Effect Of Coordination Environment Research Articles

Promoting Oxygen Evolution Electrocatalysis by Coordination Engineering in Cobalt Phosphate.

Understanding the structure-activity correlation is an important prerequisite for the rational design of high-efficiency electrocatalysts at the atomic level. However, the effect of coordination environment on electrocatalytic oxygen evolution reaction (OER) remains enigmatic. In this work, the regulation of proton transfer involved in water oxidation by coordination engineering based on Co3(PO4)2 and CoHPO4 is reported. The HPO4 2- anion has intermediate pKa value between Co(II)-H2O and Co(III)-H2O to be served as an appealing proton-coupled electron transfer (PCET) induction group. From theoretical calculations, the pH-dependent OER properties, deuterium kinetic isotope effects, operando electrochemical impedance spectroscopy (EIS) and Raman studies, the CoHPO4 catalyst beneficially reduces the energy barrier of proton hopping and modulates the formation energy of high-valent Co species, thereby enhancing OER activity. This work demonstrates a promising strategy that involves tuning the local coordination environment to optimize PCET steps and electrocatalytic activities for electrochemical applications. In addition, the designed system offers a motif to understand the structure-efficiency relationship from those amino-acid residue with proton buffer ability in natural photosynthesis.

DFT Study on Effect of Metal Type and Coordination Environment on CO2 ECR to C1 Products over M-N-C Catalysts.

Electrocatalytic reduction (ECR) of CO2 to chemical products is an important carbon emission reduction method. This work uses DFT to study the stability of N-doped graphene-supported four metal single-atom catalysts (M-N-C) and the effects of the coordination environment and metal centers on the selectivity of CO2 ECR to C1 products. The results show that Fe, Co, Ni, and Cu have good stability. The coordination environment has a significant modulating effect on product selectivity, and the change of the number of ligand nitrogen atoms will affect the size of the potential-limiting step of each product. When the number of nitrogen ligands is the same, the different metal centers of the M-N-C catalyst have a significant effect on the selectivity of different products. In addition, the introduction of nitrogen atom ligands can adjust the electronic structure of the graphene-supported metal center, increase the d-band center of most metals, and improve the reaction activity.

Theoretical Understanding of the Effect of Coordination Environment on the Activity of Metal Macrocyclic Complexes as Electrocatalysts for Oxygen Reduction Reactions

Theoretical Understanding of the Effect of Coordination Environment on the Activity of Metal Macrocyclic Complexes as Electrocatalysts for Oxygen Reduction Reactions

Effect of coordination environment on the localization behavior and band tail states of Zn0.7In0.3Fe2O4 and Zn0.3In0.7Fe2O4 nanoparticles

The interplay of the coordination environment and localization behavior in ferrites is one of the fascinating and least discussed problems. We report on the effect of the coordination environment on the localization behavior, band tail states, and the optical constants in the UV–Vis regime. X-ray diffraction data confirm the spinal structure with general formula AB2O4. Mossbauer spectroscopy data confirm the existence of Fe ion in the + 3 oxidation state occupying both the tetrahedral and octahedral positions. The Indium (In3+) ions prefer to reside in the tetrahedral A-site. Incorporation of excess In3+ ions causes excess migration of Fe+3 ions to the octahedral B-site and results in the t2g orbital splitting. This lowers the octahedral symmetry from FeO6 to FeO5 dominant coordination environment, which has a strong impact on the magnetic and optical behavior. UV–Vis diffuse reflectance spectroscopy was employed to determine the bandgap and band tail states, which are the key parameters in understanding the localization behavior.

The effect of coordination environment on the kinetic and thermodynamic stability of single-atom iron catalysts.

The stability of a single-atom catalyst is directly related to its preparation and applications, especially for high-loading single-atom catalysts. Here, the effect of a coordination environment induced by nitrogen (N) atoms coordinated with iron on the kinetic and thermodynamic stabilities of single-atom iron catalysts supported with carbon-based substrates (FeSA/CS) was investigated by density functional theory (DFT) calculations. Five FeSA/CS with different numbers of N atoms were modelled. The kinetic stability was evaluated by analyzing the migration paths of iron atoms and energy barriers. The thermodynamic stability was studied by calculating the adsorption and formation energies. Our results indicated that the coordination environment induced by N can promote the kinetic and thermodynamic stability of FeSA/CS. N atoms on the substrate promote the kinetic stability by raising the energy barrier for iron migration and not only increase the thermodynamic stability, but also contribute to catalyst synthesis. Doping N on the substrate enhances charge transfer between the iron atoms and substrates simultaneously improving the kinetic and thermodynamic stabilities. This theoretical research provides guidance for synthesizing stable and high loading single-atom catalysts by tuning the coordination environment of single-atom elements.

Effect of coordination environment on the magnetic relaxation of mononuclear DyIII field-induced single molecule magnets

Two mononuclear DyIII complexes [Dy(H2TEG)(NO3)3]·[18-crown-6] (H2TEG=triethylene glycol) (1) and [Dy(H2TEG)Cl3]·[18-crown-6] (2) have been prepared using H2TEG as ligands. Magnetic studies revealed that both complexes show field-induced double magnetic relaxation behavior with energy barriers of 28K and 54K. Distinct magnetic dynamic properties observed in 1 and 2 are mostly attributed to the dissimilar coordination environments around DyIII centers in these two complexes.

Effect of Coordination Environment in Grafted Single-Site Ti-SiO2 Olefin Epoxidation Catalysis

The effect of calixarene ligand symmetry, as dictated by lower-rim substitution pattern, on the coordination to a Ti(IV) cation is assessed in solution and when grafted on SiO2, and its effect on epoxidation catalysis by Ti(IV)-calixarene grafted on SiO2 is investigated. C2v symmetric Ti-tert-butylcalix[4]arene complexes that are 1,3-alkyl disubstituted at the lower rim (di-R-Ti) are compared to previously reported grafted Cs symmetric complexes, which are singly substituted at the lower rim (mono-R-Ti). 13C MAS NMR spectra of complexes isotopically enriched at the lower-rim alkyl position indicate that di-R-Ti predominantly grafts onto silica as the conformation found in solution, exhibiting a deshielded alkyl resonance compared to the grafted mono-R-Ti complexes, which is consistent with stronger alkyl ether→Ti dative interactions that are hypothesized to result in higher electron density at the Ti center. Moreover, 13C MAS NMR spectroscopy detects an additional contribution from an “endo” conformer for grafted di-R-Ti sites, which is not observed in solution. Based on prior molecular modeling studies and on 13C MAS NMR spectroscopy chemical shifts, this “endo” conformer is proposed to have similar Ti–(alkyl ether) distances at the lower-rim and electron density at the Ti center relative to grafted mono-R-Ti complexes. Differences between grafted mono-R-Ti and di-R-Ti sites can be observed by ligand-to-metal charge transfer edge-energies, calculated from diffuse-reflectance UV–visible spectroscopy at 2.24 ± 0.02 and 2.16 ± 0.02 eV, respectively. However, rates of tert-butyl hydroperoxide consumption in the epoxidation of 1-octene are found to be largely unchanged when compared to those of the grafted mono-R-Ti complexes, with average rate constants of ~1.5 M−2 s−1 and initial TOF of ~4 ks−1 at 323 K. This suggests that an “endo” conformation of grafted di-R-Ti may prevail during catalysis. Despite this, grafted di-C1-Ti complexes can be more selective than mono-C1-Ti complexes (45 vs. 34 % at a 50 % conversion at 338 and 353 K), illustrating the importance of the Ti coordination environment on epoxidation catalysis.

Effect of Coordination Environment on the Electronic Structure and Properties of Mo6-Based Systems: A Density Functional Treatment

Effect of Coordination Environment on the Electronic Structure and Properties of Mo6-Based Systems: A Density Functional Treatment

Effects of coordination environment on the Zr–F symmetric stretching frequency of fluorozirconate glasses, crystals, and melts

A treatment based on Badger’s rule is used to estimate symmetric stretching frequencies νs of the nonbridging fluorides of various ZrFn groups in the presence of divalent and monovalent countercations. New vibrational spectra of MgZrF6, Ba2ZrF8, and β-BaZr2F10 are presented and incorporated into the method. The factors affecting νs are outlined and discussed in detail. Compilations of estimated frequencies are used to deduce the probable local structure around Zr ions in binary barium fluorozirconate glasses and in fluorozirconate melts containing lithium and sodium ions. It is concluded that the results of Raman spectroscopy indicate the presence of seven- and eight-coordinate Zr in some barium fluorozirconate glasses.

Laser-induced, sequential two-photon redox processes of transition-metal complexes. Effects of coordination environment, laser pulse intensity, and excited-state lifetimes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLaser-induced, sequential two-photon redox processes of transition-metal complexes. Effects of coordination environment, laser pulse intensity, and excited-state lifetimesR. Sriram, John F. Endicott, and Kirkwood M. CunninghamCite this: J. Phys. Chem. 1981, 85, 1, 38–46Publication Date (Print):January 1, 1981Publication History Published online1 May 2002Published inissue 1 January 1981https://doi.org/10.1021/j150601a011RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Supporting Info (1)»Supporting Information Supporting Information Get e-Alerts