scholarly journals Revealing the Influence of Secondary Metals on Redox-Active Palladium Complexes

2022 ◽  
Author(s):  
Riddhi Golwankar ◽  
Amit Kumar ◽  
Victor Day ◽  
James Blakemore
Keyword(s):  
Electron Transfer ◽  
Metal Ions ◽  
Lewis Acids ◽  
Reorganization Energy ◽  
Palladium Complexes ◽  
Lewis Acidity ◽  
X Ray Diffraction ◽  
Isolation And Characterization ◽  
Redox Active ◽  
Energy Penalty

Incorporation of redox-inactive metals into redox-active complexes and catalysts attracts attention for engendering new reactivity modes, but this strategy has not been extensively investigated beyond the first-row of the transition metals. Here, the isolation and characterization of the first series of heterobimetallic complexes of palladium with mono-, di-, and tri-valent redox-inactive metal ions are reported. A Reinhoudt-type heteroditopic ligand with a salen-derived [N2,O2] binding site for Pd and a crown-ether-derived [O6] site has been used to prepare isolable adducts of the Lewis acidic redox-inactive metal ions (Mn+). Comprehensive data from single-crystal X-ray diffraction analysis reveal distinctive trends in the structural properties of the heterobimetallic species, including an uncommon dependence of the Pd•••M distance on Lewis acidity. The reorganization energy associated with reduction of the heterobimetallic species is strongly modulated by Lewis acidity, with the slowest heterogeneous electron transfer kinetics associated with the strongest incorporated Lewis acids. This hitherto unexplored reorganization energy penalty for electron transfer contrasts with prior thermodynamic studies, revealing that kinetic parameters should be considered in studies of reactivity involving heterobimetallic species.

scholarly journals Promotion and Tuning of the Electrochemical Reduction of Hetero- and Homobimetallic Zinc Complexes

2021 ◽  
Author(s):  
Shaun Kelsey ◽  
Amit Kumar ◽  
Allen G. Oliver ◽  
Victor W. Day ◽  
James Blakemore
Keyword(s):  
Metal Ions ◽  
Lewis Acids ◽  
Xrd Analysis ◽  
Bimetallic Complexes ◽  
Prior Work ◽  
X Ray Diffraction ◽  
Redox Active ◽  
Reorganization Energies ◽  
Potential Shifts ◽  
Cyclic Voltammetry Data

Compounds containing multiple metals attract significant interest due to the useful redox and reactivity properties of such species. Here, the electrochemical properties of a family of macrocyclic complexes that feature a zinc(II) center paired with a second redox-inactive metal cation in heterobimetallic (Na+, Ca2+, Nd3+, Y3+) motifs or a homobimetallic (Zn2+) motif have been investigated. The new complexes were prepared via a divergent strategy, isolated, and structurally characterized by single-crystal X-ray diffraction (XRD) analysis. XRD results show that the structure of the complexes is modulated by the identity of the incorporated secondary metal ions. Cyclic voltammetry data reveal that ligand-centered reduction is promoted in the bimetallic complexes and that the paired metal ions synergistically influence the redox properties of the complexes. Similar to prior work from our group and others, the bimetallic complexes containing stronger Lewis acids undergo more significant reduction potential shifts; contrasting with prior work on complexes containing redox-active metals, however, the zinc(II) complexes studied here display faster electron transfer (as judged by lower reorganization energies, λ) when incorporating di- or tri-valent Lewis acids in contrast to monovalent (and more weakly acidic) sodium. The quantified trends in these data offer insights that help distinguish metal- versus ligand-centered reduction of bimetallic complexes.<br>

scholarly journals Promotion and Tuning of the Electrochemical Reduction of Hetero- and Homobimetallic Zinc Complexes

2021 ◽  
Author(s):  
Shaun Kelsey ◽  
Amit Kumar ◽  
Allen G. Oliver ◽  
Victor W. Day ◽  
James Blakemore
Keyword(s):  
Metal Ions ◽  
Lewis Acids ◽  
Xrd Analysis ◽  
Bimetallic Complexes ◽  
Prior Work ◽  
X Ray Diffraction ◽  
Redox Active ◽  
Reorganization Energies ◽  
Potential Shifts ◽  
Cyclic Voltammetry Data

Compounds containing multiple metals attract significant interest due to the useful redox and reactivity properties of such species. Here, the electrochemical properties of a family of macrocyclic complexes that feature a zinc(II) center paired with a second redox-inactive metal cation in heterobimetallic (Na+, Ca2+, Nd3+, Y3+) motifs or a homobimetallic (Zn2+) motif have been investigated. The new complexes were prepared via a divergent strategy, isolated, and structurally characterized by single-crystal X-ray diffraction (XRD) analysis. XRD results show that the structure of the complexes is modulated by the identity of the incorporated secondary metal ions. Cyclic voltammetry data reveal that ligand-centered reduction is promoted in the bimetallic complexes and that the paired metal ions synergistically influence the redox properties of the complexes. Similar to prior work from our group and others, the bimetallic complexes containing stronger Lewis acids undergo more significant reduction potential shifts; contrasting with prior work on complexes containing redox-active metals, however, the zinc(II) complexes studied here display faster electron transfer (as judged by lower reorganization energies, λ) when incorporating di- or tri-valent Lewis acids in contrast to monovalent (and more weakly acidic) sodium. The quantified trends in these data offer insights that help distinguish metal- versus ligand-centered reduction of bimetallic complexes.<br>

Molecular assemblies based on strong axial coordination in metal complexes of saddle-distorted dodecaphenylporphyrins

2015 ◽  
Vol 19 (01-03) ◽  
pp. 32-44 ◽  
Author(s):  
Tomoya Ishizuka ◽  
Shunichi Fukuzumi ◽  
Takahiko Kojima
Keyword(s):  
Electron Transfer ◽  
Metal Ions ◽  
Metal Complexes ◽  
Photoinduced Electron Transfer ◽  
Oxidation Potential ◽  
Metal Center ◽  
Lewis Acidity ◽  
Central Metal ◽  
Axial Coordination ◽  
Keggin Type

In this mini-review, we have highlighted our works on metal complexes having saddle-distorted dodecaphenylporphyrin (DPP) and its derivative as ligands in the light of enhancement of the Lewis acidity of a metal center coordinated by the porphyrin. The important point through this mini-review is ill-overlap of the out-of-plane lone pairs of pyrrole nitrogen atoms with σ-orbitals of the metal center bound to the saddle-distorted porphyrin core. The enhanced Lewis acidity of the central metal ions enabled us to construct stable molecular complexes through axial coordination using metal–DPP (M(DPP)) moieties ( M = Mo V or Sn IV ) and molecular or ionic entities with Lewis-basic coordination sites, including Keggin-type polyoxometallates (POM), which are known to have weak Lewis basicity and thus hard to coordinate to metal ions. A discrete 1:2 complex with a Ru -substituted POM performs catalytic substrate oxidation reactions in organic solvents. A 1:1 complex between Sn IV ( DPP ) and a Keggin-type POM exhibited photoinduced electron transfer, in which the Sn IV ( DPP ) moiety acts as an electron donor and the POM as an electron acceptor. Besides POM, other electron acceptors, including μ3-oxo trinuclear Ru III clusters and anthraquinone, having carboxyl groups as a linker unit also formed stable complexes with DPP-metal complexes as axial ligands to perform photoinduced electron transfer. Successful photoreactions of the M(DPP)-acceptor complexes are mainly enabled by the enhanced Lewis acidity of the DPP-metal complexes for the stabilization of the assemblies and also by lowering the oxidation potential of the porphyrin ligand to gain larger driving force of electron transfer to form an electron-transfer state with avoiding intersystem crossing. The stability and photochemical behavior are in sharp contrast to those for metal complexes with planar porphyrins as ligands.

Enhancement of Oxidative Reaction by the Intramolecular Electron Transfer between the Coordinated Redox-Active Metal Ions in SOD1

2020 ◽  
Vol 124 (11) ◽  
pp. 2116-2123
Author(s):  
Takumi Ohyama ◽  
Kunisato Kuroi ◽  
Taiyu Wakabayashi ◽  
Nobuhiro Fujimaki ◽  
Takakazu Nakabayashi
Keyword(s):  
Electron Transfer ◽  
Metal Ions ◽  
Intramolecular Electron Transfer ◽  
Oxidative Reaction ◽  
Redox Active ◽  
Active Metal ◽  
Redox Active Metal

scholarly journals Pyrene Carboxylate Ligand Based Coordination Polymers for Microwave-Assisted Solvent-Free Cyanosilylation of Aldehydes

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1101
Author(s):  
Anirban Karmakar ◽  
Anup Paul ◽  
Elia Pantanetti Sabatini ◽  
M. Fátima C. Guedes da Silva ◽  
Armando J. L. Pombeiro
Keyword(s):  
Coordination Polymer ◽  
Single Crystal ◽  
Coordination Polymers ◽  
Metal Ion ◽  
Solvent Free ◽  
Lewis Acidity ◽  
Carboxylate Ligand ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Assisted

The new coordination polymers (CPs) [Zn(μ-1κO1:1κO2-L)(H2O)2]n·n(H2O) (1) and [Cd(μ4-1κO1O2:2κN:3,4κO3-L)(H2O)]n·n(H2O) (2) are reported, being prepared by the solvothermal reactions of 5-{(pyren-4-ylmethyl)amino}isophthalic acid (H2L) with Zn(NO3)2.6H2O or Cd(NO3)2.4H2O, respectively. They were synthesized in a basic ethanolic medium or a DMF:H2O mixture, respectively. These compounds were characterized by single-crystal X-ray diffraction, FTIR spectroscopy, thermogravimetric and elemental analysis. The single-crystal X-ray diffraction analysis revealed that compound 1 is a one dimensional linear coordination polymer, whereas 2 presents a two dimensional network. In both compounds, the coordinating ligand (L2−) is twisted due to the rotation of the pyrene ring around the CH2-NH bond. In compound 1, the Zn(II) metal ion has a tetrahedral geometry, whereas, in 2, the dinuclear [Cd2(COO)2] moiety acts as a secondary building unit and the Cd(II) ion possesses a distorted octahedral geometry. Recently, several CPs have been explored for the cyanosilylation reaction under conventional conditions, but microwave-assisted cyanosilylation of aldehydes catalyzed by CPs has not yet been well studied. Thus, we have tested the solvent-free microwave-assisted cyanosilylation reactions of different aldehydes, with trimethylsilyl cyanide, using our synthesized compounds, which behave as highly active heterogeneous catalysts. The coordination polymer 1 is more effective than 2, conceivably due to the higher Lewis acidity of the Zn(II) than the Cd(II) center and to a higher accessibility of the metal centers in the former framework. We have also checked the heterogeneity and recyclability of these coordination polymers, showing that they remain active at least after four recyclings.

scholarly journals Anodic Stripping Voltammetry with the Hanging Mercury Drop Electrode for Trace Metal Detection in Soil Samples

Chemosensors ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 107
Author(s):  
Kequan Xu ◽  
Clara Pérez-Ràfols ◽  
Amine Marchoud ◽  
María Cuartero ◽  
Gastón A. Crespo
Keyword(s):  
Metal Ions ◽  
Limit Of Detection ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Hanging Mercury Drop Electrode ◽  
Mercury Drop Electrode ◽  
Redox Active ◽  
Active Metal ◽  
Metal Detection ◽  
Trace Metal Detection

The widely spread use of the hanging mercury drop electrode (HMDE) for multi-ion analysis is primarily ascribed to the following reasons: (i) excellent reproducibility owing to the easy renewal of the electrode surface avoiding any hysteresis effect (i.e., a new identical drop is generated for each measurement to be accomplished); (ii) a wide cathodic potential window originating from the passive hydrogen evolution and solvent electrolysis; (iii) the ability to form amalgams with many redox-active metal ions; and (iv) the achievement of (sub)nanomolar limits of detection. On the other hand, the main controversy of the HMDE usage is the high toxicity level of mercury, which has motivated the scientific community to question whether the HMDE deserves to continue being used despite its unique capability for multi-metal detection. In this work, the simultaneous determination of Zn2+, Cd2+, Pb2+, and Cu2+ using the HMDE is investigated as a model system to evaluate the main features of the technique. The analytical benefits of the HMDE in terms of linear range of response, reproducibility, limit of detection, proximity to ideal redox behavior of metal ions and analysis time are herein demonstrated and compared to other electrodes proposed in the literature as less-toxic alternatives to the HMDE. The results have revealed that the HMDE is largely superior to other reported methods in several aspects and, moreover, it displays excellent accuracy when simultaneously analyzing Zn2+, Cd2+, Pb2+, and Cu2+ in such a complex matrix as digested soils. Yet, more efforts are required towards the definitive replacement of the HMDE in the electroanalysis field, despite the elegant approaches already reported in the literature.

Study on Adsorption of Crosslinked Starch Microspheres towards Heavy Metal Ions

2013 ◽  
Vol 834-836 ◽  
pp. 531-535
Author(s):  
Li Yan Yang ◽  
Yi Hui Guo ◽  
Li Li Yu ◽  
Jing You
Keyword(s):  
Metal Ions ◽  
Reversed Phase ◽  
Adsorption Rate ◽  
X Ray Diffraction ◽  
Adsorption Selectivity ◽  
X Ray ◽  
Starch Microsphere ◽  
Other Substances ◽  
Effects Of Media ◽  
Kinetics Of

A type of cross-linking starch microsphere (CSMs) has been synthesized via reversed phase suspension method. Crosslinked starch microsphere has good adsorption performance to metal ions in water. The adsorption kinetics of Co (II) on the CSMs, selectivity of adsorption CSMs towards Co (II),Cu (II),Pb (II),Cd (II) and adsorption effects of media towards Co (II) were investigated. The CSMs and its adsorption product were comparatively characterized by X-ray diffraction (XRD). The results showed that The adsorption rate is mainly controlled by liquid film diffusion, and the constant of adsorption rate is 0.0686min-1 at 308K. The crystal structure of the CSMs decreased greatly after the incorporation of Co (II). Co (II) has better adsorption selectivity on CSMs. Ions coexist and other substances in the solution have certain impact on adsorption. Those data are helpful for treatment of the wastewater containing heavy ions.

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