Inorganics

20 pages, 2512 KiB

Open AccessReview

by Éva Tóth and Célia S. Bonnet

Inorganics 2019, 7(5), 68; https://doi.org/10.3390/inorganics7050068 - 25 May 2019

Cited by 18 | Viewed by 4807

This article aimed at reviewing the advances on the development of paramagnetic complexes used as chemical exchange saturation transfer agents in magnetic resonance imaging. This relatively new type of contrast opens new avenues in the development of MRI probes for molecular imaging, and [...] Read more.

This article aimed at reviewing the advances on the development of paramagnetic complexes used as chemical exchange saturation transfer agents in magnetic resonance imaging. This relatively new type of contrast opens new avenues in the development of MRI probes for molecular imaging, and coordination chemistry lies at the center of such advances. Strategies to detect important biomarkers such as pH, cations, anions, metabolites, enzyme, and O₂ were described. The current challenges, limitations, and opportunities in this field of research were discussed. Full article

(This article belongs to the Special Issue MRI Contrast Agents)

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12 pages, 2194 KiB

Open AccessArticle

Impact of the Subunit Arrangement on the Nonlinear Absorption Properties of Organometallic Complexes with Ruthenium(II) σ-Acetylide and Benzothiadiazole as Building Units ^§

by Eleonora Garoni, Alessia Colombo, Kenji Kamada, Claudia Dragonetti and Dominique Roberto

Inorganics 2019, 7(5), 67; https://doi.org/10.3390/inorganics7050067 - 24 May 2019

Cited by 3 | Viewed by 2969

Abstract

In this paper, the nonlinear absorption properties of two complexes consisting of Ru(C≡CPh)(C≡C)(dppe)₂ (dppe = Ph₂PCH₂CH₂PPh₂) as electron donor (D) and 4,7-di(2-thienyl)benzo[c][1,2,5]thiadiazole as electron acceptor (A) units in two different arrangement, i.e., A–D–A and [...] Read more.

In this paper, the nonlinear absorption properties of two complexes consisting of Ru(C≡CPh)(C≡C)(dppe)₂ (dppe = Ph₂PCH₂CH₂PPh₂) as electron donor (D) and 4,7-di(2-thienyl)benzo[c][1,2,5]thiadiazole as electron acceptor (A) units in two different arrangement, i.e., A–D–A and D–A–D, are presented. They were measured in solution by the femtosecond open-aperture Z-scan method. The complexes show moderate two-photon absorption cross-sections σ⁽²⁾ of several hundred to one thousand GM (here 1 GM = 10⁻⁵⁰ cm⁴ s molecule⁻¹ photon⁻¹). Although they are formed by the same building units, it was found that the two-photon absorption values of the D–A–D arrangement are six times higher than that of the A–D–A one. This difference can be explained by the number of metal cores (one or two ruthenium centers), the geometrical configurations of the complexes (more or less planar), and the resonance enhancement by lowering the intermediate state. Full article

(This article belongs to the Special Issue Metal Complexes as Nonlinear Optical Molecular Materials)

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11 pages, 25371 KiB

Open AccessArticle

Titanium Doping of the Metallic One-Dimensional Antiferromagnet, Nb₁₂O₂₉

by Izabella Kruk, Joanna E. L. Waldron and Mark A. Green

Inorganics 2019, 7(5), 66; https://doi.org/10.3390/inorganics7050066 - 23 May 2019

Cited by 6 | Viewed by 3001

Abstract

Monoclinic Nb₁₂O₂₉ undergoes a charge ordering transition to form antiferromagnetic Nb⁴⁺ chains (T_N ~ 12 K) spaced 15.7 Å apart, which are coupled through mediation from a subset of metallic electrons which are present over all temperature regimes. [...] Read more.

Monoclinic Nb₁₂O₂₉ undergoes a charge ordering transition to form antiferromagnetic Nb⁴⁺ chains (T_N ~ 12 K) spaced 15.7 Å apart, which are coupled through mediation from a subset of metallic electrons which are present over all temperature regimes. We present the effects of disrupting the delicate electronic equilibrium in monoclinic Nb₁₂O₂₉ through doping Nb⁴⁺ (d¹) with Ti⁴⁺ (d⁰) ions in the series, Ti_xNb_12−xO₂₉. Powder neutron diffraction demonstrates that Ti is distributed over all of the 6 crystallographically distinct Nb positions. Magnetic susceptibility measurements reveal a rapid suppression of the magnetic ordered state on Ti doping, with a 3% percolation threshold consistent with the existence of one-dimensional Nb⁴⁺ chains. The reduction of the number of unpaired electrons on Ti⁴⁺ doping is shown to depopulate both localised and itinerant electron subsets, demonstrating that they are intrinsic to the properties of the system, which is argued to be a direct consequence of the mixture of bonding schemes within the lattice. Full article

(This article belongs to the Special Issue Magnetic Oxide Materials)

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14 pages, 3236 KiB

Open AccessArticle

Transmetalation from Magnesium–NHCs—Convenient Synthesis of Chelating π-Acidic NHC Complexes

by Julian Messelberger, Annette Grünwald, Philipp Stegner, Laura Senft, Frank W. Heinemann and Dominik Munz

Inorganics 2019, 7(5), 65; https://doi.org/10.3390/inorganics7050065 - 22 May 2019

Cited by 6 | Viewed by 6081

Abstract

The synthesis of chelating N-heterocyclic carbene (NHC) complexes with considerable π-acceptor properties can be a challenging task. This is due to the dimerization of free carbene ligands, the moisture sensitivity of reaction intermediates or reagents, and challenges associated with the workup procedure. [...] Read more.

The synthesis of chelating N-heterocyclic carbene (NHC) complexes with considerable π-acceptor properties can be a challenging task. This is due to the dimerization of free carbene ligands, the moisture sensitivity of reaction intermediates or reagents, and challenges associated with the workup procedure. Herein, we report a general route using transmetalation from magnesium–NHCs. Notably, this route gives access to transition-metal complexes in quantitative conversion without the formation of byproducts. It therefore produces transition-metal complexes outperforming the conventional routes based on free or lithium-coordinated carbene, silver complexes, or in situ metalation in dimethyl sulfoxide (DMSO). We therefore propose transmetalation from magnesium–NHCs as a convenient and general route to obtain NHC complexes. Full article

(This article belongs to the Section Organometallic Chemistry)

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8 pages, 1904 KiB

Open AccessArticle

The Role of Surface Plasmon Resonance of Gold Nanoparticles for the Enhancement of Second Harmonic Generation of Nonlinear Chromophores

by Anu Singh Bisht, Khuyen Hoang-Thi, Isabelle Ledoux-Rak, Hynd Remita, Frédéric Dumur, Audrey Guerlin, Eddy Dumas and Cédric R. Mayer

Inorganics 2019, 7(5), 64; https://doi.org/10.3390/inorganics7050064 - 18 May 2019

Cited by 1 | Viewed by 3091

Abstract

A significant enhancement of the second harmonic generation (SHG) from second-order nonlinear optical (NLO) dyes in solution has been evidenced when these dyes were grafted onto the surface of spherical gold nanoparticles (AuNPs), as compared to their NLO response without AuNPs. The length, [...] Read more.

A significant enhancement of the second harmonic generation (SHG) from second-order nonlinear optical (NLO) dyes in solution has been evidenced when these dyes were grafted onto the surface of spherical gold nanoparticles (AuNPs), as compared to their NLO response without AuNPs. The length, as well as the nature of the spacers between the gold particle and the chromophore, is shown to play an important role, a benzene linker being more favorable to AuNP-4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) interactions, as illustrated by a higher exaltation of the NLO response for DAST molecules linked to AuNP via a phenyl ring as compared to their equivalent with a CH₂–CH₂ link. Full article

(This article belongs to the Special Issue Metal Complexes as Nonlinear Optical Molecular Materials)

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7 pages, 2211 KiB

Open AccessArticle

High-Pressure Synthesis of Non-Stoichiometric Li_xWO₃ (0.5 ≤ x ≤ 1.0) with LiNbO₃ Structure

by Kohdai Ishida, Yuya Ikeuchi, Cédric Tassel, Hiroshi Takatsu, Craig M. Brown and Hiroshi Kageyama

Inorganics 2019, 7(5), 63; https://doi.org/10.3390/inorganics7050063 - 12 May 2019

Cited by 9 | Viewed by 5536

Abstract

Compounds with the LiNbO₃-type structure are important for a variety of applications, such as piezoelectric sensors, while recent attention has been paid to magnetic and electronic properties. However, all the materials reported are stoichiometric. This work reports on the high-pressure synthesis [...] Read more.

Compounds with the LiNbO₃-type structure are important for a variety of applications, such as piezoelectric sensors, while recent attention has been paid to magnetic and electronic properties. However, all the materials reported are stoichiometric. This work reports on the high-pressure synthesis of lithium tungsten bronze Li_xWO₃ with the LiNbO₃-type structure, with a substantial non-stoichiometry (0.5 ≤ x ≤ 1). Li_0.8WO₃ exhibit a metallic conductivity. This phase is related to an ambient-pressure perovskite phase (0 ≤ x ≤ 0.5) by the octahedral tilting switching between a⁻a⁻a⁻ and a⁺a⁺a⁺. Full article

(This article belongs to the Section Inorganic Solid-State Chemistry)

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7 pages, 2287 KiB

Open AccessArticle

Modeling the Catalyst Activation Step in a Metal–Ligand Radical Mechanism Based Water Oxidation System

by Nitish Govindarajan and Evert Jan Meijer

Inorganics 2019, 7(5), 62; https://doi.org/10.3390/inorganics7050062 - 9 May 2019

Cited by 11 | Viewed by 4138

Abstract

Designing catalysts for water oxidation (WOCs) that operate at low overpotentials plays an important role in developing sustainable energy conversion schemes. Recently, a mononuclear ruthenium WOC that operates via metal–ligand radical coupling pathway was reported, with a very low barrier for O–O bond [...] Read more.

Designing catalysts for water oxidation (WOCs) that operate at low overpotentials plays an important role in developing sustainable energy conversion schemes. Recently, a mononuclear ruthenium WOC that operates via metal–ligand radical coupling pathway was reported, with a very low barrier for O–O bond formation, that is usually the rate-determining step in most WOCs. A detailed mechanistic understanding of this mechanism is crucial to design highly active oxygen evolution catalysts. Here, we use density functional theory based molecular dynamics (DFT-MD) with an explicit description of the solvent to investigate the catalyst activation step for the [Ru(bpy)

_{2}

(bpy–NO)]

^{2 +}

complex, that is considered to be the rate-limiting step in the metal–ligand radical coupling pathway. We find that a realistic description of the solvent environment, including explicit solvent molecules and thermal motion, is crucial for an accurate description of the catalyst activation step, and for the estimation of the activation barriers. Full article

(This article belongs to the Special Issue Recent Advances in Water Oxidation Catalysis)

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11 pages, 3260 KiB

Open AccessArticle

Comparing the Acidity of (R₃P)₂BH-Based Donor Groups in Iridium Pincer Complexes

by Leon Maser, Christian Schneider, Lukas Alig and Robert Langer

Inorganics 2019, 7(5), 61; https://doi.org/10.3390/inorganics7050061 - 7 May 2019

Cited by 8 | Viewed by 3433

Abstract

In the current manuscript, we describe the reactivity of a series of iridium(III) pincer complexes with the general formulae [(PEP)IrCl(CO)(H)]ⁿ (n = +1, +2) towards base, where PEP is a pincer-type ligand with different central donor groups, and E is the [...] Read more.

In the current manuscript, we describe the reactivity of a series of iridium(III) pincer complexes with the general formulae [(PEP)IrCl(CO)(H)]ⁿ (n = +1, +2) towards base, where PEP is a pincer-type ligand with different central donor groups, and E is the ligating atom of this group (E = B, C, N). The donor groups encompass a secondary amine, a phosphine-stabilised borylene and a protonated carbodiphosphorane. As all ligating atoms E exhibit an E–H bond, we addressed the question of wether the coordinated donor group can be deprotonated in competition to the reductive elimination of HCl from the iridium(III) centre. Based on experimental and quantum chemical investigations, it is shown that the ability for deprotonation of the coordinated ligand decreases in the order of (R₃P)₂CH⁺ > R₂NH > (R₃P)₂BH. The initial product of the reductive elimination of HCl from [(PBP)IrCl(CO)(H)]ⁿ (1c), the square planar iridium(I) complex, [(PBP)Ir(CO)]⁺ (3c), was found to be unstable and further reacts to [(PBP)Ir(CO)₂]⁺ (5c). Comparing the C–O stretching vibrations of the latter with those of related complexes, it is demonstrated that neutral ligands based on tricoordinate boron are very strong donors. Full article

(This article belongs to the Special Issue Metal Complexes Containing Boron Based Ligands)

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12 pages, 1595 KiB

Open AccessCommunication

Functionalizing NaGdF₄:Yb,Er Upconverting Nanoparticles with Bone-Targeting Phosphonate Ligands: Imaging and In Vivo Biodistribution

by Silvia Alonso-de Castro, Emmanuel Ruggiero, Aitor Lekuona Fernández, Unai Cossío, Zuriñe Baz, Dorleta Otaegui, Vanessa Gómez-Vallejo, Daniel Padro, Jordi Llop and Luca Salassa

Inorganics 2019, 7(5), 60; https://doi.org/10.3390/inorganics7050060 - 30 Apr 2019

Cited by 11 | Viewed by 4206

Abstract

Lanthanide-doped upconverting nanoparticles (UCNPs) transform near infrared light (NIR) into higher-energy UV and visible light by multiphotonic processes. Owing to such unique feature, UCNPs have found application in optical imaging and have been investigated for the NIR light activation of prodrugs, including transition [...] Read more.

Lanthanide-doped upconverting nanoparticles (UCNPs) transform near infrared light (NIR) into higher-energy UV and visible light by multiphotonic processes. Owing to such unique feature, UCNPs have found application in optical imaging and have been investigated for the NIR light activation of prodrugs, including transition metal complexes of interest in photochemotherapy. Besides, UCNPs also function as magnetic resonance imaging (MRI) contrast agents and positron emission tomography (PET) probes when labelled with radionuclides such as ¹⁸F. In this contribution, we report on a new series of phosphonate-functionalized NaGdF₄:Yb,Er UCNPs that show affinity for hydroxyapatite (inorganic constituent of bones), and we discuss their potential as bone targeting multimodal (MRI/PET) imaging agents. In vivo biodistribution studies of ¹⁸F-labelled NaGdF₄:Yb,Er UCNPs in rats indicate that surface functionalization with phosphonates favours the accumulation of nanoparticles in bones over time. PET results reveal leakage of ¹⁸F⁻ for phosphonate-functionalized NaGdF₄:Yb,Er and control nanomaterials. However, Gd was detected in the femur for phosphonate-capped UCNPs by ex vivo analysis using ICP-MS, corresponding to 6–7% of the injected dose. Full article

(This article belongs to the Special Issue Unconventional Anticancer Metallodrugs and Strategies to Improve their Pharmacological Profile)

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19 pages, 2920 KiB

Open AccessReview

Potential of MRI in Radiotherapy Mediated by Small Conjugates and Nanosystems

by Retna Putri Fauzia, Antonia G. Denkova and Kristina Djanashvili

Inorganics 2019, 7(5), 59; https://doi.org/10.3390/inorganics7050059 - 30 Apr 2019

Cited by 5 | Viewed by 4156

Abstract

Radiation therapy has made tremendous progress in oncology over the last decades due to advances in engineering and physical sciences in combination with better biochemical, genetic and molecular understanding of this disease. Local delivery of optimal radiation dose to a tumor, while sparing [...] Read more.

Radiation therapy has made tremendous progress in oncology over the last decades due to advances in engineering and physical sciences in combination with better biochemical, genetic and molecular understanding of this disease. Local delivery of optimal radiation dose to a tumor, while sparing healthy surrounding tissues, remains a great challenge, especially in the proximity of vital organs. Therefore, imaging plays a key role in tumor staging, accurate target volume delineation, assessment of individual radiation resistance and even personalized dose prescription. From this point of view, radiotherapy might be one of the few therapeutic modalities that relies entirely on high-resolution imaging. Magnetic resonance imaging (MRI) with its superior soft-tissue resolution is already used in radiotherapy treatment planning complementing conventional computed tomography (CT). Development of systems integrating MRI and linear accelerators opens possibilities for simultaneous imaging and therapy, which in turn, generates the need for imaging probes with therapeutic components. In this review, we discuss the role of MRI in both external and internal radiotherapy focusing on the most important examples of contrast agents with combined therapeutic potential. Full article

(This article belongs to the Special Issue MRI Contrast Agents)

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12 pages, 2633 KiB

Open AccessArticle

Reactive Heterobimetallic Complex Combining Divalent Ytterbium and Dimethyl Nickel Fragments

by Ding Wang, Jules Moutet, Maxime Tricoire, Marie Cordier and Grégory Nocton

Inorganics 2019, 7(5), 58; https://doi.org/10.3390/inorganics7050058 - 26 Apr 2019

Cited by 17 | Viewed by 4945

Abstract

This article presented the synthesis and characterization of original heterobimetallic species combining a divalent lanthanide fragment and a divalent nickel center bridged by the bipyrimidine ligand, a redox-active ligand. X-ray crystal structures were obtained for the Ni monomer (bipym)NiMe₂, 1, [...] Read more.

This article presented the synthesis and characterization of original heterobimetallic species combining a divalent lanthanide fragment and a divalent nickel center bridged by the bipyrimidine ligand, a redox-active ligand. X-ray crystal structures were obtained for the Ni monomer (bipym)NiMe₂, 1, as well as the heterobimetallic dimer compounds, Cp*₂Yb(bipym)NiMe₂, 2, along with ¹H solution NMR, solid-state magnetic data, and DFT calculations only for 1. The reactivity with CO was investigated on both compounds and the stoichiometric acetone formation is discussed based on kinetic and mechanistic studies. The key role of the lanthanide fragment was demonstrated by the relatively slow CO migratory insertion step, which indicated the stability of the intermediate. Full article

(This article belongs to the Special Issue Binuclear Complexes)

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14 pages, 600 KiB

Open AccessArticle

Assessment of Double-Hybrid Density Functional Theory for Magnetic Exchange Coupling in Manganese Complexes

by Dimitrios A. Pantazis

Inorganics 2019, 7(5), 57; https://doi.org/10.3390/inorganics7050057 - 26 Apr 2019

Cited by 22 | Viewed by 4896

Abstract

Molecular systems containing magnetically interacting (exchange-coupled) manganese ions are important in catalysis, biomimetic chemistry, and molecular magnetism. The reliable prediction of exchange coupling constants with quantum chemical methods is key for tracing the relationships between structure and magnetic properties in these systems. Density [...] Read more.

Molecular systems containing magnetically interacting (exchange-coupled) manganese ions are important in catalysis, biomimetic chemistry, and molecular magnetism. The reliable prediction of exchange coupling constants with quantum chemical methods is key for tracing the relationships between structure and magnetic properties in these systems. Density functional theory (DFT) in the broken-symmetry approach has been employed extensively for this purpose and hybrid functionals with moderate levels of Hartree–Fock exchange admixture have often been shown to perform adequately. Double-hybrid density functionals that introduce a second-order perturbational contribution to the Kohn–Sham energy are generally regarded as a superior approach for most molecular properties, but their performance remains unexplored for exchange-coupled manganese systems. An assessment of various double-hybrid functionals for the prediction of exchange coupling constants is presented here using a set of experimentally characterized dinuclear manganese complexes that cover a wide range of exchange coupling situations. Double-hybrid functionals perform more uniformly compared to conventional DFT methods, but they fail to deliver improved accuracy or reliability in the prediction of exchange coupling constants. Reparametrized double-hybrid density functionals (DHDFs) perform no better, and most often worse, than the original B2-PLYP double-hybrid method. All DHDFs are surpassed by the hybrid-meta-generalized gradient approximation (GGA) TPSSh functional. Possible directions for future methodological developments are discussed. Full article

(This article belongs to the Special Issue Applications of Density Functional Theory in Inorganic Chemistry)

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9 pages, 1593 KiB

Open AccessArticle

Green Synthesis of a Functionalized Zirconium-Based Metal–Organic Framework for Water and Ethanol Adsorption

by Zhijie Chen, Xingjie Wang, Timur Islamoglu and Omar K. Farha

Inorganics 2019, 7(5), 56; https://doi.org/10.3390/inorganics7050056 - 26 Apr 2019

Cited by 27 | Viewed by 7169

Abstract

Aqueous synthesis of metal–organic frameworks (MOFs) at room temperature offers many advantages such as reduction in the generation of toxic byproducts and operation costs, as well as increased safety in the material’s production. Functional group-bearing MOFs have received growing attention compared to nonfunctionalized [...] Read more.

Aqueous synthesis of metal–organic frameworks (MOFs) at room temperature offers many advantages such as reduction in the generation of toxic byproducts and operation costs, as well as increased safety in the material’s production. Functional group-bearing MOFs have received growing attention compared to nonfunctionalized analogues due to enhanced adsorption properties of the former in many cases. Here, we report an aqueous solution-based synthesis of a robust zirconium MOF, UiO-66-NO₂, at room temperature. We evaluated the phase purity, porosity, thermal stability, particle morphology and size of the resulting material. High uptake, as well as near complete recyclability of water and ethanol vapor isotherms at room temperature supports the potential of UiO-66-NO₂ as a solid adsorbent in adsorption-based cooling applications or water harvesting systems. Full article

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

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Inorganics, Volume 7, Issue 5 (May 2019) – 13 articles

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