Metallamacrocycles and Metallacages: Foundations and Applications

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Organometallic Chemistry".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 14241

Special Issue Editors

Department of Chemistry, Universitat Konstanz, 78464 Konstanz, Germany
Interests: organometallic chemistry; ruthenium complexes; (spectro)electrochemistry; metallocenes; valence tautomerism; mixed-valent chemistry; luminescent platinum complexes; metallamacrocyclic complexes
Special Issues, Collections and Topics in MDPI journals
Institut de Chimie, Université de Neuchâtel, Avenue de Bellevaux 51, CH-2000 Neuchâtel, Switzerland
Interests: metalla-assemblies; supramolecular chemistry; host-guest chemistry; metal-based drugs; organometallic chemistry; X-ray crystallography
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Metallamacrocycles and metallacages are molecular objects of inherent beauty. Since their inception, reliable synthetic protocols that draw on the reversible formation of coordinative bonds have been developed and have granted access to structures of ever-increasing variety, complexity and dimensionality. Over the years this field has matured, and now allows for the purposeful design of metallamacrocycles and metallacages that are poised to fulfil certain tasks. Thus, they may serve as hosts for specific guests, allowing their selective uptake or detection, or as containers that can be used to transport their cargo to the desired place of action, e. g., for delivering drugs to cells. Guest uptake or release events may be triggered by redox stimuli, while their intrinsic redox properties can be exploited for redox catalysis, e. g., in water splitting or for rendering them powerful polyelectrochromics. Other schemes use metallamacrocycles or metallacages for catalysis in confined spaces. Their reduced conformational flexibility may also endow them with superior optical or luminescence properties, and still there is the dimension of the sheer aesthetics of such structures. All these aspects make metallamacrocycles and metallacages an active and advancing field of research.

This Special Issue seeks to combine all aspects of the chemistry of metallamacrocycles and metallacages, from the fundamentals of their synthesis and characterization, their structural, spectroscopic and electrochemical properties to their varied applications, by providing a platform for original research articles as well as short topic reviews.

Prof. Dr. Rainer Winter
Prof. Dr. Bruno Therrien
Guest Editors

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Keywords

  • metallamacrocycle
  • metallacage

Published Papers (7 papers)

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Research

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18 pages, 3849 KiB  
Article
Exploring the Emergent Redox Chemistry of Pd(II) Nodes with Pendant Ferrocenes: From Precursors, through Building Blocks, to Self-Assemblies
by Austin B. Gilbert, Matthew R. Crawley, Trevor J. Higgins, Yuguang C. Li, David F. Watson and Timothy R. Cook
Inorganics 2023, 11(3), 122; https://doi.org/10.3390/inorganics11030122 - 15 Mar 2023
Cited by 1 | Viewed by 1982
Abstract
Energy-relevant small molecule activations and related processes are often multi-electron in nature. Ferrocene is iconic for its well-behaved one-electron chemistry, and it is often used to impart redox activity to self-assembled architectures. When multiple ferrocenes are present as pendant groups in a single [...] Read more.
Energy-relevant small molecule activations and related processes are often multi-electron in nature. Ferrocene is iconic for its well-behaved one-electron chemistry, and it is often used to impart redox activity to self-assembled architectures. When multiple ferrocenes are present as pendant groups in a single structure, they often behave as isolated sites with no separation of their redox events. Herein, we study a suite of molecules culminating in a self-assembled palladium(II) truncated tetrahedron (TT) with six pendant ferrocene moieties using the iron(III/II) couple to inform about the electronic structure and, in some cases, subsequent reactivity. Notably, although known ferrocene-containing metallacycles and cages show simple reversible redox chemistry, this TT undergoes a complex multi-step electrochemical mechanism upon oxidation. The electrochemical behavior was observed by voltammetric and spectroelectrochemical techniques and suggests that the initial Fc-centered oxidation is coupled to a subsequent change in species solubility and deposition of a film onto the working electrode, which is followed by a second separable electrochemical oxidation event. The complicated electrochemical behavior of this self-assembly reveals emergent properties resulting from organizing multiple ferrocene subunits into a discrete structure. We anticipate that such structures may provide the basis for multiple charge separation events to drive important processes related to energy capture, storage, and use, especially as the electronic communication between sites is further tuned. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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11 pages, 3062 KiB  
Article
Controlling Chiral Self-Sorting in Truxene-Based Self-Assembled Cages
by Amina Benchohra, Simon Séjourné, Antoine Labrunie, Liam Miller, Enzo Charbonneau, Vincent Carré, Frédéric Aubriet, Magali Allain, Marc Sallé and Sébastien Goeb
Inorganics 2022, 10(7), 103; https://doi.org/10.3390/inorganics10070103 - 19 Jul 2022
Cited by 3 | Viewed by 1832
Abstract
Coordination driven self-assembly of achiral components, i.e., hexa-alkylated truxene ligands (L) with bis-metallic complexes (M2), afforded three chiral face-rotating stereoisomer polyhedra (M6L2). By tuning the length of the alkyl chains as well as the distance between both [...] Read more.
Coordination driven self-assembly of achiral components, i.e., hexa-alkylated truxene ligands (L) with bis-metallic complexes (M2), afforded three chiral face-rotating stereoisomer polyhedra (M6L2). By tuning the length of the alkyl chains as well as the distance between both ligands facing each other in the self-assemblies (M6L2), one can control the diastereomeric distribution between the expected homo- and hetero-chiral structures. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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17 pages, 2171 KiB  
Article
Chloride Binding Properties of a Macrocyclic Receptor Equipped with an Acetylide Gold(I) Complex: Synthesis, Characterization, Reactivity, and Cytotoxicity Studies
by Andrea Rivoli, Gemma Aragay, María Concepción Gimeno and Pablo Ballester
Inorganics 2022, 10(7), 95; https://doi.org/10.3390/inorganics10070095 - 05 Jul 2022
Cited by 3 | Viewed by 1868
Abstract
In this work, we report the synthesis and characterization of a mono-nuclear “two wall” aryl-extended calix[4]pyrrole receptor (2Au) decorated with an acetylide-gold(I)-PTA complex at its upper rim. We describe the 1H NMR titration experiments of 2Au and its “two wall” [...] Read more.
In this work, we report the synthesis and characterization of a mono-nuclear “two wall” aryl-extended calix[4]pyrrole receptor (2Au) decorated with an acetylide-gold(I)-PTA complex at its upper rim. We describe the 1H NMR titration experiments of 2Au and its “two wall” aryl-extended calix[4]pyrrole synthetic precursors: the non-symmetric mono-iodo-mono-ethynyl 2 and the symmetric bis-iodo 3 with TBACl in dichloromethane and acetone solution. In acetone solution, we use isothermal titration calorimetry (ITC) experiments to thermodynamically characterize the formed 1:1 chloride complexes and perform pair-wise competitive binding experiments. In both solvents, we measured a decrease in the binding constant of the mono-nuclear 2Au complex for chloride compared to the parent mono-iodo-mono-ethynyl 2. In turn, receptor 2 also shows a reduction in binding affinity for chloride compared to its precursor bis-iodo calix[4]pyrrole 3. The free energy differences (∆G) of the 1:1 chloride complexes cannot be exclusively attributed to their dissimilar electrostatic surface potential values either at the center of the meso-phenyl wall or its para-substituent. We conclude that solvation/desolvation processes play an important role in the stabilization of the chloride complexes. In acetone solution and in the presence of TBACl, 6Au, a reference compound for the acetylide Au(I)•PTA unit, produces a bis(alkynyl)gold(I) anionic complex [7Au]. Thus, the observation of two separate sets of signals for the bound aromatic calix[4]pyrrole protons, when more than 1 equiv. of the salt is added, is assigned to the formation of the chloride complexes of 2Au and of the “in situ” formed calix[4]pyrrole anionic dimer [8Au]. Finally, preliminary data obtained in cell viability assays of 2Au and 6Au with human cancer cells lines assign them with moderate activities showing that the calix[4]pyrrole unit is not relevant. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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20 pages, 3445 KiB  
Article
Tetraruthenium Macrocycles with Laterally Extended Bis(alkenyl)quinoxaline Ligands and Their F4TCNQ•− Salts
by Rajorshi Das, Michael Linseis, Laura Senft, Ivana Ivanović-Burmazović and Rainer F. Winter
Inorganics 2022, 10(6), 82; https://doi.org/10.3390/inorganics10060082 - 14 Jun 2022
Cited by 2 | Viewed by 1579
Abstract
We report on the tetraruthenium macrocycles Ru4-5 and -6 with a π-conjugated pyrene-appended 5,8-divinylquinoxaline ligand and either isophthalate or thiophenyl-2,5-dicarboxylate linkers and their charge-transfer salts formed by oxidation with two equivalents of F4TCNQ. Both macrocyclic complexes were characterized by [...] Read more.
We report on the tetraruthenium macrocycles Ru4-5 and -6 with a π-conjugated pyrene-appended 5,8-divinylquinoxaline ligand and either isophthalate or thiophenyl-2,5-dicarboxylate linkers and their charge-transfer salts formed by oxidation with two equivalents of F4TCNQ. Both macrocyclic complexes were characterized by NMR spectroscopy, mass spectrometry, cyclic and square-wave voltammetry, and by IR, UV–vis–NIR, and EPR spectroscopy in their various oxidation states. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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11 pages, 2537 KiB  
Article
A Near-Infrared BODIPY-Based Rhomboidal Metallacycle for Imaging-Guided Photothermal Therapy
by Jinjin Zhang, Jialin Yu, Wen Li, Yiqi Fan, Yang Li, Yan Sun, Shouchun Yin and Peter J. Stang
Inorganics 2022, 10(6), 80; https://doi.org/10.3390/inorganics10060080 - 13 Jun 2022
Cited by 7 | Viewed by 1889
Abstract
Although boron dipyrromethene (BODIPY)-based metallacycles are expected to be promising candidates for imaging probes and therapeutic agents, their biomedical applications are restricted by their short absorption/emission wavelengths. In this work, we report a rhombic metallacycle M with broad absorption in the near-infrared (NIR) [...] Read more.
Although boron dipyrromethene (BODIPY)-based metallacycles are expected to be promising candidates for imaging probes and therapeutic agents, their biomedical applications are restricted by their short absorption/emission wavelengths. In this work, we report a rhombic metallacycle M with broad absorption in the near-infrared (NIR) range and emissions at wavelengths >800 nm, which exhibits an efficient photothermal conversion capacity. Metallacycle M was encapsulated via Pluronic F127 to fit the biotic environment, resulting in the generation of F127/M nanoparticles (NPs) with high hydrophilicity and biocompatibility. In vitro studies demonstrated that the F127/M NPs underwent efficient cellular uptake and exhibited satisfactory photothermal therapeutic activity. Furthermore, in vivo experiments revealed that tumor growth was effectively inhibited, and the degree of undesirable biological damage was minimal in treatment with F127/M NPs and laser irradiation. Finally, the F127/M NPs could be visualized through NIR fluorescence imaging in living mice, thereby allowing their distribution to be monitored in order to enhance treatment accuracy during photothermal therapy. We envision that such BODIPY-based metallacycles will provide emerging opportunities for the development of novel therapeutic agents for biomedical applications. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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Review

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21 pages, 5621 KiB  
Review
The Applications of Metallacycles and Metallacages
by Changfeng Yin, Jiaxing Du, Bogdan Olenyuk, Peter J. Stang and Yan Sun
Inorganics 2023, 11(2), 54; https://doi.org/10.3390/inorganics11020054 - 22 Jan 2023
Cited by 5 | Viewed by 1868
Abstract
Metallacycles and metallacages constitute a class of coordination compounds composed of metal ions and organic ligands. Because of their precise stoichiometry, the flexibility and viability of design, metallacycles and metallacages have attracted considerable attention as supramolecular assemblies. Various two-dimensional polygons, three-dimensional polyhedra, and [...] Read more.
Metallacycles and metallacages constitute a class of coordination compounds composed of metal ions and organic ligands. Because of their precise stoichiometry, the flexibility and viability of design, metallacycles and metallacages have attracted considerable attention as supramolecular assemblies. Various two-dimensional polygons, three-dimensional polyhedra, and other nanoscale materials have been constructed and applied. The highly diverse structures, sizes, and shapes endow metallacycles and metallacages with unique physical and chemical properties and make them suitable for various applications such as encapsulation, separation, catalysis, and biological science. Herein, we review the recent developments in various metallacycles and metallacages in different fields. The text highlights biomedical applications involving molecular recognition and binding, antibacterial activity, and especially cancer diagnosis and treatment, including imaging, chemotherapy, PDT, and PTT. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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18 pages, 5928 KiB  
Review
Anthracene-Containing Metallacycles and Metallacages: Structures, Properties, and Applications
by Jian-Hong Tang and Yu-Wu Zhong
Inorganics 2022, 10(7), 88; https://doi.org/10.3390/inorganics10070088 - 22 Jun 2022
Cited by 5 | Viewed by 2222
Abstract
Due to its highly conjugated panel-like structure and unique photophysical and chemical features, anthracene has been widely used for fabricating attractive and functional supramolecular assemblies, including two-dimensional metallacycles and three-dimensional metallacages. The embedded anthracenes in these assemblies often show synergistic effects on enhancing [...] Read more.
Due to its highly conjugated panel-like structure and unique photophysical and chemical features, anthracene has been widely used for fabricating attractive and functional supramolecular assemblies, including two-dimensional metallacycles and three-dimensional metallacages. The embedded anthracenes in these assemblies often show synergistic effects on enhancing the desired supramolecular and luminescent properties. This review focuses on the metallasupramolecular architectures with anthracene-containing building blocks, as well as their applications in host-guest chemistry, stimulus response, molecular sensing, light harvesting, and biomedical science. Full article
(This article belongs to the Special Issue Metallamacrocycles and Metallacages: Foundations and Applications)
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