Tris Complexes Research Articles

Influence of Ligand Environment Stoichiometry on NIR-Luminescence Efficiency of Sm3+, Pr3+ and Nd3+ Ions Coordination Compounds.

Six new complexes of the ligand HQcy (-4-(cyclohexanecarbonyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one) and Ln3+ ions with emission in the near-infrared (Nd3+) or visible and near-infrared (Sm3+, Pr3+) spectral regions were synthesized and characterized using various methods, including single crystal X-ray diffraction. The study demonstrated that both tris complexes [LnQcy3(H2O)(EtOH)] and tetrakis-acids [H3O][LnQcy4] can be synthesized by varying the synthetic conditions. The photochemical properties of the complexes were investigated experimentally and theoretically using various molecular spectroscopy techniques and Judd-Ofelt theory. The objective was to quantitatively and qualitatively disclose the influence of complex stoichiometry on its luminescence properties. The study showed that the addition of an extra ligand molecule (in the tetrakis species) increased molar extinction by up to 2 times, affected the shape of photoluminescence spectra, especially of the Pr3+ complex, and increased the quantum yield of the Sm3+ complex by up to 2 times. The results obtained from this study provide insights into the luminescent properties of lanthanide coordination compounds, which are crucial for the design and development of novel photonic materials with tailored photophysical properties.

CRISPR/Cas12a-Mediated Aptasensor Based on Tris-(8-hydroxyquinoline)aluminum Microcrystals with Crystallization-Induced Enhanced Electrochemiluminescence for Acetamiprid Analysis.

Improving the electrochemiluminescence (ECL) efficiency of luminophores has always been the goal of the ECL field. Herein, a novel crystallization-induced enhanced ECL (CIE ECL) strategy was exploited to significantly enhance the ECL efficiency of metal complex tris-(8-hydroxyquinoline)aluminum (Alq3). Alq3 monomers self-assembled and directionally grew to form Alq3 microcrystals (Alq3 MCs) in the presence of sodium dodecyl sulfate. The highly ordered crystal structure of Alq3 MCs not only constrained the intramolecular rotation of Alq3 monomers to decrease nonradiative transition but also accelerated the electron transfer between Alq3 MCs and coreactant tripropylamine to increase radiative transition, thus leading to a CIE ECL effect. Alq3 MCs exhibited brilliant anode ECL emission, which was 210-fold stronger than that of Alq3 monomers. The exceptional CIE ECL performance of Alq3 MCs coupled the efficient trans-cleavage activity of CRISPR/Cas12a assisted by rolling circle amplification and catalytic hairpin assembly to fabricate a CRISPR/Cas12a-mediated aptasensor for acetamiprid (ACE) detection. The limit of detection was as low as 0.79 fM. This work not only innovatively exploited a CIE ECL strategy to enhance the ECL efficiency of metal complexes but also integrated CRISPR/Cas12a with a dual amplification strategy for the ultrasensitive monitoring of pesticides such as ACE.

Metal-Stabilized Thiyl Radicals Design Inspired by Elemental Periodic Extension Notion for Ligand-Based Alkene Addition.

Inspired by alkene addition to the Ru and Re tris(thiolate) complexes via carbon-sulfur bond formation/cleavage reactions along with a periodic extension catalysis notion, a comparative study of the electronic structures, mechanisms, and reactivities for ethylene addition to the Os and Tc tris(thiolate) complexes was performed by DFT and high-level ab initio quantum calculations. The oxidized Os and Tc complexes were revealed to exhibit sufficient radical characters on the ligands to support their reaction with ethylene, whereas neutral Tc tris(thiolate) complex featuring little thiyl radical character renders no reactivity toward ethylene. Differential reactivities of these tris(thiolate) complexes was deemed to derive from the synergy of the thiyl radical character, the electronegativity, the row, and the charge. Extending from Ru and Re tris(thiolate) complexes to their Os and Tc counterparts can help us to get insightful rationales that would promote further research on alkene addition to metal-stabilized thiyl radicals.

Coinage Metal Complexes Containing Perfluorinated Carboxylates

A variety of coinage-metal complexes containing perfluorinated carboxylate ligands, together with their structures and thermal behavior, are reported. The silver(I) salts were accessible from the direct reaction of Ag2O with the acids in toluene. Their gold(I) phosphine counterparts formed in high yields by transmetallation using the silver(I) salts. Some structurally unique, mixed-metal (Au,Ag) complexes formed upon combining solutions of the silver(I) salts with the gold(I) phosphine carboxylates. The reduction of dinuclear copper(II) compounds containing perfluorinated carboxylates with triphenylphosphine resulted in the formation of the corresponding copper(I) tris(phosphine) complexes. X-ray structures of representative complexes, together with IR- and TGA data, are reported.

Reductive C-O Cleavage of Ethereal Solvents and 18-Crown-6 in Ln(NR2)3/KC8 Reactions (R = SiMe3).

The high reactivity accessible from the reduction of the tris(amide) complexes Ln(NR2)3 (R = SiMe3) with potassium graphite in the presence of a variety of ethers is demonstrated by crystal structures of six different types of products of C-O bond cleavage reactions with Ln = Y, Ho, Er, and Lu. Specifically, 1,2-dimethoxyethane (DME) can be cleaved in Ln(NR2)3/KC8 reactions as shown by three different types of crystals: [K (crypt)][(R2N)3Y(OCH2CH2OCH3)], 1-Y, [(R2N)2Y(μ-OCH2CH2OCH3-κO,κO')]2, 2-Y, and [K2(18-c-6)3]{[(R2N)3Lu]2[(μ-OCH2CH2O)]}, 3-Lu (18-c-6 = 18-crown-6; crypt = 2.2.2-cryptand). THF can be ring opened by the Y(NR2)3/KC8 reaction system, as shown by crystals of the butoxide, [K(crypt)][(R2N)3Y(OCH2CH2CH2CH3)], 4-Y. The cyclic ether, oxetane, OC3H6, ring opens in Ln(NR2)3/KC8 reactions to form crystals of the propoxide, [K(18-c-6)(OC3H6)][(R2N)3Ln(OCH2CH2CH3)], 5-Ln, for Ln = Ho and Er. In Et2O, the Y(NR2)3/KC8 reactions do not attack the solvent, but C-O cleavage of 18-c-6 is observed to form {[(R2N)2]Y[μ-η1:η1-O2(C10H20O4)K]}2, 6-Y. These Ln(NR2)3/KC8 C-O cleavage reactions are typically accompanied by C-H bond activation reactions, which form cyclometalates such as [K(crypt)]{(R2N)2Ln[N(SiMe3)(SiMe2CH2)-κC,κN]}, 7-Ln (Ln = Y, Ho, Er), and [K(18-c-6)]{(R2N)2Y[N(SiMe3)(SiMe2CH2)-κC,κN]}, 8-Y, which are common decomposition products of Ln(NR2)3 reactions. In addition, in this study, the hydride complex, [K(18-c-6)][(R2N)3YH], 9-Y, was isolated. NMR analysis indicates that the yttrium reactions form mixtures that consistently contain the yttrium cyclometalates 7-Y and 8-Y as major components. These results show the diversity of available reaction pathways for the Ln(NR2)3/KC8 system and highlight the inherent difficulties in isolating Ln(II) complexes containing the [Ln(NR2)3]1- anion.

Synthesis of amylose and cellulose derivatives bearing bulky pendants for high-efficient chiral fluorescent sensing

Three novel amylose and cellulose phenylcarbamate derivatives bearing bulky para-substituted benzothienyl or benzofuranyl pendants were successfully synthesized as chiral fluorescent sensors through carbamoylation followed by Suzuki-Miyaura coupling reactions. The bulky derivatives showed good enantioselective fluorescent sensing properties toward a total of eight chiral quenchers in this study. Especially, a high enantiomeric fluorescence difference ratio (ef = 164.35) was achieved on amylose benzofuranylphenylcarbamates (Amy-2) to the 3-amino-3-phenylpropan-1-ol (Q5), an important chiral drug intermediate. It indicated that a favorable chiral environment was effectively constructed by arrangement of bulky π-conjugated benzothienyl or benzofuranyl pendants on the phenylcarbamate moieties surrounding the helical backbone, which is crucial for high-efficient chiral fluorescent sensing. As chiral stationary phases for high-performance liquid chromatography, the bulky benzothienylphenylcarbamates of amylose and cellulose also showed good resolution powers to thirteen racemates, including metal tris(acetylacetonate) complexes, chiral drugs, analytes with axial chirality and chiral aromatic amines, which were difficult to be efficiently separated even on the popular Chiralpak AD and Chiralcel OD. The excitation-dependent chiral fluorescent sensing probably followed different mechanisms from that for chromatographic enantioseparation relying on the dynamic collision of molecules in the ground state. The structure of the bulky derivatives was also investigated by CD spectra and POM microscopy.

Synthesis and characterization of tris(5,7-diphenyl-8-quinolinolato) aluminum(III), gallium(III), and indium(III) complexes: Effect of metal ions on the structural, photoluminescence, thermal and electrochemical properties

The 5,7-diphenyl-8-hydroxyquinoline (5,7-Phq) organic ligand was successfully synthesized via Suzuki cross-coupling reaction followed by synthesis of the novel organometallic complexes tris(5,7-diphenyl-8-quinolinolato) metal(III) [M(5,7-Phq)3; M = Al, Ga, or In]. All synthesized M(5,7-Phq)3 complexes were characterized using various analytical techniques. The molecular structure of In(5,7-Phq)3 was confirmed using single-crystal X-ray crystallography, which indicates that the three 5,7-Phq ligands are arranged in a meridional configuration around the central metal In3+ ion, and the complex is distorted from ideal octahedral geometry. There are no significant differences in the UV–visible absorption spectra of the complexes in the tetrahydrofuran (THF) solution and they are all red-shifted compared to that of the parent Mq3 (M = Al3+, Ga3+, In3+) compounds. The broad absorption band at around 417 nm is assignable to the π-π* transition. The synthesized M(5,7-Phq)3 complexes in the solution and in the solid-state show red-shifted emission compared to that of the parent unsubstituted compounds. The decrease in the solution and the solid-state emission efficiency and intensity from Al to In complexes is attributed to the heavy atom effect. Despite the electrochemical band gap energies (Egec) of the complexes determined from cyclic voltammetry being in good agreement with those reported for the unsubstituted complexes, the optical band gap energies (Egopt) determined from the Tauc plot method are smaller. The results of the fluorescence decay of the M(5,7-Phq)3 complexes both in CHCl3 solution and in solid state at 298 K show that the decays fit a bi-exponential model with two lifetimes (τ1 and τ2). The average values of fluorescence lifetimes of the complexes in CHCl3 are significantly greater than those of the complexes in the solid state.

Multitarget-Directed Gallium(III) Tris(acyl-pyrazolonate) Complexes Induce Ferroptosis in Cancer Cells via Dysregulation of Cell Redox Homeostasis and Inhibition of the Mevalonate Pathway.

A series of Ga(Qn)3 coordination compounds have been synthesized, where HQn is 1-phenyl-3-methyl-4-RC(═O)-pyrazolo-5-one. The complexes have been characterized through analytical data, NMR and IR spectroscopy, ESI mass spectrometry, elemental analysis, X-ray crystallography, and density functional theory (DFT) studies. Cytotoxic activity against a panel of human cancer cell lines was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, with interesting results in terms of both cell line selectivity and toxicity values compared with cisplatin. The mechanism of action was explored by spectrophotometric, fluorometric, chromatographic, immunometric, and cytofluorimetric assays, SPR biosensor binding studies, and cell-based experiments. Cell treatment with gallium(III) complexes promoted several cell death triggering signals (accumulation of p27, PCNA, PARP fragments, activation of the caspase cascade, and inhibition of the mevalonate pathway) and induced changes in cell redox homeostasis (decreased levels of GSH/GPX4 and NADP(H), increased reactive oxygen species (ROS) and 4-hydroxynonenal (HNE), mitochondrial damage, and increased activity of CPR and CcO), identifying ferroptosis as the mechanism responsible for cancer cell death.

Synthesis, structure, and catalytic activity of the neodymium tris(amidinate) complex [ButC(N-2,6-Me2C6H3)2]3Nd in ring-opening polymerization of ε-caprolactone

Synthesis, structure, and catalytic activity of the neodymium tris(amidinate) complex [ButC(N-2,6-Me2C6H3)2]3Nd in ring-opening polymerization of ε-caprolactone

Theoretical Understanding of Reactions of Rhenium and Ruthenium Tris(thiolate) Complexes with Unsaturated Hydrocarbons: Noninnocent Nature of the Ligand, Mechanism, and Origin of Differential Reactivity

In retrospect to the complexity induced by the noninnocent ligands in identifying the transition metal's oxidation state and correlating the ligand's noninnocence with reactivity, the reactions of alkene/alkyne addition to rhenium/ruthenium tris(thiolate) complexes are particularly good cases for shedding light on the chemistry of the dppbt ligand, including its noninnocent nature, ligand-centered mechanism, and origin of differential reactivity. Density functional theory (DFT) combined with the high-level ab initio calculations performed herein demonstrates that, upon alkene/alkyne addition, the orbital symmetry properly regulates the reaction to form ligand-centered cis-interligand dithioethers as the most favorable pathway. The neutral and cationic Re and Ru dithioethers are revealed via DFT calculations to be in a low-spin ground state; on the contrary, high-level ab initio methods confirm that the dicationic Re-dithioethers exhibit obvious multireference character with antiferromagnetic coupling between Re-dyz and S1-py. The metal-stabilized thiyl radicals play a pivotal role in delivering the reactivity of [RuL3]+ and [ReL3]+/2+ toward alkene/alkyne rather than [ReL3], where [RuL3]+ and [ReL3]+/2+ present significant radical characters on ligand S2, yet neutral [ReL3] has little such feature, from which differential reactivity arises. Faster styrene addition to Ru tris(thiolate) in contrast to Re tris(thiolate) has been properly interpreted using DFT calculations with major products assigned. The deeper understanding gained in this work would illuminate further experimental exploration in adding alkene/alkyne to other metal-stabilized thiyl radicals.

Preparation of spiroborate supramolecular and peapod polymers containing a photoluminescent ruthenium(ii) complex.

The immobilization of functional metal complexes onto polymer supports remains one of the most important research areas. In this study, we prepared spiroborate supramolecular and peapod polymers containing a cationic photoluminescent ruthenium(ii) complex. The supramolecular polymer was obtained by mixing spiroborate cyclic trimer bearing homoallyl group and a ruthenium(ii) tris(bipyridyl) complex, and was further converted into the corresponding peapod polymer by olefin metathesis polymerization. The structure of these polymers was determined by 1H NMR, dynamic light scattering, inductively coupled plasma-atomic emission spectroscopy, energy dispersive X-ray analyses, and atomic force microscopy. The absorption and emission behaviors of the ruthenium(ii) complex were almost the same for the free form and the supramolecular polymer in the mixed solvent of N,N-dimethylformamide and chloroform, although the emission intensity decreased when the chloroform portion was increased. On the other hand, the hypsochromism was observed upon the emission of the ruthenium(ii) complex in the peapod polymer, probably due to the rigidochromic effect of the tight encapsulation by the peapod structure.

Phosphine-functionalized amidinate ligated rare-earth metal complexes for highly 3,4-selective living polymerization of 1,3-conjugated dienes.

A series of rare-earth metal bis(alkyl) complexes have been prepared via protonolysis reactions of tris(aminobenzyl) complexes (Ln(CH2C6H4N(Me)2-o)3) with phosphine-functionalized amidinated ligands (DippNCN(CH2)nPPh2, n = 2 (L1-H) and n = 3 (L2-H)). The X-ray diffraction of P2-Sc (DippNCN(CH2)3PPh2Sc(CH2C6H4N(Me)2-o)2) showed the un-coordination of the diphenylphosphine group due to the inherent saturation of the central metal ion. In conjunction with [Ph3C][B(C6F5)4], all the rare-earth metal complexes showed a high catalytic activity for the polymerization of 1,3-conjugated dienes (isoprene, β-myrcene and β-farnesene), affording highly 3,4-regular polymers (up to 100% 3,4-) with high molecular weight and narrow molecular weight distribution. After the abstraction of the alkyl moiety -CH2C6H4N(Me)2-o of P1-Sc by [Ph3C][B(C6F5)4], the species with the coordination of the diphenylphosphine group to the central metal probably formed, as shown in the 31P NMR spectra and DFT calculation results, and it might serve as the true active species in the 3,4-selective polymerization of 1,3-conjugated dienes.

Ratiometric fluorescent semiconducting polymer dots for temperature sensing.

Semiconducting polymer dots (Pdots) have received much attention due to their unique characteristics, including high water solubility, good light stability, excellent biocompatibility, and low cost. Herein, we report a ratiometric nanoprobe based on Pdots-Eu for temperature sensing in vitro. The Pdots-Eu thermometer was composed of a blue temperature-insensitive semiconducting polymer, poly(9-vinylcarbazole) (PVK), a red temperature-sensitive complex tris(dibenzoylmethane)mono(5-amino-1,10-phenanthroline)europium (III) (Eu complex), and an amphiphilic polymer polystyrene graft ethylene oxide functionalized with carboxyl groups (PS-PEG-COOH). The Pdots-Eu thermometer showed two peaks at 368 nm from PVK and 611 nm from the Eu complex. The red/blue fluorescence intensity ratio of Pdots-Eu decreased with an increase in temperature, which could be used for the ratiometric monitoring of temperature change. The results showed that the red/blue fluorescence intensity ratio demonstrated a good linear relationship to the change of temperature from 25 °C to 55 °C. Impressively, the ratiometric probe featured good accuracy and high sensitivity for temperature detection in vitro, which could be used for monitoring temperature change in cells.

Metal Complexes of a 5-Nitro-8-Hydroxyquinoline-Proline Hybrid with Enhanced Water Solubility Targeting Multidrug Resistant Cancer Cells.

Multidrug resistance (MDR) in cancer is one of the major obstacles of chemotherapy. We have recently identified a series of 8-hydroxyquinoline Mannich base derivatives with MDR-selective toxicity, however with limited solubility. In this work, a novel 5-nitro-8-hydroxyquinoline-proline hybrid and its Rh(η5-C5Me5) and Ru(η6-p-cymene) complexes with excellent aqueous solubility were developed, characterized, and tested against sensitive and MDR cells. Complex formation of the ligand with essential metal ions was also investigated using UV-visible, circular dichroism, 1H NMR (Zn(II)), and electron paramagnetic resonance (Cu(II)) spectroscopic methods. Formation of mono and bis complexes was found in all cases with versatile coordination modes, while tris complexes were also formed with Fe(II) and Fe(III) ions, revealing the metal binding affinity of the ligand at pH 7.4: Cu(II) > Zn(II) > Fe(II) > Fe(III). The ligand and its Rh(III) complex displayed enhanced cytotoxicity against the resistant MES-SA/Dx5 and Colo320 human cancer cell lines compared to their chemosensitive counterparts. Both organometallic complexes possess high stability in solution, however the Ru(II) complex has lower chloride ion affinity and slower ligand exchange processes, along with the readiness to lose the arene ring that is likely connected to its inactivity.

A Study on the Luminescent Terbium(III) and Pyridine 2,6 Dicarboxylate Complexes by Experimental and TD-DFT Approaches.

Tb3+ luminescence is enhanced by complex formation in aqueous phases as its pyridine 2,6 dicarboxylate (dpa2-) complexes by using experimental spectroscopic techniques and theoretical time-dependent density functional theory (TD-DFT) calculations. The fluorimetric titration of Tb3+ ion with dpa2- ion is followed at λext/λems = 310/490 nm and 310/545 nm, the emission intensities of which are graphed against the mol ratios of the ligand to metal ion [moles of dpa2-/mol of Tb3+]. Experimental results denote that the tris complex; [Tb(dpa)3]3- is the most stable form at pH > 5.3. Molecular absorption spectra of tris complex shows a batho-chromic shift of 222nm of dpa2- band to 232nm accompanied by the hyper-chromic effect at 272nm band. The luminescence intensities at 490, 545, 592 and 620nm are enhanced over 100 times in tris complex. The coordination of complexes calculated by thermodynamic cycles and with supporting the experimental result, the most stable form was found to be nine coordinated tris complex; [Tb(dpa)]3-. The theoretical TD-DFT calculations perfectly matched the experimental absorption and emission bands of tris-complex. The novelty of this study is to present the first theoretical calculation of the phosphorescence results and energy transfer process for emission path of Tb3+ and pda2- aqua complexes.

INFLUENCE OF CYTRIMIN ON LEUKOCYTE FORMULA STRUCTURE OF FISH

An obvious trend in domestic and foreign aquaculture in recent years is usage of biologically active substances of various mechanisms of action. It was clearly demonstrated that such biologically active substances as adaptogens, probiotics, vitamins, amino acids have a positive effect on the fish organism, increasing economic parameters of the industry. In particular, usage of "Irkutin" adaptogen in early ontogenesis of fish increased survivability of larvae during transition to exogenous nutrition, survivability of the fry, growth rate, endurance and it also reduced the level of cannibalism and stress. Therefore, the search for new substances with the properties of adaptogens for fish farming is of great importance. There is reason to believe that "cytrimin" can become such new substance. "Cytrimin" is a complex of tris-(2-hydroxyethyl) amine with zinc bis-(2-methylphenoxyacetate) and has the formula: (HOCH2CH2)3N Zn(OOCCH2OC6H4CH3-2)2. A study of the spectrum of physiological activity of "cytrimin" (one of the representatives of protatrans) showed that it protects blood vessels from formation of cholesterol plaques, it is also an antidote to alcohol and can increase performance, claiming to be an adaptogen. So far, "cytrimin" has not been used in fish farming. The aim of the work was to study the effect of "cytrimin" on parameters of blood system, in particular, on the structure of leukocyte formula of the African sharptooth catfish. It was found that there were no significant changes in the content of the total number of leukocytes in the blood of African catfish in case of "cytrimin" application, however, a redistribution of functionally different groups of cells in the leukogram of the African catfish was revealed. This redistribution was expressed in a slight decrease in the proportion of lymphocytes with a significant increase in the proportion of segmented neutrophils and monocytes within the physiological norm.

Coordination-driven Synthesis of a Self-assembled Architecture Bearing Urea Groups from a Triply Helical Fe(II) Complex of a Tripodal Ligand and a Pd(II) Complex

Triply helical iron(II) complexes of a tripodal 2,2′-bipyridine ligand bearing 4-pyridyl urea groups have undergone coordination-driven self-assembly with palladium(II)-bis(1,3-diphenylphosphinopropane), dppp, units affording the 2:3 complex in an almost quantitative yield. In the coordination-driven self-assembled architecture, the 4-pyridyl moieties of the iron(II)-tris(2,2′-bipyridine) complexes coordinated to the palladium(II) cations ligated by dppp.

Synthesis and Complexation Study of New Aminoalkynyl−amidinate Ligands

AbstractThe current library of amidinate ligands has been extended by the synthesis of two novel dimethylamino‐substituted alkynylamidinate anions of the composition [Me2N−CH2−C≡C−C(NR)2]−(R =iPr, cyclohexyl (Cy)). The unsolvated lithium derivatives Li[Me2N−CH2−C≡C−C(NR)2] (1: R =iPr,2: R = Cy) were obtained in good yields by treatment ofin situ‐prepared Me2N−CH2−C≡C−Li with the respective carbodiimides, R−N=C=N−R. Recrystallization of1and2from THF afforded the crystalline THF adducts Li[Me2N−CH2−C≡C−C(NR)2] ⋅ nTHF (1 a: R =iPr,n=1;2 a: R = Cy,n=1.5). Precursor2was subsequently used to study initial complexation reactions with selected di‐ and trivalent transition metals. The dark red homoleptic vanadium(III) tris(alkynylamidinate) complex V[Me2N−CH2−C≡C−C(NCy)2]3(3) was prepared by reaction of VCl3(THF)3with 3 equiv. of2(75 % yield). A salt‐metathesis reaction of2with anhydrous FeCl2in a molar ratio of 2 : 1 afforded the dinuclear homoleptic iron(II) alkynylamidinate complex Fe2[Me2N−CH2−C≡C−C(NCy)2]4(4) in 69 % isolated yield. Similarly, treatment of Mo2(OAc)4with 3 or 4 equiv. of2provided the dinuclear, heteroleptic molybdenum(II) amidinate complex Mo2(OAc)[Me2N−CH2−C≡C−C(NCy)2]3(5; yellow crystals, 50 % isolated yield). The cyclohexyl‐substituted title compounds2 a,4, and5were structurally characterized through single‐crystal X‐ray diffraction studies.

Non-Metallic Phosphorus Corrole as Efficient Electrocatalyst in Hydrogen Evolution Reaction.

The economical consideration of using an electrocatalyst in energy-related field, composed of non-precious/sustainable elements is quite noteworthy. In this work, the phosphorus(V) complex of tris-(pentafluorophenyl)corrole [(TPFC)PV (OH)2 ] was reported as electrocatalyst for the hydrogen evolution reaction (HER). The electrochemical studies revealed that the HER experienced a ECEC pathway (E: electron transfer step, C: chemical step), and the possible intermediate [PV ]-H species was suggested. (TPFC)PV (OH)2 displayed excellent HER activity in dimethylformamide (DMF) with trifluoroacetic acid (TFA) as the proton source, and the turnover frequency (TOF) reached 31.75 s-1 at an overpotential of 900 mV. Interestingly, the HER electrocatalytic performance remained extraordinary even applying water as a proton source in acetonitrile/water (v/v=2 : 3), with a TOF of 18.40 mol molcat -1 h-1 at an overpotential of 900 mV.

A High Potential, Low Capacity Fade Rate Iron Complex Posolyte for Aqueous Organic Flow Batteries

AbstractAn iron complex, tris(4,4′‐bis(hydroxymethyl)‐2,2′‐bipyridine) iron dichloride is reported, which operates at near‐neutral pH with a redox potential of 0.985 V versus SHE. This high potential compound is employed in the posolyte of an aqueous flow battery, paired with bis(3‐trimethylammonio)propyl viologen tetrachloride in the negolyte, exhibiting an open‐circuit voltage of 1.3 V at near‐neutral pH. It demonstrates excellent cycling performance with a low temporal capacity fade rate of 0.07% per day over 35 days of cycling. The extended cycling lifetime is the result of low permeability and improved structural stability of the newly developed iron complex compared to that of the iron tris(bipyridine) complex. The combination of high redox potential and low capacity fade rate compares favorably with those of all previously demonstrated organic and organometallic aqueous posolytes. Extensive investigation into the possible degradation mechanisms, including post‐mortem chemical and electrochemical analyses, indicates that stepwise ligand dissociations of the iron complex are responsible for the reported capacity loss during cell cycling. This investigation provides unprecedented insight to guide further improvements of such metalorganic compounds for energy storage and conversion applications.