Reaction Of Pt Research Articles

Activation of small molecules by the unsaturated complex Pt(IBut)(PBut3): First structural characterization of a peroxycarbonate complex of platinum

The reaction of Pt(COD)2 with one equivalents of IBut and PBut3 at room temperature yields the unsaturated platinum mixed N-heterocyclic carbene and phosphine complex Pt(IBut)(PBut3), 1. Complex 1 reacts rapidly with O2 and CO to form the dioxygen adduct Pt(IBut)(PBut3)(η2-O2), 2 and Pt3 trimer cluster complex [Pt(IBut)(CO)]3, 3, respectively. Complex 2 further reacts with CO2 at room temperature to give the peroxycarbonate complex Pt(IBut)(PBut3)[η2-OOC(O)O], 4, and the first example characterized by single crystal X-ray diffraction. The reaction of complex 2 with acetone also resulted in the formation of the peroxoacetonate complex Pt(IBut)(PBut3)[η2-OOC(CH3)2O], 5. All the structures for the complexes 1–5 were characterized by X-ray crystallographic studies.

Structural characterization of [M,C,2H]+ products formed by reaction of 5d metal cations Pt+ and Ir+ with ethylene oxide and Ta+ with methane using messenger spectroscopy

Structural characterization of gas-phase [M,C,2H]+ (M = Ta, Ir, Pt), formed by reacting laser ablation formed M+ with ethylene oxide (c-C2H4O) or methane under multiple collision conditions, is achieved using infrared multiple-photon dissociation (IR-MPD) spectroscopy with the intracavity free-electron laser FELICE. After product formation, part of the product distribution is complexed with Ar, allowing for simultaneous recording of IR-MPD spectra of both bare [M,C,2H]+, which dissociates via dehydrogenation, and [M,C,2H]+∙Ar, which loses Ar. Comparison of the spectra with density functional theory (DFT) calculations allows for an internally consistent assignment of the spectra to the Ta+CH2 (3A′′) distorted carbene, Pt+CH2 (2A1) carbene, and to the HIr+CH (1A′) carbyne-hydride. Evidence for a symmetric Ta+CH2∙Ar (3B2) complex is also obtained. For Pt and Ir, these structures match those found in previous work when these species were formed by reaction of M+ with methane, CH4 and CD4. Under the current conditions, no clear signs of the previously observed Ir+CH2 (3A2) carbene product were found, consistent with its higher energy, especially after Ar complexation. Potential energy surfaces for the reactions of Pt+ and Ir+ with c-C2H4O are also computed.

Transformation of atomically dispersed platinum in SAPO-37 into platinum clusters: catalyst for ethylene hydrogenation

Atomically dispersed supported platinum catalysts were synthesized by the reaction of Pt(acac)2 (acac = acetylacetonato) with the silicoaluminophosphate molecular sieve SAPO-37, with infrared spectra showing that the reaction involved SAPO OH groups.

Electronic and steric impact of bis-NHC ligands on reactions of Pt3S2 cores in trinuclear complexes bearing bis-NHC ligands with various lengths of alkylene bridges.

Alkylene-bridged bis-N-heterocyclic carbene ligands working as strong σ-donors enhance the reactivity of the Pt3S2 core in a triplatinum complex. Although an Ag(I) ion possibly reacts with the Pt-Pt bond, one of the sulfide ligands coordinates to an Ag(I) ion due to the steric hindrance of the ligands.

Electrodeposition Behavior of Extracted Platinum Complex in Ionic Liquids Evaluated By Electrochemical Quartz Crystal Microbalance

1. Introduction From the perspective of process simplification and secondary waste reduction, the solvent extraction-electrodeposition method is effective in which the ionic liquid (IL) phase containing the extracted complexes is used as an electrodeposition bath and the extracted complexes are electrodeposition to recover the metals efficiently. We have applied the solvent extraction-electrodeposition method to Ru [1], In [2] and Nd [3] in the IL system based on bis(trifluoromethyl)sulfonyl amide (NTf2 -). In addition, the complexation states between [NTf2 -] and the metal have been clarified from a computational chemical point of view [4] based on Raman spectroscopy and density functional theory. The electrochemical quartz crystal microbalance method (EQCM) was used to evaluate the electrodeposition behavior of the extracted platinum complex in the IL phase after the extraction by solvent extraction. The purpose of this study is to analyze the electrodeposition behavior of extracted platinum complex, the weight change of the electrode interface, and the alternation of viscosity or density of the IL at the electrode interface. 2. Experimental The resonance frequency and resistance of an AT-cut Pt-coated quartz oscillator [9 MHz, φ=5.0 mm, Seiko EG&G, QA-A9M-PT(P)] were determined using an electrochemical quartz crystal microbalance (EQCM) system (Seiko EG&G, QCA922) with a well-type cell. The EQCM system was heated with a heating mantle controlled by a thermostat with a PID controller. The applicability of the EQCM technique at elevated temperature was demonstrated in our previous study [5]. Voltammetric measurements were carried out using an electrochemical analyzer (ALS-440A, BAS Inc.) with a Pt-coated quartz oscillator in the EQCM system as a working electrode. The surface area of the QCM crystal was 1.9635×10-5 m2. Two Pt wires with inner diameters of 0.5 mm were used as the counter and quasi-reference electrodes (QRE). The counter electrode was surrounded by a Vycor glass filter at the bottom to prevent diffusion of the decomposition components from the anode into the electrolyte. The Pt QRE showed high stability and good reproducibility of the potential at elevated temperature. The potential was compensated against a Fc/Fc+ redox couple. The electrochemical behavior of the extracted platinum complex was investigated at 323 K with a sweep rate of 2.0 mV s-1. 3. Results and discussion The result of the CV/EQCM analysis of [R3NH]2[PtCl6]IL in Alamine336/[P2225][NTf2] was shown in Fig. 1. Preliminary, in the case of Alamine336/[P2225][NTf2] system, which did not contain the Pt(IV) extraction complex and consisted of the extractant and the diluent, there were no main peaks other than the solvent decomposition during this potential region. It indicated that Alamine336 extractant did not undergo the electrochemical decomposition. On the other hand, a slight reduction peak was observed at -0.53 V for the extracted Pt(IV) complex, which showed little change with respect to Δm, suggesting that it was corresponded to the charge transfer reaction of Pt(IV)/Pt(II). The main reduction peak was observed at -1.65 V, and simultaneously an increase in Δm and a decrease in Δηρ were also observed in this study. The molecular weight of the electrodeposited species: M app was corresponded to be 193.7 calculated from Δm, suggesting that the main reduction reaction was the electrodeposition of Pt(II)/Pt(0); the decrease in Δηρ represented a localized viscous change in the IL phase near the electrode interface, indicating the consumption of Pt(II) by the electrodeposition process. The change in Δηρ during the electrodeposition process was consistent with the EQCM analysis of Ag(I)/Ag(0) [6].

Ligand-Mediated C-Br Oxidative Addition to Cycloplatinated(II) Complexes and Benzyl-Me C-C Bond Reductive Elimination from a Cycloplatinated(IV) Complex.

Reaction of the Pt(II) complexes [PtMe2(pbt)], 1a, (pbt = 2-(2-pyridyl)benzothiazole) and [PtMe(C^N)(PPh2Me)] [C^N = deprotonated 2-phenylpyridine (ppy), 1b, or deprotonated benzo[h]quinoline (bhq), 1c] with benzyl bromide, PhCH2Br, is studied. The reaction of 1a with PhCH2Br gave the Pt(IV) product complex [PtBr(CH2Ph)Me2(pbt)]. The major trans isomer is formed in a trans oxidative addition (2a), while the minor cis products (2a′ and 2a″) resulted from an isomerization process. A solution of Pt(II) complex 1a in the presence of benzyl bromide in toluene at 70 °C after 7 days gradually gave the dibromo Pt(IV) complex [Pt(Br)2Me2(pbt)], 4a, as determined by NMR spectroscopy and single-crystal XRD. The reaction of complexes 1b and 1c with PhCH2Br gave the Pt(IV) complexes [PtMeBr(CH2Ph)(C^N)(PPh2Me)] (C^N = ppy; 2b; C^N = bhq, 2c), in which the phosphine and benzyl ligands are trans. Multinuclear NMR spectroscopy ruled out other isomers. Attempts to grow crystals of the cycloplatinated(IV) complex 2b yielded a previously reported Pt(II) complex [PtBr(ppy)(PPh2Me)], 3b, presumably from reductive elimination of ethylbenzene. UV–vis spectroscopy was used to study the kinetics of reaction of Pt(II) complexes 1a–1c with benzyl bromide. The data are consistent with a second-order SN2 mechanism and the first order in both the Pt complex and PhCH2Br. The rate of reaction decreases along the series 1a ≫ 1c > 1b. Density functional theory calculations were carried out to support experimental findings and understand the formation of isomers.

Support structure-catalyst electroactivity relation for oxygen reduction reaction on platinum supported by two-dimensional titanium carbide

It is demonstrated that the electroactivity of the oxygen reduction reaction (ORR) of Pt depends on the structure of a support. Highly conductive two-dimensional titanium carbide (Ti3C2) was selected as the support for Pt because of the expected strong metal-support interaction (SMSI) between Pt and Ti. To control the edge-to-basal ratio, the number of Ti3C2 layers was modulated by exfoliation. Pt nanoparticles (4 nm) were loaded on three different Ti3C2 supports including multi-, few-, and mono-layered Ti3C2 (22L-, 4L-, and 1L-Ti3C2, respectively). The edge-to-basal ratio of layered Ti3C2 increased as the number of layers increased. The edge-dominant support (22L-Ti3C2) donated more electrons to Pt than the basal-dominant supports (4L-Ti3C2 and 1L-Ti3C2). As a result, electron-rich Pt with less d-band vacancies (e.g., Pt/22L-Ti3C2) showed higher ORR activity. In addition, the electron transfer from the support to Pt inducing the strong interaction between Pt and Ti improved the durability of the ORR electroactivity of Pt.

Synthesis and Evaluation of PtNi Electrocatalysts for CO and Methanol Oxidation in Low Temperature Fuel Cells

Pt(Ni)/C and PtRu(Ni)/C catalysts were synthesized by electroless deposition of Ni on a carbon dispersion followed by sequenced Pt deposition and spontaneous deposition of Ru species. The structural analyses of the catalysts with 88:12 and 98:2 Pt:Ni atomic ratios pointed out to the formation of small hexagonal Ni crystallites covered by thin cubic Pt surface structures with no evidence about PtNi alloy formation. The onset potentials for CO oxidation on Pt(Ni)/C and PtRu(Ni)/C were about 0.10 and 0.24 V more negative than those of Pt/C, thus indicating their better CO tolerance. The surface Ru species appeared to have the major effect by facilitating the CO removal by the bifunctional mechanism. The onset potential for the methanol oxidation reaction (MOR) of Pt(Ni)/C was about 0.15 V lower than that of Pt/C. The mass and specific activities together with the exchange current densities of the Pt(Ni)/C catalysts were also higher than those of Pt/C, making in evidence their higher activity in front of the MOR. The Tafel slopes for the MOR on Pt(Ni)/C suggested different reaction mechanism than on Pt/C. The electronic (ligand) effect of Ni on Pt was considered the main reason to explain the higher activity of Pt(Ni)/C in front of the CO oxidation and the MOR.

Pd@Pt Core–Shell Nanoflowers as Efficient Catalyst Toward Methanol Oxidation

Among the various morphologies, the nanoflowers have attracted considerable attention because the nanoflowers own higher surface area and lower density, providing more reaction sites for the adsorbates involved in a close range. In this study, Pd@Pt core–shell nanoflowers were obtained by a simple method. From the experiment results, it would be concluded that the core–shell structure was generated owing to the separate reactions of Pt and Pd processors and the flower-like morphologies were generated because of the effect of CTAC. This special structure enabled excellent performance for the oxidation of methanol due to the synergistic effect between Pd and Pt elements and the resulted larger surface area. Specifically, the specific activity of Pd@Pt core–shell nanoflowers was 0.70 mA cm−2, which was more outstanding than that of Pt black according to the electrochemical tests. Moreover, the Pd@Pt core–shell nanoflowers exhibited better durability than Pt black.

New Insights of the pH Effect on Hydrogen Evolution and Oxidation Reactions Mechanisms in Alkaline Solutions

The sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) of Pt in alkaline solutions than in acid remains elusive. Elucidation of the mechanisms of the HER/HOR in alkaline can not only deepen our understandings of alkaline electrochemistry, but also help to rationalize the design of highly active catalysts for alkaline fuel cells and electrolyzers. Herein, we investigate the HER/HOR kinetics of a variety of catalysts including monometallic catalysts (Ni, Pt, Ru, Au) and bimetallic catalysts (NiMo, Pt-M) by comparing their HER/HOR performance in 0.1 M KOH and 1 M KOH. We found that the HER/HOR kinetics of these systems are not always slower in 1 M KOH (pH =14) than in 0.1 M KOH (pH = 13). These observations do not follow the general trend that the HER/HOR kinetics of a wide range of elements slows down with increasing pH1. We propose to resolve this inconsistency by pointing out that the pH is only one of the factors that affect the transport of the HER/HOR intermediates (hydroxyl for HER, Had for HOR) throughout the double layer region, among other factors such as the oxophicility of the surface sites, the cation environment, etc. These factors co-determine the HER/HOR kinetics of catalysts (such as Pt/C) that is limited by the transport of reactions throughout the double layer region. As the electrolyte changes from 0.1 M KOH to 1 M KOH, the pH shifts from 13 to 14, slowing down the HER/HOR kinetics. Meanwhile, the K+ concentration increases one order of magnitude, which promotes the transport of OHad according to the hard-soft acid-base (HSAB) mechanism we proposed recently2, thereby improving the HER but not the HOR until the K+ saturates. The change of the HER/HOR kinetics of a catalyst as the electrolyte changes from 0.1 M KOH to 1 M KOH is a counterbalance between these two effects, and thus varies case by case. Acknowledgements.This work was supported by the Department of Energy (DOE) under award number DE-EE0008082, Office of Naval Research (ONR) under award number N00014-18-1-2155 and the Graduate Thesis/Dissertation Grant of Northeastern University. This research used beamline 7-BM (QAS) and 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. References (1) Herranz, J.; Durst, J.; Fabbri, E.; Patru, A.; Cheng, X.; Permyakova, A. A.; Schmidt, T. J. Interfacial Effects on the Catalysis of the Hydrogen Evolution, Oxygen Evolution and CO2-Reduction Reactions for (Co-)Electrolyzer Development. Nano Energy 2016, 29, 4–28.(2) Liu, E.; Li, J.; Jiao, L.; Doan, H. T. T.; Liu, Z.; Zhao, Z.; Huang, Y.; Abraham, K. M.; Mukerjee, S.; Jia, Q. Unifying the Hydrogen Evolution and Oxidation Reactions Kinetics in Base by Identifying the Catalytic Roles of Hydroxyl-Water-Cation Adducts. J. Am. Chem. Soc. 2019, 141 (7), 3232–3239.

Two routes to platinum-based carboxylate-bridged heterometallics

A series of novel platinum(II) and platinum(IV) acetate-bridged heterometallic complexes was prepared by (1) one-step reaction of platinum acetate blue Pt(OOCMe)2.5–2.75 (PAB) with the complementary metal carboxylates in rather low (10–40%) yield and (2) two-step synthesis starting from potassium hexa(hydroxido)platinate(IV) in much higher (up to 90%) yield. The complexes were structurally characterized by single-crystal XRD and studied by quantum-chemical methods.

Pulse-reverse electrodeposition of Pt–Co bimetallic catalysts for oxygen reduction reaction in acidic medium

Pt–Co electrodeposited by pulse reverse current on carbon cloth (CC) and glassy carbon (GC) are studied. On both substrates, applying a higher reverse current or a longer reverse-time increases the Pt content due to higher Co dissolution from Pt–Co structures, but does not affect the morphology. Despite similar morphologies and compositions deposited on CC or GC, the electrochemical behaviors of Pt–Co on both substrates are significantly different. Distinct hydrogen under-potential deposition (HUPD) adsorption/desorption peaks are not observed on CC, while well-defined peaks are established on GC. Oxygen reduction reaction (ORR) of Pt–Co on CC is significantly higher than on GC due to its highly porous structure. The ORR on GC changes with the Pt content controlled by varying the reverse pulse during electrodeposition, where Pt–Co with 58 at.% Pt or higher provides a better activity than Pt, with 77 at.% Pt having the highest ORR activity.

Chemically Ordered Pt–Co–Cu/C as Excellent Electrochemical Catalyst for Oxygen Reduction Reaction

This paper reveals the ordered structure and composition effect to electrochemical catalytic activity towards oxygen reduction reaction (ORR) of ternary metallic Pt–Co–Cu/C catalysts. Bimetallic Pt-Co alloy nanoparticles (NPs) represent an emerging class of electrocatalysts for ORR, but practical applications, e.g. in fuel cells, have been hindered by low catalytic performances owning to crystal phase and atomic composition. Cu is introduced into Pt-Co/C lattices to form PtCoxCu1−x/C (x = 0.25, 0.5 and 0.75) ternary-face-centered tetragonal (fct) ordered ternary metallic NPs. The chemically ordered Pt–Co–Cu/C catalysts exhibit excellent performance of 1.31 A mg−1Pt in mass activity and 0.59 A cm−2Pt in specific activity which are significantly higher than Pt-Co/C and commercial Johnson Matthey (JM) Pt/C catalysts, because of the ordered crystal phase and composition control modified the Pt-Pt atoms distance and the surface electronic properties. The presence of Cu improves the surface electronic structure, as well as enhances the stability of catalysts.

Oxidative addition of Bi-C bonds to Pt(0): reaction of Pt(PEt3)3 with cyclic organobismuth compounds.

The reaction of cyclic organobismuth compounds, 12-phenyl- and 12-chloro-5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocines, with Pt(PEt3)3 was examined. Oxidative addition of the exocyclic Bi-C bond to Pt(0) selectively took place in the reaction of the 12-phenyl derivative. Oxidative addition of the exocyclic Bi-Cl bond reversibly took place and was kinetically preferred, while endocyclic Bi-C bond oxidative addition products were thermodynamically favored and became the final products in the reaction of 12-chloro derivatives. These results demonstrate the oxidative addition of a Bi-C bond to a transition metal complex for the first time.

Visible light driven generation and alkyne insertion reactions of stable bis-cyclometalated Pt(iv) hydrides.

Hydride complexes resulting from the oxidative addition of C–H bonds are intermediates in hydrocarbon activation and functionalization reactions. The discovery of metal systems that enable their direct formation through photoexcitation with visible light could lead to advantageous synthetic methodologies. In this study, easily accessible dimers [Pt2(μ-Cl)2(C^N)2] (C^N = cyclometalated 2-arylpyridine) are demonstrated as a very convenient source of Pt(C^N) subunits, which promote photooxidative C–H addition reactions with different 2-arylpyridines (N′^C′H) upon irradiation with blue light. The resulting [PtH(Cl)(C^N)(C′^N′)] complexes are the first isolable Pt(iv) hydrides arising from a cyclometalation reaction. A transcyclometalation process involving three photochemical steps is elucidated, which occurs when the C^N ligand is a monocyclometalated 2,6-diarylpyridine, and a detailed analysis of the photoreactivity associated with the Pt(C^N) moiety is provided. Alkyne insertions into the Pt–H bond of a photogenerated Pt(iv) hydride are also reported as a demonstration of the ability of this class of compounds to undergo subsequent organometallic reactions.

Reactions of a photoactivatable diazido Pt(iv) anticancer complex with a single-stranded oligodeoxynucleotide.

Platinum based anticancer agents are widely applied in clinic and their major target is believed to be DNA. Herein, the interaction of a photoactivatable diazido Pt(iv) anticancer prodrug trans,trans,trans-[Pt(N3)2(OH)2(py)2] (py = pyridine; 1) with a 15-mer single-G-containing oligodeoxynucleotide (ODN I: 5'-CT2CTCTTG8T9CT11TCTC-3') was investigated by mass spectrometric methods. Up to penta-platinated ODN I adducts were identified from primary mass spectra while the mono- and di-platinated adducts had the highest intensity. Fragmentation of mono-, di- and tri-platinated I adducts in tandem MS revealed that T2, G8, T11 and T9 are binding sites. No cytosine sites were identified which may be due to the facile loss of Pt adducts from cytosine during CID. The intensity of {Pt(py)2}-bound adducts was comparable to that of {Pt(N3)(py)2}-bound adducts, indicating that the photo-reduction pathway of complex 1 from Pt(iv) to Pt(ii) through two one-electron donations from two azides was substantial. Moreover, no transformation of N3 to NH3 on the {Pt(N3)(py)2}-bound adducts was observed, whereas it is very popular during the reactions of complexes with short ODNs or mono-nucleotides. The oxidation on I induced by the reactive oxygen species (ROS) formed by the photodecomposition of complex 1 was significant, and the oxidation of G8 to 8-hydroxyguanine (8-OH-G), spiroiminodihydantoin (Sp) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG) was discovered. These results unambiguously revealed a sequence-length-dependent photochemical reactivity of complex 1 when it interacted with different ODNs, providing deeper understanding in the reactivity of photoactivatable diazido anticancer Pt(iv) prodrugs to DNA.

Effect of nitrogen substitution and π-conjugation on photophysical properties and excited state intramolecular proton transfer reactions of methyl salicylate derivatives: Theoretical investigation

Effects of nitrogen substitution and π-conjugation on the strength of intramolecular hydrogen bond (H-bond), photophysical properties, and excited-state intramolecular proton transfer (ESIPT) reactions of MS derivatives have been systematically investigated using DFT and TD-DFT methods at the B3LYP/TZVP level. The H-bond strength of all studied compounds becomes stronger in the S1 than in the S0. This result is confirmed by vibrational IR spectra and topological analysis. The H-bond strength of nitrogen substituted compounds is lower than those of compounds with the π-extended conjugation. For photophysical properties, the HOMO-LUMO energy gaps in normal and tautomer forms of nitrogen substituted compounds are insignificantly increased, whereas those of compounds with the π-extended conjugation are notably decreased. The slight widening of the energy gaps results in the slight blue-shifts of the absorption and emission peaks of nitrogen substituted compounds compared to those of MS, whereas the significant narrowing of the energy gaps makes the incredible red-shifts of both electronic spectra of compounds with the π-extended conjugation. Thus, remarkably large Stokes shifts of about 1000 cm−1 are observed for compounds with the π-extended conjugation (M3HN, M2HQC, and M3HQC). In addition, potential energy curves along the PT reaction indicate that the ESIPT of all studied compounds should occurred due to low PT barriers in the exothermic reaction. Dynamic simulations reveal that the ESIPT reactions of studied compounds are observed in an ultrafast time scale (38–130 fs). Most of them have remarkably high PT probabilities (0.84–1.00) except M3HP (0.56), which are in good agreement with the results of H-bond strength. Therefore, the photophysical properties of studied compounds can be significantly tuned by controlling the effect of π-conjugation.

Correlation between Precursor Properties and Performance in the Oxygen Reduction Reaction of Pt and Co “Core-shell” Carbon Nitride-Based Electrocatalysts

This report shows the synthesis of a new family of “core-shell” carbon nitride (CN)-based electrocatalysts (ECs) for the oxygen reduction reaction (ORR) in acid medium. The ECs comprise “cores” of carbon black nanoparticles (NPs) that are covered by a CN “shell” embedding the active sites. The latter include Pt as the “active metal” and Co as the “co-catalyst.” The interplay between the synthesis parameters, the chemical composition, and the ORR performance of the final ECs is elucidated. In particular, the ORR performance and reaction mechanism are studied both in an: (i) “ex-situ” setup, by means of cyclic voltammetry with thin-film rotating ring-disk electrode (CV-TF-RRDE) measurements; and (ii) “in-situ” experiment, i.e., in single proton exchange membrane fuel cells (PEMFCs) tested under operating conditions. A structural hypothesis is proposed that explains both the “ex situ” and the “in situ” ORR results on the basis of: (i) the relative amounts of the reactants used in the precursor synthesis; and (ii) the main temperature of the pyrolysis process (Tf) adopted in the preparation of the ECs. It is shown that the understanding of the fundamental features of the physicochemical processes involved in the preparation of the ECs is crucial in order to improve the proposed synthesis route and to yield ORR ECs exhibiting a performance level beyond the state of the art.

Ni(II), Pd(II), and Pt(II) Complexes of the Hedgehog Pathway Inhibitor GANT61-D.

GANT61-D is an important hedgehog pathway inhibitor and an interesting ligand candidate for metal coordination. The first examples of metal complexes of the potent hedgehog pathway inhibitor GANT61-D are described. The reaction of Ni(II), Pd(II), and Pt(II) precursors with the hedgehog pathway inhibitor GANT61-D gave [NiII(GANT61-D)(OH2)3(μ2-SO4)(μ3-SO4)] (1), [PdII(Cl)(GANT61-D)]Cl (2), [PtII(Cl)(GANT61-D)]Cl, and [PtII(CBDCA-2H)(GANT61-D)]. X-ray crystal structure analysis revealed that GANT61-D is a versatile N-donor ligand that can act as a bidentate ligand via the diaminopropane (DAP) N atoms or a tridentate ligand via the DAP N atoms and one dimethylaniline N atom. Protonation constants of the GANT61-D ligand in water and in a 60:40 (w/w) dimethyl sulfoxide-water solvent mixture were determined. Potentiometric and spectroscopic data on the NiII(GANT61-D) system indicate the formation of octahedral 1:1 species with medium stability in solution. 1 and 2 exhibited noteworthy in vitro cytotoxicity against medulloblastoma cancer cells.

A Universal Picture of the HER/HOR Kinetics of Pt in Alkaline Solution

Some progress has been recently made in understanding the sluggish kinetics of hydrogen evolution and oxidation reactions (HER/HOR) of Pt in alkaline solutions. The pH dependence of the HER/HOR activity of Pt was reasonably accounted for by the potential of zero free charge (pzfc) theory.1 We lately proposed the 2B theory to account for the alkali cation effects on the HER/HOR activity of Pt and the beneficial roles of the second metal such as the Ni on the HER/HOR activity of Pt.2,3 Meanwhile, the Ru-induced improvement of the HOR activity of Pt was ascribed to the bifunctional mechanism4,5 or the hydrogen binding energy.6,7 However, these different theories often conflict with each other, and have not been unified into a coherent picture depicting the kinetics of HER/HOR in alkaline solutions. Herein, we propose a new theory to account for the Ni and Ru induced improvement of the HOR activity of Pt in alkaline solutions, on the basis of combined electrochemical and in situ spectroscopic data. The combination of this new theory with the pzfc and 2B theories appears to give a coherent picture of the HER/HOR kinetics of Pt in alkaline solutions. Acknowledgements This work was supported by the Office of Naval Research (ONR) under award number N00014-18-1-2155. The authors declare no competing financial interests. Use of Beamline ISS 8-ID of the National Synchrotron Light Source (NSLS) II was supported by the NSLS-II, Brookhaven National Laboratory, under U.S. DOE Contract No. DE-SC0012704. Use of beamline 5-BM-D at the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31–109-Eng-38. Jia acknowledged the help from Eli Stavitski, Klaus Attenkofer from ISS, NSLS-II; Qing Ma from DND-CAT, APS at ANL; and Todd E Miller, Lynne LaRochelle Richard from Northeastern University on the XAS data collection. References (1) Ledezma-Yanez, I.; Wallace, W. D. Z.; Sebastián-Pascual, P.; Climent, V.; Feliu, J. M.; Koper, M. T. M., Nat. Energy 2017, 2, 17031. (2) Liu, E.; Li, J.; Jiao, L.; Doan, H. T. T.; Liu, Z.; Zhao, Z.; Huang, Y.; Abraham, K. M.; Mukerjee, S.; Jia, Q., J. Am. Chem. Soc. 2019, 141, 3232. (3) Jia, Q.; Liu, E.; Jiao, L.; Li, J.; Mukerjee, S., Current Opinion in Electrochemistry 2018, 12, 209. (4) Li, J.; Ghoshal, S.; Bates, M. K.; Miller, T. E.; Davies, V.; Stavitski, E.; Attenkofer, K.; Mukerjee, S.; Ma, Z.-F.; Jia, Q., Angew. Chem. Int. Ed. 2017, 56, 15594. (5) Strmcnik, D.; Uchimura, M.; Wang, C.; Subbaraman, R.; Danilovic, N.; Van Der Vliet, D.; Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M., Nat. Chem. 2013, 5, 300. (6) Schwämmlein, J. N.; Stühmeier, B. M.; Wagenbauer, K.; Dietz, H.; Tileli, V.; Gasteiger, H. A.; El-Sayed, H. A., J. Electrochem. Soc. 2018, 165, H229. (7) Wang, Y.; Wang, G.; Li, G.; Huang, B.; Pan, J.; Liu, Q.; Han, J.; Xiao, L.; Lu, J.; Zhuang, L., Energy Environ. Sci. 2015, 8, 177.