectively. We believe that such imprinted nanorods may provide an appealing substitute for natural receptors in homogeneous recognition related fields.

Self-suspended polypyrrole with liquid crystal property

Polypyrrole (PPy) has attracted wide attention due to its high conductivity, environmental stability, low cost, facile synthesis and doping. However, the rigid backbone and π-conjugation structure of polypyrrole lead to the poor solubility and processability and thus restricting its applications. In this letter, self-suspended PPy was obtained by using a long-chain protonic acid CH3(CH2)8C6H4(OCH2-CH2)10SO3H (NPES) as dopant and then through a common dialysis. Such unique structured PPy is a kind of solvent-free fluid which can flow at or near room temperature. The solubility and processability of self-suspended polypyrrole have been improved effectively due to the introduction of oxyethylene groups and alkyl group. And it also directly presents unique liquid crystal property. Moreover, the self-suspended polypyrrole exhibited a relatively high electrical conductivity reached up to 0.11 S/m, presenting a typical characteristic of the semiconductor. Such self-suspended polypyrrole could be a promising alternative in the field of lightweight battery, super capacitor and metal anti-corrosion.

Proton Conducting Polyoxometalate/Polypyrrole Films and Their Humidity Sensing Performance

Proton conducting polyoxometalate has received considerable attention because of its unique structural properties. This article reports the fabrication of hybrid polymer films of polypyrrole/polyoxometalate and their resistive-type humidity sensing performance. Hybrid polymer films with different thicknesses were prepared via the coelectrodeposition of free pyrrole monomers with metal oxide clusters. A sensing response of 1.9 s and a recovery time of 1.1 s were exhibited in a 59 nm thick sample at 98% relative humidity and in a sensing range of 11–98% relative humidity. The outstanding sensing in the polypyrrole chain could be ascribed to the synergistic effect of the proton acid doping structure and the oxidation doping structure. The humidity sensor based on the nanocomposite was repeatable even after two months with good response and recovery times.

Solution processed intrinsically conductive polymer films with high thermoelectric properties and good air stability

Dedoping of protonic acid doping can significantly increase the Seebeck coefficient.

PH switch for OH-photoacidity in 5-amino-2-naphthol and 8-amino-2-naphthol.

Photoactive charge transfer compounds are of strong interest for their potential applications in material, chemical, and biological science and their abilities to elucidate fundamental charge transfer mechanisms. Aminonaphthols, photoacids with both oxygen (OH) and nitrogen-based (NH2) protonation sites, have been reported to undergo simultaneous excited-state proton transfer (ESPT) in water upon excitation. In this paper, the ESPT mechanism for zwitterion formation in 8-amino-2-naphthol (8N2OH) and 5-amino-2-naphthol (5N2OH) was examined using a combination of time-resolved emission spectroscopy and time-dependent density functional theory (TD-DFT) calculations. The measurements prompted a re-assignment of the zwitterion state in the steady-state emission spectra; analysis of the time-correlated single-photon counting emission data showed that the zwitterion was formed only from excitation of protonated 5N2OH and 8N2OH such that ESPT occurred only at the single hydroxyl group. The protonation state of the amino group dramatically altered the photoacidity of OH, such that the pH behaved as an on/off switch for photoacidity. In the protonated state (NH3+), the pKa*(OH) values of 5N2OH and 8N2OH were both 1.1 ± 0.2, while in the deprotonated state (NH2), the two pKa*(OH) values were similar to the ground state proton acidity, pKa(OH) = 9.5 ± 0.2. The switching of the photoacidity was investigated using TD-DFT calculations and the linear free energy Hammett relation. The latter was shown to not describe the excited state data over the broad pH range.

Comparison of Molecular Acidity of Proton Acids

Comparison of Molecular Acidity of Proton Acids