Molecules

21 pages, 3098 KiB

Open AccessArticle

Nickel(II) Complex of N₄ Schiff Base Ligand as a Building Block for a Conducting Metallopolymer with Multiple Redox States

by Mikhail Karushev, Evgenia Smirnova and Irina Chepurnaya

Molecules 2021, 26(9), 2646; https://doi.org/10.3390/molecules26092646 - 30 Apr 2021

Cited by 3 | Viewed by 2694

Abstract

Metal–ligand interactions in monomeric and polymeric transition metal complexes of Schiff base ligands largely define their functional properties and perspective applications. In this study, redox behavior of a nickel(II) N₄-anilinosalen complex, [NiAmben] (where H₂Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) was [...] Read more.

Metal–ligand interactions in monomeric and polymeric transition metal complexes of Schiff base ligands largely define their functional properties and perspective applications. In this study, redox behavior of a nickel(II) N₄-anilinosalen complex, [NiAmben] (where H₂Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) was studied by cyclic voltammetry in solvents of different Lewis basicity. A poly-[NiAmben] film electrochemically synthesized from a 1,2-dichloroethane-based electrolyte was investigated by a combination of cyclic voltammetry, electrochemical quartz crystal microbalance, in situ UV-Vis spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag⁺. The polymer displayed multistep redox processes involving reversible transfer of the total of ca. 1.6 electrons per repeat unit, electrical conductivity over a wide potential range, and multiple color changes in correlation with electrochemical processes. Performance advantages of poly-[NiAmben] over its nickel(II) N₂O₂ Schiff base analogue were identified and related to the increased number of accessible redox states in the polymer due to the higher extent of electronic communication between metal ions and ligand segments in the nickel(II) N₄-anilinosalen system. The obtained results suggest that electrosynthesized poly-[NiAmben] films may be viable candidates for energy storage and saving applications. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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17 pages, 5490 KiB

Open AccessArticle

Tin-Naphthalene Sulfonic Acid Complexes as Photostabilizers for Poly(vinyl chloride)

by Hadeer Jasem, Angham G. Hadi, Gamal A. El-Hiti, Mohammed A. Baashen, Hassan Hashim, Ahmed A. Ahmed, Dina S. Ahmed and Emad Yousif

Molecules 2021, 26(12), 3629; https://doi.org/10.3390/molecules26123629 - 14 Jun 2021

Cited by 11 | Viewed by 3926

Abstract

Poly(vinyl chloride) degrades when exposed to ultraviolet light for long durations; therefore, the photostability of polymeric materials should be enhanced through the application of additives. New organotin complexes containing 4-aminonaphthalene-1-sulfonic acid were synthesized and their role as poly(vinyl chloride) photostabilizers were evaluated. The [...] Read more.

Poly(vinyl chloride) degrades when exposed to ultraviolet light for long durations; therefore, the photostability of polymeric materials should be enhanced through the application of additives. New organotin complexes containing 4-aminonaphthalene-1-sulfonic acid were synthesized and their role as poly(vinyl chloride) photostabilizers were evaluated. The reaction of 4-amino-3-hydroxynaphthalene-1-sulfonic acid and appropriate di- or trisubstituted tin chloride (triphenyltin chloride, tributyltin chloride, dibutyltin dichloride, and dimethyltin dichloride) in methanol under reflux gave the corresponding tin-naphthalene complexes with yields of 75%–95%. Elemental analyses and spectroscopic techniques including infrared and nuclear magnetic resonance (proton and tin) were used to confirm their structures. The tin complexes were added to poly(vinyl chloride) to produce thin films that irradiated with ultraviolet light. Various parameters were assessed, such as the weight loss, formation of specific functional groups, changes in the surface due to photoirradiation, and rate constant of photodegradation, to test the role played by the organotin complexes to reduce photodegradation in polymeric films. The results proved that organotin complexes acted as photostabilizers in these circumstances. The weight loss, formation of fragments containing specific functional groups, and undesirable changes in the surface of polymeric films were limited in the presence of organotin complexes. Organotin complexes containing three phenyl groups showed the most desirable stabilization effect. These act as efficient primary and secondary photostabilizers, and as decomposers for peroxides. In addition, such an additive inhibits the dehydrochlorination process, which is the main cause of poly(vinyl chloride) photodegradation. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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18 pages, 2479 KiB

Open AccessArticle

Nickel(II)-Based Building Blocks with Schiff Base Derivatives: Experimental Insights and DFT Calculations

by Néstor Novoa, Carolina Manzur, Thierry Roisnel, Samia Kahlal, Jean-Yves Saillard, David Carrillo and Jean-René Hamon

Molecules 2021, 26(17), 5316; https://doi.org/10.3390/molecules26175316 - 1 Sep 2021

Cited by 6 | Viewed by 3338

Abstract

We have recently reported a series of neutral square planar tridentate Schiff base (L) complexes of the general formula [(L)M(py)], showing relatively high first-order hyperpolarizabilities and NLO redox switching behavior. In the present study, new members of this family of compounds have been [...] Read more.

We have recently reported a series of neutral square planar tridentate Schiff base (L) complexes of the general formula [(L)M(py)], showing relatively high first-order hyperpolarizabilities and NLO redox switching behavior. In the present study, new members of this family of compounds have been prepared with the objective to investigate their potential as building blocks in the on-demand construction of D-π-A push–pull systems. Namely, ternary nickel(II) building blocks of general formula [(L^A/D)Ni(4-pyX)] (4–7), where L^A/D stands for an electron accepting or donating dianionic O,N,O-tridentate Schiff base ligand resulting from the monocondensation of 2-aminophenol or its 4-substituted nitro derivative and β-diketones R-C(=O)CH₂C(=O)CH₃ (R = methyl, anisyl, ferrocenyl), and 4-pyX is 4-iodopyridine or 4-ethynylpyridine, were synthesized and isolated in 60–78% yields. Unexpectedly, the Sonogashira cross-coupling reaction between the 4-iodopyridine derivative 6 and 4-ethynylpyridine led to the formation of the bis(4-pyridyl) acetylene bridged centrosymmetric dimer [{(L^D)Ni}₂(µ²-py-C≡C-py)] (8). Complexes 4–8 were characterized by elemental analysis, FT-IR and NMR spectroscopy, single crystal X-ray diffraction and computational methods. In each compound, the four-coordinate Ni(II) metal ion adopts a square planar geometry with two nitrogen and two oxygen atoms as donors occupying trans positions. In 8, the Ni…Ni separation is of 13.62(14) Å. Experimental results were proved and explained theoretically exploiting Density Functional Theory calculations. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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21 pages, 5477 KiB

Open AccessArticle

Crystallographic and Spectroscopic Investigations on Oxidative Coordination in the Heteroleptic Mononuclear Complex of Cerium and Benzoxazine Dimer

by Worawat Wattanathana, Natapol Suetrong, Peetikamol Kongsamai, Kantapat Chansaenpak, Nutthawat Chuanopparat, Yuranan Hanlumyuang, Pongsakorn Kanjanaboos and Suttipong Wannapaiboon

Molecules 2021, 26(17), 5410; https://doi.org/10.3390/molecules26175410 - 6 Sep 2021

Cited by 16 | Viewed by 3883

Abstract

Among lanthanide-based compounds, cerium compounds exhibit a significant role in a variety of research fields due to their distinct tetravalency, high economic feasibility, and high stability of Ce(IV) complexes. Herein, a systematic investigation of crystallographic information, chemical properties, and mechanistic formation of the [...] Read more.

Among lanthanide-based compounds, cerium compounds exhibit a significant role in a variety of research fields due to their distinct tetravalency, high economic feasibility, and high stability of Ce(IV) complexes. Herein, a systematic investigation of crystallographic information, chemical properties, and mechanistic formation of the novel Ce(IV) complex synthesized from cerium(III) nitrate hexahydrate and 2,2′-(methylazanediyl)bis(methylene)bis(4-methylphenol) (MMD) ligand has been explored. According to the analysis of the crystallographic information, the obtained complex crystal consists of the Ce(IV) center coordinated with two nitrate ligands and two bidentate coordinated (N-protonated and O,O-deprotonated) MMD ligands. The fingerprint plots and the Hirshfeld surface analyses suggest that the C–H⋯O and C–H⋯π interactions significantly contribute to the crystal packing. The C–H⋯O and C–H⋯π contacts link the molecules into infinite molecular chains propagating along the [100] and [010] directions. Synchrotron powder X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques have been employed to gain an understanding of the oxidative complexation of Ce(IV)-MMD complex in detail. This finding would provide the possibility to systematically control the synthetic parameters and wisely design the precursor components in order to achieve the desired properties of novel materials for specific applications. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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20 pages, 4495 KiB

Open AccessReview

The Development of Ru(II)-Based Photoactivated Chemotherapy Agents

by Yongjie Chen, Lijuan Bai, Pu Zhang, Hua Zhao and Qianxiong Zhou

Molecules 2021, 26(18), 5679; https://doi.org/10.3390/molecules26185679 - 18 Sep 2021

Cited by 31 | Viewed by 3981

Abstract

Photoactivated chemotherapy (PACT) is a novel cancer treatment method that has drawn increasing attention due to its high selectivity and low side effects by spatio-temporal control of irradiation. Compared with photodynamic therapy (PDT), oxygen-independent PACT is more suitable for treating hypoxic tumors. By [...] Read more.

Photoactivated chemotherapy (PACT) is a novel cancer treatment method that has drawn increasing attention due to its high selectivity and low side effects by spatio-temporal control of irradiation. Compared with photodynamic therapy (PDT), oxygen-independent PACT is more suitable for treating hypoxic tumors. By finely tuning ligand structures and coordination configurations, many Ru(II) complexes can undergo photoinduced ligand dissociation, and the resulting Ru(II) aqua species and/or free ligands may have anticancer activity, showing their potential as PACT agents. In this mini-review, we summarized the progress in Ru(II)-based PACT agents, as well as challenges that researchers in this field still face. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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18 pages, 4000 KiB

Open AccessArticle

Luminescent Complexes of Europium (III) with 2-(Phenylethynyl)-1,10-phenanthroline: The Role of the Counterions

by Denitsa Elenkova, Rumen Lyapchev, Julia Romanova, Bernd Morgenstern, Yana Dimitrova, Deyan Dimov, Martin Tsvetkov and Joana Zaharieva

Molecules 2021, 26(23), 7272; https://doi.org/10.3390/molecules26237272 - 30 Nov 2021

Cited by 8 | Viewed by 3077

Abstract

New antenna ligand, 2-(phenylethynyl)-1,10-phenanthroline (PEP), and its luminescent Eu (III) complexes, Eu(PEP)₂Cl₃ and Eu(PEP)₂(NO₃)₃, are synthesized and characterized. The synthetic procedure applied is based on reacting of europium salts with ligand in hot acetonitrile [...] Read more.

New antenna ligand, 2-(phenylethynyl)-1,10-phenanthroline (PEP), and its luminescent Eu (III) complexes, Eu(PEP)₂Cl₃ and Eu(PEP)₂(NO₃)₃, are synthesized and characterized. The synthetic procedure applied is based on reacting of europium salts with ligand in hot acetonitrile solutions in molar ratio 1 to 2. The structure of the complexes is refined by X-ray diffraction based on the single crystals obtained. The compounds [Eu(PEP)₂Cl₃]·2CH₃CN and [Eu(PEP)₂(NO₃)₃]∙2CH₃CN crystalize in monoclinic space group P2_1/n and P2_1/c, respectively, with two acetonitrile solvent molecules. Intra- and inter-ligand π-π stacking interactions are present in solid stat and are realized between the phenanthroline moieties, as well as between the substituents and the phenanthroline units. The optical properties of the complexes are investigated in solid state, acetonitrile and dichloromethane solution. Both compounds exhibit bright red luminescence caused by the organic ligand acting as antenna for sensitization of Eu (III) emission. The newly designed complexes differ in counter ions in the inner coordination sphere, which allows exploring their influence on the stability, molecular and supramolecular structure, fluorescent properties and symmetry of the Eu (III) ion. In addition, molecular simulations are performed in order to explain the observed experimental behavior of the complexes. The discovered structure-properties relationships give insight on the role of the counter ions in the molecular design of new Eu (III) based luminescent materials. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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12 pages, 1873 KiB

Open AccessArticle

A DFT/PCM Study on the Affinity of Salinomycin to Bind Monovalent Metal Cations

by Todor Dudev, Diana Cheshmedzhieva, Peter Dorkov and Ivayla Pantcheva

Molecules 2022, 27(2), 532; https://doi.org/10.3390/molecules27020532 - 14 Jan 2022

Cited by 3 | Viewed by 1862

Abstract

The affinity of the polyether ionophore salinomycin to bind IA/IB metal ions was accessed using the Gibbs free energy of the competition reaction between SalNa (taken as a reference) and its rival ions: [M⁺-solution] + [SalNa] → [SalM] + [Na⁺ [...] Read more.

The affinity of the polyether ionophore salinomycin to bind IA/IB metal ions was accessed using the Gibbs free energy of the competition reaction between SalNa (taken as a reference) and its rival ions: [M⁺-solution] + [SalNa] → [SalM] + [Na⁺-solution] (M = Li, K, Rb, Cs, Cu, Ag, Au). The DFT/PCM computations revealed that the ionic radius, charge density and accepting ability of the competing metal cations, as well as the dielectric properties of the solvent, have an influence upon the selectivity of salinomycin. The optimized structures of the monovalent metal complexes demonstrate the flexibility of the ionophore, allowing the coordination of one or two water ligands in SalM-W₁ and SalM-W₂, respectively. The metal cations are responsible for the inner coordination sphere geometry, with coordination numbers spread between 2 (Au⁺), 4 (Li⁺ and Cu⁺), 5/6 (Na⁺, K⁺, Ag⁺), 6/7 (Rb⁺) and 7/8 (Cs⁺). The metals’ affinity to salinomycin in low-polarity media follows the order of Li⁺ > Cu⁺ > Na⁺ > K⁺ > Au⁺ > Ag⁺ > Rb⁺ > Cs⁺, whereas some derangement takes place in high-dielectric environment: Li⁺ ≥ Na⁺ > K⁺ > Cu⁺ > Au⁺ > Ag⁺ > Rb⁺ > Cs⁺. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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19 pages, 4761 KiB

Open AccessArticle

Mononuclear Transition Metal Cymantrenecarboxylates as Precursors for Spinel-Type Manganites

by Pavel S. Koroteev, Andrey B. Ilyukhin, Andrey V. Gavrikov, Konstantin A. Babeshkin and Nikolay N. Efimov

Molecules 2022, 27(3), 1082; https://doi.org/10.3390/molecules27031082 - 6 Feb 2022

Cited by 4 | Viewed by 4022

Abstract

Novel mononuclear cymantrenecarboxylate complexes of transition metals, [Co(H₂O)₆](CymCO₂)₂·4H₂O (Cym = (η⁵-C₅H₄)Mn(CO)₃) (1), [Ni(H₂O)₆](CymCO₂)₂·4H₂O [...] Read more.

Novel mononuclear cymantrenecarboxylate complexes of transition metals, [Co(H₂O)₆](CymCO₂)₂·4H₂O (Cym = (η⁵-C₅H₄)Mn(CO)₃) (1), [Ni(H₂O)₆](CymCO₂)₂·4H₂O (2), [Zn(H₂O)₆](CymCO₂)₂·4H₂O (3), [Co(CymCO₂)₂(imz)₂] (imz = imidazole, 4), [Co(CymCO₂)₂(bpy)₂]·2PhMe (bpy = 2,2′-bipyridyl, 5), [Ni(CymCO₂)(bpy)₂(H₂O)][CymCO₂]·0.5MePh·2H₂O (6), [Cu(CymCO₂)₂(imz)₂] (7), and [Cu(CymCO₂)₂(bpy)(H₂O)] (8), were obtained and characterized by single-crystal X-ray analysis. Complexes 1–3 are isostructural. Magnetism of the Co complexes 1, 4, and 5 was studied; it was shown that they exhibit the properties of field-induced single-molecule magnets with magnetization reversal barriers (ΔE/k_B) of 44, 13, and 10 K, respectively. Thermal decomposition of complexes 1–8 was studied by means of DSC and TGA methods. The final products of thermolysis of 1–6 in air, according to powder XRD data, are the pure spinel phases MMn₂O₄; for the cases of copper complexes, the mixtures of CuMn₂O₄ and CuO were found in the products. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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20 pages, 6561 KiB

Open AccessEditor’s ChoiceArticle

Molecular Engineering of Quinone-Based Nickel Complexes and Polymers for All-Organic Li-Ion Batteries

by Yanislav Danchovski, Hristo Rasheev, Radostina Stoyanova and Alia Tadjer

Molecules 2022, 27(20), 6805; https://doi.org/10.3390/molecules27206805 - 11 Oct 2022

Cited by 2 | Viewed by 2063

Abstract

All-organic Li-ion batteries appear to be a sustainable and safer alternative to the currently-used Li-ion batteries but their application is still limited due to the lack of organic compounds with high redox potentials toward Li⁺/Li⁰. Herein, we report a [...] Read more.

All-organic Li-ion batteries appear to be a sustainable and safer alternative to the currently-used Li-ion batteries but their application is still limited due to the lack of organic compounds with high redox potentials toward Li⁺/Li⁰. Herein, we report a computational design of nickel complexes and coordination polymers that have redox potentials spanning the full voltage range: from the highest, 4.7 V, to the lowest, 0.4 V. The complexes and polymers are modeled by binding low- and high-oxidized Ni ions (i.e., Ni(II) and Ni(IV)) to redox-active para-benzoquinone molecules substituted with carboxyl- and cyano-groups. It is found that both the nickel ions and the quinone-derived ligands are redox-active upon lithiation. The type of Ni coordination also has a bearing on the redox potentials. By combining the complex of Ni(IV) with 2-carboxylato-5-cyano-1,4-benzoquinones as a cathode and Ni(II)-2,5-dicarboxylato-3,6-dicyano-1,4-benzoquinone coordination polymer as an anode, all-organic Li-ion batteries could be assembled, operating at an average voltage exceeding 3.0 V and delivering a capacity of more than 300 mAh/g. Full article

(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)

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