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Special Issue "Scorpionate Ligands: Ever-Young Chemistry Tools"

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

Deadline for manuscript submissions: closed (31 May 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Carlo Santini

School of Science and Technology, Chemistry Division, University of Camerino, via Sant’Agostino 1, 62032 Camerino (MC), Italy
Website | E-Mail
Interests: metal-based drugs; coordination chemistry; functional metal complexes; hybrid materials; inorganic and organometallic chemistry; scorpionate ligands; phosphanes; N-heterocyclic carbenes
Guest Editor
Prof. Dr. Maura Pellei

School of Science and Technology, Chemistry Division, University of Camerino, via Sant’Agostino 1, 62032 Camerino (MC), Italy
Website | E-Mail
Phone: 0737402213
Interests: metal-based drugs; bioinorganic chemistry; coordination chemistry; inorganic materials; organometalllic chemistry; copper; scorpionate ligands; phosphanes N-heterocyclic carbenes

Special Issue Information

Dear Colleagues,

Since the introduction of tris(pyrazolyl)borates by Trofimenko, in the 1960s, in a pivotal paper on “Boron-Pyrazole Chemistry”, scorpionate ligands are some of the most widely-used ligands in chemistry. They readily coordinate a wide variety of metal ions, affording stable metal complexes: the term scorpionate derives from the interchange between their bi- and tri-dentate coordination modes. In the last 50 years, the success of poly(azolyl)borates has inspired the development of a new generation Scorpionates, including the analogous poly(azolyl)alkanes, which are excellent supporting ligands for most metals of the Periodic Table. Even if this shows that, in this field, a great deal of research has been done, Scorpionates chemistry and their applications have not been fully explored yet.

The purpose of this Special Issue is to present the latest advances in the field of scorpionate ligands, highlighting their stimulating and innovative applications in coordination chemistry, organometallics, catalysis, supramolecular assembly, materials science, medicinal inorganic chemistry or enzymes modeling.

Prof. Dr. Carlo Santini
Prof. Dr. Maura Pellei
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • poly(azolyl)borates
  • poly(azolyl)alkanes
  • coordination chemistry
  • metals
  • complexes
  • organometallics
  • catalysis
  • medicinal inorganic chemistry

Published Papers (4 papers)

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Research

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Open AccessArticle Novel Methinic Functionalized and Dendritic C-Scorpionates
Molecules 2018, 23(12), 3066; https://doi.org/10.3390/molecules23123066
Received: 24 September 2018 / Revised: 16 November 2018 / Accepted: 18 November 2018 / Published: 23 November 2018
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Abstract
The study of chelating ligands is undoubtedly one of the most significant fields of research in chemistry. The present work is directed to the synthesis of new functionalized derivatives of tripodal C-scorpionate compounds. Tris-2,2,2-(1-pyrazolyl)ethanol, HOCH2C(pz)3 (1), one of
[...] Read more.
The study of chelating ligands is undoubtedly one of the most significant fields of research in chemistry. The present work is directed to the synthesis of new functionalized derivatives of tripodal C-scorpionate compounds. Tris-2,2,2-(1-pyrazolyl)ethanol, HOCH2C(pz)3 (1), one of the most important derivatives of hydrotris(pyrazolyl)methane, was used as a building block for the synthesis of new functionalized C-scorpionates, aiming to expand the scope of this unexplored class of compounds. The first dendritic C-scorpionate was successfully prepared and used in the important industrial catalytic reactions, Sonogashira and Heck C-C cross-couplings. Full article
(This article belongs to the Special Issue Scorpionate Ligands: Ever-Young Chemistry Tools)
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Graphical abstract

Open AccessArticle New Coordination Complexes Based on the 2,6-bis[1-(Phenylimino)ethyl] Pyridine Ligand: Effective Catalysts for the Synthesis of Propylene Carbonates from Carbon Dioxide and Epoxides
Molecules 2018, 23(9), 2304; https://doi.org/10.3390/molecules23092304
Received: 12 July 2018 / Revised: 21 August 2018 / Accepted: 30 August 2018 / Published: 10 September 2018
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Abstract
We aimed to develop new effective catalysts for the synthesis of propylene carbonate from propylene oxide and carbon dioxide. A kind of Mx+LClx coordination complex was fabricated based on the chelating tridentate ligand 2,6-bis[1-(phenylimino)ethyl] pyridine (L). The
[...] Read more.
We aimed to develop new effective catalysts for the synthesis of propylene carbonate from propylene oxide and carbon dioxide. A kind of Mx+LClx coordination complex was fabricated based on the chelating tridentate ligand 2,6-bis[1-(phenylimino)ethyl] pyridine (L). The obtained products were characterized by elemental analysis, infrared spectroscopy, ultraviolet spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. It was found that the catalytic activity of the complexes with different metal ions, the same ligand differed and co-catalyst, where the order of greatest to least catalytic activity was 2 > 3 > 1. The catalytic system composed of complex 2 and DMAP proved to have the better catalytic performance. The yields for complex 2 systems was 86.7% under the reaction conditions of 100 °C, 2.5 MPa, and 4 h. The TOF was 1026 h1 under the reaction conditions of 200 °C, 2.5 MPa, and 1 h. We also explored the influence of time, pressure, temperature, and reaction substrate concentration on the catalytic reactions. A hypothetical catalytic reaction mechanism is proposed based on density functional theory (DFT) calculations and the catalytic reaction results. Full article
(This article belongs to the Special Issue Scorpionate Ligands: Ever-Young Chemistry Tools)
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Open AccessArticle Cobalt(II) Complexes with N,N,N-Scorpionates and Bidentate Ligands: Comparison of Hydrotris(3,5-dimethylpyrazol-1-yl)borate Tp* vs. Phenyltris(4,4-dimethyloxazolin-2-yl)borate ToM to Control the Structural Properties and Reactivities of Cobalt Centers
Molecules 2018, 23(6), 1466; https://doi.org/10.3390/molecules23061466
Received: 25 May 2018 / Revised: 13 June 2018 / Accepted: 15 June 2018 / Published: 16 June 2018
Cited by 1 | PDF Full-text (4437 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Scorpionate ligands Tp* (hydrotris(3,5-dimethylpyrazol-1-yl)borate) and ToM (tris(4,4-dimethyloxazolin-2-yl)phenylborate) complexes of cobalt(II) with bidentate ligands were synthesized. Both Tp* and ToM coordinate to cobalt(II) in a tridentate fashion when the bidentate ligand is the less hindered acetylacetonate. In crystal structures, the geometry of
[...] Read more.
Scorpionate ligands Tp* (hydrotris(3,5-dimethylpyrazol-1-yl)borate) and ToM (tris(4,4-dimethyloxazolin-2-yl)phenylborate) complexes of cobalt(II) with bidentate ligands were synthesized. Both Tp* and ToM coordinate to cobalt(II) in a tridentate fashion when the bidentate ligand is the less hindered acetylacetonate. In crystal structures, the geometry of cobalt(II) supported by the N3O2 donor set in the Tp* complex is a square-pyramid, whereas that in the ToM complex is close to a trigonal-bipyramid. Both Tp*- and ToM-acac complexes exhibit solvatochromic behavior, although the changing structural equilibria of these complexes in MeCN are quite different. In the bis(1-methylimidazol-2-yl)methylphenylborate (LPh) complexes, Tp* retains the tridentate (к3) mode, whereas ToM functions as the bidentate (к2) ligand, giving the tetrahedral cobalt(II) complex. The bowl-shaped cavity derived from the six methyl groups on ToM lead to susceptibility to the bulkiness of the opposite bidentate ligand. The entitled scorpionate compounds mediate hydrocarbon oxidation with organic peroxides. Allylic oxidation of cyclohexene occurs mainly on the reaction with tert-butyl hydroperoxide (TBHP), although the catalytic efficiency of the scorpionate ligand complexes is lower than that of Co(OAc)2 and Co(acac)2. On cyclohexane oxidation with meta-chloroperbenzoic acid (mCPBA), both ToM and Tp* complexes function as catalysts for hydroxylation. The higher electron-donating ToM complexes show faster initial reaction rates compared to the corresponding Tp* complexes. Full article
(This article belongs to the Special Issue Scorpionate Ligands: Ever-Young Chemistry Tools)
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Review

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Open AccessReview Technetium Complexes and Radiopharmaceuticals with Scorpionate Ligands
Molecules 2018, 23(8), 2039; https://doi.org/10.3390/molecules23082039
Received: 2 August 2018 / Revised: 9 August 2018 / Accepted: 14 August 2018 / Published: 15 August 2018
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Abstract
Scorpionate ligands have played a crucial role in the development of technetium chemistry and, recently, they have also fueled important advancements in the discovery of novel diagnostic imaging agents based on the γ-emitting radionuclide technetium-99m. The purpose of this short review is to
[...] Read more.
Scorpionate ligands have played a crucial role in the development of technetium chemistry and, recently, they have also fueled important advancements in the discovery of novel diagnostic imaging agents based on the γ-emitting radionuclide technetium-99m. The purpose of this short review is to provide an illustration of the most general and relevant results in this field, however without being concerned with the details of the analytical features of the various compounds. Thus, emphasis will be given to the description of the general features of technetium complexes with scorpionate ligands including coordination modes, structural properties and an elementary bonding description. Similarly, the most relevant examples of technetium-99m radiopharmaceuticals derived from scorpionate ligands and their potential interest for nuclear imaging will be summarized. Full article
(This article belongs to the Special Issue Scorpionate Ligands: Ever-Young Chemistry Tools)
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