Correlation between rate constants for water substitution in inner coordination spheres of metal ions and their electrochemical activities in metal deposition reactions

1975 ◽  
Vol 79 (13) ◽  
pp. 1252-1254 ◽  
Author(s):  
Ashok K. Vijh ◽  
J. P. Randin
Keyword(s):  
Metal Ions ◽  
Rate Constants ◽  
Metal Deposition ◽  
Coordination Spheres

Binuclear metal chelate complexes of anthraquinones having a MO4 chromophore. Part 1. Quinizarin

1987 ◽  
Vol 65 (7) ◽  
pp. 1485-1490 ◽  
Author(s):  
M. N. Bakola-Christianopoulou ◽  
P. D. Akrivos ◽  
M. Baumgarten
Keyword(s):  
Metal Ions ◽  
Magnetic Measurements ◽  
Metal Chelate ◽  
Transition Elements ◽  
Chelate Complexes ◽  
Cobalt Nickel ◽  
Oxygen Donor ◽  
Nickel Copper ◽  
Square Planar ◽  
Coordination Spheres

Homobinuclear metal chelate complexes having 1,4-dihydroxy-9,10-anthracenedione (quinizarin) as a bridging unit have been prepared with four bivalent first row transition elements, namely cobalt, nickel, copper, and zinc. The coordination spheres of the metal ions consist of two nearly equivalent six-membered rings with oxygen donor atoms derived from the quinizarin and the terminal ligands which are either β-diketones or salicylic aldehyde. TG, spectroscopic (ir, uv–vis, epr), and magnetic measurements have been applied to an investigation of the geometry adopted by the MO4 chromophores. The results are consistent with varying degrees of distortion from the ideal square planar toward a tetrahedral arrangement around the metal ions, closely related to the specific metal center involved.

scholarly journals The Kinetics and Stoichiometry of Metal Cation Reduction on Multi-Crystalline Silicon in a Dilute Hydrofluoric Acid Matrix

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2545
Author(s):  
Stefan Schönekerl ◽  
Jörg Acker
Keyword(s):  
Metal Ions ◽  
Valence Band ◽  
Metal Cation ◽  
Hydrofluoric Acid ◽  
Metal Ion ◽  
Crystalline Silicon ◽  
Metal Deposition ◽  
Equilibrium Potential ◽  
Valence Bands ◽  
Energetic Level

In this study, the process of metal cation reduction on multi-crystalline silicon in a dilute hydrofluoric acid (HF) matrix is described using Ag(I), Cu(II), Au(III) and Pt(IV). The experimental basis utilized batch tests with various solutions of different metal cation and HF concentrations and multi-crystalline silicon wafers. The metal deposition kinetics and the stoichiometry of metal deposition and silicon dissolution were calculated by means of consecutive sampling and analysis of the solutions. Several reaction mechanisms and reaction steps of the process were discussed by overlaying the results with theoretical considerations. It was deduced that the metal deposition was fastest if the holes formed during metal ion reduction could be transferred to the valence bands of the bulk and surface silicon with hydrogen termination. By contrast, the kinetics were lowest when the redox levels of the metal ion/metal half-cells were weak and the equilibrium potential of the H3O+/H2 half-cells was high. Further minima were identified at the thresholds where H3O+ reduction was inhibited, the valence transfer via valence band mechanism was limited by a Schottky barrier and the dissolution of oxidized silicon was restricted by the activity of the HF species F−, HF2− and H2F3−. The findings of the stoichiometric conditions provided further indications of the involvement of H3O+ and H2O as oxidizing agents in addition to metal ions, and the hydrogen of the surface silicon termination as a reducing agent in addition to the silicon. The H3O+ reduction is the predominant process in dilute metal ion solutions unless it is disabled due to the metal-dependent equilibrium potential of the H3O+/H2 half-cell and the energetic level of the valence bands of the silicon. As silicon is not oxidized up to the oxidation state +IV by the reduction of the metal ions and H3O+, water is suspected of acting as a secondary oxidant. The stoichiometric ratios increased up to a maximum with higher molalities of the metal ions, in the manner of a sigmoidal function. If, owing to the redox level of the metal half-cells and the energetic level of the valence band at the metal–silicon contact, the surface silicon can be oxidized, the hydrogen of the termination is the further reducing agent.

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