Inorganics

17 pages, 5120 KiB

Open AccessArticle

Controlling the Lifetime of the Triplet MLCT State in Fe(II) Polypyridyl Complexes through Ligand Modification

by Jianfang Wu, Marc Alías and Coen de Graaf

Inorganics 2020, 8(2), 16; https://doi.org/10.3390/inorganics8020016 - 20 Feb 2020

Cited by 10 | Viewed by 6305

A computational study is presented in which two strategies of ligand modifications have been explored to invert the relative energy of the metal-to-ligand charge transfer (MLCT) and metal-centered (MC) state in Fe(II)-polypyridyl complexes. Replacing the bipyridines by stronger

σ

donors increases the ligand-field [...] Read more.

A computational study is presented in which two strategies of ligand modifications have been explored to invert the relative energy of the metal-to-ligand charge transfer (MLCT) and metal-centered (MC) state in Fe(II)-polypyridyl complexes. Replacing the bipyridines by stronger

σ

donors increases the ligand-field strength and pushes the MC state to higher energy, while the use of ligands with a larger

π

conjugation leads to lower MLCT energies. Full article

(This article belongs to the Special Issue Novel Ligand Design in Coordination Compounds)

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10 pages, 2556 KiB

Open AccessCommunication

On the Possible Coordination on a ³MC State Itself? Mechanistic Investigation Using DFT-Based Methods

by Adrien Soupart, Fabienne Alary, Jean-Louis Heully and Isabelle M. Dixon

Inorganics 2020, 8(2), 15; https://doi.org/10.3390/inorganics8020015 - 19 Feb 2020

Cited by 6 | Viewed by 3085

Abstract

Understanding light-induced ligand exchange processes is key to the design of efficient light-releasing prodrugs or photochemically driven functional molecules. Previous mechanistic investigations had highlighted the pivotal role of metal-centered (MC) excited states in the initial ligand loss step. The question remains whether they [...] Read more.

Understanding light-induced ligand exchange processes is key to the design of efficient light-releasing prodrugs or photochemically driven functional molecules. Previous mechanistic investigations had highlighted the pivotal role of metal-centered (MC) excited states in the initial ligand loss step. The question remains whether they are equally important in the subsequent ligand capture step. This article reports the mechanistic study of direct acetonitrile coordination onto a ³MC state of [Ru(bpy)₃]²⁺, leading to [Ru(bpy)₂(κ¹-bpy)(NCMe)]²⁺ in a ³MLCT (metal-to-ligand charge transfer) state. Coordination of MeCN is indeed accompanied by the decoordination of one pyridine ring of a bpy ligand. As estimated from Nudged Elastic Band calculations, the energy barrier along the minimum energy path is 20 kcal/mol. Interestingly, the orbital analysis conducted along the reaction path has shown that creation of the metallic vacancy can be achieved by reverting the energetic ordering of key dσ* and bpy-based π* orbitals, resulting in the change of electronic configuration from ³MC to ³MLCT. The approach of the NCMe lone pair contributes to destabilizing the dσ* orbital by electrostatic repulsion. Full article

(This article belongs to the Special Issue Photochemistry & Photophysics of Transition Metal Complexes)

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11 pages, 1882 KiB

Open AccessArticle

Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands

by Patrick Herr and Oliver S. Wenger

Inorganics 2020, 8(2), 14; https://doi.org/10.3390/inorganics8020014 - 17 Feb 2020

Cited by 9 | Viewed by 3951

Abstract

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo⁰ complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic Ru^II polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo [...] Read more.

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo⁰ complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic Ru^II polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo⁰ complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo⁰ center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to Ru^II polypyridines, the molecular distortions in the luminescent ³MLCT state relative to the electronic ground state seem to be smaller in the Mo⁰ complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo⁰ tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)₃]²⁺. Full article

(This article belongs to the Special Issue Photochemistry & Photophysics of Transition Metal Complexes)

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10 pages, 6012 KiB

Open AccessArticle

Structural Damage of Two-Dimensional Organic–Inorganic Halide Perovskites

by Biao Yuan, Enzheng Shi, Chao Liang, Letian Dou and Yi Yu

Inorganics 2020, 8(2), 13; https://doi.org/10.3390/inorganics8020013 - 6 Feb 2020

Cited by 5 | Viewed by 4391

Abstract

Organic–inorganic halide perovskites are promising photovoltaic materials with excellent optoelectronic properties. However, the extreme structural instability hinders their wide application as well as the microstructure characterization using high energy beams such as transmission electron microscopy (TEM). Here, taking BA₂FAPb₂I [...] Read more.

Organic–inorganic halide perovskites are promising photovoltaic materials with excellent optoelectronic properties. However, the extreme structural instability hinders their wide application as well as the microstructure characterization using high energy beams such as transmission electron microscopy (TEM). Here, taking BA₂FAPb₂I₇ and BA₂MAPb₂I₇ as examples, we investigate their structural evolution resulting from high energy electron irradiation, moist air, and low temperature, respectively. The results show that the long organic chains are the first to be damaged under electron beam, which is mainly arising from their instability and weak bonding with the framework of [PbI₆]⁴⁻ octahedrons. Then the short organic cations and the framework of [PbI₆]⁴⁻ octahedrons collapses gradually. The final products are clusters of detached PbI₂ particles, which can also be observed in the sample degraded in moist air. In addition, the structures of BA₂FAPb₂I₇ and BA₂MAPb₂I₇ are discovered to undergo a phase transformation at liquid nitrogen temperature, which calls attention to the community that cryo-TEM methods should be used cautiously for organic–inorganic halide perovskite materials. Full article

(This article belongs to the Special Issue Inorganic Materials for Solar Energy Conversion)

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9 pages, 1080 KiB

Open AccessArticle

Investigation of Hydrogen Storage Characteristics of MgH₂ Based Materials with Addition of Ni and Activated Carbon

by Eli Grigorova, Diana Nihtianova, Boyko Tsyntsarski and Ivanka Stoycheva

Inorganics 2020, 8(2), 12; https://doi.org/10.3390/inorganics8020012 - 2 Feb 2020

Cited by 8 | Viewed by 3176

Abstract

Magnesium-based materials are promising as hydrogen storage media due to their high theoretical hydrogen absorption capacity, abundance and low price. The subject of this study are the hydrogen sorption characteristics of the composites 80 wt % MgH₂-15 wt % Ni-5 wt [...] Read more.

Magnesium-based materials are promising as hydrogen storage media due to their high theoretical hydrogen absorption capacity, abundance and low price. The subject of this study are the hydrogen sorption characteristics of the composites 80 wt % MgH₂-15 wt % Ni-5 wt % activated carbon (synthesized from polyolefin wax, a waste product of polyethylene production at low pressure which will be denoted further in the text as POW) and 90 wt % MgH₂-5 wt % Ni-5 wt % POW, prepared by ball milling under argon atmosphere. Structure, phase and surface composition of the samples before and after hydrogenation are determined by XRD and TEM. The maximum absorption capacity value of the composites at a temperature 573 K and after 60 min. of hydrogenation are 5.3 wt % H₂ for the material with higher Ni content and 5.5 wt % H₂ for the other sample. The presence of both additives—nickel and activated carbon derived from POW—has a positive impact on hydrogenation kinetics and the capacity achieved. The results from TEM characterization, e.g., the polycrystalline SAED (selected area electron diffraction) show the presence of graphite, Mg and monoclinic Mg₂NiH₄. Full article

(This article belongs to the Special Issue Beyond Hydrogen Storage—Metal Hydrides as Multifunctional Materials for Energy Storage and Conversion)

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11 pages, 5648 KiB

Open AccessEditor’s ChoiceCommunication

Magnetic Composite Submicron Carriers with Structure-Dependent MRI Contrast

by Anastasiia A. Kozlova, Sergey V. German, Vsevolod S. Atkin, Victor V. Zyev, Maxwell A. Astle, Daniil N. Bratashov, Yulia I. Svenskaya and Dmitry A. Gorin

Inorganics 2020, 8(2), 11; https://doi.org/10.3390/inorganics8020011 - 30 Jan 2020

Cited by 18 | Viewed by 3885

Abstract

Magnetic contrast agents are widely used in magnetic resonance imaging in order to significantly change the signals from the regions of interest in comparison with the surrounding tissue. Despite a high variety of single-mode T₁ or T₂ contrast agents, there is [...] Read more.

Magnetic contrast agents are widely used in magnetic resonance imaging in order to significantly change the signals from the regions of interest in comparison with the surrounding tissue. Despite a high variety of single-mode T₁ or T₂ contrast agents, there is a need for dual-mode contrast from the one agent. Here, we report on the synthesis of magnetic submicron carriers, containing Fe₃O₄ nanoparticles in their structure. We show the ability to control magnetic resonance contrast by changing not only the number of magnetite nanoparticles in one carrier or the concentration of magnetite in the suspension but also the structure of the core–shell itself. The obtained data open up the prospects for dual-mode T₁/T₂ magnetic contrast formation, as well as provides the basis for future investigations in this direction. Full article

(This article belongs to the Special Issue Smart Tools for Smart Applications: New Insights into Inorganic Magnetic Systems and Materials)

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10 pages, 2595 KiB

Open AccessArticle

Adsorption Properties of Ce₅(BDC)_7.5(DMF)₄ MOF

by Cesare Atzori, Jayashree Ethiraj, Valentina Colombo, Francesca Bonino and Silvia Bordiga

Inorganics 2020, 8(2), 9; https://doi.org/10.3390/inorganics8020009 - 26 Jan 2020

Cited by 13 | Viewed by 4306

Abstract

In this article we report on the spectroscopic and adsorptive studies done on Ce(III)-based MOF possessing, upon desolvation, open metal sites, and a discrete surface area. The Ce-based MOF was synthesized from terephthalic acid linker (H₂BDC) and Ce³⁺ cations by [...] Read more.

In this article we report on the spectroscopic and adsorptive studies done on Ce(III)-based MOF possessing, upon desolvation, open metal sites, and a discrete surface area. The Ce-based MOF was synthesized from terephthalic acid linker (H₂BDC) and Ce³⁺ cations by the classical solvothermal method. Preliminary powder X-ray diffraction analysis showed that the obtained materials corresponded to the ones reported by other authors. Spectroscopic techniques, such as XAS and in situ FTIR with probe molecules were used. In situ FTIR spectroscopy confirmed the successful removal of DMF molecules within the pore system at temperatures above 250 °C. Moreover, the use of CO as a probe molecule evidenced the presence of a Ce³⁺ open metal sites. Detailed volumetric and calorimetric CO₂ adsorption studies are also reported. Full article

(This article belongs to the Special Issue Functional Coordination Polymers and Metal–Organic Frameworks)

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30 pages, 5309 KiB

Open AccessReview

Evaluating Ligand Modifications of the Titanocene and Auranofin Moieties for the Development of More Potent Anticancer Drugs

by Lauren Fernández-Vega, Valeria A. Ruiz Silva, Tania M. Domínguez-González, Sebastián Claudio-Betancourt, Rafael E. Toro-Maldonado, Luisa C. Capre Maso, Karina Sanabria Ortiz, Jean A. Pérez-Verdejo, Janeishly Román González, Grecia T. Rosado-Fraticelli, Fabiola Pagán Meléndez, Fabiola M. Betancourt Santiago, Daniel A. Rivera-Rivera, Carlos Martínez Navarro, Andrea C. Bruno Chardón, Axel O. Vera and Arthur D. Tinoco

Inorganics 2020, 8(2), 10; https://doi.org/10.3390/inorganics8020010 - 26 Jan 2020

Cited by 19 | Viewed by 6768

Abstract

Over time platinum-based anticancer drugs have dominated the market, but their side effects significantly impact the quality of life of patients. Alternative treatments are being developed all over the world. The titanocene and auranofin families of compounds, discovered through an empirical search for [...] Read more.

Over time platinum-based anticancer drugs have dominated the market, but their side effects significantly impact the quality of life of patients. Alternative treatments are being developed all over the world. The titanocene and auranofin families of compounds, discovered through an empirical search for other metal-based therapeutics, hold tremendous promise to improve the outcomes of cancer treatment. Herein we present a historical perspective of these compounds and review current efforts focused on the evolution of their ligands to improve their physiological solution stability, cancer selectivity, and antiproliferative performance, guided by a clear understanding of the coordination chemistry and aqueous speciation of the metal ions, of the cytotoxic mechanism of action of the compounds, and the external factors that limit their therapeutic potential. Newer members of these families of compounds and their combination in novel bimetallic complexes are the result of years of scientific research. We believe that this review can have a positive impact in the development and understanding of the metal-based drugs of gold, titanium, and beyond. Full article

(This article belongs to the Special Issue Novel Ligand Design in Coordination Compounds)

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14 pages, 5790 KiB

Open AccessArticle

Bi₂O₃-Modified Ceramics Based on BaTiO₃ Powder Synthesized in Water Vapor

by Anastasia Kholodkova, Aleksey Smirnov, Marina Danchevskaya, Yurii Ivakin, Galina Muravieva, Sergey Ponomarev, Alexandr Fionov and Vladimir Kolesov

Inorganics 2020, 8(2), 8; https://doi.org/10.3390/inorganics8020008 - 23 Jan 2020

Cited by 12 | Viewed by 4388

Abstract

Bi₂O₃ was investigated in the role of a modifier for BaTiO₃ powder synthesized in a water vapor atmosphere at 200 °C and 1.55 MPa. Modification was aimed at increasing the sinterability of the powder as well as improving the [...] Read more.

Bi₂O₃ was investigated in the role of a modifier for BaTiO₃ powder synthesized in a water vapor atmosphere at 200 °C and 1.55 MPa. Modification was aimed at increasing the sinterability of the powder as well as improving the structural and dielectric properties of the obtained ceramics. The morphology and phase contents of the synthesized BaTiO₃ powder were controlled by the methods of SEM and XRD. Properties of pure and Bi-doped BaTiO₃ ceramics were comprehensively studied by XRD, SEM, dielectric spectroscopy, and standard approaches for density and mechanical strength determination. Doping with Bi₂O₃ favored BaTiO₃ ceramic densification and strengthening. The room-temperature dielectric constant and the loss tangent of Bi-doped BaTiO₃ were shown to stabilize within the frequency range of 20 Hz to 2 MHz compared to non-doped material. The drop of dielectric constant between room temperature and Curie point was significantly reduced after Bi₂O₃ addition to BaTiO₃. Bi₂O₃ appeared to be an effective modifier for BaTiO₃ ceramics produced from non-stoichiometric powder synthesized in water vapor. Full article

(This article belongs to the Special Issue Electroceramic Materials: Composition–Structure–Property Relationships 2021)

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Inorganics, Volume 8, Issue 2 (February 2020) – 9 articles

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