Advances on Coordination Chemistry with Nitrogen Ligands and Its Applications

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Chemical and Molecular Sciences".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 17450

Special Issue Editors


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Guest Editor
Department of Chemistry and Pharmacy, University of Sassari, I-07100 Sassari, Italy
Interests: electroanalysis; electrochemical sensors and biosensors; voltammetry; conducting polymers; substituted thiophenes; transition metal ions complexes; nitrogen ligands; polyphenolic compounds; photocatalysis; photoresponsive devices; analytical chemistry; validation of analytical methods; food chemistry and analysis
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Guest Editor
Department of Chemistry and Pharmacy, University of Sassari, 07100 Sassari, Italy
Interests: organometallic and coordination chemistry of noble metals with nitrogen ligands; metal-mediated C-H bond activation; cyclometalation reaction; reactivity of metal-carbon bonds; reactivity and properties of inorganic and organometallic complexes of noble metals with nitrogen ligands, including organic synthesis, catalytic and biological activity, applications as innovative materials

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Guest Editor
Faculty of Chemistry, University of Wrocław, Wrocław, Poland
Interests: coordination and supramolecular chemistry - structure, reactivity; catalysis in aqueous (aqueous/organic) media, photocatalysis; crystal engineering for synthesis and characterization of MOF’s and CP’s; luminescent properties; reversible sensors; antiviral, antimicrobial and antitumor properties; synthesis a new water-soluble ligands

Special Issue Information

Dear Colleagues,

Nitrogen ligands play a key role in several fields of Coordination Chemistry, namely catalysis, materials, C-H bond activation, organometallic chemistry, medicinal chemistry, electrochemistry, bioinorganic chemistry, photochemistry, energy, etc. Fundamental and advanced chemistry, as well as theoretical aspects, of coordination compounds with mono- and polydentate N-ligands have always been subjects of large interest in the scientific community. Among the most cited classes of nitrogen ligands we mention substituted and unsubstituted heterocycles (pyridine and poly-pyridines, pyrazole, pyrimidine, imidazole, phenanthroline, quinoline, triazole, etc.), as well as macrocycles and tridimensional structures. Mono- and polynuclear metal species have attracted also great attention.

The aim of this Special Issue is to attract researchers, involved in the wide field of coordination chemistry with nitrogen ligands, in reporting their studies and interests in this topic, including the large variety of aspects ranging from synthetic approach and characterization techniques to possible applications.

Prof. Dr. Maria I. Pilo
Prof. Dr. Antonio Zucca
Prof. Dr. Piotr Smolenski
Guest Editors

Manuscript Submission Information

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Keywords

  • Coordination compounds
  • Organometallic complexes
  • Spectroscopic characterization
  • Photochemistry
  • Homogeneous catalysis
  • Heterogeneous catalysis
  • Electrochemistry
  • Sensors
  • Biological activity
  • Synthesis
  • Monodentate ligands
  • Polydentate ligands
  • Mononuclear complexes
  • Polynuclear complexes
  • N-donor ligands
  • Substituted N-ligands
  • Polypyridines

Published Papers (5 papers)

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Research

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12 pages, 1792 KiB  
Article
Ru(terpy)-Based Conducting Polymer in Electrochemical Biosensing of Epinephrine
by Francesca Meloni, Maria I. Pilo, Gavino Sanna, Nadia Spano and Antonio Zucca
Appl. Sci. 2021, 11(5), 2065; https://doi.org/10.3390/app11052065 - 26 Feb 2021
Cited by 4 | Viewed by 1458
Abstract
A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically polymerized to give the corresponding metal-containing conducting polymer on gold and glassy carbon electrodes. The polymerization of the Ru(II) complex was allowed by a terthiophene functionalization on one of the two [...] Read more.
A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically polymerized to give the corresponding metal-containing conducting polymer on gold and glassy carbon electrodes. The polymerization of the Ru(II) complex was allowed by a terthiophene functionalization on one of the two terpy coordinating fragments, whereas the presence of -COOH substituents on the second terpy ligand enabled the film to immobilize a tyrosinase enzyme by cross-linking with glutaraldehyde. Then, the Ru(terpy) conducting polymer worked as a transducer as well as an immobilizing agent in the design of amperometric biosensors for the determination of epinephrine. The electrochemical behavior of enzymatic sensors containing Ru(terpy)-based conducting polymers was investigated by differential pulse voltammetry and chronoamperometry. Analytical performances and kinetic parameters were calculated, suggesting a potential application of the reported biosensors in the determination of epinephrine in pharmaceutical products. Full article
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15 pages, 2387 KiB  
Article
Hydroxyl Radical Generation by the H2O2/CuII/Phenanthroline System under Both Neutral and Alkaline Conditions: An EPR/Spin-Trapping Investigation
by Elsa Walger, Nathalie Marlin, Gérard Mortha, Florian Molton and Carole Duboc
Appl. Sci. 2021, 11(2), 687; https://doi.org/10.3390/app11020687 - 12 Jan 2021
Cited by 16 | Viewed by 5607
Abstract
The copper–phenanthroline complex CuI(Phen)2 was the first artificial nuclease studied in biology. The mechanism responsible for this activity involves CuII(Phen)2 and H2O2. Even if H2O2/Cu systems have been extensively [...] Read more.
The copper–phenanthroline complex CuI(Phen)2 was the first artificial nuclease studied in biology. The mechanism responsible for this activity involves CuII(Phen)2 and H2O2. Even if H2O2/Cu systems have been extensively studied in biology and oxidative chemistry, most of these studies were carried out at physiological pH only, and little information is available on the generation of radicals by the H2O2/CuII-Phen system. In the context of paper pulp bleaching to improve the bleaching ability of H2O2, this system has been investigated, mostly at alkaline pH, and more recently at near-neutral pH in the case of dyed cellulosic fibers. Hence, this paper aims at studying the production of radicals with the H2O2/CuII-Phen system at near-neutral and alkaline pHs. Using the EPR/spin-trapping method, HO formation was monitored to understand the mechanisms involved. DMPO was used as a spin-trap to form DMPO–OH in the presence of HO, and two HO scavengers were compared to identify the origin of the observed DMPO–OH adduct, as nucleophilic addition of water onto DMPO leads to the same adduct. H2O2 decomposition was enhanced by the addition of CuII–Phen (and only slightly by addition of CuSO4), reaching a level similar to the Fenton reagent at near-neutral pH. This evidences the role of Phen, which improves the effect of CuII by tuning the electronic structure and structural properties of the corresponding CuII complexes. Full article
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25 pages, 8787 KiB  
Article
Pt(II) Derivatives with Rollover-Coordinated 6-substituted 2,2′-bipyridines: Ligands with Multiple Personalities
by Antonio Zucca, Luca Maidich, Maria I. Pilo, Sara Pischedda, Mondina Sedda and Sergio Stoccoro
Appl. Sci. 2020, 10(19), 6665; https://doi.org/10.3390/app10196665 - 23 Sep 2020
Cited by 3 | Viewed by 2405
Abstract
We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated rollover complexes with two substituted bipyridines, 6-ethyl-2,2′-bipyridine (bpy6Et) and 6-methoxy-2,2′-bipyridine (bpy6OMe), in comparison with previously studied 2,2′-bipyridine complexes. The two ligands have similar steric hindrance [...] Read more.
We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated rollover complexes with two substituted bipyridines, 6-ethyl-2,2′-bipyridine (bpy6Et) and 6-methoxy-2,2′-bipyridine (bpy6OMe), in comparison with previously studied 2,2′-bipyridine complexes. The two ligands have similar steric hindrance but different electronic properties. As a result, the reactivity of the two series of complexes follows very different routes. In particular, the new complexes behave differently towards protonation reactions, differences given by substituents and ancillary ligands, added to the presence of several nucleophilic centers. Reaction of complex [Pt(bpy6OMe-H)(PPh3)Me)] with [H3O⋅18-crown-6][BF4] results in a retro-rollover reaction whose final product is the cationic adduct [Pt(bpy6OMe)(PPh3)Me)]+. Surprisingly, only the isomer with the cis-PPh3-OMe geometry is formed; in spite of an expected instability due to steric hindrance, Density-Functional theory (DFT) calculations showed that this isomer is the most stable. This result shows that the cone angle is far from being a real “solid cone” and should lead to a different interpretation of well-known concepts concerning steric bulk of ligands, such as cone angle. Proton affinity values of ligands, neutral complexes and their protonated counterparts were analyzed by means of DFT calculations, allowing a comparison of their properties. Full article
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19 pages, 4415 KiB  
Article
Synthesis, Structures, Electrochemistry, and Catalytic Activity towards Cyclohexanol Oxidation of Mono-, Di-, and Polynuclear Iron(III) Complexes with 3-Amino-2-Pyrazinecarboxylate
by Anirban Karmakar, Luísa M.D.R.S. Martins, Yuliya Yahorava, M. Fátima C. Guedes da Silva and Armando J. L. Pombeiro
Appl. Sci. 2020, 10(8), 2692; https://doi.org/10.3390/app10082692 - 13 Apr 2020
Cited by 3 | Viewed by 3164
Abstract
The synthesis and characterization of a set of iron(III) complexes, viz. the mononuclear [Fe(L)3] (1) and [NHEt3][Fe(L)2(Cl)2] (2), the dinuclear methoxido-bridged [Fe(L)2(μ-OMe)]2.DMF.1.5MeOH (3), and the [...] Read more.
The synthesis and characterization of a set of iron(III) complexes, viz. the mononuclear [Fe(L)3] (1) and [NHEt3][Fe(L)2(Cl)2] (2), the dinuclear methoxido-bridged [Fe(L)2(μ-OMe)]2.DMF.1.5MeOH (3), and the heteronuclear Fe(III)/Na(I) two-dimensional coordination polymer [Fe(N3)(μ-L)2(μ-O)1/2(Na)(μ-H2O)1/2]n (4), are reported. Reactions of 3-amino-2-pyrazinecarboxylic acid (HL) with iron(III) chloride under different reaction conditions were studied, and the obtained compounds were characterized by elemental analysis, Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray single-crystal diffraction. Compound 1 is a neutral mononuclear complex, whereas 2 is mono-anionic with its charge being neutralized by triethylammonium cation. Compounds 3 and 4 display a di-methoxido-bridged dinuclear complex and a two-dimensional heterometallic Fe(III)/Na(I) polynuclear coordination polymer, respectively. Compounds 3 and 4 are the first examples of methoxido- and oxido-bridged iron(III) complexes, respectively, with 3-amino-2-pyrazinecarboxylate ligands. The electrochemical study of these compounds reveals a facile single-electron reversible Fe(III)-to-Fe(II) reduction at a positive potential of 0.08V vs. saturated calomel electrode (SCE), which is in line with their ability to act as efficient oxidants and heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation (with tert-butyl hydroperoxide) of cyclohexanol to cyclohexanone (almost quantitative yields after 1 h). Moreover, the catalysts are easily recovered and reused for five consecutive cycles, maintaining a high activity and selectivity. Full article
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Review

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22 pages, 21376 KiB  
Review
Ru(II)-Dppz Derivatives and Their Interactions with DNA: Thirty Years and Counting
by Maria Letizia Di Pietro, Giuseppina La Ganga, Francesco Nastasi and Fausto Puntoriero
Appl. Sci. 2021, 11(7), 3038; https://doi.org/10.3390/app11073038 - 29 Mar 2021
Cited by 10 | Viewed by 3887
Abstract
Transition metal complexes with dppz-type ligands (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) are extensively studied and attract a considerable amount of attention, becoming, from the very beginning and increasingly over time, a powerful tool for investigating the structure of the DNA helix. In particular, [Ru(bpy)2 [...] Read more.
Transition metal complexes with dppz-type ligands (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) are extensively studied and attract a considerable amount of attention, becoming, from the very beginning and increasingly over time, a powerful tool for investigating the structure of the DNA helix. In particular, [Ru(bpy)2(dppz)]2+ and [Ru(phen)2(dppz)]2+ and their derivatives were extensively investigated as DNA light-switches. The purpose of this mini-review, which is not and could not be exhaustive, was to first introduce DNA and its importance at a biological level and research in the field of small molecules that are capable of interacting with it, in all its forms. A brief overview is given of the results obtained on the Ru-dppz complexes that bind to DNA. The mechanism of the light-switch active in this type of species is also briefly introduced along with its effects on structural modifications on both the dppz ligand and the ancillary ligands. Finally, a brief mention is made of biological applications and the developments obtained due to new spectroscopic techniques, both for understanding the mechanism of action and for cellular imaging applications. Full article
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