Editorial Board Members’ Collection Series in “Featuring Ligands and Their Applications in Coordination Chemistry”

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

Deadline for manuscript submissions: 31 March 2024 | Viewed by 9537

Special Issue Editors

Department of Chemistry, Colorado State University, Fort Colllins, CO 80523, USA
Interests: biological, bioinorganic, bioorganic and bioanalytical chemistries; drugs for diseases such as tuberculosis, Alzheimer’s diabetes and cancer; organic drugs and transition metal-based drugs; menaquinone, pyrazinamide, metformin, platinum and vanadium derivatives; lipid systems and micro-emulsion environments
Special Issues, Collections and Topics in MDPI journals
Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Circuito Exterior S/N, 15 C.P. 04510, Coyoacán, Ciudad de México, México
Interests: supramolecular chemistry; crystal engineering; medicinal chemistry; metallopharmaceuticals, green chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Ligands are at the core of both coordination and organometallic chemistry. They provide the proper environment, both steric and electronic, for metal centers to function either as a selective catalyst or as a highly efficient metallodrug—sometimes even by being part of the different processes where the whole complexes are involved, being not only spectators but assuming the non-innocent role of being a true protagonist in a given process. Thus, this Special Issue, although ultimately devoted to coordination and organometallic compounds and their applications, will cover both the design and participation of ligands in the performance of their corresponding complexes.

Prof. Dr. Debbie C. Crans
Prof. Dr. David Morales-Morales
Guest Editors

Manuscript Submission Information

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Keywords

  • design and synthesis of ligands
  • non-innocent ligands
  • privileged ligand platforms

Published Papers (7 papers)

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Research

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13 pages, 3692 KiB  
Article
Ferrocene-Bearing Homoleptic and Heteroleptic Paddlewheel-Type Dirhodium Complexes
Inorganics 2024, 12(2), 41; https://doi.org/10.3390/inorganics12020041 - 26 Jan 2024
Viewed by 586
Abstract
Two ferrocenecarboxylate (fca)-bridged dirhodium (Rh2) complexes, [Rh2(fca)4] (1) and [Rh2(fca)(piv)3] (2; piv = pivalate), were prepared through the carboxylate-exchange reactions of [Rh2(O2CCH3)4 [...] Read more.
Two ferrocenecarboxylate (fca)-bridged dirhodium (Rh2) complexes, [Rh2(fca)4] (1) and [Rh2(fca)(piv)3] (2; piv = pivalate), were prepared through the carboxylate-exchange reactions of [Rh2(O2CCH3)4(H2O)2] and [Rh2(piv)4], respectively, with fcaH and characterized by 1H NMR, ESI-TOF-MS, and elemental analyses. Single-crystal X-ray diffraction analyses of [Rh2(fca)4(MeOH)2] (1(MeOH)2) and [Rh2(fca)(piv)3(MeOH)2] (2(MeOH)2), which are recrystallized from MeOH-containing solutions of 1 and 2, revealed that (1) 1(MeOH)2 and 2(MeOH)2 possess homoleptic and heteroleptic paddlewheel-type dinuclear structures, respectively; (2) both complexes have a single Rh–Rh bond (2.3771(3) Å for 1(MeOH)2, 2.3712(3) Å for 2(MeOH)2); and (3) the cyclopentadienyl rings of the fca ligands in 1(MeOH)2 adopt an eclipsed conformation, whereas those in 2(MeOH)2 are approximately 12–14° rotated from the staggered conformation. Density functional theory (DFT) calculations revealed that (1) the electronic configurations of the Rh2 core in 1(MeOH)2 and 2(MeOH)2 are π4σ2δ2π*2δ*2π*2 and π4σ2δ2δ*2π*4, respectively; and (2) the occupied molecular orbitals (MOs) localized on the fca ligands are energetically degenerate and relatively more unstable than those on the Rh2 cores. Absorption features and electrochemical properties of 1 and 2 were investigated in a 9:1 CHCl3-MeOH solution and compared with those of fcaH and [Rh2(piv)4]. Through examining the obtained results in detail using time-dependent DFT (TDDFT) and unrestricted DFT, we found that 1 and 2 exhibit charge transfer excitations between the fca ligands and Rh2 cores, and 1 shows electronic interactions between ferrocene units through the Rh2 core in the electrochemical oxidation process. Full article
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23 pages, 5405 KiB  
Article
The Hexacoordinate Si Complex SiCl4(4-Azidopyridine)2—Crystallographic Characterization of Two Conformers and Probing the Influence of SiCl4-Complexation on a Click Reaction with Phenylacetylene
Inorganics 2023, 11(12), 473; https://doi.org/10.3390/inorganics11120473 - 05 Dec 2023
Viewed by 1100
Abstract
4-Azidopyridine (1) and SiCl4 react with the formation of the hexacoordinate silicon complex SiCl4(4-azidopyridine)2 (2). Upon dissolving in warm chloroform, the complex dissociates into the constituents 1 and SiCl4 and forms back upon cooling. [...] Read more.
4-Azidopyridine (1) and SiCl4 react with the formation of the hexacoordinate silicon complex SiCl4(4-azidopyridine)2 (2). Upon dissolving in warm chloroform, the complex dissociates into the constituents 1 and SiCl4 and forms back upon cooling. Depending on the cooling, two different crystalline modifications of 2 were obtained, which feature two different trans-conformers. Slow cooling to room temperature afforded conformer 2′, which features coplanar pyridine rings. Rapid cooling to −39 °C afforded crystals of conformer 2″, in which the planes of the pyridine ligands are nearly orthogonal to one another. Whereas 2′ resembles the molecular arrangement of various other known SiX4(pyridine)2 (X = halide) complexes, 2″ represents the first crystallographically confirmed example of a SiX4(pyridine)2 complex in this conformation. Conformers 2′ and 2″ were studied with 13C and 29Si solid state NMR spectroscopy. Their differences in 29Si chemical shift anisotropy, as well as energetic differences, were further investigated with computational analyses. In spite of the similar stabilities of the two conformers as isolated molecules, the crystal packing of 2″ is less stable, and its crystallization is interpreted as a kinetically controlled effect of seed formation. (3+2)-cycloaddition of 1 and phenylacetylene in toluene at 110 °C yields a mixture of 1-(4-pyridyl)-4-phenyl-1,2,3-triazole (1,4-3) and 1-(4-pyridyl)-5-phenyl-1,2,3-triazole (1,5-3) in approximate 1:2 molar ratio. The crystal structures of the two isomers were determined via X-ray diffraction. In chloroform (at 60 °C), this reaction is slow (less than 2% conversion within 4 h), but the presence of SiCl4 enhanced the rate of the reaction slightly, and it shifted the triazole isomer ratio to ca. 1:6 in favor of 1,5-3. Full article
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19 pages, 3395 KiB  
Article
Novel Sulfone 2-Aminobenzimidazole Derivatives and Their Coordination Compounds: Contribution of the Ethyl and Phenyl Substituents on Non-Covalent Molecular Interactions; Biological Antiproliferative Activity
Inorganics 2023, 11(10), 392; https://doi.org/10.3390/inorganics11100392 - 03 Oct 2023
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Abstract
New sulfone 2-aminobenzimidazole derivatives were designed and synthesized. Their nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II) compounds were obtained and fully characterized by spectroscopic and analytical techniques. Single crystal X-ray structural analysis was performed in order to study the relevant intra and inter non-covalent [...] Read more.
New sulfone 2-aminobenzimidazole derivatives were designed and synthesized. Their nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II) compounds were obtained and fully characterized by spectroscopic and analytical techniques. Single crystal X-ray structural analysis was performed in order to study the relevant intra and inter non-covalent interactions, mainly H···π, lone pair···π, and π···π, highlighting the difference between the terminal ethyl and phenyl groups in such interactions. Dimeric and trimeric supramolecular syntons were found for some of these compounds. Additionally, their antiproliferative activity was investigated, finding that the copper(II) compounds with the sulfone phenyl derivative were the most active. Full article
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10 pages, 1473 KiB  
Article
Coupling Pyrazine to Dithiocarbonates for Molybdopterin Model Ligands—Indispensable Tin
Inorganics 2023, 11(5), 188; https://doi.org/10.3390/inorganics11050188 - 26 Apr 2023
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Abstract
Several synthetic cross-coupling procedures were (re-)evaluated for the tethering of pyrazine to dithiocarbonates. The resultant species constitute pro-ligands and can be converted by removal of the C=O moiety into ene-dithiolate ligand systems that model molybdopterin. The coupling of 2-iodopyrazine with the stannylated dithiocarbonate [...] Read more.
Several synthetic cross-coupling procedures were (re-)evaluated for the tethering of pyrazine to dithiocarbonates. The resultant species constitute pro-ligands and can be converted by removal of the C=O moiety into ene-dithiolate ligand systems that model molybdopterin. The coupling of 2-iodopyrazine with the stannylated dithiocarbonate units mediated by copper(I)-thiophene-2-carboxylate in stoichiometric equivalents proved to be the most efficient and the only reliable route to the targeted compounds. Single-crystal X-ray structural analysis confirmed the final structures of two pursued pyrazine-derived dithiocarbonates and those of two intermediates. Full article
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21 pages, 4535 KiB  
Article
Structural, Spectroscopic, and Thermal Decomposition Features of [Carbonatotetraamminecobalt(III)] Iodide—Insight into the Simultaneous Solid-Phase Quasi-Intramolecular Redox Reactions
Inorganics 2023, 11(2), 68; https://doi.org/10.3390/inorganics11020068 - 01 Feb 2023
Cited by 2 | Viewed by 2059
Abstract
2-O,O′-Carbonatotetraamminecobalt(III)] iodide, or [Co(NH3)4CO3]I, named in this paper as compound 1, was prepared and characterized comprehensively with spectroscopic (IR, Raman and UV) and single-crystal X-ray diffraction methods. Compound 1 was orthorhombic, and isomorphous with the [...] Read more.
2-O,O′-Carbonatotetraamminecobalt(III)] iodide, or [Co(NH3)4CO3]I, named in this paper as compound 1, was prepared and characterized comprehensively with spectroscopic (IR, Raman and UV) and single-crystal X-ray diffraction methods. Compound 1 was orthorhombic, and isomorphous with the analogous bromide. The four ammonia ligands and the carbonate anion were coordinated to the central cobalt cation in a distorted octahedral geometry. The carbonate ion formed a four-membered symmetric planar chelate ring. The complex cations were bound to each other by N-H···O hydrogen bonds and formed zigzag sheets via an extended 2D hydrogen bond network. The complex cations and iodide ions were arranged into ion pairs and each cation bound its iodide pair through three hydrogen bonds. The thermal decomposition started with the oxidation of the iodide ion by CoIII in the solid phase resulting in [Co(NH3)4CO3] and I2. This intermediate CoII-complex in situ decomposed into Co3O4 and C-N bond containing intermediates. In inert atmosphere, CO or C-N bond containing compounds, and also, due to the in situ decomposition of CoCO3 intermediate, Co3O4 was formed. The quasi-intramolecular solid-phase redox reaction of [Co(NH3)4CO3] might have resulted in the formation of C-N bond containing compounds with substoichiometric release of ammonia and CO2 from compound 1. The C-N bond containing intermediates reduced Co3O4 into CoO and Co, whereas in oxygen-containing atmosphere, the end-product was Co3O4, even at 200 °C, and the endothermic ligand loss reaction coincided with the consecutive exothermic oxidation processes. Full article
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Review

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29 pages, 9236 KiB  
Review
Exploring the Use of Intracellular Chelation and Non-Iron Metals to Program Ferroptosis for Anticancer Application
Inorganics 2024, 12(1), 26; https://doi.org/10.3390/inorganics12010026 - 08 Jan 2024
Viewed by 1219
Abstract
The discovery of regulated cell death (RCD) revolutionized chemotherapy. With caspase-dependent apoptosis initially being thought to be the only form of RCD, many drug development strategies aimed to synthesize compounds that turn on this kind of cell death. While yielding a variety of [...] Read more.
The discovery of regulated cell death (RCD) revolutionized chemotherapy. With caspase-dependent apoptosis initially being thought to be the only form of RCD, many drug development strategies aimed to synthesize compounds that turn on this kind of cell death. While yielding a variety of drugs, this approach is limited, given the acquired resistance of cancers to these drugs and the lack of specificity of the drugs for targeting cancer cells alone. The discovery of non-apoptotic forms of RCD is leading to new avenues for drug design. Evidence shows that ferroptosis, a relatively recently discovered iron-based cell death pathway, has therapeutic potential for anticancer application. Recent studies point to the interrelationship between iron and other essential metals, copper and zinc, and the disturbance of their respective homeostasis as critical to the onset of ferroptosis. Other studies reveal that several coordination complexes of non-iron metals have the capacity to induce ferroptosis. This collective knowledge will be assessed to determine how chelation approaches and coordination chemistry can be engineered to program ferroptosis in chemotherapy. Full article
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31 pages, 6582 KiB  
Review
Copper-Coordinated Thiazoles and Benzothiazoles: A Perfect Alliance in the Search for Compounds with Antibacterial and Antifungal Activity
Inorganics 2023, 11(5), 185; https://doi.org/10.3390/inorganics11050185 - 25 Apr 2023
Cited by 2 | Viewed by 2078
Abstract
Throughout human history, bacteria and fungi have caused infections that are difficult to combat. For this reason, countless research groups have developed novel compounds to solve this problem. Thiazole and benzothiazole are present in different structures with interesting biological effects and are used [...] Read more.
Throughout human history, bacteria and fungi have caused infections that are difficult to combat. For this reason, countless research groups have developed novel compounds to solve this problem. Thiazole and benzothiazole are present in different structures with interesting biological effects and are used to develop new effective antimicrobial agents. Moreover, nitrogen atoms that are present in this heterocycle allow for coordination with various metals, forming metal complexes that enhance the biological activity of organic ligands that are often used as commercial drugs. This bibliographical review summarizes the copper complexes that use thiazole and benzothiazole as ligands and that report efficient antimicrobial activity against different bacteria and fungi. Full article
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