Vanadyl Research Articles

Synthesis, Characterization and In-vitro Antibacterial Activity Studies of Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and 1,10-Phenanthroline Ligands

Oxovanadium(IV) complexes of the type [VO(L)(phen)] (VO-1 to VO-5) have been synthesized and characterized by FTIR and UV-Vis spectra, molar conductance, melting points, and magnetic susceptibilities measurements, where L= N-salicylidene-β-alanine (sal-ala), N-salicylidene-glycine (sal-gly), N-salicylidene-DL-β-phenylalanine (sal-pheala), N-salicylidene-leucine (sal-leu), and N-salicylidene-DL-methionine (sal-met), and phen is 1,10-phenanthtroline. The infrared spectral data reveals that the tridentate nature of the amino acid-based Schiff base ligand and the coordination of the ligand through azomethine nitrogen, phenolic oxygen and carboxylate oxygen with vanadyl (VO2+) ion. All of these complexes were determined to be non-electrolyte in nature, according to conductivity measurements. The magnetic moment measurements have been attributed that these complexes are paramagnetic and have d1 configuration of vanadium (IV) ion. The antimicrobial activity of the synthesized complexes was evaluated against four pathogenic bacteria viz. Escherichia coli, Proteus vulgaris, Bacillus subtilis and Staphylococcus aureus.

Constructing yeast-modified polypropylene amidoxime membrane toward highly-selective adsorption of U(VI) from seawater

To extract uranium from seawater, the adsorbent needs to have high selectivity for uranium and good hydrophilicity, and could resist biological pollution and prevent Marine microorganisms from blocking chelate sites. For effective uranium extraction, a straightforward crosslinking technique is used to create a highly selective and biofouling-resistant poly(amidoxime) (PAO-Y) membrane. PAO-Y is characterized by FT-IR, SEM, EDS, XPS, BET, WCA and NMR techniques. The effects of solution acidity, concentration, and adsorption time on its adsorption of uranyl ions and vanadyl ions are investigated. The composite material (PAO-Y) exhibits higher selective adsorption and affinity towards U(VI) compared to V(V). In simulated marine environment experiments, the material exhibited an adsorption capacity of 10.39 mg·g−1 for U(Ⅵ), which is five times higher than that for V(V). Furthermore, the adsorption partition constant for U(Ⅵ) is 1.44 × 105 mL·g−1, two orders of magnitude greater than that for V(V). The DFT calculations revealed specific coordination modes between PAO-Y and uranyl/vanadyl ions, elucidating the selective adsorption mechanism of uranium. The pentadentate coordination mode is shown by DFT calculations to be the most stable one. DFT calculations also show that the increase in the number of amino acid groups increases the interaction between the coordinating ligands and uranyl, but decreases the interaction between the coordinating ligands and vanadyl. These findings suggest that PAO-Y effectively enhance the selectivity and affinity towards uranyl ions during uranium extraction from marine environments and may find practical applications. After 15 days of continuous flow of 30 L natural seawater, PAO-Y obtained a total uranium capture capacity of 1.969 mg·g−1 in the fixed-bed adsorption system, making it a suitable candidate for uranium extraction from natural seawater.

Spectral analysis and characterization of Na2O-SiO2-ZrO2 glasses doped with V2O5

Na2O-SiO2-ZrO2 glasses doped with V2O5 were prepared with the melt quenching method, and were then analyzed using various techniques; in particular, with X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and optical absorption, photoluminescence, electron spin resonance (ESR), and Fourier transform infrared (FT-IR) transmission spectroscopy. The obtained results indicate that, in the studied glasses, vanadyl complexes tend to undergo a reduction from V5+ ions to V4+ ions. XRD and EDS data suggest that the glasses have amorphous nature with randomly distributed grains within the glass matrix. The optical absorption spectra show two transitions: 2B2g→2B1g and 2B2g→2Eg. The photoluminescence spectra exhibit a broad band from 750-900 nm, indicating the 2E→2T2 transition of vanadyl ions. The energies of the band gaps decreased gradually with increasing V2O5 content. The ESR spectra suggest that V4+ ions are situated in octahedral sites with tetragonal compression. The FT-IR spectra confirm the presence of various structural units within the glasses. Finally, the dielectric properties of the glasses were also measured, showing that the dielectric constant (ε′) and the loss tangent (tan δ) increase as the content of vanadium ions increases, indicating presence of V4+ ions within the glass matrix.

Geochemistry and mineralogy of the shale-hosted vanadium Van Property deposit, Mackenzie Mountains, Northwest Territories

Abstract Shales and mudstones are fine-grained rocks formed in sedimentary basins throughout Earth’s history. These lithologies are increasingly important targets for mineral deposit exploration since they can have economic resources of critical minerals including vanadium (V), an essential component of redox-flux batteries in solar cells. However, many Paleozoic shale-hosted V deposits are metamorphosed and deformed. This commonly obscures primary features including V-bearing host phases and the original composition of organic material. In this study, we present geochemical and mineralogical data from the Paleozoic Van Property deposit, Northwest Territories, Canada, to show that V can be released from organic matter during metamorphism and incorporated in clay phases such as illite. The siliceous argillites at the Van Property hosts up to 0.69% V2O5 and were metamorphosed to (sub-)greenschist facies. Their mineralogy is dominated by quartz with minor graphite, illite, muscovite, pyrite, sphalerite, rutile, and carbonates. Although, some illite (i.e., high-V illite) can have up to 13 wt% V2O3 and rutile can have up to 4.4 wt% V2O3, mass balance calculations are insufficient to explain V enrichment at the Van Property utilizing only illite and rutile. The third V host is inferred to be carbonaceous matter in which V accumulated syn-deposition on the seafloor. Subsequent metamorphism led to the demetallation of V-bearing geoporphyrins and the release of vanadyl ions (VO2+), some of which were then incorporated into high-V illite and rutile. This process of V enrichment highlights the role of organic matter in scavenging V from superficial reservoirs and the importance of metamorphism on subsequent V release and its incorporation into inorganic phases. The geochemistry of siliceous, V-rich argillites at the Van Property is also compared to other V-enriched shale and mudstone deposits, highlighting the diversity of shale-hosted V deposits, and emphasizing the need for further research to close the knowledge gaps related to variations in composition, mineralogy and V enrichment processes.

Capturing Hydrated Vanadium Ion Dynamics in Ionomer Nanocomposites Used for Redox Flow Batteries.

Herein, we employed high-flux backscattering spectroscopy to capture for the first time the motions of hydrated vanadyl ions in ionomer nanocomposites prepared by both solution-cast and in situ sol-gel condensation methods. Both local and jump diffusion coefficients of the hydrated vanadyl (VO2+) ions as well as the dynamic length scales of ion motions and the fraction of immobile hydrogen atoms were extracted from the scattering spectra. Notably, for solution-cast membranes, the jump and local diffusion coefficients of hydrated VO2+ ions were seen to decrease by over 10- and 4-fold, respectively, with the introduction of 10 mass % silica nanoparticles (SiNPs) compared to their neat counterparts. Further, the VO2+ diffusion coefficients were observed to decrease with thermal annealing, though the impact of annealing was less significant than that seen with the introduction of SiNPs. Finally, in general, thermal annealing and the introduction of SiNPs had no measurable impact on the fraction of immobile hydrogen atoms in both solution-cast and sol-gel ionomer nanocomposites. The data observed in this work, in conjunction with previous structural and chain dynamics studies on hydrated Nafion-SiNP nanocomposites, suggest that a combination of stiffening of the segmental dynamics as well as a decrease in available sulfonic acid groups facilitating transport leads to an overall decrease in mobility of vanadium ions in these ionomer nanocomposites.

Polymeric carriers of vanadyl ions based on copolymers of N-vinylpyrrolidone with vinylimines

In this study, a series of new chelating copolymers containing 20% azomethine groups, poly(N-vinylpyrrolidone-co-vinylsalicylideneimine) (poly[VP-co-VSalI]), poly(N-vinylpyrrolidone-co-vinylpicolinideneimine) (poly[VP-co-VPicI]), poly(N-vinylpyrrolidone-co-vinylpyridoxylideneimine) (poly[VP-co-VPyrI]) with M = 63000 Da and their vanadium(IV) complexes – poly(VP-co-VSalI)-VO, poly(VP-co-VPicI)-VO, poly(VP-co-VPyrI)-VO, were designed and synthesized. These are intended for the delivery and pH-dependent release of vanadium species in the intestine environment. The chelating polymers were obtained from poly(N-vinylpyrrolidone-co-N-vinylamine) (poly[VP-VAm]) by polymer-analogous transformations with the corresponding aldehydes. The vanadium content, determined by ICP-AES and spectrophotometric methods, was 5.36%, 4.99%, and 9.1% of the dry mass for poly(VP-co-VSalI)-VO, poly(VP-co-VPyrI)-VO, and poly(VP-co-VPicI)-VO, respectively. XPS data confirmed that only vanadium(IV) is presented in the complexes. All complexes demonstrated a pH-dependent release of low molecular weight vanadium species, making them promising candidates for the development of vanadium-containing systems for oral administration. These systems protect the main vanadium content in the stomach but can release biologically active ions in the intestine.

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and 2,2'-Bipyridine Ligands: Synthesis, Characterization and Investigation of their Biological Potency

Five new oxovanadium(IV) complexes of the type [VO(L)(bpy)], [where L= 3-hydroxybenzaldehyde-α-alanine (hb-ala), 3-hydroxybenzaldehyde-DL-phenylalanine (hb-pheala), 3-hydroxybenzaldehyde-leucine (hb-leu), 3-hydroxybenzaldehyde-glycine (hb-gly) and 3-hydroxybenzaldehyde-DL-methionine (hb-met) and bpy = 2,2´-bipyridine] have been synthesized and characterized by some physicochemical properties, molar conductance, magnetic susceptibilities measurements, elemental analysis, UV-Visible and FTIR and ESI-MS spectral studies. The molar conductance values showed that the complexes are non-electrolytic in nature. The magnetic moment values of the complexes are in accordance with the d1 electronic configuration of the VIVO2+ moiety and indicates the paramagnetic nature of the complexes. IR spectral data indicates the coordination of tridentate amino acid Schiff base ligands to the vanadyl (VO2+) ion through O, N, O-donor. ESI-MS spectral studies supports the proposed structure of the complexes. The magnetic moment value coupled with electronic spectral data suggested the distorted octahedral geometry of the complexes. All the complexes were screened for their antibacterial activity against three human pathogenic bacteria- Escherichia coli, Staphylococcus aureus and Bacillus cereus with Kanamycin (K-30) standard. The result shows that all the complexes possess to have moderate to strong potential antibacterial activity against all the tested pathogens.

A theoretical study on a new drug combines between vanadyl sulfate and vitamin E in a single component: A novel antioxidant medication in female reproductive health

This study explores the theoretical properties of a novel complex formed by combining vitamin E (VitE) and vanadyl(II) sulfate. The complex, [VO(VitE)2(H2O)2]2H2O (Vcom), was synthesized in solid form through a reaction between VitE and VOSO4.xH2O in a specific solvent mixture and pH. VitE binds to the vanadyl ion as a single ligand via its deprotonated phenolic oxygen. To characterize the complex, various analytical techniques were employed, including elemental analysis, spectral analysis, conductivity measurements, thermal analysis, X-ray diffraction, and microscopy. Electronic and magnetic properties were also investigated. Theoretical calculations - molecular docking simulations were used to assess the binding affinity of Vcom with two receptors known to interact with vitamin E: α-tocopherol transfer protein (α-TTP) and p105 subunit of nuclear factor NF-kappa-B p105 subunit (NF-κB). The findings revealed a square pyramidal geometry for the Vcom complex. Additionally, Density Functional Theory (DFT) were performed on both VitE and Vcom, focusing on their optimized structures, electrostatic properties, and HOMO-LUMO energy gaps. In summary, this research delves into the theoretical aspects of a newly formed VitE-vanadyl complex, providing insights into its structure, properties, and potential interactions with relevant receptors. KEY WORDS: New drug, Vanadyl sulfate, Vitamin E, Antioxidant, Female, Reproductive health, DFT Bull. Chem. Soc. Ethiop. 2024, 38(4), 989-1001. DOI: https://dx.doi.org/10.4314/bcse.v38i4.14

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and Polypyridyl Ligands: Synthesis, Characterization and Antimicrobial Activity

Oxovanadium(IV) complexes of the type [VO(L)(bpy)] (V-1 to V-5) have been synthesized and characterized by FTIR and UV-Vis spectra, molar conductance, melting points, and magnetic susceptibilities measurements, where L= N-salicylidene-β-alanine (sal-ala), N-salicylidene-glycine (sal-gly), N-salicylidene-DL-β-phenylalanine (sal-pheala), N-salicylidene-leucine (sal-leu), and N-salicylidene-DL-methionine (sal-met), and bpy is 2,2´-bipyridine. The infrared spectral data reveals that the tridentate nature of the amino acid-based Schiff base ligand and the coordination of the ligand through azomethine nitrogen, phenolic oxygen and carboxylate oxygen with vanadyl (VO2+) ion. All of these complexes were determined to be non-electrolyte in nature, according to conductivity measurements. The magnetic moment measurements have been attributed that these complexes are paramagnetic and have d1 configuration of vanadium (IV) ion. In Virto antimicrobial activity of the synthesized complexes was evaluated against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and two gram-negative (Escherichia coli, Proteus vulgaris) bacterial strains.

In situ electron paramagnetic resonance spectroscopy using single nanodiamond sensors

An ultimate goal of electron paramagnetic resonance (EPR) spectroscopy is to analyze molecular dynamics in place where it occurs, such as in a living cell. The nanodiamond (ND) hosting nitrogen-vacancy (NV) centers will be a promising EPR sensor to achieve this goal. However, ND-based EPR spectroscopy remains elusive, due to the challenge of controlling NV centers without well-defined orientations inside a flexible ND. Here, we show a generalized zero-field EPR technique with spectra robust to the sensor’s orientation. The key is applying an amplitude modulation on the control field, which generates a series of equidistant Floquet states with energy splitting being the orientation-independent modulation frequency. We acquire the zero-field EPR spectrum of vanadyl ions in aqueous glycerol solution with embedded single NDs, paving the way towards in vivo EPR.

A comprehensive review of anti-diabetic activity of vanadium-based complexes via PTP-1B inhibition mechanism

Inorganic salts of the vanadium have been found to mimic insulin in treating diabetic mellitus. In comparison to inorganic vanadium salts, complexes of vanadium with appropriate organic ligands can improve tissue absorption, efficacy, and reduce toxicity of the metal. An organic vanadyl derivative [bis(ethylmaltolato)oxovanadium(IV)] has been reported as a potential diabetes medication and is currently undergoing phase II clinical trials. The mechanism suggests that vanadium complexes inhibit the enzyme protein tyrosine phosphatase-1B(PTP-1B). Pharmacological, Biochemical and genetic evidences strongly suggest that inhibiting the PTP-1B enzyme could treat both diabetes and obesity, making PTP-1B an interesting target for drug development. Studies have also showed that the over expression of PTP-1B is involved in diabetic and obese patients and its inhibition may be an effective strategy in their treatment. Despite the fact that many natural PTP-1B inhibitors demonstrated promising clinical potential, there is no clinically used PTP-1B inhibitor, most likely due to low activity or a lack of selectivity. Search for more potent and selective PTP-1B inhibitors is still going on. As a result, inhibiting protein tyrosine 1B could be a new therapeutic option for patients at risk of type II diabetes mellitus and obesity. Many vanadium compounds are available as of now, as experimental probes for examining the mechanism of altered insulin action. However more studies are needed to establish its clinical use. Hence it has been proposed to prepare and characterize novel vanadium metal complexes with different coordination environments around vanadyl ion and check their anti diabetes activity.

Enhancing photocatalytic degradation of potassium butyl xanthate in mineral processing wastewater: Novel VO2+-doped LiZnBO3 nanosheets under visible light

Metal borates have attracted significant scientific attention due to their remarkable functional properties, making them versatile materials for applications in photocatalysis and energy storage. For the current investigation, three different concentration (1, 3, and 5 mol %) of vanadyl ions doped LiZnBO3 nanosheets (VO2+-doped LZB) were synthesized by an in-situ hydrothermal method. To better understand the properties of these prepared samples, a thorough characterization has been carried out, utilizing a range of structural and optical spectroscopy techniques. This study investigated the photocatalytic performance of the synthesized materials in the context of removing the mineral pollutant potassium butyl xanthate (PBX). Remarkably, at a 3 mol % concentration, the LZB-VO3 nanocomposite displayed significantly higher photocatalytic activity, achieving an impressive PBX degradation rate of 96.58 % within a short duration of 70 min. In contrast, the pure LZB material exhibited a more modest degradation efficiency of only 30.58 % when exposed to visible light. The optimized catalyst demonstrated a maximum rate constant of 0.0392 min−1, representing a remarkable enhancement of approximately 7.13 times compared to pure LZB. These findings underscore the remarkable potential of vanadyl ion doping, as it improves the absorption of the visible light spectrum and facilitates the efficient detachment of photoinduced charges, thereby significantly enhancing overall photocatalytic activity.

Resonance Raman spectra of blue copper proteins: Variable temperature spectra of Thermus thermophilus HB27 laccase

The resonance Raman (rR) spectra of the oxidized type 1 copper active site (CuT1) in Thermus thermophilus HB27 laccase (Tth-lac) has been determined in the 20 to 80 °C temperature range using 633-nm excitation. The positions and relative intensities of rR peaks are virtually independent of temperature, indicating that CuT1 ligation is robust over the investigated range. The intensity-weighted average of Tth-lac Cu-SCys vibrations (<ν(Cu-SCys)>) = 423 cm−1) is higher than those of most cupredoxins but is comparable to those of other multicopper oxidases (MCOs). <ν(Cu-SCys)> values for Tth-lac and several CuT1 centers in cupredoxins and MCOs do not correlate well with Cu-SCys bond lengths but do exhibit systematic trends with redox thermodynamic properties. PrologueF. Ann Walker was a great scholar and dear friend. While at Columbia in the early 1960s, I (HBG) followed her graduate work at Brown on the effects of axial ligands on vanadyl ion EPR spectra. Dick Carlin, her thesis adviser, invited me to serve as external member of her thesis committee. I joined, made my way to Providence, met her just before the exam, and greatly admired (enjoyed!) her thoughtful responses to questions from physical chemists about metal-oxo electronic structures. Our friendship grew stronger over the years, enhanced by lively discussions of heme protein chemistry in San Francisco, Pasadena, Tucson, and at Gordon Research Conferences. Ann was a superstar in biological inorganic chemistry. She will be sorely missed but not forgotten.

Vanadyl as a Spectroscopic Probe of Tunable Ligand Donor Strength in Bimetallic Complexes.

Incorporation of secondary metal ions into heterobimetallic complexes has emerged as an attractive strategy for rational tuning of compounds' properties and reactivity, but direct solution-phase spectroscopic interrogation of tuning effects has received less attention than it deserves. Here, we report the assembly and study of a series of heterobimetallic complexes containing the vanadyl ion, [VO]2+, paired with monovalent cations (Cs+, Rb+, K+, Na+, and Li+) and a divalent cation (Ca2+). These complexes, which can be isolated in pure form or generated in situ from a common monometallic vanadyl-containing precursor, enable experimental spectroscopic and electrochemical quantification of the influence of the incorporated cations on the properties of the vanadyl moiety. The data reveal systematic shifts in the V-O stretching frequency, isotropic hyperfine coupling constant for the vanadium center, and V(V)/V(IV) reduction potential in the complexes. These shifts can be interpreted as charge density effects parametrized through the Lewis acidities of the cations, suggesting broad potential for the vanadyl ion to serve as a spectroscopic probe in multimetallic species.

Estimation of the covalent binding parameters and the ground state wave functions in complexes doped with vanadyl ion

In octahedral complexes doped with transition metal ions the Steven’s model has been used for computing the covalent binding parameters. This model is further used for interpreting the g-factors in various single crystals containing paramagnetic VO2+ ion. Theoretical expressions were given for the g-factors of Vanadyl ions in the crystalline field of cubic nature with components of tetragonal symmetry. The g-factors have been given in terms of covalent binding parameters || and taking into account the tetragonal crystalline field and covalent binding. Computations show that should be less than 0.064 in order to fit the experimental g-values. Using crystal field theory, the ground state wave functions (GSWF) for VO2+ ions in different single crystals has been determined. It is found that GSWF is in dxy state with slight admixture of excited states dx2-y2, dxz and dyz. The hyperfine interaction parameter P and Fermi contact term X have also been calculated.

Modification of Nafion Membrane by Polycation in the Presemce of Lower Alyphatic Alcohols and Salt

Significant increase of ion selectivity was observed for Nafion membranes modified by poly(diallyldimethylammonium chloride), PDADMAC, in the presence of lower aliphatic alcohols and NaCl. It was found that addition of the salt into the alcohol-containing modification solutions resulted not only in decrease of diffusional permeability towards vanadyl ions, P, but also in simultaneous two- to threefold growth of proton conductivity, σ, in comparison with the membranes modified in the alcohol-water solutions in the absence of a salt. As a result, ion selectivity of the membranes calculated as σ/P ratio was increased in ∼4 orders of magnitude as compared with pristine Nafion 112 membrane. Conceivable mechanism of the ion selectivity increasing is proposed for the membranes modified by PDADMAC in the presence of lower aliphatic alcohols and NaCl.

Fast extraction of vanadyl ion using grafted cotton fiber inserted with amidoxime moiety

Egyptian cotton cellulose fibers have been adapted by graft copolymerization of polyacrylonitril (PAN) and then by ingestion of amidoxime moiety to finally generate C-AXO chelating fibers, which have been characterized by various instrumental techniques such as SEM, FTIR, EDX and XRD spectra. Using batch tests, the obtained C-AXO is used for removal and extraction of VO2 + from its aqueous solution. The kinetic studies have shown that the pseudo&nbsp;second-order model is the best fit for the experimental data.

In Vitro Studies Demonstrate Antitumor Activity of Vanadium Ions from a CaO-P2O5-CaF2:V2O5 Glass System in Human Cancer Cell Lines A375, A2780, and Caco-2.

In this research, we investigated the structural and biological properties of phosphate glasses (PGs) after the addition of V2O5. A xV2O5∙(100 − x)[CaF2∙3P2O5∙CaO] glass system with 0 ≤ x ≤ 16 mol% was synthesized via a conventional melt-quenching technique. Several analysis techniques (dissolution tests, pH, SEM-EDS, FT-IR, and EPR) were used to obtain new experimental data regarding the structural behavior of the system. In vitro tests were conducted to assess the antitumor character of V2O5-doped glass (x = 16 mol%) compared to the matrix (x = 0 mol%) and control (CTRL-) using several tumoral cell lines (A375, A2780, and Caco-2). The characterization of PGs showed an overall dissolution rate of over 90% for all vitreous samples (M and V1−V7) and the high reactivity of this system. EPR revealed a well-resolved hyperfine structure (hfs) typical of vanadyl ions in a C4v symmetry. FT-IR spectra showed the presence of all structural units expected for P2O5, as well as very clear depolymerization of the vitreous network induced by V2O5. The MTT assay indicated that the viability of tumor cells treated with V7-glass extract was reduced to 50% when the highest concentration was used (10 µg/mL) compared to the matrix treatment (which showed no cytotoxic effect at any concentration). Moreover, the matrix treatment (without V2O5) provided an optimal environment for tumor cell attachment and proliferation. In conclusion, the two types of treatment investigated herein were proven to be very different from a statistical point of view (p < 0.01), and the in vitro studies clearly underline the cytotoxic potential of vanadium ions from phosphate glass (V7) as an antitumor agent.

Preactivated zeolite nanosheet plate-tiled membrane on porous PVDF film: Synthesis and study of proton-selective ion conduction

Preactivated MFI zeolite nanosheet plates (ZNPs) with large areas (∼2.0 × 2.0 μm2) and nanometer thicknesses (∼60 nm) were prepared directly in liquid-dispersed state. The individual ZNP was a stack of 4-nm-thick single crystalline zeolite nanosheets (ZNs) interlinked by Si–O–Si bonds between neighboring ZN surfaces. The dispersed open-pore ZNPs allowed formulating suspensions for tiling ZNP membranes on polymer substrates without requiring post-coating activation. A pinhole-free ZNP-tiled (ZNPT) membrane has been achieved on macroporous PVDF film by a self-repairing vacuum-assisted filtration coating method. The resultant ZNPT layer was ∼500 nm-thick consisting of about 7 ZNP layers with inter-ZNP width and inter-ZNP entrance porosity around 9 nm and 2%, respectively. The ZNPT-PVDF membrane exhibited high selectivity to proton transport over vanadyl ion and low resistances to proton conduction in aqueous solutions. The membrane also demonstrated to function as an efficient ion separator for the vanadium redox flow battery. The reported synthesis of preactivated ZNP suspension may overcome the major hurdle to realizing polymer-supported ZN membranes, which is the inefficiency of existing methods in obtaining readily dispersible open-pore ZNs. The ZNPT-PVDF membrane can be a more affordable and sustainable alternative to the Nafion-based ion separation membranes.

Influence of Electronic Configurations on the Modulation of Fermi/Orbital Junction Energies for Directional Electron Transport through 3d1, 3d3, and 3d5 Metallosurfactants

Two new metallosurfactants containing the 3d1 vanadyl(IV) and 3d3 chromium(III) ions bound to the phenylenediamine-bridged phenolate-rich ligand LN2O2 were designed, deposited as monolayer films on gold electrodes, and probed for directional electron transfer in Au|LB|Au junctions. Both [V═OIVLN2O2] (1) and [CrIII(LN2O2)(MeOH)(H2O)]Cl (2) promote current rectification. Through a concerted experimental and computational effort, we compare the behavior of 1 and 2 with that of our previously studied 3d5 [FeIII(LN2O2)Cl] (3). Based on the analysis of comprehensive electrochemical, spectroscopic, and microscopy results allied to DFT calculations, we propose distinct mechanisms by which electronic configurations influence the energy gap between the electrode Fermi levels and the different molecular orbitals responsible for electron transport. While the 3d5 species 3 shows electron transport through the metal-based SOMO located above the Fermi levels of the electrode, the 3d1 species 1 uses a metal-based SOMO below Fermi, and the 3d3 species 2 takes advantage of a ligand-based HOMO, which becomes available when a bias is applied.