International Journal of Molecular Sciences

Research

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14 pages, 6131 KiB

Open AccessArticle

Synthesis of Novel Tetra(µ₃-Methoxo) Bridged with [Cu(II)-O-Cd(II)] Double-Open-Cubane Cluster: XRD/HSA-Interactions, Spectral and Oxidizing Properties

by Abderrahim Titi, Mouslim Messali, Rachid Touzani, Mohammed Fettouhi, Abdelkader Zarrouk, Nabil Al-Zaqri, Ali Alsalme, Fahad A. Alharthi, Amjad Alsyahi and Ismail Warad

Int. J. Mol. Sci. 2020, 21(22), 8787; https://doi.org/10.3390/ijms21228787 - 20 Nov 2020

Cited by 5 | Viewed by 1827

Abstract

A new double-open-cubane core Cd(II)-O-Cu(II) bimetallic ligand mixed cluster of type [Cl₂Cu₄Cd₂(NNO)₆(NN)₂(NO₃)₂].CH₃CN was made available in EtOH/CH₃CN solution. The 1-hydroxymethyl-3,5-dimethylpyrazole (NNOH) and 3,5-dimethylpyrazole (NNH) act [...] Read more.

A new double-open-cubane core Cd(II)-O-Cu(II) bimetallic ligand mixed cluster of type [Cl₂Cu₄Cd₂(NNO)₆(NN)₂(NO₃)₂].CH₃CN was made available in EtOH/CH₃CN solution. The 1-hydroxymethyl-3,5-dimethylpyrazole (NNOH) and 3,5-dimethylpyrazole (NNH) act as N,O-polydentate anion ligands in coordinating the Cu(II) and Cd(II) centers. The structure of the cluster in the solid state was proved by XRD study and confirmed in the liquid state by UV-vis analysis. The XRD result supported the construction of two octahedral and one square pyramid geometries types around the four Cu(II) centers and only octahedral geometry around Cd(II) two centers. Interestingly, NNOH ligand acts as a tetra-µ³-oxo and tri-µ²-oxo ligand; meanwhile, the N-N in NNH acts as classical bidentate anion/neutral ligands. The interactions in the lattice were detected experimentally by the XRD-packing result and computed via Hirschfeld surface analysis (HSA). The UV-vis., FT-IR and Energy Dispersive X-ray (EDX), supported the desired double-open cubane cluster composition. The oxidation potential of the desired cluster was evaluated using a 3,5-DTB-catechol 3,5-DTB-quinone as a catecholase model reaction. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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14 pages, 4592 KiB

Open AccessArticle

Vinylene-Bridged Cyclic Dipyrrin and BODIPY Trimers

by Songlin Xue, Daiki Kuzuhara, Naoki Aratani and Hiroko Yamada

Int. J. Mol. Sci. 2020, 21(21), 8041; https://doi.org/10.3390/ijms21218041 - 28 Oct 2020

Cited by 8 | Viewed by 2141

Abstract

Vinylene-bridged cyclic boron–difluoride complex of dipyrrin (BODIPY) trimers were successfully prepared from expanded dimethyl-vinylene bridged hexaphyrin(2.1.2.1.2.1) Me-Hex that has the structure of alternate dipyrrins and vinylene bridges. The hexaphyrin(2.1.2.1.2.1) Me-Hex can coordinate with boron ions to afford five kinds of cyclic BODIPYs given [...] Read more.

Vinylene-bridged cyclic boron–difluoride complex of dipyrrin (BODIPY) trimers were successfully prepared from expanded dimethyl-vinylene bridged hexaphyrin(2.1.2.1.2.1) Me-Hex that has the structure of alternate dipyrrins and vinylene bridges. The hexaphyrin(2.1.2.1.2.1) Me-Hex can coordinate with boron ions to afford five kinds of cyclic BODIPYs given by step-by-step boron complexations. Crystal structures of all cyclic BODIPYs except for 3BF₂-Me-Hex(b) formed non-planar structures. The theoretical calculation predicted that mono-/bis-boron cyclic BODIPYs show the intramolecular charge transfer (ICT) characteristics, whereas tri-boron cyclic BODIPYs have no ICT characteristics. Reflecting these electronic properties, tri-boron cyclic BODIPYs exhibit weak fluorescence in the red region, but mono-/bis-boron cyclic BODIPYs exhibit no emission. Vinylene bridged cyclic dipyrrin trimer Me-Hex is the novel porphyrinoid ligand allowed to control the boron coordination under different reaction conditions to form various boron complexes. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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20 pages, 4865 KiB

Open AccessArticle

A Complete Cross Section Data Set for Electron Scattering by Pyridine: Modelling Electron Transport in the Energy Range 0–100 eV

by Filipe Costa, Ali Traoré-Dubuis, Lidia Álvarez, Ana I. Lozano, Xueguang Ren, Alexander Dorn, Paulo Limão-Vieira, Francisco Blanco, Juan C. Oller, Antonio Muñoz, Adrián García-Abenza, Jimena D. Gorfinkiel, Alessandra S. Barbosa, Marcio H. F. Bettega, Peter Stokes, Ronald D. White, Darryl B. Jones, Michael J. Brunger and Gustavo García

Int. J. Mol. Sci. 2020, 21(18), 6947; https://doi.org/10.3390/ijms21186947 - 22 Sep 2020

Cited by 21 | Viewed by 3334

Abstract

Electron scattering cross sections for pyridine in the energy range 0–100 eV, which we previously measured or calculated, have been critically compiled and complemented here with new measurements of electron energy loss spectra and double differential ionization cross sections. Experimental techniques employed in [...] Read more.

Electron scattering cross sections for pyridine in the energy range 0–100 eV, which we previously measured or calculated, have been critically compiled and complemented here with new measurements of electron energy loss spectra and double differential ionization cross sections. Experimental techniques employed in this study include a linear transmission apparatus and a reaction microscope system. To fulfill the transport model requirements, theoretical data have been recalculated within our independent atom model with screening corrected additivity rule and interference effects (IAM-SCAR) method for energies above 10 eV. In addition, results from the R-matrix and Schwinger multichannel with pseudopotential methods, for energies below 15 eV and 20 eV, respectively, are presented here. The reliability of this complete data set has been evaluated by comparing the simulated energy distribution of electrons transmitted through pyridine, with that observed in an electron-gas transmission experiment under magnetic confinement conditions. In addition, our representation of the angular distribution of the inelastically scattered electrons is discussed on the basis of the present double differential cross section experimental results. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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25 pages, 5549 KiB

Open AccessArticle

Thermally Stable Nitrothiacalixarene Chromophores: Conformational Study and Aggregation Behavior

by Anton Muravev, Tatiana Gerasimova, Robert Fayzullin, Olga Babaeva, Ildar Rizvanov, Ayrat Khamatgalimov, Marsil Kadirov, Sergey Katsyuba, Igor Litvinov, Shamil Latypov, Svetlana Solovieva and Igor Antipin

Int. J. Mol. Sci. 2020, 21(18), 6916; https://doi.org/10.3390/ijms21186916 - 21 Sep 2020

Cited by 6 | Viewed by 2187

Abstract

Achieving high thermal stability and control of supramolecular organization of functional dyes in sensors and nonlinear optics remains a demanding task. This study was aimed at the evaluation of thermal behavior and Langmuir monolayer characteristics of topologically varied nitrothiacalixarene multichromophores and phenol monomers. [...] Read more.

Achieving high thermal stability and control of supramolecular organization of functional dyes in sensors and nonlinear optics remains a demanding task. This study was aimed at the evaluation of thermal behavior and Langmuir monolayer characteristics of topologically varied nitrothiacalixarene multichromophores and phenol monomers. A nitration/azo coupling alkylation synthetic route towards partially O-substituted nitrothiacalixarenes and 4-nitrophenylazo-thiacalixarenes was proposed and realized. Nuclear magnetic resonance (NMR) spectroscopy and X-ray diffractometry of disubstituted nitrothiacalix[4]arene revealed a rare 1,2-alternate conformation. A synchronous thermal analysis indicated higher decomposition temperatures of nitrothiacalixarene macrocycles as compared with monomers. Through surface pressure/potential-molecular area measurements, nitrothiacalixarenes were shown to form Langmuir monolayers at the air–water interface and, through atomic force microscopy (AFM) technique, Langmuir–Blodgett (LB) films on solid substrates. Reflection-absorption spectroscopy of monolayers and electronic absorption spectroscopy of LB films of nitrothiacalixarenes recorded a red-shifted band (290 nm) with a transition from chloroform, indicative of solvatochromism. Additionally, shoulder band at 360 nm was attributed to aggregation and supported by gas-phase density functional theory (DFT) calculations and dynamic light scattering (DLS) analysis in chloroform–methanol solvent in the case of monoalkylated calixarene 3. Excellent thermal stability and monolayer formation of nitrothiacalixarenes suggest their potential as functional dyes. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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15 pages, 5465 KiB

Open AccessArticle

Doubly-Charged Negative Ions as Novel Tunable Catalysts: Graphene and Fullerene Molecules Versus Atomic Metals

by Kelvin Suggs and Alfred Z. Msezane

Int. J. Mol. Sci. 2020, 21(18), 6714; https://doi.org/10.3390/ijms21186714 - 13 Sep 2020

Cited by 3 | Viewed by 4435

Abstract

The fundamental mechanism underlying negative-ion catalysis involves bond-strength breaking in the transition state (TS). Doubly-charged atomic/molecular anions are proposed as novel dynamic tunable catalysts, as demonstrated in water oxidation into peroxide. Density Functional Theory TS calculations have found a tunable energy activation barrier [...] Read more.

The fundamental mechanism underlying negative-ion catalysis involves bond-strength breaking in the transition state (TS). Doubly-charged atomic/molecular anions are proposed as novel dynamic tunable catalysts, as demonstrated in water oxidation into peroxide. Density Functional Theory TS calculations have found a tunable energy activation barrier reduction ranging from 0.030 eV to 2.070 eV, with Si²⁻, Pu²⁻, Pa²⁻ and Sn²⁻ being the best catalysts; the radioactive elements usher in new application opportunities. C₆₀²⁻ significantly reduces the standard C₆₀⁻ TS energy barrier, while graphene increases it, behaving like cationic systems. According to their reaction barrier reduction efficiency, variation across charge states and systems, rank-ordered catalysts reveal their tunable and wide applications, ranging from water purification to biocompatible antiviral and antibacterial sanitation systems. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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15 pages, 4147 KiB

Open AccessArticle

2D Coordination Network of Trioxotriangulene with Multiple Redox Abilities and Its Rechargeable Battery Performance

by Tsuyoshi Murata, Taro Koide, Hirofumi Nobukuni, Ryotaro Tsuji and Yasushi Morita

Int. J. Mol. Sci. 2020, 21(13), 4723; https://doi.org/10.3390/ijms21134723 - 02 Jul 2020

Cited by 10 | Viewed by 2877

Abstract

A three-fold symmetric trioxotriangulene derivative with three pyridyl groups as coordinating sites was designed and synthesized. In a cyclic voltammetry measurement, the trioxotriangulene skeleton exhibited a multi-stage redox ability from neutral radical to radical tetra-anion species. In the zinc complex of monoanion species, [...] Read more.

A three-fold symmetric trioxotriangulene derivative with three pyridyl groups as coordinating sites was designed and synthesized. In a cyclic voltammetry measurement, the trioxotriangulene skeleton exhibited a multi-stage redox ability from neutral radical to radical tetra-anion species. In the zinc complex of monoanion species, three pyridyl groups coordinated to the zinc ion to build up a two-dimensional coordination network with a cavity larger than 12 Å in diameter. This complex was utilized as a cathode active material of a lithium ion battery, and it exhibited a capacity of ca. 60 mAh g⁻¹ per the weight of the active material with a stable cycling performance up to 1000 cycles. This work shows that the coordination network formed by the trioxotriangulene-based ligand was effective in the improvement of cycle performance of the organic rechargeable battery. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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9 pages, 1849 KiB

Open AccessCommunication

Synthesis and Diels–Alder Reactivity of 4-Fluoro-4-Methyl-4H-Pyrazoles

by Nile S. Abularrage, Brian J. Levandowski and Ronald T. Raines

Int. J. Mol. Sci. 2020, 21(11), 3964; https://doi.org/10.3390/ijms21113964 - 31 May 2020

Cited by 7 | Viewed by 2790

Abstract

4H-Pyrazoles are emerging scaffolds for “click” chemistry. Late-stage fluorination with Selectfluor^® is found to provide a reliable route to 4-fluoro-4-methyl-4H-pyrazoles. 4-Fluoro-4-methyl-3,5-diphenyl-4H-pyrazole (MFP) manifested 7-fold lower Diels–Alder reactivity than did 4,4-difluoro-3,5-diphenyl-4H-pyrazole (DFP), but higher stability [...] Read more.

4H-Pyrazoles are emerging scaffolds for “click” chemistry. Late-stage fluorination with Selectfluor^® is found to provide a reliable route to 4-fluoro-4-methyl-4H-pyrazoles. 4-Fluoro-4-methyl-3,5-diphenyl-4H-pyrazole (MFP) manifested 7-fold lower Diels–Alder reactivity than did 4,4-difluoro-3,5-diphenyl-4H-pyrazole (DFP), but higher stability in the presence of biological nucleophiles. Calculations indicate that a large decrease in the hyperconjugative antiaromaticity in MFP relative to DFP does not lead to a large loss in Diels–Alder reactivity because the ground-state structure of MFP avoids hyperconjugative antiaromaticity by distorting into an envelope-like conformation like that in the Diels–Alder transition state. This predistortion enhances the reactivity of MFP and offsets the decrease in reactivity from the diminished hyperconjugative antiaromaticity. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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9 pages, 3853 KiB

Open AccessArticle

Synthesis of Fluorescent Dansyl Derivatives of Methoxyamine and Diphenylhydrazine as Free Radical Precursors

by Bianca Patrascu, Sorin Mocanu, Anca Coman, Augustin M. Madalan, Codruta Popescu, Anca Paun, Mihaela Matache and Petre Ionita

Int. J. Mol. Sci. 2020, 21(10), 3559; https://doi.org/10.3390/ijms21103559 - 18 May 2020

Cited by 5 | Viewed by 3041

Abstract

Starting from dansyl-chloride, in reaction with 1,1-diphenylhydrazine and methoxyamine, two new fluorescent derivatives 1 and 2 were obtained and characterized by NMR, IR, UV-Vis, HR-MS, and fluorescence spectroscopy. The single-crystal X-ray structure was obtained for compound 2. Both compounds generate free radicals [...] Read more.

Starting from dansyl-chloride, in reaction with 1,1-diphenylhydrazine and methoxyamine, two new fluorescent derivatives 1 and 2 were obtained and characterized by NMR, IR, UV-Vis, HR-MS, and fluorescence spectroscopy. The single-crystal X-ray structure was obtained for compound 2. Both compounds generate free radicals by oxidation, as demonstrated by ESR spectroscopy. Compound 1 generates the corresponding hydrazyl-persistent free radical, evidenced directly by ESR spectroscopy, while compound 2 generates in the first instance the methoxyaminyl short-lived free radical, which decomposes rapidly with the formation of the methoxy radical, evidenced by the ESR spin-trapping technique. By oxidation of compounds 1 and 2, their fluorescence is quenched. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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11 pages, 2013 KiB

Open AccessArticle

Fullerene Negative Ions: Formation and Catalysis

by Zineb Felfli, Kelvin Suggs, Nantambu Nicholas and Alfred Z. Msezane

Int. J. Mol. Sci. 2020, 21(9), 3159; https://doi.org/10.3390/ijms21093159 - 30 Apr 2020

Cited by 6 | Viewed by 3660

Abstract

We first explore negative-ion formation in fullerenes C₄₄ to C₁₃₆ through low-energy electron elastic scattering total cross sections calculations using our Regge-pole methodology. Then, the formed negative ions C₄₄ˉ to C₁₃₆ˉ are used to investigate the catalysis [...] Read more.

We first explore negative-ion formation in fullerenes C₄₄ to C₁₃₆ through low-energy electron elastic scattering total cross sections calculations using our Regge-pole methodology. Then, the formed negative ions C₄₄ˉ to C₁₃₆ˉ are used to investigate the catalysis of water oxidation to peroxide and water synthesis from H₂ and O₂. The exploited fundamental mechanism underlying negative-ion catalysis involves hydrogen bond strength-weakening/breaking in the transition state. Density Functional Theory transition state calculations found C₆₀ˉ optimal for both water and peroxide synthesis, C₁₀₀ˉ increases the energy barrier the most, and C₁₃₆ˉ the most effective catalyst in both water synthesis and oxidation to H₂O₂. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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Review

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33 pages, 17104 KiB

Open AccessReview

Development of Heterocycle-Substituted and Fused Azulenes in the Last Decade (2010–2020)

by Taku Shoji, Tetsuo Okujima and Shunji Ito

Int. J. Mol. Sci. 2020, 21(19), 7087; https://doi.org/10.3390/ijms21197087 - 25 Sep 2020

Cited by 31 | Viewed by 4294

Abstract

Azulene derivatives with heterocyclic moieties in the molecule have been synthesized for applications in materials science by taking advantage of their unique properties. These derivatives have been prepared by various methods, involving electrophilic substitution, condensation, cyclization, and transition metal-catalyzed cross-coupling reactions. Herein, we [...] Read more.

Azulene derivatives with heterocyclic moieties in the molecule have been synthesized for applications in materials science by taking advantage of their unique properties. These derivatives have been prepared by various methods, involving electrophilic substitution, condensation, cyclization, and transition metal-catalyzed cross-coupling reactions. Herein, we present the development of the synthetic methods, reactivities, and physical properties for the heterocycle-substituted and heterocycle-fused azulenes reported in the last decade. Full article

(This article belongs to the Special Issue Synthesis and Reactivity of Novel Aromatic Compounds)

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