Solvent Exchange Kinetics Research Articles

In Situ Observation of Solvent Exchange Kinetics in a MOF with Coordinatively Unsaturated Sites.

Solvent exchange of synthesis solvent within metal-organic frameworks (MOFs) is an essential process for the activation of coordinatively unsaturated sites (CUS) to achieve an optimal surface area; activation of the CUS is required to exploit the versatile applications of MOFs. However, it is challenging to replace CUS-bound synthesis solvent prior to MOF activation, which can lead to a structural collapse and reduced surface area post-evacuation. Herein, we quantify the exchange behavior of a copper paddlewheel-based CUS-MOF (HKUST-1) in the presence of three different solvents: ethanol (EtOH), dichloromethane (DCM), and N,N-dimethylformamide (DMF). The DMF release profiles are monitored via in situ observation of the exchange solvent composition via 1H NMR and Raman spectroscopy at the macroscopic scale. Furthermore, the change in solvent within a single crystal is measured to directly elucidate the exchange behavior. We demonstrate the DMF release profile from HKUST-1 exhibits different rate laws depending on whether the solvent exchange occurs at the CUS or is purely diffusive through the pores. This contribution represents the first characterization of release from a CUS-MOF as a function exchange solvent and reveals that solvent exchange in a CUS-MOF is not diffusion-limited, but rather is limited by the solvent exchange kinetics at the metal center. Insights from this study can be generalized to the variety of copper-paddlewheel-based MOFs, informing best practices for solvent exchange.

Protein gel shrinkage during solvent exchange: Quantification of gel compaction, mass transfer and compressive strength

In this work, we experimentally investigate into one step solvent exchange of cylindrical shaped whey protein isolate (WPI) gels, where the pore fluid water inside the pores is replaced by ethanol. Solvent exchange has three major impacts on macroscopic gel properties, leading to an increase in compressive strength, shrinkage of the gel cylinders diameter and consequently a change in the spatial protein distribution. 1D-Raman spectroscopy was employed for in-situ investigation of pore fluid composition and protein density distribution, together with a conventional camera to track the diameter change of the gel during solvent exchange. Compressive strength of the gel cylinders is measured ex-situ using a universal testing machine. For gels with three different protein concentrations, we report comparable shrinkage of the diameter to about 85% of the initial size, with most shrinkage taking place during the first stages of solvent exchange, when ethanol is detected in the outermost layers only. Further shrinkage is prevented by a sharp increase in mechanical stiffness of the gels. Solvent exchange leads to an inhomogeneous protein density distribution for most gels, with a compaction towards the radial center. We showed a complex interaction of solvent exchange kinetics and pore fluid dependent stiffness of the gel matrix controls the final size and density distribution of the gel.

Initial Leuprolide Acetate Release from Poly(d,l-lactide-co-glycolide) in Situ Forming Implants as Studied by Ultraviolet-Visible Imaging.

The initial drug release from in situ forming implants is affected by factors such as the physicochemical properties of the active pharmaceutical ingredient, the type of the excipients utilized, and the surrounding environment. The feasibility of UV-vis imaging for characterization of the initial behavior of poly(d,l-lactide-co-glycolide) (PLGA)/1-methyl-2-pyrrolidinone (NMP) in situ forming implants was investigated. The in vitro release of leuprolide acetate (LA) and implant formation in real time were monitored using dual-wavelength imaging at 280 and 525 nm, respectively, in matrices based on agarose gel and hyaluronic acid (HA) solution emulating the subcutaneous matrix. Three hours upon injection of the pre-formulation, approximately 15% of the total amount of LA administered was found in the agarose gel, while 5% was released from the implant into the HA solution. Concurrently, more extensive swelling of the implants in the HA solution as compared to implants in the agarose gel was observed. Transport of both LA and the solvent NMP was investigated using UV-vis imaging in a small-scale cell where the geometry of the formulation was controlled, showing a linear correlation between drug release and solvent escape. Light microscopy showed that the microstructures of the resulting implants in agarose gel and HA solution were different, which may be attributed to the different solvent exchange rates. UV imaging was also used to examine the interaction of LA with the release medium by characterizing the diffusion of LA in agarose gel, HA solution, and phosphate buffered saline. The reduced LA diffusivity in HA solution as compared to agarose gel and the LA distribution coefficient in the agarose gel-HA system indicated the presence of interactions between LA and HA. Our findings show that the external environment affects the solvent exchange kinetics for in situ forming implants in vitro, resulting in different types of initial release behavior. UV-vis imaging in combination with biorelevant matrices may offer an interesting approach in the development of in situ forming implant delivery systems.

Rapid Guest Exchange and Ultra‐Low Surface Tension Solvents Optimize Metal–Organic Framework Activation

AbstractExploratory research into the critical steps in metal–organic framework (MOF) activation involving solvent exchange and solvent evacuation are reported. It is discovered that solvent exchange kinetics are extremely fast, and minutes rather days are appropriate for solvent exchange in many MOFs. It is also demonstrated that choice of a very low surface tension solvent is critical in successfully activating challenging MOFs. MOFs that have failed to be activated previously can achieve predicted surface areas provided that lower surface tension solvents, such as n‐hexane and perfluoropentane, are applied. The insights herein aid in the efficient activation of MOFs in both laboratory and industrial settings and provide best practices for avoiding structural collapse.

Rapid Guest Exchange and Ultra-Low Surface Tension Solvents Optimize Metal-Organic Framework Activation.

Exploratory research into the critical steps in metal-organic framework (MOF) activation involving solvent exchange and solvent evacuation are reported. It is discovered that solvent exchange kinetics are extremely fast, and minutes rather days are appropriate for solvent exchange in many MOFs. It is also demonstrated that choice of a very low surface tension solvent is critical in successfully activating challenging MOFs. MOFs that have failed to be activated previously can achieve predicted surface areas provided that lower surface tension solvents, such as n-hexane and perfluoropentane, are applied. The insights herein aid in the efficient activation of MOFs in both laboratory and industrial settings and provide best practices for avoiding structural collapse.

On the Road to Biopolymer Aerogels-Dealing with the Solvent.

Aerogels are three-dimensional ultra-light porous structures whose characteristics make them exciting candidates for research, development and commercialization leading to a broad scope of applications ranging from insulation and catalysis to regenerative medicine and pharmaceuticals. Biopolymers have recently entered the aerogel foray. In order to fully realize their potential, progressive strategies dealing with production times and costs reduction must be put in place to facilitate the scale up of aerogel production from lab to commercial scale. The necessity of studying solvent/matrix interactions during solvent exchange and supercritical CO2 drying is presented in this study using calcium alginate as a model system. Four frameworks, namely (a) solvent selection methodology based on solvent/polymer interaction; (b) concentration gradient influence during solvent exchange; (c) solvent exchange kinetics based on pseudo second order model; and (d) minimum solvent concentration requirements for supercritical CO2 drying, are suggested that could help assess the role of the solvent in biopolymer aerogel production.

Solvent exchange kinetics in poly(N-isopropylacrylamide) microgel-based etalons

Poly (N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgel-based etalons are constructed by depositing thin Au layers (mirrors) on either side of a planar microgel layer. When immersed in water, the microgel layer swells and the etalon exhibits visual color. The thermoresponsivity of the pNIPAm-based microgels allows the Au mirror spacing, and hence the device color, to be dynamically modulated. Necessarily, when the mirror spacing is modulated solvent in the microgel layer must be expelled to the surroundings. Previously, we determined that the etalon deswelling kinetics depended critically on the thickness of the Au layer covering the microgels. Here, we report on solvent exchange kinetics. We found that the time required for solvent entry into the microgel layer is much longer than solvent exit. In addition, the rate was found to again depend critically on the thickness of the Au layer covering the microgel layer; thicker Au layers corresponded to slower solvent exchange kinetics.

Solvation of Li+ by Acetone, THF, and Diethyl Ether in the Gas Phase and the Ion−Molecule Association Mechanism

Fourier transform ion cyclotron resonance spectrometry has been employed to study the solvation of the Li+ ion with acetone, tetrahydrofuran (THF), and diethyl ether (DEE) in the gas phase. LiILi+ triple ions are produced in the ICR cell by the laser desorption ionization of a lithium iodide/dibenzo-18-crown-6-ether matrix pasted on a Teflon substrate. All O donors abstract Li+ from the triple ion and form solvated complexes with a maximum solvation number of three at room temperature, around 10-6 Torr. All third solvent binding energies are determined from van't Hoff plots. Structures and energetics of the Li+·(S)n complexes, where n = 1−4 for acetone and THF and n = 1−3 for DEE, have been calculated at the Hartree−Fock level with a 6-311+G(d,p) basis set. Solvation enthalpies and free energies are calculated, and solvent binding enthalpies are compared with experiments. The kinetics of solvent exchange and the association reactions of Li+·(acetone-h6)(acetone-d6) with a 1:1 acetone-h6/acetone-d6 mixture have been measured as a function of pressure. The lifetime of the collision complexes are derived and compared with phase space theory calculations. The isotope effect on the radiative cooling rate is discussed.

Solvent Exchange Kinetics and Proton Relaxation in Solutions of Cobalt(II) Dioximes

Solvent Exchange Kinetics and Proton Relaxation in Solutions of Cobalt(II) Dioximes

Structure of copper(II) ethylenediamine complexes in aqueous and neat ethylenediamine solutions and solvent-exchange kinetics of the copper(II) ion in ethylenediamine as studied by EXAFS and NMR methods

The structures of copper(II) complexes with ethylenediamine (en) in aqueous and neat ethylenediamine solutions have been determined by the EXAFS (extended X-ray absorption fine structure) method. The copper(II) ion in en has an axially elongated octahedral structure with three en molecules. The Cu-N bond lengths in the four equatorial and two axial positions are 204(1) and 239(2) pm, respectively. The dynamic exchange reaction between en molecules in the bulk and en molecules bound to the copper(II) ion has been studied by the nitrogen-14 NMR line-broadening method

Dissociative Pathways in Platinum(ll) Chemistry

Abstract Steric and electronic factors favor the addition of a fifth ligand to a square planar d8 complex to form five coordinate species either as discrete compounds or reaction intermediates. The search for factors promoting the conversion of the normal associative mode of reaction into a dissociative process has attracted much attention. The attempt to achieve this goal by using bulky ancillary ligands has been unsuccessful. More convincing evidence in favor of a dissociative mechanism involving a Pt(II) 3-coordinate intermediate comes not from classical Werner compounds but from reactions involving organometallic substrates. It is now reasonably clear that the formation of such 3-coordinate 14-electron compounds offers a favorable reaction route to a number of fundamental processes as an alternative to the intermediacy of 4- and 5-coordinate species. Among them, the uncatalyzed cis to trans isomerization of complexes of the type cis-[Pt(PE3)2(R)X] (R = alkyl or aryl groups; X = halide ion), β-hydride elimination from symmetrical and unsymmetrical dialkyldiphosphino platinum(II) complexes and other processes that will be briefly discussed in this paper. Very recently, kinetics of solvent exchange and displacement by bidentate ligands on cis-[Pt(R)2(L)2] (R = CH3 or C6H5; L = sulfoxide or thioether) complexes have provided a clear-cut example of ligand dissociation as the dominant step in substitution reactions of square-planar complexes. While in most of the cases extensive electron density transfer associated with the presence of a Pt-C σ bond seems to be a prerequisite to produce a sharp changeover of reaction pathways, we are far from a complete understanding of the factors that promote the formation and stabilization of coordinatively unsaturated species, as well as of the efficiency with which they can be intercepted in solution by ligands or by the solvent itself.

Ions in solution: basic principles of chemical interactions

Introduction Solvation numbers Ion-solvent distances Ion-solvent interactions Acid-base behaviour: Hydrolysis and polymerisation Stability constants Redox potentials Kinetics and thermodynamics Kinetics and mechanisms: solvent exchange Kinetics and mechanisms: complex formation Kinetics and mechanisms: substitution at complex ions Kinetics and mechanisms: redox reactions Past, present, and future Glossary Further reading Exercises, problems and projects.

Equilibrium studies and kinetics of solvent exchange with five- and six-co-ordinate mono- and bis-(solvent)(1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane)nickel(II) perchlorate by oxygen-17 nuclear magnetic resonance spectroscopy

Natural-abundance 17O n.m.r. spectroscopy at 54.24 MHz has been used to measure the rates of D2O and N,N-dimethylformamide (dmf) exchange with [NiLSn]2+ ions (S = solvent: L =R,S,R,S- and R,S,S,R-1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane with n= 1 and 2 respectively). The rate constants and activation parameters for D2O and dmf exchange with the five-co-ordinate trans-(I) complexes are 10–7kexI/s–1= 1.59 ± 0.11 and 1.51 ± 0.08, ΔH‡/kJ mol–1= 24.7 ± 1.4 and 30.1 ± 0.7, and ΔS‡/J K–1 mol–1=–24.0 ± 5.2 and –6.4 ± 2.9 respectively; for the six-co-ordinate trans-(III) species, 10–7kexI/s–1= 15.8 ± 1.8 and 32.8 ± 4.1, ΔH‡/kJ mol–1= 37.4 ± 2.4 and 38.3 ± 1.4, and ΔS‡/JK–1 mol–1=+ 37.6 ± 9.0 and + 46.7 ± 5.6 for D2O and dmf respectively. These rates are the largest ever observed for solvent exchange at Ni2+, and show the pronounced labilising effect of a tetra-aza macrocyclic ligand. The activation parameters are interpreted in terms of an associative-interchange (la) mechanism for the five-co-ordinate species, and a dissociative-interchange (ld) mechanism for the six-co-ordinate complexes. Equilibrium constants and associated thermodynamic parameters were determined, either by spectrophotometry or by 1H or 17O n.m.r. shifts, for equilibria between diamagnetic four-co-ordinate [NiL]2+ and the corresponding five- or six-co-ordinate paramagnetic solvates. The rate of dmf exchange with [Ni(dmf)6]2+ was redetermined by natural-abundance 17O n.m.r.

Relating Cation Solvation in Solvent Mixtures with Solvent Exchange Rates — A 1H‐NMR Study on Co(II)‐Ions

AbstractSpecific and statistical solvation of Co(II)‐ions in mixtures of methanol with dimethylformamide respectively hexamethylphosphoric triamide was found by 1H‐NMR‐spectroscopy. Relations are given, which correlate these possible solvation models with the kinetics of solvent exchange. On this basis, specific outersphere solvation of the methanol rich Co(II)‐solvate‐complexes by dimethylformamide can be deduced. For mixtures of hexamethylphosphoric triamide with methanol, the statistical solvation behaviour is additionally favoured by a strong solvent‐solvent interaction.

Five coordinate tetramethylcyclam complexes of Co(II) and Ni(II); associative interchange and dissociative mechanisms for solvent exchange in acetonitrile

Variable temperature and pressure 13C NMR measurements have been used to study the kinetics of solvent exchange of the five coordinate complexes of Co(II) and Ni(II) with 1,4,8,11-tetramethyl-1,4,8, 11-tetraazacyclotetradecane in acetonitrile. While the activation volume value of −9.6 ± 0.5 ml mol −1 supports the proposal of an associative interchange, I a, mechanism for the Co(II) system, the value of +2.3 ± 1.3 ml mol −1 for the Ni(II) system suggests a dissociative, D, mechanism. UV-visible spectral measurements of the Ni(II) complex in acetronitrile over a range of temperatures are consistent with the presence of an equilibrium involving the five coordinate and a square planar form of the complex. It is proposed that the solvent exchange on the five coordinate Ni(II) complex takes place via this four coordinate species.

Predominance of initial-state properties in volume relations for solvent exchange kinetics

In the exchange of solvent water with M2+(aq)(M = Mn, Fe, Co, Ni) or with M(NH3)5(OH2)3+(aq)(M = Cr, Co, Rh, Ir), the partial molar volumes of the transition states display less than one-third of the variability of the partial molar volumes of the initial states as M is varied within each series.

ChemInform Abstract: SOLVENT‐EXCHANGE KINETICS IN ACETIC ACID SOLUTION OF TETRAKIS(μ‐ACETATO)‐DICOPPER(II) STUDIED BY NUCLEAR MAGNETIC RESONANCE LINE BROADENING

Chemischer InformationsdienstVolume 12, Issue 45 Organoelement Compounds ChemInform Abstract: SOLVENT-EXCHANGE KINETICS IN ACETIC ACID SOLUTION OF TETRAKIS(μ-ACETATO)-DICOPPER(II) STUDIED BY NUCLEAR MAGNETIC RESONANCE LINE BROADENING S. FUNAHASHI, S. FUNAHASHISearch for more papers by this authorT. NISHIMOTO, T. NISHIMOTOSearch for more papers by this authorA. HIOKI, A. HIOKISearch for more papers by this authorM. TANAKA, M. TANAKASearch for more papers by this author S. FUNAHASHI, S. FUNAHASHISearch for more papers by this authorT. NISHIMOTO, T. NISHIMOTOSearch for more papers by this authorA. HIOKI, A. HIOKISearch for more papers by this authorM. TANAKA, M. TANAKASearch for more papers by this author First published: November 10, 1981 https://doi.org/10.1002/chin.198145293AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue45November 10, 1981 RelatedInformation

Solvent-exchange kinetics in acetic acid solution of tetrakis(.mu.-acetato)-dicopper(II) studied by nuclear magnetic resonance line broadening

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolvent-exchange kinetics in acetic acid solution of tetrakis(.mu.-acetato)-dicopper(II) studied by nuclear magnetic resonance line broadeningShigenobu Funahashi, Tetsuo Nishimoto, Akiharu Hioki, and Motoharu TanakaCite this: Inorg. Chem. 1981, 20, 8, 2648–2651Publication Date (Print):August 1, 1981Publication History Published online1 May 2002Published inissue 1 August 1981https://doi.org/10.1021/ic50222a051RIGHTS & PERMISSIONSArticle Views46Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (463 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Quantum chemical description of ions in solution

The application of the MESQUAC-MO method, a mixed electrostatic quantum chemical approach [1, 2], allows the calculation of models simulating ions in solution in solution including one, two, three or more explicitly considered solvation shells, i.e. up to the level, where the region of the bulk solvent begins. Such calculations have been performed for most metal ions up to the atomic number 30 (Zinc). Since these calculations have been carried out mainly for aqueous solutions, values for binding energies of water molecules in the various hydration layers could be obtained, allowing a theoretical prediction of the size of the hydration spheres of these ions. The total binding energies can be compared well to the experimentally determined hydration energies and reflect well known effects as the ‘ligand field stabilization’ within the transition metal ions. A comparison of the calculated binding energies at various coordination numbers with experimental data for the kinetics of solvent exchange in the first hydration layer allowed to discuss some models for the mechanism of exchange, indicating am important role of the water molecules in the second layer, which is confirmed by some tentative calculations on the corresponding transition state. Finally, some first calculations on a model pathway for the ionic dissociation in solution have been carried out giving some theoretical background on the basis of quantum chemistry for this fundamental process of solution chemistry.

ChemInform Abstract: SOLVENT‐EXCHANGE KINETICS IN NICKEL(II) SOLUTIONS OF AQUEOUS TRIS(DIMETHYLAMINO)PHOSPHINE OXIDE STUDIED BY PULSED PHOSPHORUS‐31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

Chemischer InformationsdienstVolume 10, Issue 4 Organoelement Compounds ChemInform Abstract: SOLVENT-EXCHANGE KINETICS IN NICKEL(II) SOLUTIONS OF AQUEOUS TRIS(DIMETHYLAMINO)PHOSPHINE OXIDE STUDIED BY PULSED PHOSPHORUS-31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY J.-C. BOUBEL, J.-C. BOUBELSearch for more papers by this authorJ.-J. DELPUECH, J.-J. DELPUECHSearch for more papers by this authorA. PEGUY, A. PEGUYSearch for more papers by this author J.-C. BOUBEL, J.-C. BOUBELSearch for more papers by this authorJ.-J. DELPUECH, J.-J. DELPUECHSearch for more papers by this authorA. PEGUY, A. PEGUYSearch for more papers by this author First published: January 23, 1979 https://doi.org/10.1002/chin.197904264Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue4January 23, 1979 RelatedInformation