Isopropanol Molecules Research Articles

The Role of Frustrated Lewis Pair in Catalytic Transfer Hydrogenation of Furfural using Nickel Single-Atom Catalysts: A Theoretical Study.

The burgeoning field of frustrated Lewis pair (FLP) heterogeneous catalysts has garnered significant interest in recent years, primarily due to their inherent ability to activate H-source molecules, thereby facilitating hydrogenation reactions. In this study, non-precious transition metal atoms were anchored onto several models of pyridinic nitrogen incorporated graphene sheet. Theoretical calculations substantiated energy barriers as low as 0.10 eV for isopropanol activation, thereby positioning these catalysts as highly promising candidates for catalytic transfer hydrogenation of furfural. Electronic structure analyses revealed that the H-O bond breakage in isopropanol molecules was significantly facilitated by the presence of FLP sites within the catalysts. Notably, both Ni-C2N and Ni-N6-C demonstrated exceptional potential as selective catalysts for the hydrogenation of furfural into furfuryl alcohol, exhibiting remarkably low barriers of only 0.65-0.72 eV for the rate-determining steps. The findings in this study are helpful to design FLP containing single atom catalysts for hydrogenation reactions.

1,2-bis(triethoxysilyl)methane (BTESM)-derived organic–inorganic membranes with controlled sol particle size: Preparation and pervaporation dehydration performance of isopropanol aqueous solutions

1,2-bis(triethoxysilyl)methane (BTESM) is a bridged-type organoalkoxysilane, which was utilized for organic–inorganic membranes preparation via a sol–gel method to achieve high permselectivity, thus are promising for dehydration and purification of organic solvents. However, the particle size of the derived sol is crucial for membrane preparation during sol–gel processing, significantly influencing the membrane’s performance. Herein, we reported a novel strategy of controlling the sol particle size by adjusting the pH during the preparation process. BTESM-derived membranes were prepared by BTESM-H+ sol and BTESM-swing sol, which were subsequently employed for the dehydration of isopropanol (IPA) through pervaporation (PV). Compared with the BTESM-H+ sol, the particle size of the BTESM-swing sol prepared by the pH-swing method was increased from 1.3 nm to 32.7 nm. The larger particle size could hinder the permeation into the intermediate layer. Meanwhile, the dense arrangement of silica particles could efficiently retain IPA molecules, thereby substantially enhancing the rejection rate of IPA. The average particle size of the BTESM-swing sol was 18.7 nm at an acid-base ratio of 1.2 and acid-silicon ratio of 0.55, resulting a permeate flux of 1.04 kg·m−2·h−1 and separation factor of 521, while IPA rejection rate was 97.84 %. This work has shown that adjusting the pH during the process is a useful strategy of controlling the sol size for the preparation of organic–inorganic membranes. Hence, the control of sol particle size to achieve a high-performing membrane layer offers a novel approach to producing diverse membrane materials.

Broadband multiple resonant metasurface for mixture surface-enhanced infrared absorption based on polarization-sensitive folded nanoantennas

Multiple resonant metasurfaces for mixture component detection by surface-enhanced infrared absorption in a broadband spectrum region are still highly desirable. This paper presents a polarization-sensitive multi-resonant broadband metasurface in the mid-infrared (MIR) region based on an odd symmetric folded antenna array. Six major resonant modes are effectively excited in 6–15 μm covering the absorption peak of multiple gases and biomolecules. In addition, the calculation indicates the maximum electric field intensity enhancement reaches 3607 and the average electric enhancement factors are dominantly amplified to a maximum of 75.08. The excited multiple hotspots provide more spatial overlap with analytes and would be beneficial for label-free detection. Moreover, owing to the contributions of the intrinsic phonons and polaritons in the ENZ material, the spectroscopy features are relatively stable when changing the geometry parameters and the incident angles, allowing more fabrication tolerance and experiment flexibility. Furthermore, the multiple resonant metasurface is also effectively enabled under orthogonal circular polarizations. Finally, the sensing abilities of the designed metasurface for polyethylene terephthalate and isopropanol molecules have been computationally validated. These results indicate the potential for nanophotonic detection and mixture spectroscopy analysis.

Amorphous SiO2 Surface Irregularities and their Influence on Liquid Molecule Adsorption by Molecular Dynamics Analysis

As the semiconductor industry relentlessly reduces device sizes, efficient and precise cleaning processes have become increasingly critical to address challenges such as nanostructure stiction. Gaining insight into the molecular behavior of water and isopropyl alcohol (IPA) on silicon dioxide (SiO2) surfaces is essential for controlling semiconductor wet cleaning processes. This study investigated the interactions between these liquids and SiO2 surfaces. Using molecular dynamics (MD) simulations, we examined the adsorption behavior of water and IPA molecules on both amorphous and crystalline SiO2 (a-SiO2 and c-SiO2) surfaces. Our findings reveal a preferential adsorption of water molecules on a-SiO2 surfaces compared to c-SiO2. This preference can be ascribed to the irregularity of the a-SiO2 surface, which results in the presence of silanol groups that remain inaccessible to the liquid molecules. In contrast, the c-SiO2 surface exhibits a more uniform and accessible structure. This study not only imparts crucial insights into the molecular behavior of water and IPA on SiO2 surfaces but also provides valuable information for future enhancements and optimization of semiconductor wet surface preparation, cleaning, etching and drying.

Calculation of Self, Corrected, and Transport Diffusivities of Isopropyl Alcohol in UiO-66.

The UiO-6x family of metal-organic frameworks has been extensively studied for applications in chemical warfare agent (CWA) capture and destruction. An understanding of intrinsic transport phenomena, such as diffusion, is key to understanding experimental results and designing effective materials for CWA capture. However, the relatively large size of CWAs and their simulants makes diffusion in the small-pored pristine UiO-66 very slow and hence impractical to study directly with direct molecular simulations because of the time scales required. We used isopropanol (IPA) as a surrogate for CWAs to investigate the fundamental diffusion mechanisms of a polar molecule within pristine UiO-66. IPA can form hydrogen bonds with the μ3-OH groups bound to the metal oxide clusters in UiO-66, similar to some CWAs, and can be studied by direct molecular dynamics simulations. We report self, corrected, and transport diffusivities of IPA in pristine UiO-66 as a function of loading. Our calculations highlight the importance of the accurate modeling of the hydrogen bonding interactions on diffusivities, with about an order of magnitude decrease in diffusion coefficients when the hydrogen bonding between IPA and the μ3-OH groups is included. We found that a fraction of the IPA molecules have very low mobility during the course of a simulation, while a small fraction are highly mobile, exhibiting mean square displacements far greater than the ensemble average.

Triboelectric-induced ion mobility for artificial intelligence-enhanced mid-infrared gas spectroscopy

Isopropyl alcohol molecules, as a biomarker for anti-virus diagnosis, play a significant role in the area of environmental safety and healthcare relating volatile organic compounds. However, conventional gas molecule detection exhibits dramatic drawbacks, like the strict working conditions of ion mobility methodology and weak light-matter interaction of mid-infrared spectroscopy, yielding limited response of targeted molecules. We propose a synergistic methodology of artificial intelligence-enhanced ion mobility and mid-infrared spectroscopy, leveraging the complementary features from the sensing signal in different dimensions to reach superior accuracy for isopropyl alcohol identification. We pull in “cold” plasma discharge from triboelectric generator which improves the mid-infrared spectroscopic response of isopropyl alcohol with good regression prediction. Moreover, this synergistic methodology achieves ~99.08% accuracy for a precise gas concentration prediction, even with interferences of different carbon-based gases. The synergistic methodology of artificial intelligence-enhanced system creates mechanism of accurate gas sensing for mixture and regression prediction in healthcare.

Facile Synthesis of Mn-Doped CuO Nanoflower Spheres and Their Enhanced Sensing Performance for Isopropanol

In this work, the Mn-doped CuO nanoflower spheres (CuO-1% Mn nanoflower spheres) are synthesized through a facile low-temperature hydrothermal method. The as-prepared sample is characterized by XRD, SEM, TEM, EDS, XPS, Raman and BET analylsis. The results indicate that the nanoflower spheres with the diameters of 5-10 μm are assembled by a huge number of nanosheets. And, Mn ions are uniformly doped into the CuO nanoflower spheres. The surface areas of the CuO-1% Mn nanoflower spheres is 33.079 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /g. Under the optimize temperature of 235 °C, when the Mn doping amount is 1%, the CuO-1% Mn nanoflower spheres exhibit the best sensing property toward isopropanol, and the response of which is almost 11.5 times higher than that of pure CuO. In a wide range of 1-100 ppm, the CuO-1% Mn nanoflower spheres exhibit linear response in isopropanol detection. The doped sample also exhibit excellent selectivity, repeatability and durability. It is believed that the doping of Mn ions would be the reason of the improvement of sensing properties. Due to the doping introduced more defects and spillover effect, more oxygen anions would be generated and more isopropanol molecules can be oxidized on the surface of the CuO-1% Mn nanoflower spheres. It is believed that product has great application potential in isopropanol detection.

Molecularly Imprinted Polymer-Based Optical Sensor for Isopropanol Vapor

Recent advances have allowed the monitoring of several volatile organic compounds (VOCs) in human exhaled breath, and many of them are being utilized as a biomarker to diagnose several diseases, including diabetes. Among several VOCs, isopropanol (IPA) has been reported as a common volatile compound in the exhaled breath of patients with type 1 and type 2 diabetes. In this article, an experimental approach is discussed to develop a highly selective and sensitive IPA vapor sensor system. The fabricated sensor is comprised of a small and portable glass slide coated with molecularly imprinted polymer containing specific binding sites compatible with IPA molecules. The developed sensor is based on the wavelength interrogation technique. The fabricated device is analyzed for the detection of IPA vapor with different concentrations varying from 50% to 100%. The sensor exhibits maximum sensitivities of 0.37, 0.30, and 0.62 nm/%IPA, respectively, for 30, 60, and 90 min, respectively, and an excellent sensitivity of 0.63 nm/%IPA for 120 min exposure along with good selectivity among a similar class of VOCs. The major features of the sensor i.e., small size, portability, cost-effectiveness, high sensitivity, and good selectivity, make it a potential candidate for diabetes monitoring. The promising results of the sensor illustrate its potential in diabetes monitoring applications.

Mechanism of Catalytic Transfer Hydrogenation for Furfural Using Single Ni Atom Catalysts Anchored to Nitrogen-Doped Graphene Sheets.

Catalytic transfer hydrogenation (CTH) of α,β-unsaturated aldehydes using single metal atom catalysts supported on nitrogen-incorporated graphene sheet (M-Nx-Gr) materials has attracted increasing attention recently, yet the reaction mechanism remains to be explored. Compared to the Ni-N4-Gr model in which the dissociation of isopropanol is highly unfavorable as a result of steric hindrance and inertness of the Ni-N4 site embedded in graphene, the Ni-N3 site in Ni-N3-Gr is more active and facilitates the formation of *H with isopropanol as the H donor, where the dissociation of H from isopropanol with an energy barrier of 0.83 eV is the rate-determining step. An alternative reaction path starts from the coadsorption of isopropanol and furfural molecules at the Ni-N3 site, followed by a direct hydrogen transfer between the two molecules; however, the rate-determining step has a much higher energy barrier of 1.32 eV. Our calculations suggest that the hydrogenation of the aldehyde group is kinetically more favorable than the C═C hydrogenation, revealing the high chemoselectivity of furfural to furfuryl alcohol. Our investigations reveal that the CTH mechanism using the Ni-N3-Gr catalyst is different from that on traditional metal oxides, where the former has only one single active site, while two active sites are required for the latter. The proposed reaction mechanism of CTH for furfural in this study should be helpful to guide the design of single metal atom catalysts with appropriate N coordination for application in chemoselective hydrogenation reactions.

Understanding the Working Mechanism of the Novel HKUST-1@BPS Composite Materials as Stationary Phases for Liquid Chromatography.

Composite materials have been used based on coordination polymers or microporous metal-organic frameworks (MOFs) combined with mesoporous matrices for adsorption-related techniques, which enable outflanking some adverse phenomena manifested during pristine components operation and enhance the performance and selectivity of the resulting materials. In this work, for the first time, the novel HKUST-1@BPS composites synthesized by the microwave-assisted (MW) technique starting from microporous HKUST-1 (Cu3(btc)2) MOF and biporous silica matrix (BPS) with bimodal mesopore size distribution were comparatively studied as materials for liquid-phase adsorption techniques utilizing the high-performance liquid chromatography (HPLC) method and benzene as a model adsorbate. It was established that the studied HKUST-1@BPS composites can function as stationary phases for HPLC, unlike the pristine HKUST-1 and bare BPS materials, due to the synergetic effect of both components based on the preliminary enhanced adsorbate mass transfer throughout the silica mesopores and, subsequently, its penetrating into HKUST-1 micropores. The suggested mechanism involves the initial deactivation of open metal Cu2+ sites in the HKUST-1 framework structure by isopropanol molecules upon adding this polar component into the mobile phase in the region of the isopropanol concentration of 0.0 to 0.2 vol.%. Thereafter, at the medium range of varying the isopropanol concentration in the eluent of 0.2 to 0.3 vol.%, there is an expansion of the previously inaccessible adsorption centers in the HKUST-1@BPS composites. Subsequently, while further increasing the isopropanol volume fraction in the eluent in the region of 0.3 to 5.0 vol.%, the observed behavior of the studied chromatographic systems is similar to the quasi-normal-phase HPLC pattern. According to the obtained thermodynamic data, benzene adsorption into HKUST-1 micropores from solutions with a vol.% of isopropanol in the range of 0.4 to 5.0 follows the unique entropy-driven mechanism previously described for the MIL-53(Al) framework. It was found that HKUST-1 loading in the composites and their preparation conditions have pronounced effects on their physicochemical properties and adsorption performance, including the adsorption mechanism.

Synthesis of Bi2O2CO3/In(OH)3·xH2O nanocomposites for isopropanol sensor with excellent performances at low temperature

The ability to detect a volatile organic compound in real-time, such as isopropanol (IPA) gas, is critical for human health and safety protection, especially since the sensor can operate at low temperatures and behave outstanding sensing performances. Herein, the Bi2O2CO3/In(OH)3·xH2O nanocomposites are synthesized using a two-step hydrothermal process, particularly the surfaces of Bi2O2CO3 (BCO) nanosheets were embellished with In(OH)3·xH2O nanoparticles. It is found that the BCO/In(OH)3·xH2O sensors exhibit an excellent response of 20.39, wide concentration detection range from 1 to 1000 ppm, the working temperature as low as 100 ºC, and the rapid response/recovery times of 5 s and 4 s towards 100 ppm IPA. On the other hand, the selectivity of the BCO/In(OH)3·xH2O sensor towards IPA is eye-catching. In particular, the enhanced IPA sensing performances might be attributed to the large specific area (52.46 m2/g). The increased conductivity of BCO/In(OH)3·xH2O nanocomposites due to incorporation of the In(OH)3·xH2O, which can significantly promote the surface-catalyzed reaction between oxygen species such as O- and IPA molecules.

Comparative Atomic-Level Analysis of Sorption and Diffusion Properties of Membrane Materials on the Base of Polymer and Its Prepolymer: A Case Study of Polyheteroarylenes.

The sorption properties of polymers and the mobility of penetrants are the main factors which determine the trans-membrane processes. Other factors concern the membrane material structure and chemical nature. In this paper, we consider the case of polymers with similar structure units, namely a polymer and its pre-polymer (polybenzoxazinoneimide and imide-containing polyamic acid). The available experimental data show a great difference in the pervaporation process using these two polymeric membranes. Some explanation of this difference can be found at the atomic-level study. A comparative analysis of the diffusion of water and isopropanol molecules was carried out using the density functional theory and molecular dynamics simulations

Electrically Conductive Silicone-Based Nanocomposites Incorporated with Carbon Nanotubes and Silver Nanowires for Stretchable Electrodes.

Stretchable electrode materials have attracted great attention as next-generation electronic materials because of their ability to maintain intrinsic properties with rare damage when undergoing repetitive deformations, such as folding, twisting, and stretching. In this study, an electrically conductive PDMS nanocomposite was manufactured by combining the hybrid nanofillers of carbon nanotubes (CNTs) and silver nanowires (AgNWs). The amphiphilic isopropyl alcohol molecules temporarily adhered simultaneously to the hydrophobic CNT and hydrophilic AgNW surfaces, thereby improving the dispersity. As the CNT/AgNW ratio (wt %/wt %) decreased under the constant nanofiller content, the tensile modulus decreased and the elongation at break increased owing to the poor interaction between the AgNWs and matrix. The shear storage moduli of all nanocomposites were higher than the loss moduli, indicating the elastic behavior with a cross-linked network. The electrical conductivities of the nanocomposite containing the hybrid nanofillers were superior to those of the nanocomposite containing either CNT or AgNW at the same filler content (4 wt %). The hybrid nanofillers were rearranged and deformed by 5000 cyclic strain tests, relaxing the PDMS matrix chain and weakening the interfacial bonding. However, the elastic behavior was maintained. The dynamic electrical conductivities gradually increased under the cyclic strain tests due to the rearrangement and tunneling effect of the nanofillers. The highest dynamic electrical conductivity (10 S/m) was obtained for the nanocomposite consisting of 2 wt % of CNTs and 2 wt % of AgNWs.

Impact of isopropanol on nucleation and growth of polyaniline nanofibers towards capacitive charge storage enhancement

The nanofibrous morphology and chain orientation have predominant impacts on the charge storage ability of polyaniline (PANi) that could be promoted by introducing small molecules such as alcohols to affect the formation of the nanofibers. In this work, one kind of continuous–flow polymerization was designed to separate the seed formation and subsequently assembly process of PANi nanofibers, making it possible to evaluate independently the influence of isopropanol on the nucleation and growth of PANi nanofibers, i.e. isopropanol molecules were involving in the initial reaction in the flow polymerization, or only in the subsequent assembly and growth of nanofibrous seeds produced through flow polymerization. Furthermore, the effects of isopropanol content on the morphologies, microstructures and capacitance performances of PANi nanofibers were discussed. It is found that the isopropanol could give a great improvement in charge storage ability of the nanofibers when a small amount of alcohol molecules were only used for affecting the assembly and growth of PANi nanofibers. Benefiting relatively large diameter–to–length ratio and high conductivity, PANi nanofibers prepared at 5 wt. % content of isopropanol possessed the greatest specific capacitance of 1082 F g–1 at the scan rate of 1 mV s–1 and 530.2 F g–1 at the current density of 1 A g–1, which was improved by 10% compared with pure PANi. The understanding of effect of small organic molecules on the capacitance performances of PANi could provide a much easier route in fabricating high performance electrode of PANi as promising candidates for lightweight and flexible energy storage devices.

Crystal structure and magnetic properties of 3,5-pyridinedicarboxylate-bridged Re(II)M(II) heterodinuclear complexes (M = Cu, Ni and Co)

The use of the mononuclear rhenium(II) precursor NBu4[Re(NO)Br4(H2pydc)]·i-PrOH (1) (H2pydc = 3,5-pyridinedicarboxylic acid) as a metalloligand towards Cu(II), Ni(II) and Co(II) afforded three new heterobimetallic complexes [Re(NO)Br4(μ-Hpydc)Cu(4,4′-dmbipy)2]·(CH3)2CO·0.25MeCN (2), [Re(NO)Br4(μ-Hpydc)Ni(dmphen)2]·MeCN (3) and [Re(NO)Br4(μ-Hpydc)Co(dmphen)2]·2H2O (4), respectively [4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and Bu4N+ = tetra-n-butylammonium]. The crystal structures of 1 and 2 are reported herein together with the cryomagnetic investigation of 1–4 in the temperature range of 2.0–300 K. 1 is a mononuclear compound whose structure is made of [Re(NO)Br4(H2pydc)]- complex anions, tetra-n-butylammonium cations and isopropanol molecules of crystallization. Each rhenium(II) ion in 1 is six-coordinate with four bromide ligands in the equatorial positions and a nitrosyl group and one pyridyl-nitrogen atom from an H2pydc ligand filling the axial sites. 2 is a neutral heterobimetallic compound where the [Re(NO)Br4(Hpydc)]2- complex anion acts as a monodentate ligand towards the [Cu(4,4′-dmbipy)2]2+ complex cation through one carboxylate–oxygen atom. The rhenium(II) ion is six-coordinate in a somewhat distorted octahedral surrounding similar to that in 1. The copper(II) ion in 2 is five-coordinate with four nitrogen atoms from two bidentate 4,4′-dmbipy ligands and one carboxylate–oxygen atom, describing a surrounding intermediate between square pyramidal and trigonal bipyramidal. Compound 1 behaves as a quasi-magnetically isolated spin doublet with weak antiferromagnetic interactions through space Br⋯Br contacts, ligand field, spin–orbit coupling, tetragonal distortion, and covalence effects considered as variable parameters in a successful simulation of the magnetic data. Compounds 2–4 exhibit also weak intramolecular antiferromagnetic interactions (J) covering the range −0.60(1) to −1.50(1) cm−1 with the Hamiltonian being defined as H = -JSReSM, M = Cu (2), Ni (3) and Co (4).

Effect of 2-propanol content on solute retention mechanisms determined using amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase under normal- and reversed-phase conditions

The electrostatic interactions between chiral solutes and polysaccharide (PS)-based chiral selectors are the key to achieving chiral recognition; however, PS-based sorbents, derivatized of phenyl moieties, can exhibit considerably non-polar characteristics, and they are also useful for the separation of enantiomers in the reversed-phase mode. In this study, an immobilized amylose 3,5-dimethylphenylcarbamate-based sorbent was used to investigate the balance between electrostatic interactions and solvophobic interactions, with complementary effects on solute retention behavior when the isopropanol (IPA) concentration was altered. It was proposed that in both normal- and reversed-phase modes, information on the retention mechanisms could be obtained by observing the curvature of the logarithm of the retention factor versus the logarithm of the IPA concentration, and the slope values of the curves were related to the number of displaced IPA molecules upon solute adsorption. Using the proposed model and the two-site adsorption model, the retention behaviors of pantolactone (PL) enantiomers in both normal- and reversed-phase modes were investigated. The PL−sorbent interactions were classified into four types: electrostatic/enantioselective, electrostatic/nonselective, solvophobic/enantioselective, and solvophobic/nonselective. At IPA concentrations below 50 vol.% in n-hexane, the retention behaviors of PL were dominated by electrostatic/enantioselective sites, whereas at IPA concentrations beyond 50 vol.%, the solvophobic interactions of PL−sorbent were strengthened and mostly nonselective. By contrast, in the reversed-phase mode, a reverse in the enantiomeric elution order of PL was observed at 10 vol.% IPA, and considerably different enantioselectivity behaviors were found below and above 20 vol.%, indicating an abrupt change in the sorbent molecular environment. At IPA concentrations beyond 40 vol.%, the presence of PL-sorbent electrostatic interactions enhanced chiral recognition.

A Computational Study of Isopropyl Alcohol Adsorption and Diffusion in UiO-66 Metal-Organic Framework: The Role of Missing Linker Defect.

Defect engineering leads to an effective manipulation of the physical and chemical properties of metal-organic frameworks (MOFs). Taking the common missing linker defect as an example, the defective MOF generally possesses larger pores and a greater surface area/volume ratio, both of which favor an increased amount of adsorption. When it comes to the self-diffusion of adsorbates in MOFs, however, the missing linker is a double-edged sword: the unsaturated metal sites, due to missing linkers, could interact more strongly with adsorbates and result in a slower self-diffusion. Therefore, it is of fundamental importance to evaluate the two competing factors and reveal which one is dominating, a faster self-diffusion due to larger volume or a slower self-diffusion owing to strong interactions at unsaturated sites. In this work, via Monte Carlo and molecular dynamics simulations, we investigate the behavior of isopropyl alcohol (IPA) in the Zr-based UiO-66 MOFs, with a specific focus on the missing linker effects. The results reveal that unsaturated Zr sites bind strongly with IPA molecules, which in return would significantly reduce the self-diffusion coefficient of IPA. Besides this, for the same level of missing linkers, the location of defective sites also makes a difference. We expect such a theoretical study will provide an in-depth understanding of self-diffusion under confinement, inspire better defect engineering strategics, and promote MOF based materials toward challenging real-life applications.

Crystal Structure and Magnetic Properties of 3,5-Pyridinedicarboxylate-Bridged Re(Ii)M(Ii) Heterodinuclear Complexes (M = Cu, Ni and Co)

The use of the mononuclear rhenium(II) precursor NBu 4 [Re(NO)Br 4 (H 2 pydc)]· i -PrOH ( 1 ) (H 2 pydc = 3,5-pyridinedicarboxylic acid) as a metalloligand towards Cu(II), Ni(II) and Co(II) afforded three new heterobimetallic complexes [Re(NO)Br 4 (μ-Hpydc)Cu(4,4’-dmbipy) 2 ]·(CH 3 ) 2 CO·0.25MeCN ( 2 ), [Re(NO)Br 4 (μ-Hpydc)Ni(dmphen) 2 ]·MeCN ( 3 ) and [Re(NO)Br 4 (μ-Hpydc)Co(dmphen) 2 ]·2H 2 O ( 4 ), respectively [4,4’-dmbipy = 4,4’-dimethyl-2,2’-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and n -Bu 4 N + = tetra- n -butylammonium]. The crystal structures of 1 and 2 are reported herein together with the cryomagnetic investigation of 1 - 4 in the temperature range of 2.0-300 K. 1 is a mononuclear compound whose structure is made of [Re(NO)Br 4 (H 2 pydc)] - complex anions, tetra- n -butylammonium cations and isopropanol molecules of crystallization. Each rhenium(II) ion in 1 is six-coordinate with four bromide ligands in the equatorial positions and a nitrosyl group and one pyridyl-nitrogen atom from an H 2 pydc ligand filling the axial sites. 2 is a neutral heterobimetallic compound where the [Re(NO)Br 4 (Hpydc)] 2- complex anion acts as a monodentate ligand towards the [Cu(dmphen) 2 ] 2+ complex cation through one carboxylate-oxygen atom. The rhenium(II) ion is six-coordinate in a somewhat distorted octahedral surrounding similar to that in 1 . The copper(II) ion in 2 is five-coordinate with four nitrogen atoms from two bidentate 4,4’-dmbipy ligands and one carboxylate-oxygen atom, describing a surrounding intermediate between square pyramidal and trigonal bipyramidal. Compound 1 behaves as a quasi-magnetically isolated spin doublet with weak antiferromagnetic interactions through space Br⋯Br contacts, ligand field, spin-orbit coupling, tetragonal distortion, and covalence effects considered as variable parameters in a successful simulation of the magnetic data . Compounds 2 – 4 exhibit also weak intramolecular antiferromagnetic interactions ( J ) covering the range -0.60(1) to -1.50(1) cm -1 with the Hamiltonian being defined as H = - J S Re S M , M = Cu ( 2 ), Ni ( 3 ) and Co ( 4 ).

Forces between silica particles in isopropanol solutions of 1:1 electrolytes

Interactions between silica surfaces across isopropanol solutions are measured with colloidal probe technique based on atomic force microscope. In particular, the influence of 1:1 electrolytes on the interactions between silica particles is investigated. A plethora of different forces are found in these systems. Namely, van der Waals, double-layer, attractive non-DLVO, repulsive solvation, and damped oscillatory interactions are observed. The measured decay length of the double-layer repulsion is substantially larger than Debye lengths calculated from nominal salt concentrations. These deviations are caused by pronounced ion pairing in alcohol solutions. At separation below 10 nm, additional attractive and repulsive non-DLVO forces are observed. The former are possibly caused by charge heterogeneities induced by strong ion adsorption, whereas the latter originate from structuring of isopropanol molecules close to the surface. Finally, at increased concentrations the transition from monotonic to damped oscillatory interactions is uncovered.

Concentration‐Driven Disruption of Single‐File Water

AbstractStrong hydrogen bonding is known to entail some of the spectacular physical properties of liquid water, including fast diffusion under nanoconfinement. Similar to biological channels, the single‐file or collective motion of interconnected water molecules has been observed in nanotubes and laminar structures, exhibiting tremendous potential for energy‐efficient separation applications. Desalination, breaking azeotropes, and dehumidification have been all addressed with the membranes enabling selective transport of water while most attention has been paid to the fabrication and morphological characteristics of the respective microporous materials. However, the performance of membrane processes also depends on the properties of the chemical systems to be treated, often facing problems under realistic conditions such as concentration polarization. In this study, adsorption controlled permeation is employed to explore the interfacial behavior of water–alcohol mixtures in nanostructured membranes as a function of concentration. The permeation rate of water is found to sink manifold as the molar fraction of isopropanol molecules increases, indicating breakdown of the single‐file mechanism. A phenomenological model is devised to account for intermolecular interactions in the binary liquid–liquid mixture whereas kinetic simulations agree well with the experimental data. The results point to the fundamental limitations of water‐selective conduits for dehydrating organic solvents.