MeOH Vapor Research Articles

Cover Feature: Polarity and Dielectric Property Control Triggered by a Coordinated Solvent Molecule Exchange in Luminescent Mononuclear Aluminium(III) Complexes (Chem. Eur. J. 33/2023)

Luminescent mononuclear aluminium(III) complexes that can control molecular arrangements and dielectric properties by exposure to solvent vapor in the solid state have been reported. In this image, the left side represents the nonpolar structure under MeOH vapor, and the right side represents the polar structure under DMSO vapor. The second harmonic generation (SHG) behavior attributed to the structural transformation to the polar structure is depicted as red and green lights. More information can be found in the Research Article by F. Kobayashi, M. Tadokoro, and co-workers (DOI: 10.1002/chem.202203937).

A conductometric enzymatic methanol sensor based on polystyrene - PAMAM dendritic polymer electrospun nanofibers

Methanol (MeOH) is a solvent and cleaning agent used in industry, but it is poisonous when ingested. The recommended release threshold for MeOH vapor is 200 ppm. We present a novel sensitive micro-conductometric MeOH biosensor created by grafting alcohol oxidase (AOX) onto electrospun polystyrene-poly(amidoamine) dendritic polymer blend nanofibers (PS-PAMAM-ESNFs) on interdigitated electrodes (IDEs). The analytical performance of the MeOH microsensor was evaluated using gaseous MeOH, ethanol, and acetone samples collected from the headspace above aqueous solution with known concentration. The sensor's response time (tRes) fluctuates from 13 s to 35 s from lower to higher concentrations. The conductometric sensor has a sensitivity of 150.53 μS.cm-1 (v/v) for MeOH and a detection limit of 100 ppm in the gas phase. The MeOH sensor is 7.3 times less sensitive to ethanol and 136.8 times less sensitive to acetone. The sensor was verified for detecting MeOH in commercial rubbing alcohol samples.

Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition

Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition

Biochemical Methanol Gas Sensor (MeOH Bio-Sniffer) for Non-Invasive Assessment of Intestinal Flora from Breath Methanol

Methanol (MeOH) in exhaled breath has potential for non-invasive assessment of intestinal flora. In this study, we have developed a biochemical gas sensor (bio-sniffer) for MeOH in the gas phase using fluorometry and a cascade reaction with two enzymes, alcohol oxidase (AOD) and formaldehyde dehydrogenase (FALDH). In the cascade reaction, oxidation of MeOH was initially catalyzed by AOD to produce formaldehyde, and then this formaldehyde was successively oxidized via FALDH catalysis together with reduction of oxidized form of β-nicotinamide adenine dinucleotide (NAD+). As a result of the cascade reaction, reduced form of NAD (NADH) was produced, and MeOH vapor was measured by detecting autofluorescence of NADH. In the development of the MeOH bio-sniffer, three conditions were optimized: selecting a suitable FALDH for better discrimination of MeOH from ethanol in the cascade reaction; buffer pH that maximizes the cascade reaction; and materials and methods to prevent leaking of NAD+ solution from an AOD-FALDH membrane. The dynamic range of the constructed MeOH bio-sniffer was 0.32–20 ppm, which encompassed the MeOH concentration in exhaled breath of healthy people. The measurement of exhaled breath of a healthy subject showed a similar sensorgram to the standard MeOH vapor. These results suggest that the MeOH bio-sniffer exploiting the cascade reaction will become a powerful tool for the non-invasive intestinal flora testing.

Dichroic Fourier Transform Infrared Spectroscopy Characterization of the β-Sheet Orientation in Spider Silk Films on Silicon Substrates.

Orientation analysis of the β-sheet structure within films of the established recombinant spider silk protein eADF4(C16) was performed using a concept based on dichroic transmission- and attenuated total reflection-Fourier transform infrared spectroscopy, lineshape analysis, assignment of amide I components to specific vibration modes, and transition dipole moment directions of β-sheet structures. Based on the experimental dichroic ratio R, the order parameter S of β-sheet structures was calculated with respect to uniaxial orientation. Films of eADF4(C16) were deposited on untexturized (Si) and unidirectionally scratched silicon substrates (Si-sc) and post-treated with MeOH vapor. Freshly cast thin and thick eADF4(C16) films out of hexafluoroisopropanol featured β-sheet contents of ≈6%, which increased to >30% after MeOH post-treatment in dependence of time. Pseudo-first order folding kinetics were obtained, suggesting a transition from an unfolded to a folded state. In MeOH post-treated thin films with diameters in the nanometer range, a significant orientation of β-sheets was obtained regardless of the texturization of the silicon substrate (Si, Si-sc). This was rationalized by dichroic ratios of the amide I component at 1696 cm-1 assigned to the (0, π) mode of antiparallel β-sheet structures, whose transition dipole moment M is located in parallel to both β-sheet plane and chain direction. The calculated high molecular order parameter S ≈ 0.40 suggested vertically (out-of-plane) oriented antiparallel β-sheet stacks with tilt angles of γ ≈ 39° to the surface normal. Microscale (thick) films, in contrast, revealed low order parameters S ≈ 0. Scanning force microscopy on thin eADF4 films at silicon substrates showed dewetted polymer film structures rather at the micro-scale. These findings give new insights in the role of the β-sheet crystallite orientation for the mechanical properties of spider silk materials.

Combustible ice mimicking behavior of hydrogen-bonded organic framework at ambient condition

Adsorption of guest molecules by porous materials proceeds in a spontaneous exothermic way, whereas desorption usually requires external energy input as an endothermic process. Reducing such energy consumption makes great sense in practice. Here we report the reversible and automatic methanol (MeOH) adsorption/release in an ionic hydrogen-bonded organic framework (iHOF) constructed from guanidinium cation and borate anion ([B(OCH3)4]3[C(NH2)3]4Cl•4CH3OH, termed Gd-B) at ambient condition. The metastable Gd-B automatically releases all sixteen MeOH molecules (63.4 wt%) via desorption and tetra-methyl borate hydrolysis at ambient atmosphere and the structure can be recovered when re-exposed to MeOH vapor or liquid, mimicking combustible ice behavior but at ambient condition. Reversible capture/release of four guest MeOH molecules is also realized without destroying its crystal structure. The combustible Gd-B paves a way for exploring metastable iHOF materials as carrier for alternative energy source and drug delivery etc.

Reverse photoluminescence responses of Ln(iii) complexes to methanol vapor clarify the differentiated energy transfer pathway and potential for methanol detection and encryption

A VOC detection and optical encryption model based on the uncommon reverse photoluminescence response of isomorphic Eu(iii) and Tb(iii) complexes to MeOH vapor.

Mechanical-Stimulation-Triggered and Solvent-Vapor-Induced Reverse Single-Crystal-to-Single-Crystal Phase Transitions with Alterations of the Luminescence Color.

Luminescence alterations in solid-state materials upon external stimulations have attracted much attention due to their potential for the development of highly functional devices or sensors. We have previously reported the first examples of mechano-induced single-crystal-to-single-crystal (SCSC) phase transitions of gold(I) isocyanide complexes under concomitant emission-color changes. However, the reverse phase transitions of the crystals obtained after mechanical stimulation have not yet been achieved. Herein, a reversible change of the luminescence based on two SCSC phase transitions via mechanical cutting and solvent-vapor adsorption is described. Crystallization of a gold(I) complex that bears CF3 and biaryl moieties from CH2Cl2/MeOH afforded a green-emitting single crystal packed in a polar space group (Pna21). The green-emitting single crystals included MeOH molecules. Upon cutting the crystal under MeOH vapor at 22 °C, the green-emitting single crystal spontaneously changed into a centrosymmetric orange-emitting single crystal (P1̅) under concomitant release of MeOH. Remarkably, the initial green-emitting crystal could be recovered from the orange-emitting crystal by a solvent-induced SCSC transition under saturated MeOH vapor. The combination of two different types of SCSC phase transitions enables the reversible structural and photoluminescent alternations.

Aggregation-induced-emission-active vinamidinium salts with tunable emissions, reversible mechanochromic response and the application in data-security protection

The development of aggregation-induced-emission (AIE)-active and reversible mechanochromic fluorescent organic materials has been of great interest in recent years because of their potential and practical application in many fields. Five vinamidinium salts that bear different aryl substitutes (Ar = phenyl (N1), p-methylphenyl (N2), p-bromophenyl (N3), p-nitrophenyl (N4) and naphthyl (N5)) were designed and synthesized. Their photophysical properties were investigated via a series of spectroscopic and theoretical methods. All compounds exhibit intense 1π-π*/intramolecular charge-transfer (1ICT) absorption bands in the region from ca. 300 nm–450 nm. All compounds except N5 display aggregation induced enhanced emission behavior in DMSO-CH2Cl2 mixtures, and relatively high quantum efficiency in solid-states (ΦF = 0.06–0.22). Compounds N1 and N3 with yellow and orange solid fluorescence, respectively, show mechanochromic and vapochromic response. Upon grinding, the emission of N1 and N3 could be transformed to green–yellow and yellow, respectively, and restored when the ground powders were fumed with MeOH vapor. Powder X-ray diffraction spectroscopy indicates that the reversible mechanochromism is ascribed to the transformation of a crystalline state into an amorphous state. Compound N1 is used in data-security protection and is of assistance in the rational design of smart luminescent materials.

Centimeter-Sized Inorganic Lead Halide Perovskite CsPbBr3 Crystals Grown by an Improved Solution Method

As a member of the lead-halide perovskite family, inorganic perovskite CsPbBr3 exhibits excellent optical and electrical properties with higher stability to the environment. However, former efforts to obtain large-size CsPbBr3 single crystals with satisfactory quality using low temperature solution methods reached limited results. In this work, we have studied the growth of CsPbBr3 crystals using the antisolvent vapor-assisted crystallization (AVC) method. By adjusting the mole ratio of PbBr2 and CsBr, the phase diagram of the final products is acquired. Five regions are identified, including the Cs4PbBr6 single phase region, Cs4PbBr6 and CsPbBr3 two phases region, CsPbBr3 single phase region, CsPbBr3 and PbBr2·2[(CH3)2SO] metastable two phases region, and CsPbBr3 and PbBr2·2[(CH3)2SO] two phases region. Three methods are adopted to improve the size and crystalline quality of CsPbBr3. The growth rate is effectively tailored by diluting the antisolvent MeOH solution using DMSO to reduce the MeOH vapor pres...

Self-assembly of poly(p-phenylene)-based flower-like 3D micro-nanostructures

Poly(2,5-dioctyloxy-p-phenylene) was fabricated into Chrysanthemum-like, rose-like, and coil-like micro-nanostructures and porous sponge-like three-dimensional (3D) network via solution-phase self-assembly by two types of phase separations (continuous and dispersed phases) occurred by the dissolution of polar MeOH vapor and nonpolar hexane vapor into the polymer solutions, respectively. Morphological changes of polymers produced significant changes in the optical properties. It was concluded that the choice of a good solvent and nonsolvent vapor for hairy-rod polymers is a facile way to design and fabricate various super-macromolecular architectures.

Crystalline transformations of dinaphthyridinylamine derivatives with alteration of solid-state emission in response to external stimuli

Dinaphthyridinylamine derivatives, (1,8Nap)2NR (R = H (1), Me (2) and Ph (3)), were prepared as fluorophores in response to external stimuli. From crystallization, single crystals (1) containing water molecules as crystal solvents and crystal polymorphs (3-α and 3-β) containing MeOH molecules were obtained. In the crystal packing of 1, a γ-herringbone (γ-HB) fashion with π–π interaction was observed. In contrast, the packing of 3-α was in a HB fashion with intermolecular CH–N interaction, while the packing of 3-β was in a slipped columnar fashion with π–π interaction between the naphthyridine planes. The observed difference of crystal packings influenced the solid-state emission spectra. Crystals 1, 2 and 3 showed piezochromic behaviors, in which by thoroughly grinding the crystals, the solid-state emission blue color (λfmax = ca. 450 nm) turned into yellowish green (λfmax = ca. 510 nm) for the amorphous solid. In addition, crystals 3-α and 3-β showed various phase transitions including single-crystal-to-single-crystal (SC-to-SC) transformation in response to external stimuli. Crystal 3-β desorbed the MeOH molecules under ambient atmosphere to provide crystal 3-β′ (λfmax = 449 nm), while the resulting crystal 3-β′ returned to crystal 3-β upon exposure to MeOH vapor, indicating vapochromic behavior. Furthermore, crystal 3-β′ was heated at ca. 160 °C to afford crystal 3-α (SC-to-SC transformation). The gummy oil in the resulting supercooled liquid (SCL) state after melting the crystals was scratched by using a fine wire at and above 80 °C (>Tg, glass temperature) to form crystal 3-α with blue emission (SCL-to-SC transformation).

Polynaphthalenes prepared by solid-state oxidative coupling polymerization and their microspheres self-assembled via nonsolvent vapor method

Polynaphthalenes have successfully been synthesized by solid-state oxidative polymerization of naphthalene with FeCl3 as oxidant for 30min with a total polymerization yield of 98% at 25°C. On the basis of FT-IR, 1H NMR, elemental analysis and extended Hückel charge calculation results, the intermolecular 1,4-linked coupling is the main way to extend the polynaphthalene chain, accompanied with the formation of intramolecular coupling. The UV–Vis spectral band at 517nm also confirmed the formation of large π-conjugated structure. The chloroform-insoluble part of the polynaphthalenes with a high char yield of 85% after heated up to 600°C in nitrogen. In MeOH vapor atmosphere, the chloroform-soluble part of the polynaphthalenes can self-assemble to form microspheres patterns (average diameter 0.76μm) by the nonsolvent vapor method. The microspheres with nanosheets were obtained due to the semicrystalline structure of the polynaphthalenes.

Bubble stripping in closed system to remove residual methanol from crude biodiesel

SummaryA novel, simple, compact, efficient system based on a unit operation of bubble stripping was developed for intensive methanol (MeOH) removal from crude biodiesel (BDF) which was synthesized by potassium hydroxide‐catalyzed transesterification reaction of triacylglycerol (TAG) with MeOH. As TAG both rapeseed oil and used cooking oil were tested. In the system, gas was supplied by a gas pump through a gas bubbler into the crude biodiesel, then the exit gas containing MeOH vapor passed through a condenser (0°C) and the condensed MeOH was collected in a vessel. MeOH‐free gas from the condenser returned into the inlet of the gas pump, thus gas was circulated in a closed system. After the intensive MeOH removal by the bubble stripping, insoluble sediment always appeared in the biodiesel so that it was removed by centrifugation. As a final step, trace amounts of potassium (K) and free glycerol were removed by adsorbent treatment. MeOH, K, free glycerol, fatty acid methyl ester, and water contents, acid, and iodine values and oxidation stability of the purified biodiesel cleared the specifications of EN 14214 Standard. The proposed dry process consisting of the three steps will be applicable to an industrial production of high‐quality biodiesel.Practical applications: Bubble stripping that has been developed in this study is simple but very effective to remove almost completely residual methanol from the crude biodiesel. Compared with the conventional wet process, the dry process that authors' have proposed has no necessity of washing water, hence no waste water treatment. Elimination of sediment after the intensive residual MeOH removal by the bubble stripping before the final adsorption step will make it possible to decrease significantly the amount of the adsorbent (kg) required per kg of the crude biodiesel or to prolong the life span of its packed bed column, resulting in the cost reduction of the biodiesel production. The proposed dry process consisting of the three steps will be applicable to an industrial production of high‐quality biodiesel.

Photoluminescence Switching with Changes in the Coordination Number and Coordinating Volatile Organic Compounds in Tetracyanidonitridorhenium(V) and -technetium(V) Complexes

Six-coordinate distorted octahedral tetracyanidonitridorhenium(V) and -technetium(V) complexes with a volatile organic compound (VOC) coordinating at the trans position of a nitrido ligand, (PPh4)2[MN(CN)4L] (M = Re, L = MeOH, EtOH, acetone, or MeCN; M = Tc, L = MeOH), and five-coordinate square-pyramidal tetracyanidonitrido complexes without an axial ligand, (PPh4)2[MN(CN)4] (M = Re or Tc), were synthesized and characterized. Single-crystal X-ray structural analysis was carried out for (PPh4)2[MN(CN)4L] (M = Re, L = MeOH, EtOH, or acetone; M = Tc, L = MeOH) and (PPh4)2[ReN(CN)4]. All complexes studied showed photoluminescence in the solid state at room temperature. Reversible luminescence switching between six- and five-coordinate rhenium(V) complexes and between the relevant six-coordinate rhenium(V) complexes except that between the MeCN and acetone complexes was achieved by exposing them to VOC vapor in the solid state at room temperature. Luminescence changes were observed from the five-coordinate technetium(V) complexes in a MeOH vapor atmosphere in the solid state. In contrast, no vapochromic luminescence was observed from the five- and six-coordinate complexes in an acetone vapor atmosphere.

“On−Off” Au(I)···Cu(I) Interactions in a Au(NHC)2 Luminescent Vapochromic Sensor

Reaction of the Au(I) N-heterocyclic carbene (NHC) compound [Au(im(CH(2)py)(2))(2)]PF(6) with 2 equiv of [Cu(MeCN)(4)]PF(6) affords the tricationic compound [Au(im(CH(2)py)(2))(2)(Cu(MeCN)(2))(2)](PF(6))(3) (1), which exhibits blue luminescence (lambda(max) = 462 nm). Reaction of 1 with either liquid MeOH or MeOH vapor affords [Au(im(CH(2)py)(2))(2)(Cu(MeOH))(2)](PF(6))(3) (2), which produces green luminescence (lambda(max) = 520 nm) under UV excitation. The molecular structures of 1 x 2MeCN and 2 x 2MeOH.2Et(2)O were determined by single-crystal X-ray diffraction. Compound 1 contains a linearly coordinated [Au(NHC)(2)](+) core in which each picolyl side arm bridges a [Cu(MeCN)(2)](+) center. The Au...Cu separations are long at 4.596 A. Compound 2 exhibits two short Au...Cu interactions of 2.7195(7) A, with the Au(NHC)(2) core acting as an additional ligand toward each copper center to complete its tetrahedral coordination mode. Exposure of 2 to atmosphere produces a partial loss of MeOH accompanied by a luminescence color change to yellow (lambda(max) = 543 nm). The uptake and loss of MeOH vapor is rapid and reversible. Exposure of 2 to vacuum affords complete loss of MeOH, and the luminescence changes to yellow-orange (lambda(max) = 573 nm). Treatment of 2 with MeCN vapor regenerates 1. The interconversion of 1 and 2 was confirmed by powder X-ray diffraction. Compound 1 also reacts with acetone and H(2)O vapors, leading to species that produce yellow-orange (lambda(max) = 591 nm) and green (lambda(max) = 519 nm) emission, respectively. Compounds 1 and 2 are examples of molecular vapochromic materials that exhibit large changes in the emission though ligand substitution reactions between the solid complex and solvent vapors. The dramatic color change likely results from the "on-off" Au...Cu interactions induced by the ligand exchange reaction.

Air-breathing fuel cells fed with dimethoxymethane (DMM) vapor

The dimethoxymethane vapor-fed fuel cell (V-DMMFC) described in this paper is an innovative design for passive water management without the need for a complex micro-fluidic subsystem. DMM is a promising fuel for vapor-fed fuel cells because it has high energy density, an absence of C–C bonds, and lower toxicity as well as high vapor pressure. In a polarization measurement, the V-DMMFC showed an open circuit voltage of around 0.55 V and a high power density of 34.7 mW cm − 2 at 0.315 V, which is higher than that of a fuel cell with MeOH vapor. The V-DMMFC achieved a fast response in fuel feeding and a higher Faradic efficiency (76.1%) than that of fuel cells fed with MeOH vapor (53.7%); these improvements result from a higher vapor pressure and a lower fuel crossover of DMM. For constant voltage (CV) mode, the V-DMMFC provided evidence for the long-term stability of the device and for the sustainability of humidity within the self-humidified MEA without any additional provision of water.

Chronic maternal methanol inhalation in nonhuman primates ( Macaca fascicularis): reproductive performance and birth outcome

The present study was designed to characterize maternal reproductive performance and early offspring effects following exposure to methanol (MeOH) vapor in a nonhuman primate model. The two-cohort study design used 48 adult female Macaca fascicularis (24/cohort) monkeys exposed to 0, 200, 600, or 1800 ppm MeOH vapor for approximately 2.5 h/day, 7 days/week prior to breeding and throughout pregnancy. Maternal body weight measurement, clinical observations and health assessments were conducted routinely throughout the study. Menstrual cyclicity was monitored during the pre-breeding and breeding periods and timed matings were conducted with nonexposed males. Females were monitored closely during the last month of pregnancy. At birth, infant physical characteristics were measured and a newborn health assessment was conducted. Methanol exposure did not alter menstrual cycles, the number of breedings to conception or conception rate. A total of 34 live-born infants were delivered (control=8, 200 ppm=9, 600 ppm=8, 1800 ppm=9). One female each in the control and 600-ppm group delivered a stillborn infant and a cesarean section (C-section) was required to deliver a hydrocephalic infant who died in utero in the maternal 1800-ppm group. Although not statistically significant, five MeOH-exposed females were C-sectioned due to pregnancy complications such as uterine bleeding and prolonged unproductive labor. These complications were not observed in the control group. The mean length of pregnancy in the MeOH-exposed groups was significantly decreased by 6 to 8 days when compared to controls. There were no MeOH-related effects on offspring birthweight or newborn health status. The consistent reduction in length of pregnancy observed in the MeOH females may reflect a treatment effect on the fetal neuroendocrine system. Given that the fetal hypothalamic–-pituitary–adrenal axis controls pregnancy length in most species, these results suggest a modest but significant effect of MeOH on the biochemical events that control the timing of birth.

Enantiomer separation of rac-2,2′-dihydroxy-1,1′-binaphthyl (BNO) by inclusion complexation with racemic or achiral ammonium salts and a novel transformation of a 1:1:1 racemic complex of BNO, Me 4N +·Cl − and MeOH into a conglomerate complex in the solid state

The complete simultaneous and mutual enantiomer resolution of 2,2′-dihydroxy-1,1′-binaphthyl (BNO) and N-(3-chloro-2-hydroxypropyl)- N, N, N-trimethylammonium chloride, Me 3N +CH 2CH(OH)CH 2Cl·Cl − into their enantiomers by inclusion complexation between their racemates in EtOH in the presence of a chiral seed crystal is reported. The enantiomer resolution of the rac-BNO was also accomplished easily by inclusion complexation with achiral ammonium salts, N-(2-hydroxyethyl)- N, N, N-trimethylammonium chloride, Me 3N +CH 2CH 2OH·Cl − and tetramethylammonium chloride, Me 4N +·Cl −. Inclusion complexation of the rac-BNO with Me 3N + CH 2CH 2OH·Cl − gave only a 1:1 conglomerate inclusion complex but not a racemic complex. Recrystallization of the rac-BNO and an equimolar amount of Me 4N +·Cl − from MeOH (7 ml) and MeOH (15 ml) gave a 1:1:1 racemic complex, BNO·Me 4N +·Cl −·MeOH and a 1:1 conglomerate complex, BNO·Me 4N +·Cl −, respectively. Novel transformation of the former racemate into the latter conglomerate occurred by heating or by exposure to MeOH vapor in the solid state.

Alkoxide Route to Mixed Oxides of Rhenium, Niobium, and Tantalum. Preparation and X-ray Single-Crystal Study of a Novel Rhenium−Niobium Methoxo Complex, Nb2(OMe)8(ReO4)2

Thermal decomposition of complex oxomethoxo compounds Nb4O2(OMe)14(ReO4)2 (I) and Ta4O2(OMe)14(ReO4)2 (II) has been investigated. The decomposition of (II) at temperatures exceeding 100 °C results in the formation of MeOMe, MeOCH2OMe, MeOH, and H2O vapor and is accompanied by sublimation at temperatures over 135 °C. Plausible mechanisms of the processes studied are discussed. A new bimetallic methoxo compound, Nb2(OMe)8(ReO4)2 (III), was synthesized by interaction between Re2O7 and Nb2(OMe)10 in toluene solution and its structure was determined by means of an X-ray single-crystal study. The structure can be considered as a product of substitution for terminal methoxo groups with two perrhenate groups in dimeric Nb2(OMe)10 molecules. Decomposition of II in an inert atmosphere at 900 °C gave a Re−Ta mixed oxide phase, supposedly based on the L-Ta2O5 structure. Decomposition of I and III under similar conditions leads to the formation of rhenium−niobium oxide phases. The results obtained provide a basis for ...