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Special Issue "Bipyridines: Synthesis, Functionalization and Applications"

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

Deadline for manuscript submissions: closed (15 November 2019).

Special Issue Editor

Dr. Victor Mamane
Website
Guest Editor
Institute of Chemistry (UMR 7177), University of Strasbourg, 1 Rue Blaise Pascal, 67000 Strasbourg, France
Interests: organic chemistry; atropisomery; chirality; halogen and chalcogen bonds; 4,4’-bipyridine; enantioseparations; functionalization of carbon nanotubes

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to all aspects of bipyridine chemistry. Bipyridines represent the important family of heterocycles, having two pyridines directly linked together giving either symmetrical isomers (2,2′, 3,3′, and 4,4′) or asymmetrical ones (2,3′, 2,4′, and 3,4′). These compounds, especially the 2,2’ and 4,4’ isomers, are known as excellent ligands in coordination chemistry, with an impact in many fields including catalysis and material chemistry. Besides coordination to metals, the nitrogen atoms of bipyridines are able to interact with different molecules through non-covalent interactions (hydrogen or halogen bonds), leading to supramolecular structures with interesting properties. Another important aspect of bipyridine chemistry is the possibility of introducing chirality through ring functionalization or restricted rotation (atropisomery), thus increasing their importance in asymmetry-based applications. Finally, with regard to 4,4’-bipyridines, the quaternization of nitrogens generates viologens, which are known for their good electrochemical properties.

This Special Issue welcomes the submission of papers based on original research, or reviews that describe the synthesis of functionalized bipyridines and their applications, ranging from novel synthetic transformations to the design and development of new materials.

Dr. Victor Mamane
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 semimonthly 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 2000 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

  • Atropisomery
  • Chirality
  • Catalysis
  • Coordination chemistry
  • Coordination polymers and MOFs
  • Ligand design
  • Non-covalent interactions
  • Synthetic methods
  • Viologens

Published Papers (9 papers)

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Research

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Open AccessArticle
Synthesis, Structural, and Cytotoxic Properties of New Water-Soluble Copper(II) Complexes Based on 2,9-Dimethyl-1,10-Phenanthroline and Their One Derivative Containing 1,3,5-Triaza-7-Phosphaadamantane-7-Oxide
Molecules 2020, 25(3), 741; https://doi.org/10.3390/molecules25030741 - 08 Feb 2020
Abstract
A series of water-soluble copper(II) complexes based on 2,9-dimethyl-1,10-phenanthroline (dmphen) and mixed-ligands, containing PTA=O (1,3,5-triaza-7-phosphaadamantane-7-oxide) have been synthesized and fully characterized. Two types of complexes have been obtained, monocationic [Cu(NO3)(O-PTA=O)(dmphen)][PF6] (1), [Cu(Cl)(dmphen)2][PF6] ( [...] Read more.
A series of water-soluble copper(II) complexes based on 2,9-dimethyl-1,10-phenanthroline (dmphen) and mixed-ligands, containing PTA=O (1,3,5-triaza-7-phosphaadamantane-7-oxide) have been synthesized and fully characterized. Two types of complexes have been obtained, monocationic [Cu(NO3)(O-PTA=O)(dmphen)][PF6] (1), [Cu(Cl)(dmphen)2][PF6] (2), and neutral [Cu(NO3)2(dmphen)] (3). The solid-state structures of all complexes have been determined by single-crystal X-ray diffraction. Magnetic studies for the complex 13 indicated a very weak antiferromagnetic interaction between copper(II) ions in crystal lattice. Complexes were successfully evaluated for their cytotoxic activities on the normal human dermal fibroblast (NHDF) cell line and the antitumor activity using the human lung carcinoma (A549), epithelioid cervix carcinoma (HeLa), colon (LoVo), and breast adenocarcinoma (MCF-7) cell lines. Complexes 1 and 3 revealed lower toxicity to NHDF than A549 and HeLa cells, meanwhile compound 2 appeared to be more toxic to NHDF cell line in comparison to all cancer lines. Additionally, interactions between the complexes and human apo-transferrin (apo-Tf) using fluorescence and circular dichroism (CD) spectroscopy were also investigated. All compounds interacted with apo-transferrin, causing same changes of the protein conformation. Electrostatic interactions dominate in the 1/2 – apo- Tf systems and hydrophobic and ionic interactions in the case of 3. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessFeature PaperArticle
Coordination Chemistry of Ru(II) Complexes of an Asymmetric Bipyridine Analogue: Synergistic Effects of Supporting Ligand and Coordination Geometry on Reactivities
Molecules 2020, 25(1), 27; https://doi.org/10.3390/molecules25010027 - 19 Dec 2019
Abstract
The reactivities of transition metal coordination compounds are often controlled by the environment around the coordination sphere. For ruthenium(II) complexes, differences in polypyridyl supporting ligands affect some types of reactivity despite identical coordination geometries. To evaluate the synergistic effects of (i) the supporting [...] Read more.
The reactivities of transition metal coordination compounds are often controlled by the environment around the coordination sphere. For ruthenium(II) complexes, differences in polypyridyl supporting ligands affect some types of reactivity despite identical coordination geometries. To evaluate the synergistic effects of (i) the supporting ligands, and (ii) the coordination geometry, a series of dicarbonyl–ruthenium(II) complexes that contain both asymmetric and symmetric bidentate polypyridyl ligands were synthesized. Molecular structures of the complexes were determined by X-ray crystallography to distinguish their steric configuration. Structural, computational, and electrochemical analysis revealed some differences between the isomers. Photo- and thermal reactions indicated that the reactivities of the complexes were significantly affected by both their structures and the ligands involved. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessArticle
Chiral Chalcogen Bond Donors Based on the 4,4′-Bipyridine Scaffold
Molecules 2019, 24(24), 4484; https://doi.org/10.3390/molecules24244484 - 06 Dec 2019
Cited by 3
Abstract
Organocatalysis through chalcogen bonding (ChB) is in its infancy, as its proof-of-principle was only reported in 2016. Herein, we report the design and synthesis of new chiral ChB donors, as well as the catalytic activity evaluation of the 5,5′-dibromo-2,2′-dichloro-3-((perfluorophenyl)selanyl)-4,4′-bipyridine as organocatalyst. The latter [...] Read more.
Organocatalysis through chalcogen bonding (ChB) is in its infancy, as its proof-of-principle was only reported in 2016. Herein, we report the design and synthesis of new chiral ChB donors, as well as the catalytic activity evaluation of the 5,5′-dibromo-2,2′-dichloro-3-((perfluorophenyl)selanyl)-4,4′-bipyridine as organocatalyst. The latter is based on the use of two electron-withdrawing groups, a pentafluorophenyl ring and a tetrahalo-4,4′-bipyridine skeleton, as substituents at the selenium center. Atropisomery of the tetrahalo-4,4′-bipyridine motif provides a chiral environment to these new ChB donors. Their synthesis was achieved through either selective lithium exchange and trapping or a site-selective copper-mediated reaction. Pure enantiomers of the 3-selanyl-4,4′-bipyridine were obtained by high performance liquid chromatography enantioseparation on specific chiral stationary phase, and their absolute configuration was assigned by comparison of the measured and calculated electronic circular dichroism spectra. The capability of the selenium compound to participate in σ-hole-based interactions in solution was studied by 19F NMR. Even if no asymmetric induction has been observed so far, the new selenium motif proved to be catalytically active in the reduction of 2-phenylquinoline by Hantzsch ester. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessFeature PaperArticle
Towards Covalent Photosensitizer-Polyoxometalate Dyads-Bipyridyl-Functionalized Polyoxometalates and Their Transition Metal Complexes
Molecules 2019, 24(24), 4446; https://doi.org/10.3390/molecules24244446 - 04 Dec 2019
Abstract
A triol-functionalized 2,2′-bipyridine (bpy) derivative has been synthesized and used for the tris-alkoxylation of polyoxometalate (POM) precursors. The resultant POM-bpy conjugates of the Wells–Dawson- and Anderson-type feature a C–C bond as a linkage between the POM and bpy fragments. This structural motif is [...] Read more.
A triol-functionalized 2,2′-bipyridine (bpy) derivative has been synthesized and used for the tris-alkoxylation of polyoxometalate (POM) precursors. The resultant POM-bpy conjugates of the Wells–Dawson- and Anderson-type feature a C–C bond as a linkage between the POM and bpy fragments. This structural motif is expected to increase the hydrolytic stability of the compounds. This is of particular relevance with respect to the application of POM-bpy metal complexes, as photocatalysts, in the hydrogen-evolution reaction (HER) in an aqueous environment. Accordingly, Rh(III) and Ir(III) complexes of the POM-bpy ligands have been prepared and characterized. These catalyst-photosensitizer dyads have been analyzed with respect to their electrochemical and photophysical properties. Cyclic and square-wave voltammetry, as well as UV/vis absorption and emission spectroscopy, indicated a negligible electronic interaction of the POM and metal-complex subunits in the ground state. However, emission–quenching experiments suggested an efficient intramolecular electron-transfer process from the photo-excited metal centers to the POM units to account for the non-emissive nature of the dyads (thus, suggesting a strong interaction of the subunits in the excited state). In-depth photophysical investigations, as well as a functional characterization, i.e., the applicability in the HER reaction, are currently ongoing. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessArticle
A Novel Ruthenium(II) Polypyridyl Complex Bearing 1,8-Naphthyridine as a High Selectivity and Sensitivity Fluorescent Chemosensor for Cu2+ and Fe3+ Ions
Molecules 2019, 24(22), 4032; https://doi.org/10.3390/molecules24224032 - 07 Nov 2019
Abstract
A novel ruthenium(II) polypyridyl complex bearing 1,8-naphthyridine was successfully designed and synthesized. This complex was fully characterized by EI-HRMS, NMR, and elemental analyses. The recognition properties of the complex for various metal ions were investigated. The results suggested that the complex displayed high [...] Read more.
A novel ruthenium(II) polypyridyl complex bearing 1,8-naphthyridine was successfully designed and synthesized. This complex was fully characterized by EI-HRMS, NMR, and elemental analyses. The recognition properties of the complex for various metal ions were investigated. The results suggested that the complex displayed high selectivity and sensitivity for Cu2+ and Fe3+ ions with good anti-interference in the CH3CN/H2O (1:1, v/v) solution. The fluorescent chemosensor showed obvious fluorescence quenching when the Cu2+ and Fe3+ ions were added. The detection limits of Cu2+ and Fe3+ were 39.9 nmol/L and 6.68 nmol/L, respectively. This study suggested that this Ru(II) polypyridyl complex can be used as a high selectivity and sensitivity fluorescent chemosensor for Cu2+ and Fe3+ ions. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessFeature PaperArticle
Hinged and Wide: A New P^P Ligand for Emissive [Cu(P^P)(N^N)][PF6] Complexes
Molecules 2019, 24(21), 3934; https://doi.org/10.3390/molecules24213934 - 31 Oct 2019
Cited by 1
Abstract
Heteroleptic [Cu(BIPHEP)(N^N)][PF6] complexes (BIPHEP = 1,1′-biphenyl-2,2′-diylbis(diphenylphosphane)), in which N^N is 2,2′-bipyridine (bpy), 6-methyl-2,2′-bipyridine (6-Mebpy), 6-ethyl-2,2′-bipyridine (6-Etbpy), or 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), have been synthesized and characterized using multinuclear NMR spectroscopies and electrospray ionization mass spectrometry. The single crystal structures of [Cu(BIPHEP)(bpy)][PF [...] Read more.
Heteroleptic [Cu(BIPHEP)(N^N)][PF6] complexes (BIPHEP = 1,1′-biphenyl-2,2′-diylbis(diphenylphosphane)), in which N^N is 2,2′-bipyridine (bpy), 6-methyl-2,2′-bipyridine (6-Mebpy), 6-ethyl-2,2′-bipyridine (6-Etbpy), or 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), have been synthesized and characterized using multinuclear NMR spectroscopies and electrospray ionization mass spectrometry. The single crystal structures of [Cu(BIPHEP)(bpy)][PF6]∙CH2Cl2, [Cu(BIPHEP)(5,5′-Me2bpy)][PF6]∙CH2Cl2, [Cu(BIPHEP)(6-Mebpy)][PF6]∙Et2O∙0.5H2O and [Cu(BIPHEP)(6-Etbpy)][PF6] confirm distorted tetrahedral {Cu(P^P)(N^N)} coordination environments. Each compound shows a quasi-reversible Cu+/Cu2+ process. In deaerated solution, the compounds are weak emitters. Powdered samples are yellow emitters (λemmax in the range 558–583 nm) and [Cu(BIPHEP)(5,5′-Me2bpy)][PF6] exhibits the highest photoluminescence quantum yield (PLQY = 14%). On cooling to 77 K (frozen 2-methyloxolane), the emission maxima are red-shifted and the excited state lifetimes increase from τ1/2 < 8 μs, to τ1/2 values of up to 53 μs, consistent with the compounds with N^N = 6-Mebpy, 6-Etbpy and 5,5′-Me2bpy exhibiting thermally activated delayed fluorescence (TADF). Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Review

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Open AccessReview
Applications of Bolm’s Ligand in Enantioselective Synthesis
Molecules 2020, 25(4), 958; https://doi.org/10.3390/molecules25040958 - 20 Feb 2020
Abstract
One pathway for the preparation of enantiomerically pure compounds from prochiral substrates is the use of metal complex catalysis with chiral ligands. Compared to the other frequently used chiral ligands, chiral 2,2’-bipyridines have been underexploited, despite the data indicating that such ligands have [...] Read more.
One pathway for the preparation of enantiomerically pure compounds from prochiral substrates is the use of metal complex catalysis with chiral ligands. Compared to the other frequently used chiral ligands, chiral 2,2’-bipyridines have been underexploited, despite the data indicating that such ligands have considerable potential in synthetic chemistry. One of those is the so-called Bolm’s ligand, a compound possessing chiral alcohol moieties in the side chains attached to the 2,2’-bipyridine scaffold. Various metal salts have been used in combination with Bolm’s ligand as potent catalysts able to bring about enantioselective alkylations, allylations, conjugate additions, desymmetrization of meso-epoxides, aldol reactions, etc. This review aims to summarize Bolm’s ligand applications in the area of enantioselective synthesis over the last three decades since its preparation. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessReview
Mono- and Di-Quaternized 4,4′-Bipyridine Derivatives as Key Building Blocks for Medium- and Environment-Responsive Compounds and Materials
Molecules 2020, 25(1), 1; https://doi.org/10.3390/molecules25010001 - 18 Dec 2019
Cited by 1
Abstract
Mono- and di-quaternized 4,4′-bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4′-bipyridine-based derivatives are exploited: [...] Read more.
Mono- and di-quaternized 4,4′-bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4′-bipyridine-based derivatives are exploited: their redox activity and their electrochromic aptitude. Contemporary materials and compounds encompassing these skeletons as building blocks are often characterized as multifunctional, as their presence often gives rise to interesting phenomena, e.g., various types of chromism. This research trend is acknowledged, and, in this review article, recent examples of multifunctional chromic materials/compounds of this class are presented. Emphasis is placed on solvent-/medium- and environment-responsive 4,4′-bipyridine derivatives. Two important classes of 4,4′-bipyridine-based products with solvatochromic and/or environment-responsive character are reviewed: viologens (i.e., N,N′-disubstituted derivatives) and monoquats (i.e., monosubstituted 4,4′-bipyridine derivatives). The multifunctional nature of these derivatives is analyzed and structure–property relations are discussed in connection to the role of these derivatives in various novel applications. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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Open AccessReview
The Early Years of 2,2′-Bipyridine—A Ligand in Its Own Lifetime
Molecules 2019, 24(21), 3951; https://doi.org/10.3390/molecules24213951 - 31 Oct 2019
Cited by 2
Abstract
The first fifty years of the chemistry of 2,2′-bipyridine are reviewed from its first discovery in 1888 to the outbreak of the second global conflict in 1939. The coordination chemistry and analytical applications are described and placed in the context of the increasingly [...] Read more.
The first fifty years of the chemistry of 2,2′-bipyridine are reviewed from its first discovery in 1888 to the outbreak of the second global conflict in 1939. The coordination chemistry and analytical applications are described and placed in the context of the increasingly sophisticated methods of characterization which became available to the chemist in this time period. Many of the “simple” complexes of 2,2′-bipyridine reported in the early literature have been subsequently shown to have more complex structures. Full article
(This article belongs to the Special Issue Bipyridines: Synthesis, Functionalization and Applications)
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