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Molecular Metal Clusters: Fundamental and Applied Aspects

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Inorganic Chemistry".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 23133

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Special Issue Editors

Dr. Artem Gushchin

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Guest Editor

A. V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
Interests: chemistry of coordination and cluster compounds of transition metals; chalcogenide clusters of early transition metals; transition metal complexes with redox-active ligands
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Maxim N. Sokolov

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Guest Editor

Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Prospekt Acad. Lavrentieva, dom 3, 630090 Novosibirsk, Russia
Interests: chemistry of coordination and cluster compounds of 4D and 5D transition metals; chemistry of polyoxometalates; inorganic synthesis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The central and most interesting problem of modern inorganic chemistry is the reactivity of coordination compounds, especially in connection with such practically important tasks as the transformation of organic compounds into products that are useful and valuable to humans, activation of inert molecules, and study of photochemical processes (sunlight harvesting, generation of singlet oxygen, hydrogen production, photocatalysis etc). New practical needs combined with new capabilities for synthesis and characterization of coordination compounds put on the agenda the task of expanding the material basis of coordination chemistry, namely, synthesis and study of new and non-trivial classes of coordination compounds, in particular, cluster compounds having polymetallic cores with direct metal-metal interactions. In this case, we can expect to obtain compounds with a new, unexpected set of chemical and physical properties.

This special issue is devoted to various aspects of the chemistry of discrete molecular transition metal clusters, whose properties and applications very often differ from more familiar mononuclear compounds. Two main classes of clusters can be distinguished. They are low-valent or organometallic clusters, and high-valent or inorganic clusters (mainly chalcogenide and halide-bridged), which are characterized by great structural diversity and a plethora of potentially useful physico-chemical properties. These features are often combined with the stability of the cluster core (in ligand exchange processes and redox reactions) and the relatively simple modification of the ligand environment. Both types of clusters are considered as model objects for heterogeneous catalysts on metal surfaces (organometallic clusters) and metal chalcogenides (chalcogenide metal clusters). In addition, molecular clusters themselves are effective catalysts and can catalyze quite a few reactions better than momonuclear catalysts. In other words, molecular clusters are an intermediate link between mononuclear complexes and heterogeneous catalysts, and also represent a bridge between molecular and solid state chemistry. Their study opens up new prospects in material science, catalysis, and fundamental chemistry.

Dr. Artem L. Gushchin
Prof. Dr. Maxim N. Sokolov
Guest Editors

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Keywords

Low-valent (organometallic) clusters
Highly valent (inorganic) clusters
Transition metals
Synthesis
Crystal structure
Reactivity
Catalysis
Small molecule activation
Photochemistry
Electronic structure

Published Papers (10 papers)

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Research

Jump to: Review

11 pages, 1750 KiB

Open AccessArticle

Structural Diversity of Di-Metalized Arginine Evidenced by Infrared Multiple Photon Dissociation (IRMPD) Spectroscopy in the Gas Phase

by Ruxia Feng, Yicheng Xu and Xianglei Kong

Molecules 2021, 26(21), 6546; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26216546 - 29 Oct 2021

Cited by 4 | Viewed by 1266

Abstract

Although metal cations are prevalent in biological media, the species of multi-metal cationized biomolecules have received little attention so far. Studying these complexes in isolated state is important, since it provides intrinsic information about the interaction among them on the molecular level. Our investigation here demonstrates the unexpected structural diversity of such species generated by a matrix-assisted laser desorption ionization (MALDI) source in the gas phase. The photodissociation spectroscopic and theoretical study reflects that the co-existing isomers of [Arg+Rb+K−H]⁺ can have energies ≥95 kJ/mol higher than that of the most stable one. While the result can be rationalized by the great isomerization energy barrier due to the coordination, it strongly reminds us to pay more attention to their structural diversities for multi-metalized fundamental biological molecules, especially for the ones with the ubiquitous alkali metal ions. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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16 pages, 2283 KiB

Open AccessArticle

Kinetics and Thermodynamics of CO Oxidation by (TiO₂)₆

by Navjot Kaur, Neetu Goel, Michael Springborg and Mohammad Molayem

Molecules 2021, 26(21), 6415; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26216415 - 24 Oct 2021

Viewed by 1322

Abstract

Molecular level insights into the mechanism and thermodynamics of CO oxidation by a (TiO

_{2}

)

_{6}

cluster have been obtained through density functional calculations. Thereby, in this study, as an example, two different structural isomers of (TiO

_{2}

)

_{6}

are considered [...] Read more.

Molecular level insights into the mechanism and thermodynamics of CO oxidation by a (TiO

_{2}

)

_{6}

cluster have been obtained through density functional calculations. Thereby, in this study, as an example, two different structural isomers of (TiO

_{2}

)

_{6}

are considered with the purpose of understanding the interplay between local structure and activity for the CO oxidation reaction. Active sites in the two isomeric forms were identified on the basis of global and local reactivity descriptors. For the oxidation of CO to CO

_{2}

, the study considered both sequential and simultaneous adsorption of CO and O

_{2}

on (TiO

_{2}

)

_{6}

cluster through the ER and LH mechanisms, respectively. Three different pathways were obtained for CO oxidation by (TiO

_{2}

)

_{6}

cluster, and the mechanistic route of each pathway were identified by locating the transition-state and intermediate structures. The effect of temperature on the rate of the reaction was investigated within the harmonic approximation. The structure-dependent activity of the cluster was rationalized through reactivity descriptors and analysis of the frontier orbitals. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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Figure 1

11 pages, 5929 KiB

Open AccessArticle

Temperature and Composition Dependent Structural Evolution: Thermodynamics of Cu_nAg_135−n (n = 0–135) Nanoalloys during Cooling

by Jinhan Liu, Naipeng Sun and Lin Zhang

Molecules 2021, 26(20), 6242; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26206242 - 15 Oct 2021

Cited by 2 | Viewed by 1096

Abstract

Molecular dynamics simulations are performed to investigate the changes of packing structures, and thermodynamic quantities including internal energy, entropy, and free energy are used to determine temperature regime and transition time of atomic packing structures. The simulation results show different packing structures as the component composition changes, and there are different packing patterns during cooling. For these Cu-Ag alloy clusters containing only a small number of atoms of Cu, they present FCC packing structures in different parts at high temperatures, and then there are transformations to icosahedral structures. With the increase in content of Cu atoms, there is a transition mechanism from molten state to icosahedron. When the content of Cu atoms is appropriate, core-shell structures can be formed at room temperature. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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11 pages, 6898 KiB

Open AccessArticle

Exploring the Dual Characteristics of CH₃OH Adsorption to Metal Atomic Structures on Si (111)-7 × 7 Surface

by Wenxin Li, Jiawen Wang, Wanyu Ding, Youping Gong, Huipeng Chen and Dongying Ju

Molecules 2021, 26(19), 5824; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26195824 - 26 Sep 2021

Cited by 1 | Viewed by 1495

Abstract

Metal atoms were deposited on an Si (111)-7 × 7 surface, and they were adsorbed with alcohol gases (CH₃OH/C₂H₅OH/C₃H₇OH). Initially, C_nH_2n+1OH adsorption was simply used as an intermediate layer to prevent the chemical reaction between metal and Si atoms. Through scanning tunneling microscopy (STM) and a mass spectrometer, the C_nH_2n+1OH dissociation process is further derived as the construction of a surface quasi-potential with horizontal and vertical directions. With the help of three typical metal depositions, the surface characteristics of CH₃OH adsorption are more clearly presented in this paper. Adjusting the preheating temperature, the difference of thermal stability between CH₃O^– and H⁺ could be obviously derived in Au deposition. After a large amount of H⁺ was separated, the isolation characteristic of CH₃O^– was discussed in the case of Fe deposition. In the process of building a new metal-CH₃O^–-H⁺ model, the dual characteristics of CH₃OH were synthetically verified in Sn deposition. CH₃O^– adsorption is prone to influencing the interaction between the metal deposition and substrate surface in the vertical direction, while H⁺ adsorption determines the horizontal behavior of metal atoms. These investigations lead one to believe that, to a certain extent, the formation of regular metal atomic structures on the Si (111)-7 × 7-CH₃OH surface is promoted, especially according to the dual characteristics and adsorption models we explored. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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17 pages, 2891 KiB

Open AccessArticle

Adsorption/Desorption Behaviors and SERS Chemical Enhancement of 6-Mercaptopurine on a Nanostructured Gold Surface: The Au₂₀ Cluster Model

by Nguyen Thi Nhat Hang, Nguyen Thanh Si, Minh Tho Nguyen and Pham Vu Nhat

Molecules 2021, 26(17), 5422; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26175422 - 06 Sep 2021

Cited by 6 | Viewed by 2769

Abstract

Computational approaches are employed to elucidate the binding mechanism and the SERS phenomenon of 6-mercaptopurine (6MP) adsorbed on the tetrahedral Au₂₀ cluster as a simple model for a nanostructured gold surface. Computations are carried out in both vacuum and aqueous environments using a continuum model. In the gaseous phase and neutral conditions, interaction of 6MP with the gold cluster is mostly dominated by a covalent Au−S bond and partially stabilized by the Au⋅⋅⋅H−N coupling. However, in acidic solution, the nonconventional Au⋅⋅⋅H−S hydrogen-bond becomes the most favorable binding mode. The 6MP affinity for gold clusters decreases in the order of vacuum > neutral solution > acidic medium. During the adsorption, the energy gap of Au₂₀ substantially declines, leading to an increase in its electrical conductivity, which can be converted to an electrical noise. Moreover, such interaction is likely a reversible process and triggered by either the low pH in sick tissues or the presence of cysteine residues in protein matrices. While N−H bending and stretching vibrations play major roles in the SERS phenomenon of 6MP on gold surfaces in neutral solution, the strongest enhancement in acidic environment is mostly due to an Au⋅⋅⋅H−S coupling, rather than an aromatic ring-gold surface π overlap as previously proposed. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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18 pages, 4588 KiB

Open AccessArticle

Supramolecular Frameworks Based on Rhenium Clusters Using the Synthons Approach

by Nathalie Audebrand, Antoine Demont, Racha El Osta, Yuri V. Mironov, Nikolay G. Naumov and Stéphane Cordier

Molecules 2021, 26(9), 2662; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26092662 - 01 May 2021

Cited by 4 | Viewed by 2038

Abstract

The reaction of the K₄[{Re₆Sⁱ₈}(OH)^a₆]·8H₂O rhenium cluster salt with pyrazine (Pz) in aqueous solutions of alkaline or alkaline earth salts at 4 °C or at room temperature leads to apical ligand exchange and to the formation of five new compounds: [trans-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₂(H₂O)^a₂] (1), [cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₂(H₂O)^a₂] (2), (NO₃)[cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a(H₂O)^a₃](Pz)·3H₂O (3), [Mg(H₂O)₆]_0.5[cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₃(H₂O)^a]·8.5H₂O (4), and K[cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₃(H₂O)^a]·8H₂O (5). Their crystal structures are built up from trans- or cis-[{Re₆Sⁱ₈}(Pz)^a₂(OH)^a_4−x(H₂O)^a_x]^x−2 cluster units. The cohesions of the 3D supramolecular frameworks are based on stacking and H bonding, as well as on H₃O₂₋bridges in the cases of (1), (2), (4), and (5) compounds, while (3) is built from stacking and H bonding only. This evidences that the nature of the synthons governing the cluster unit assembly is dependent on the hydration rate of the unit. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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18 pages, 3947 KiB

Open AccessArticle

Polymerization Isomerism in Co-M (M = Cu, Ag, Au) Carbonyl Clusters: Synthesis, Structures and Computational Investigation

by Cristiana Cesari, Beatrice Berti, Francesco Calcagno, Cristina Femoni, Marco Garavelli, Maria Carmela Iapalucci, Ivan Rivalta and Stefano Zacchini

Molecules 2021, 26(6), 1529; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26061529 - 11 Mar 2021

Cited by 5 | Viewed by 4489

Abstract

The reaction of [Co(CO)₄]⁻ (1) with M(I) compounds (M = Cu, Ag, Au) was reinvestigated unraveling an unprecedented case of polymerization isomerism. Thus, as previously reported, the trinuclear clusters [M{Co(CO)₄}₂]⁻ (M = Cu, 2; Ag, 3; Au, 4) were obtained by reacting 1 with M(I) in a 2:1 molar ratio. Their molecular structures were corroborated by single-crystal X-ray diffraction (SC-XRD) on isomorphous [NEt₄][M{Co(CO)₄}₂] salts. [NEt₄](3)represented the first structural characterization of 3. More interestingly, changing the crystallization conditions of solutions of 3, the hexanuclear cluster [Ag₂{Co(CO)₄}₄]²⁻ (5) was obtained in the solid state instead of 3. Its molecular structure was determined by SC-XRD as Na₂(5)·C₄H₆O₂, [PPN]₂(5)·C₅H₁₂ (PPN = N(PPh₃)₂]⁺), [NBu₄]₂(5) and [NMe₄]₂(5) salts. 5 may be viewed as a dimer of 3 and, thus, it represents a rare case of polymerization isomerism (that is, two compounds having the same elemental composition but different molecular weights) in cluster chemistry. The phenomenon was further studied in solution by IR and ESI-MS measurements and theoretically investigated by computational methods. Both experimental evidence and density functional theory (DFT) calculations clearly pointed out that the dimerization process occurs in the solid state only in the case of Ag, whereas Cu and Au related species exist only as monomers. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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9 pages, 609 KiB

Open AccessFeature PaperArticle

Hydrolysis of Element (White) Phosphorus under the Action of Heterometallic Cubane-Type Cluster {Mo₃PdS₄}

by Airat M. Kuchkaev, Nikita Y. Shmelev, Aidar M. Kuchkaev, Aleksandr V. Sukhov, Vasily M. Babaev, Khasan R. Khayarov, Artem L. Gushchin, Maxim N. Sokolov, Oleg G. Sinyashin and Dmitry G. Yakhvarov

Molecules 2021, 26(3), 538; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26030538 - 21 Jan 2021

Viewed by 2001

Abstract

Reaction of heterometallic cubane-type cluster complexes—[Mo₃{Pd(dba)}S₄Cl₃(dbbpy)₃]PF₆, [Mo₃{Pd(tu)}S₄Cl₃(dbbpy)₃]Cl and [Mo₃{Pd(dba)}S₄(acac)₃(py)₃]PF₆, where dba—dibenzylideneacetone, dbbpy—4,4′-di-tert-butyl-2,2′-bipyridine, tu—thiourea, acac—acetylacetonate, py—pyridine, with white phosphorus (P₄) in the presence of water leads to the formation of phosphorous acid H₃PO₃ as the major product. The crucial role of the Pd atom in the cluster core {Mo₃PdS₄} has been established in the hydrolytic activation of P₄ molecule. The main intermediate of the process, the cluster complex [Mo₃{PdP(OH)₃}S₄Cl₃(dbbpy)₃]⁺ with coordinated P(OH)₃ molecule and phosphine PH₃, have been detected by ³¹P NMR spectroscopy in the reaction mixture. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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17 pages, 3198 KiB

Open AccessArticle

Cyanide Complexes Based on {Mo₆I₈}⁴⁺ and {W₆I₈}⁴⁺ Cluster Cores

by Aleksei S. Pronin, Spartak S. Yarovoy, Yakov M. Gayfulin, Aleksey A. Ryadun, Konstantin A. Brylev, Denis G. Samsonenko, Ilia V. Eltsov and Yuri V. Mironov

Molecules 2020, 25(24), 5796; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25245796 - 08 Dec 2020

Cited by 5 | Viewed by 2230

Abstract

Compounds based on new cyanide cluster anions [{Mo₆I₈}(CN)₆]^2–, trans-[{Mo₆I₈}(CN)₄(MeO)₂]^2– and trans-[{W₆I₈}(CN)₂(MeO)₄]²⁻ were synthesized using mechanochemical or solvothermal synthesis. The crystal and electronic structures as well as spectroscopic properties of the anions were investigated. It was found that the new compounds exhibit red luminescence upon excitation by UV light in the solid state and solutions, as other cluster complexes based on {Mo₆I₈}⁴⁺ and {W₆I₈}⁴⁺ cores do. The compounds can be recrystallized from aqueous methanol solutions; besides this, it was shown using NMR and UV-Vis spectroscopy that anions did not undergo hydrolysis in the solutions for a long time. These facts indicate that hydrolytic stabilization of {Mo₆I₈} and {W₆I₈} cluster cores can be achieved by coordination of cyanide ligands. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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Review

Jump to: Research

17 pages, 2168 KiB

Open AccessReview

Towards a Synthetic Biology Toolset for Metallocluster Enzymes in Biosynthetic Pathways: What We Know and What We Need

by Helena Shomar and Gregory Bokinsky

Molecules 2021, 26(22), 6930; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26226930 - 17 Nov 2021

Cited by 4 | Viewed by 2717

Abstract

Microbes are routinely engineered to synthesize high-value chemicals from renewable materials through synthetic biology and metabolic engineering. Microbial biosynthesis often relies on expression of heterologous biosynthetic pathways, i.e., enzymes transplanted from foreign organisms. Metallocluster enzymes are one of the most ubiquitous family of enzymes involved in natural product biosynthesis and are of great biotechnological importance. However, the functional expression of recombinant metallocluster enzymes in live cells is often challenging and represents a major bottleneck. The activity of metallocluster enzymes requires essential supporting pathways, involved in protein maturation, electron supply, and/or enzyme stability. Proper function of these supporting pathways involves specific protein–protein interactions that remain poorly characterized and are often overlooked by traditional synthetic biology approaches. Consequently, engineering approaches that focus on enzymatic expression and carbon flux alone often overlook the particular needs of metallocluster enzymes. This review highlights the biotechnological relevance of metallocluster enzymes and discusses novel synthetic biology strategies to advance their industrial application, with a particular focus on iron-sulfur cluster enzymes. Strategies to enable functional heterologous expression and enhance recombinant metallocluster enzyme activity in industrial hosts include: (1) optimizing specific maturation pathways; (2) improving catalytic stability; and (3) enhancing electron transfer. In addition, we suggest future directions for developing microbial cell factories that rely on metallocluster enzyme catalysis. Full article

(This article belongs to the Special Issue Molecular Metal Clusters: Fundamental and Applied Aspects)

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