Addition Of HCl Research Articles

Hydrothermal conversion of dewatered sewage sludge: Focusing on the transformation mechanism and recovery of phosphorus

The recovery of phosphorus from sewage sludge was critical due to the depletion of phosphate ore. The present research aims to identify the phosphorus speciation and reveal the phosphorus transformation mechanism of dewatered sewage sludge during hydrothermal conversion (HTC) process, as well as to achieve the high efficiency recovery of phosphorus. Multiple analysis of SMT method, VK diagram, XANES and NMR showed that most phosphorus (>80%) was transferred to the hydrochar and presented as inorganic phosphorus (IP) after the HTC process. A dehydration trend was observed of the HTC process with the increase of sub-critical temperature. Ca-associated phosphorus increased significantly as the temperature increased. The Pyro-P gradually transformed to Ortho-P with the increase of HTC temperature and disappeared at 320 °C. The addition of HCl (6.13 and 12.3 mmol/g) in the HTC process resulted in a high percentage (>80%) of phosphorus transferred to the aqueous phase, and the bioavailability of the residual phosphorus increased significantly. The recovery rate of phosphorus could achieve 98.37% at the pH of 7.52, with the struvite purity of 90.41%. The results of this study provide new insights into the selective transfer of phosphorus in dewatered sludge by HTC process, in addition to some efficient ways for the utilisation of the HTC products.

Efficient hydrogen production with controlled hydrochloric acid addition using Ni-based catalyst synthesized in ethanol solvent

ABSTRACTA Ni-based catalyst was synthesized in ethanol solvent by chemical reduction with sodium borohydride(NaBH4). This catalyst was used to catalyze the hydrolysis reaction of NaBH4 with hydrochloric acid (HCl) including different concentrations. Surface morphologies and characteristic properties of the Ni-based catalysts synthesized in the ethanol and water solvents were studied using scanning electron microscopy (SEM), X‐ray diffraction (XRD), surface area measurements, and Fourier-transform infrared spectroscopy (FTIR) analyses, respectively. The maximum HGRs of the Ni-based (water) and Ni-based (ethanol) catalysts were 173 and 1054 ml g−1min−1, respectively. In addition, the HGR with 0.25 M HCl addition on the hydrolysis reaction using the Ni-based catalyst prepared in the ethanol solvent was about 1526 ml g−1min−1. Kinetic studies are performed according to the power law kinetic model. The activation energy (Ea) for the HG from the acidified hydrolysis reaction of NaBH4 using the Ni-based (ethanol) catalyst was found as 49 kJ mol−1.

Effect of Addition of Other Acids into Butyric Acid on Selective Leaching of Zinc from Basic Oxygen Steelmaking Filter Cake

The selective leaching of zinc over iron from basic oxygen steelmaking (BOS) filter cake was investigated using mixtures of butyric acid with acetic and/or propionic acid, HCl, or H2SO4. The main focus was to assess the effects of other acids on the zinc and iron leaching in butyric acid. The results show that slight reduction of zinc leaching and increase in iron leaching may take place with addition of acetic and propionic acids, causing a minor decrease in the selectivity of zinc leaching over iron. Intermittent addition of H2SO4 and HCl was required to control the pH to be not less than that of pure butyric acid solution. Overall, an excellent selectivity can be maintained with the butyric acid–other acid mixtures. The results demonstrate the feasibility to use raw butyric acid without purification or waste butyric acid containing other impurity acids for leaching of zinc from the BOS filter cake to be recycled. Using high content of H2SO4 in leaching is not recommended because it has a more detrimental effect on the selectivity of zinc leaching and may cause deposition of CaSO4 in the leaching residue which may increase the SO2 or CO2 emission in later high-temperature recycling processes.

Features of homogeneous oxidation of glyoxal to glyoxylic acid

The values and nature of induction periods (IP) for the oxidation of commercial glyoxal (CG) to glyoxylic acid (GA) by HNO3—HCl mixtures were studied under diff erent reaction conditions. The physicochemical interpretation of the IP enables one to control the oxidation of CG to target GA. It was established by UV spectroscopy that the addition of HCl favored the disintegration of n-mers of CG and simultaneous accumulation of structures with aldehyde groups (SAG), which are active forms of CG during its oxidation to GA. The rate constants and activation energies of SAG accumulation were determined. The theoretical UV spectra, which are well consistent with the experimental curves, and thermochemistry of equilibria of the CG forms were calculated in the Gaussian/09 program package. The IP values at varied temperature, ratio of CG to hydrochloric acid, and time of storage of the reaction mixture were determined on the Arduino-based unit with a temperature sensor. The IP value is almost halved with an increase in the amount of HCl. The IP is also nearly halved as the time of storage of a CG—HCl mixture increases by three times. The obtained regularities indicate that the character of the IP of CG oxidation is related to the continuous disintegration of n-mers in CG solutions, i.e., to the permanent accumulation of SAG, which are fi nally oxidized to GA.

Antimicrobial activity of naphthalene lysine conjugated peptide hydrogels

The synthesis of hydrogel scaffolds with inherent antimicrobial activity has advantages for their use in tissue engineering. An ultra-short naphthalene lysine conjugated peptide, NapFFK’K’, containing naphthalene (Nap) as a molecule of high aromaticity for gel strength, phenylalanine (F) and epsilon variant lysine (K’) has previously been shown by us to self-assemble forming hydrogels with inherent antimicrobial properties against a limited number of pathogens tested. The aim of this work was to extend the antimicrobial activity studies on NapFFK’K’ including pathogenic bacteria associated with dental infections. NapFFK’K’ was synthesised using the 9-fluorenylmethoxucarbonyl Solid Phase Peptide Synthesis. Peptide purity was analysed by mass spectrometry. Hydrogel formulation was achieved by suspending the peptide in sterile deionized water followed by addition of NaOH and HCl. Hydrogels were tested at peptide concentrations of 1 %, 1.5 % and 2 % w/v against the Gram-positive bacteria Enterococcus faecalis and Staphylococcus aureus, and the Gram-negative bacterium Fusobacterium nucleatum. Bacteria inoculumns were exposed on hydrogel surface for 24 h. Bacterial susceptibility assay, employing the Miles and Misra method, was used to determine antimicrobial activity of hydrogels after 24 h incubation. Our results show that peptide hydrogels exhibit antimicrobial properties against both groups of bacteria but at different peptide concentrations. The 1 % peptide hydrogels was most effective against Gram-positive bacteria whereas the 2 % peptide hydrogel was effective against Fusobacterium nucleatum. Given the efficacy of the self-assembling NapFFK’K’ peptide hydrogels against oral pathogens, they may have potential use in tissue engineering approaches for regenerative endodontic treatments.

Effects of Additives on Alumina Preparation from Aluminum Chloride Solution by Electrolytic Transformation

A new electrotransformation process based on bubbling CO2 into the electrolyte in an electrolytic process to cause precipitation of aluminum salt is proposed herein to solve problems such as the high energy consumption in the process of alumina extraction by acid leaching. The effects of different additives in this electrotransformation process applied to aluminum chloride solution and the resulting roasting products were studied. When using different additives (HCl, Na2CO3, and NaHCO3) at an initial concentration of 10 g/L, the solution pH value and solution temperature gradually increased with increasing electrotransformation time, and the final pH value approached 3.2. The roasting products were all sheet alumina with cubic crystal structure. Use of all the additives refined the granularity of the alumina product, improved the solution conductivity, and increased the chlorine content in the alumina product. Addition of HCl improved the recovery rate of Al, but use of the additives Na2CO3 and NaHCO3 greatly reduced the recovery rate of Al.

An efficient, cost-effective method for determining the growth rate of sulfate-reducing bacteria using spectrophotometry

The use of sulfate reducing bacteria (SRBs) in laboratory studies is a common approach for investigating microbially influenced corrosion (MIC). The characteristic formation of black iron sulfide precipitates during SRB growth, however, preclude the use of traditional spectrophotometric approaches for capturing growth data instead necessitating labour-intensive or technically specialized approaches. As such, an understanding of SRB growth responses to experimental conditions is often missing from MIC studies. Bernardez and de Andrade Lima (2015) have outlined a spectrophotometric approach for estimating SRB cell mass via the addition of HCl. This method has potential for the study SRB growth however its applicability is currently limited by the use of large aliquot volumes (45 mL), which restrict the number of timepoints that can sampled from one culture, and the extensive time devoted to cell preparation prior to OD readings.•We demonstrate an improved method for capturing SRB growth data via spectrophotometry following acidification. We incorporate lower sample volumes and adapt the method described in Bernardez and de Andrade Lima (2015) to a high throughput microtiter plate approach that increases the efficiency of this method and its applicability to growth rate studies.•Our results allay theoretical concerns that acidification may distort growth rate analysis by impacting cells differently depending on their metabolic state.•We further demonstrate that this method (acid-amended OD measurements) is more accurate and far more cost efficient than traditional methods (dilution spread-plate counting) and popular molecular methods (quantitative PCR) currently in use in SRB growth research.

Addressing the Fabrication Difficulties of Femtosecond Laser Written Surface Waveguides for Enhanced Evanescent Coupling

In this work, the fabrication of optical waveguides embedded in fused silica (Suprasil1) and boro-aluminosilicate glass (Eagle2000) is demonstrated with femtosecond laser direct writing, as well as their suitability to be brought to the surface, through wet etching, for enhanced evanescent coupling with the external dielectric medium. Fused silica demonstrated to be inappropriate in this particular application, as the guiding region is at the bottom of the induced modification, creating a barrier between the guided mode and the substrate’s boundary. Furthermore, the existence of nanogratings meant that, upon contact of the top of the induced modification with the substrate’s boundary, the waveguide is quickly etched. Eagle2000 demonstrated to be superior to fused silica due to its characteristic modification cross-section and absence of nanogratings, which allowed the placement of the guiding region as close to the substrate’s surface as required. However, surface roughness arising from the creation of insoluble products in the HF solution was found. The addition of HCl to dissolve these products was implemented.

Extractive Spectrophotometric Determination of Ulipristal Acetate using Naphthol Blue Black

Ulipristal acetate is used to treat uterine fibroids and for emergency birth control. The present study is a first report on development of a visible spectrophotometric method for determination of Ulipristal acetate present in bulk and tablet formulation. The method involves the sequential addition of HCl (0.1 N) and Napthol Blue Black solution to Ulipristal acetate. Cation formed on tertiary amine group of Ulipristal acetate attracts anion of naphthol blue black (an acid dye) to develop a coloured ion-association complex. From the aqueous phase, the chromophore is extractable into chloroform, which exhibits λmax at 640 nm. As per the existing guidelines of ICH, various parameters of the method were tested for validation. Regression analysis (r > 0.999) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (2.50 – 15.00 μg mL-1). The % recovery values falls in 99.80 – 100.72 range. %RSD results of both precision studies were observed in the range 0.007 – 0.560, indicating the satisfactory precision of the method. Low values of R.S.D. (< 1 %) were observed indicating that the proposed method is reproducible, accurate and precise. The proposed method can be used in quality control laboratories for routine analysis of Ulipristal acetate (bulk drug and pharmaceutical dosage forms) without requirement of expensive instruments.

Carbocation stability as predictor for electrophilic addition of HCl to chlorinated ethenes and propenes in the gas phase

AbstractElectrophilic addition of halo acids to alkenes is commonly discussed in terms of the stability of the corresponding carbocation intermediate. In solution, this may be rationalized by reference to Hammond's postulate. The corresponding gas‐phase reaction takes place via a concerted mechanism without the formation of a cationic intermediate. Still, the series ethene, propene, and 2‐methylpropene show excellent correlation between proton affinities (PA) and gas‐phase activation energies for the addition of halo acids, with the activation energy decreasing linearly with increasing PA. Thus, PA presents itself as a potential predictor of reactivity also in the gas phase. To explore this possibility, we have performed high‐level calculations of cation stability (as reflected in PA) and activation energy for addition of HCl (Ea) for 12 chlorinated ethenes and propenes. Contrary to the hypothesis, for the present set of substrates, the correlation between PA and Ea is weak, and moreover, for subsets such as the series ethene, 1,2‐dichloroethene, and tetrachloroethene, Ea increases with increasing PA. An alternative approach of correlating Ea to carbon 1s ionization energies rather than PA shows moderately higher correlation overall and much better correlation within subsets of compounds that share the same number of chlorines attached to the carbon subject to electrophilic attack/core ionization.

Recovery of WC and Co from cemented carbide scraps by remelting and electrodissolution

A novel method was proposed in this study to recycle WC and Co from cemented carbide scraps by remelting and electrodissolution. WC was recrystallized and purified through melting process. The WC that embedded in alloy was independent of each other and thus was easily separated by electrodissolution. The effects of dissolving parameters were investigated, and the results indicated that the maximum dissolving rate was 0.045 g·h−1·cm−2 and the anodic passivation was not found even at 500 A·m−2 of current density. In addition, the temperature and concentration of HCl were irrelevant to the rate and the current efficiency of the electrolysis. The SEM showed that the final WC powder was 5–20 μm in particle size with a regular shape, and the Co was directly recycled from the cathode at the same time.

The effect concentration of tetraethylorthosilicate and variation HCl 0.1M for synthesis mesoporous silica using oleic acid as template and 3-aminopropyltrimethoxysilane as co-structure directing Agent

Synthesis mesoporous silica using oleic acid as template and 3-aminopropyltrimethoxysilane as co-structure directing agent has been conducted. As a silica source used tetraetylorthosilicate. The reaction was carried out under three conditions: first, reducing the concentration of tetraethylortosilicate and 3-aminopropyltrimethoxysilane and varying the volume of HCl 0.1M; second, increasing the concentration of tetraethylortosilicate and 3-aminopropyltrimethoxysilane by varying the addition of HCl 0.1M and the third was carried out with the addition of methanol but without the addition of HCl 0.1M. The obtained silica mesopores were characterized by infrared spectrometer, X-ray diffraction and adsorpsi-desorption isotherm and scanning electron microscopy.

Liquid-Phase Hydrogenation of Halobenzenes in the Presence of Palladium-Containing Nanodiamonds

The catalytic activity of palladium-containing nanodiamonds (Pd/ND) is studied in the model reaction of liquid-phase hydrodehalogenation of monohalobenzenes (chlorobenzene, bromobenzene, and iodobenzene) and ortho-, meta-, and para-isomers of dichlorobenzene under mild conditions (Т = 45°С, $${{P}_{{{{{\text{H}}}_{2}}}}}$$ = 1 atm). The obtained results are compared with the catalytic behavior of the palladium-containing activated carbon (Pd/C) under identical conditions. It is found that catalyst Pd/ND is more active than Pd/C and is more stable against the poisonous effect of hydrogen halide forming during the reaction. Study of the effect of HCl and NaOH additives on the catalyst activity shows that, in the presence of HCl, poisoning of the catalyst occurs: the rate of reaction decreases; in the presence of NaOH, the catalyst activity grows; the rate of reaction increases as a result of hydrogen chloride neutralization by an alkali. For both catalysts the rate of reaction decreases in the sequence Cl > Br > I for monohalobenzenes and in the sequence para- > ortho- > meta-isomer in the case of dichlorobenzenes. The obtained dependences are explained using the quantum-chemical modeling of substrates of model reactions.

Controlling Nuclearity and Stereochemistry in Vanadyl(V) and Mixed Valent VIV/VV Complexes of Oxido‐Pincer Pyridine‐2,6‐dimethanol Ligands

The coordination chemistry of three oxido‐pincer ligands 2,6‐(HOCR2)2(pyridine) (H2L) based on 2,6‐pyridinedimethanol [R = H (H2pydim), Me (H2pydip), Ph (H2pyphen)] towards vanadium(V) was explored. Reaction of NH4VO3 with the protoligands H2L gave the dinuclear complexes [(L)OV(μ‐O)VO(L)]. Mononuclear anionic species [VO2(L)]–, which were isolated as alkaline metal salts were obtained from reactions of [VO(acac)2] (acac– = acetylacetonate) and H2L under basic conditions and addition of HCl to these species allowed to isolate the unprecedented oxido chlorido complexes [VOCl(L)] for pydip and pyphen. Cyclic voltammograms of the dinuclear [V2O3(L)2] and mononuclear [VOCl(L)] complexes show reversible VV/VIV reduction waves, while corresponding waves of the anionic [VO2(L)]– are completely irreversible. The mixed‐valent VIV/VV species [V2O3(L)2]·– were characterized by EPR and UV/Vis spectroelectrochemistry revealing a delocalized system with a 15 line EPR spectrum and an intervalence charge transfer (IVCT) band for the bulky pyphen ligand but localized radicals in case of the pydim and pydip derivatives (8 line EPR, no IVCT). DFT calculated structures of the three derivatives show an V–O–V arrangement for [V2O3(pyphen)2]·– of about 145° ideally suited for delocalization, whereas for [V2O3(pydip)2]·– an angle of 128° was found.

Potentially helical imidazole-containing conjugated oligomers: synthesis, optical properties, and conformation

Three imidazole-containing conjugated oligomers (O1, O2, and O3) were synthesized by a Suzuki–Miyaura cross-coupling polymerization in combination with a post-polymerization reaction to clarify the structure–property–conformation relationship and ultimately develop a method for accessing helical secondary structures in the future. HR-ESI-MS analysis of the model reaction mixture revealed that debromination is responsible for the low molecular weight of these oligomers. The absorption and emission peak maxima gradually redshifted moving from O2 to O1 to O3, which can be rationalized by the number of intramolecular hydrogen bonds (IHBs). O2, with no IHBs, and O3, which forms multiple robust IHBs, were insensitive to the nature of the solvent, while O1, with weak IHBs, exhibited solvent-dependent absorption spectra. O3 was susceptible to both acid and base treatment, namely, the addition of HCl caused a blueshift in the absorption spectra, and the addition of NaOH resulted in a complex shift in the peak depending on the degree of deprotonation. A conformational study based on DFT calculations indicated that the formation of the IHB network potentially endows O3 with a helical conformation. The formation of multiple intramolecular hydrogen bonds (IHBs) is a reliable method for obtaining conjugated oligomers with helical secondary structures, and imidazole with both proton-accepting and proton-donating abilities plays an important role. On the basis of its optical properties in conjunction with DFT calculations, a conjugated oligomer composed of alternating imidazole and 1,4-dihydroxybenzene units was found to (1) form robust IHBs, (2) be susceptible to both acid and base treatment, and (3) potentially adopt a helical conformation.

Exploration of reaction mechanism between acid gases and elemental mercury on the CeO2–WO3/TiO2 catalyst via in situ DRIFTS

Although the oxidation of elemental mercury (Hg0) on catalyst can be significantly affected by acid gases, its mechanism is still unclear. This study used in situ DRIFT to research the influence of acid gases (NO, HCl and SO2) on the performance of mercury oxidation on catalyst CeO2(5)–WO3(9)/TiO2. The catalyst could capture a large amount of Hg0 on the surface yet not oxidize all Hg0 into gaseous oxidation mercury (Hg2+) due to the limit of oxidation sites (CeO2). The addition of NO and HCl improved the mercury oxidation efficiency because this process transformed the adsorbed mercury on the catalyst into gaseous Hg2+ and formed new active sites. The in situ DRIFTS result indicated that NO2 and nitrate served as active sites for mercury oxidation. The formation of active chlorine (Cl∗) via HCl adsorption on the catalyst promoted the transformation of mercury into gaseous HgCl2. The NO and HCl addition could keep the mercury oxidation efficiency over 91.5% with the presence of 500–3000 ppm SO2 and increase the SO2 resistance of the catalyst. The reaction of NO and Hg0 conforms to the Eley-Ridcal mechanism, while the reaction of HCl and Hg0 follows the Languir-Hinshelwood mechanism.

Ligand-Centered Borenium Reactivity in Triaminoborane-Bridged Diphosphine Complexes.

Borenium ions (i.e., three-coordinate boron cations) are known to promote a wide variety of stoichiometric and catalytic reactions because of their high Lewis acidity. As demonstrated by the growing number of chemically reactive borane ligands, there is considerable interest in developing ligands with highly electrophilic boron sites that promote multisite reactivity in metal complexes. However, there are currently few examples of ligand-centered borenium ions, especially with ligands that form coordination complexes with a wide range of metals. Here we report borenium-like reactivity on a highly versatile diphosphine ligand. Treating (PhTBDPhos)NiCl2 (1) with strong Bronsted acids such as HBF4·Et2O, HOTf, or HNTf2 resulted in fluoride or chloride abstraction from BF4- or NiCl2, respectively, to form trans N-H and B-X bonds on the ligand backbone. HCl addition to the bridgehead N-B bond is reversible, and the reactivity depends on the identity of the supporting counteranions, as observed when treating [(PhTBDPhos)NiCl]2X2, where X = NTf2- (3), OTf- (4), or BArF4- (5), with HCl. The reaction of 4 with HNTf2 instead of HCl yielded NMR evidence of the latent borenium cation in solution and showed how poor nucleophiles such as triflate bind to the borenium ion in the solid state. Remarkably, replacing the chloride ligands in 1 with chelating and less-labile thiolates or catecholates, or changing the phosphorus substituents (phenyl to isopropyl), attenuates the reactivity on the ligand backbone. Density functional theory was used to quantify the reaction free energies, and the theoretical results corroborate the experimental observations. Given the broad utility of diphosphines in homogeneous catalysis and the known benefits of strong Lewis acid promotors in many catalytic reactions, we anticipate that the results will provide new opportunities for dual-site reactivity involving boron ligands and metals.

A small molecular boron-phenylpyrrin sensor for H+/Fe3+ and its application as a digital demultiplexer

A julolidine-based boron-phenylpyrrin small molecule has been designed and synthesized through a one-pot condensation-complexation procedure. Systematic optical studies show that this compound displays two distinct optical responses to the addition of HCl and Fe[Formula: see text] in succession: the addition of HCl induces an obvious red shift in its maximum absorption and fluorescence emission bands accompanied with the fluorescence quenching, whereas after synchronously adding H[Formula: see text] and Fe[Formula: see text], the maximum absorption and fluorescence emission wavelength were found to shift little but with an obvious decrease in the absorbance and fluorescence intensity, suggesting the dual-detecting nature of this compound to H[Formula: see text] and Fe[Formula: see text] under acid conditions. More interestingly, based on the HCl/Fe[Formula: see text]-mediated absorption and fluorescence signal features, JBPP can function as AND, NAND, INH and IMP logic gates which can be further developed into a 2:4 digital demultiplexer These will endow this small molecule compound with great potential for applications in molecular logic material, chemosensors and biological fields.

Preparation of AgCl photocatalyst by recovering silver from discarded cyanide-free silver electrodeposition bath: insightful investigation of quantum chemical calculations and experiment

The recovery of silver from cyanide-free silver electrodeposition bath to prepare AgCl photocatalyst was studied by quantum chemical calculations and experiment. Quantum chemical calculations were used to predict the coordinated bonds broken mechanism as well as silver recovery and AgCl photocatalyst formation. Based on the prediction, HCl was used in silver recovery and preparation of AgCl. With addition of HCl into silver electrodeposition bath, coordinated bonds between Ag+ and composite complexing agents, 5,5-dimethylhydantoin (DMH) and nicotinic acid (NA), were broken and the Ag+ was recovered as AgCl with high purity. The composition of products was studied byXRD and XPS measurements. The introduced method is effective and economical for silver recovery from investigated bath and wastewaters. The insight view of coordination interaction of complexing agents for metal ions in this manuscript is a great strength to perfect the investigation of novel metal recovery and resources recycling in aspect of technique and mechanism.

A Stimuli-Responsive Molecular Capsule with Switchable Dynamics, Chirality, and Encapsulation Characteristics.

In this study, we report the preparation, conformational dynamics, and recognition characteristics of novel molecular capsule 1 comprising a bowl-shaped framework conjugated to a tris(2-pyridylmethyl)amine (TPA) lid. With the assistance of experiment (1H NMR spectroscopy) and theory (MM and DFT) we found that C3 symmetric 1 is poorly preorganized with three pyridines at the rim adopting a propeller-like orientation and undergoing P-to- M (or vice versa) stereoisomerization (Δ G⧧ < 8 kcal/mol, VT 1H NMR). Capsule 1 binds CH4, CH3Cl, CH2Cl2, CHCl3, and CCl4 with Ka < 7 M-1. Protonation of 1 with HCl, however, gives [1·H]-Cl, with the solid-state structure showing the TPA lid being "flattened" and the +N-H---Cl hydrogen-bonded group residing outside. Importantly, the P-to- M stereoisomerization would for [1·H]-Cl occur with Δ G⧧ = 11 kcal/mol (VT 1H NMR). Less dynamic and more preorganized [1·H]-Cl binds CH4, CH3Cl, CH2Cl2, CHCl3, and CCl4 guests with a greater affinity ( Ka = 100-400 M-1) than 1. The results of our studies suggest that the complexation of increasingly larger guests takes place in an induced-fit fashion, with [1·H]-Cl (a) elongating along its vertical axis and concurrently potentially (b) twisting pyridines from P into M (and vice versa) orientation. The addition of Et3N to [1·H]-Cl⊂CH2Cl2 causes deprotonation of the capsule and the release of CH2Cl2 with the process being fully reversed after the addition of HCl. Allosteric capsule 1 with unique structural and dynamic characteristics is expected to, in the future, assist the construction of complex molecular machines and smart functional materials.