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18 pages, 2210 KiB

Open AccessArticle

Interligand Charge-Transfer Processes in Zinc Complexes

by Carlo Ciarrocchi, Guido Colucci, Massimo Boiocchi, Donatella Sacchi, Maduka L. Weththimuni, Alessio Orbelli Biroli and Maurizio Licchelli

Chemistry 2022, 4(3), 717-734; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4030051 - 21 Jul 2022

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Abstract

Electron donor–acceptor (EDA) complexes are characterized by charge-transfer (CT) processes between electron-rich and electron-poor counterparts, typically resulting in a new absorption band at a higher wavelength. In this paper, we report a series of novel 2,6-di(imino)pyridine ligands with different electron-rich aromatic substituents and [...] Read more.

Electron donor–acceptor (EDA) complexes are characterized by charge-transfer (CT) processes between electron-rich and electron-poor counterparts, typically resulting in a new absorption band at a higher wavelength. In this paper, we report a series of novel 2,6-di(imino)pyridine ligands with different electron-rich aromatic substituents and their 1:2 (metal/ligand) complexes with zinc(II) in which the formation of a CT species is promoted by the metal ion coordination. The absorption properties of these complexes were studied, showing the presence of a CT absorption band only in the case of aromatic substituents with donor groups. The nature of EDA interaction was confirmed by crystallographic studies, which disclose the electron-poor and electron-rich moieties involved in the CT process. These moieties mutually belong to both the ligands and are forced into a favorable spatial arrangement by the coordinative preferences of the metal ion. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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16 pages, 5281 KiB

Open AccessArticle

The Dielectric Behavior of Protected HKUST-1

by Simona Sorbara, Nicola Casati, Valentina Colombo, Filippo Bossola and Piero Macchi

Chemistry 2022, 4(2), 576-591; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4020041 - 10 Jun 2022

Viewed by 2105

Abstract

We investigated the adsorption properties and the dielectric behavior of a very well-known metal-organic framework (MOF), namely Cu₃(BTC)₂ (known as HKUST-1; BTC = 1,3,5-benzenetricarboxylate), before and after protection with some amines. This treatment has the purpose of reducing the inherent [...] Read more.

We investigated the adsorption properties and the dielectric behavior of a very well-known metal-organic framework (MOF), namely Cu₃(BTC)₂ (known as HKUST-1; BTC = 1,3,5-benzenetricarboxylate), before and after protection with some amines. This treatment has the purpose of reducing the inherent hygroscopic nature of HKUST-1, which is a serious drawback in its application of as low-dielectric-constant (low-κ) material. Moreover, we investigated the structure of HKUST-1 under a strong electric field, confirming the robustness of the framework. Even under dielectric perturbation, the water molecules adsorbed by the MOF remained almost invisible to X-ray diffraction, apart from those directly bound to the metal ions. However, the replacement of H₂O with a more visible guest molecule such as CH₂Br₂ made the cavity that traps the guest more visible. Finally, in this work we demonstrate that impedance spectroscopy is a valuable tool for identifying water sorption in porous materials, providing information that is complementary to that of adsorption isotherms. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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12 pages, 3434 KiB

Open AccessArticle

Kinetics of Thermal Decomposition of Particulate Samples of MgCO₃: Experiments and Models

by Francesca Mancarella, Marcella D’Elia, Gaia Micca Longo, Savino Longo and Vincenzo Orofino

Chemistry 2022, 4(2), 548-559; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4020039 - 31 May 2022

Cited by 6 | Viewed by 2119

Abstract

In this work, we study the kinetics of thermal decomposition of MgCO₃ in the form of particles of known size. In the experiments, the material is heated to a known temperature in a vacuum oven, and it is characterized, both before and [...] Read more.

In this work, we study the kinetics of thermal decomposition of MgCO₃ in the form of particles of known size. In the experiments, the material is heated to a known temperature in a vacuum oven, and it is characterized, both before and after heating, by infrared spectroscopy and gravimetry. The agreement between the results of the two techniques is excellent. These results are rationalized by means of a model based on Languir’s law, and the comparison with the experiments allows us to estimate the activation energy of the process. The reabsorption of atmospheric water by the oxide is shown spectroscopically, finding that is strongly influenced by the temperature of the process. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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15 pages, 2053 KiB

Open AccessArticle

Structural Diversity of Lithium Oligo-α-Pyridylamides

by Arsen Raza, Adele Mucci, Alessio Nicolini and Andrea Cornia

Chemistry 2022, 4(2), 520-534; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4020037 - 25 May 2022

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Abstract

Lithium oligo-α-pyridylamides are useful intermediates in coordination chemistry. Upon trans-metalation they have afforded a variety of extended metal atom chains (EMACs), which are currently investigated as molecular wires and single-molecule magnets. However, structural information on this class of compounds is scarce. [...] Read more.

Lithium oligo-α-pyridylamides are useful intermediates in coordination chemistry. Upon trans-metalation they have afforded a variety of extended metal atom chains (EMACs), which are currently investigated as molecular wires and single-molecule magnets. However, structural information on this class of compounds is scarce. Two trilithium salts of a new, sterically encumbered oligo-α-pyridylamido ligand were isolated in crystalline form and structurally characterized in the solid state and in solution. Lithiation of N²-(trimethylsilyl)-N⁶-{6-[(trimethylsilyl)amino]pyridin-2-yl}pyridine-2,6-diamine (H₃L) with n-BuLi in thf yielded dimeric adduct [Li₆L₂(thf)₆] (1), which was crystallized from n-hexane/thf as 1·C₆H₁₄. Crystals of a tetra-thf solvate with formula [Li₆L₂(thf)₄] (2) were also obtained. The compounds feature two twisted L³⁻ ligands exhibiting a cis-cis conformation and whose five nitrogen donors are all engaged in metal coordination. The six Li⁺ ions per molecule display coordination numbers ranging from 3 to 5. Compound 1·C₆H₁₄ was investigated by multinuclear 1D and 2D NMR spectroscopy, including ¹H DOSY experiments, which indicated retention of the dimeric structure in benzene-d₆ solution. To the best of our knowledge, 1 and 2 are the longest-chain lithium oligo-α-pyridylamides structurally authenticated so far, thereby qualifying as appealing intermediates to access high-nuclearity EMACs by trans-metalation. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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16 pages, 3986 KiB

Open AccessArticle

Raman Activities of Cyano-Ester Quinoidal Oligothiophenes Reveal Their Diradical Character and the Proximity of the Low-Lying Double Exciton State

by Yasi Dai, Laura Bonometti, José Luis Zafra, Kazuo Takimiya, Juan Casado and Fabrizia Negri

Chemistry 2022, 4(2), 329-344; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4020025 - 15 Apr 2022

Cited by 1 | Viewed by 2203

Abstract

Quinoidal oligothiophenes have received considerable attention as interesting platforms with remarkable amphoteric redox behavior associated with their diradical character increasing with the conjugation lengths. In this work, we considered a family of quinoidal oligothiophenes bearing cyano-ester terminal groups and characterized them by UV-Vis-NIR [...] Read more.

Quinoidal oligothiophenes have received considerable attention as interesting platforms with remarkable amphoteric redox behavior associated with their diradical character increasing with the conjugation lengths. In this work, we considered a family of quinoidal oligothiophenes bearing cyano-ester terminal groups and characterized them by UV-Vis-NIR absorption and Raman spectroscopy measurements at different excitation wavelengths. The experimental investigation is complemented by quantum-chemical studies to assess the quality of computed density functional theory (DFT) ground state structures and their influence on predicted Raman intensities. In addition, resonance conditions with the optically active HOMO→LUMO transition as well as with the more elusive state dominated by the doubly excited HOMO,HOMO→LUMO,LUMO configuration, are determined with DFT-MRCI calculations and their contributions to Raman activity enhancement are discussed in terms of computed vibrational Huang–Rhys (HR) factors. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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10 pages, 1686 KiB

Open AccessArticle

A Sustainable Synthetic Approach to the Indaceno[1,2-b:5,6-b′]dithiophene (IDT) Core through Cascade Cyclization–Deprotection Reactions

by Giacomo Forti, Andrea Nitti, Gabriele Bianchi, Riccardo Po and Dario Pasini

Chemistry 2022, 4(1), 206-215; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4010018 - 21 Mar 2022

Cited by 2 | Viewed by 2436

Abstract

Bulk heterojunction organic solar cells (BHJs) are competitive within the emerging photovoltaic technologies for solar energy conversion because of their unique advantages. Their development has been boosted recently by the introduction of nonfullerene electron acceptors (NFAs), to be used in combination with a [...] Read more.

Bulk heterojunction organic solar cells (BHJs) are competitive within the emerging photovoltaic technologies for solar energy conversion because of their unique advantages. Their development has been boosted recently by the introduction of nonfullerene electron acceptors (NFAs), to be used in combination with a polymeric electron donor in the active layer composition. Many of the recent advances in NFAs are attributable to the class of fused-ring electron acceptors (FREAs), which is now predominant, with one of the most notable examples being formed with a fused five-member-ring indaceno[1,2-b:5,6-b′]dithiophene (IDT) core. Here, we propose a novel and more sustainable synthesis for the IDT core. Our approach bypasses tin derivatives needed in the Stille condensation, whose byproducts are toxic and difficult to dispose of, and it makes use of cascade reactions, effectively reducing the number of synthetic steps. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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12 pages, 5639 KiB

Open AccessArticle

Q-Tube®-Assisted Alkylation and Arylation of Xanthines and Other N-H-Containing Heterocycles in Water

by Cecilia Scimmi, Margherita Cardinali, Laura Abenante, Marina Amatista, Francesca Giulia Nacca, Eder J. Lenardao, Luca Sancineto and Claudio Santi

Chemistry 2021, 3(4), 1126-1137; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040082 - 01 Oct 2021

Cited by 2 | Viewed by 2858

Abstract

In this paper, a simple and clean process for the alkylation and arylation of nitrogen-containing heterocycles is reported. The reactions were conducted using the Q-tube® as a non-conventional technology, in water as a green solvent, at overboiling temperature. The developed strategy was used [...] Read more.

In this paper, a simple and clean process for the alkylation and arylation of nitrogen-containing heterocycles is reported. The reactions were conducted using the Q-tube® as a non-conventional technology, in water as a green solvent, at overboiling temperature. The developed strategy was used to improve two steps in the total synthesis of caffeine, as reported by Narayan, and then extended to the preparation of N-decorated xanthines. Finally, piperidine, methyl piperazine, and isatine were proven to be suitable substrates for the protocol proposed herein. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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20 pages, 2184 KiB

Open AccessFeature PaperReview

New Materials and Phenomena in Membrane Distillation

by Francesca Alessandro, Francesca Macedonio and Enrico Drioli

Chemistry 2023, 5(1), 65-84; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry5010006 - 02 Jan 2023

Cited by 3 | Viewed by 2720

Abstract

In recent decades, membrane-based processes have been extensively applied to a wide range of industrial processes, including gas separation, food industry, drug purification, and wastewater treatment. Membrane distillation is a thermally driven separation process, in which only vapour molecules transfer through a microporous [...] Read more.

In recent decades, membrane-based processes have been extensively applied to a wide range of industrial processes, including gas separation, food industry, drug purification, and wastewater treatment. Membrane distillation is a thermally driven separation process, in which only vapour molecules transfer through a microporous hydrophobic membrane. At the operational level, the performance of membrane distillation is negatively affected by wetting and temperature polarization phenomena. In order to overcome these issues, advanced membranes have been developed in recent years. This review, which focuses specifically on membrane distillation presents the basic concepts associated with the mass and heat transfer through hydrophobic membranes, membrane properties, and advances in membrane materials. Photothermal materials for solar-driven membrane distillation applications are also presented and discussed. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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17 pages, 370 KiB

Open AccessReview

Modified Mycotoxins, a Still Unresolved Issue

by Alberto Angioni, Mariateresa Russo, Cinzia La Rocca, Ornella Pinto and Alberto Mantovani

Chemistry 2022, 4(4), 1498-1514; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4040099 - 09 Nov 2022

Cited by 2 | Viewed by 1700

Abstract

Mycotoxins are toxic secondary metabolites produced by filamentous microfungi on almost every agricultural commodity worldwide. After the infection of crop plants, mycotoxins are modified by plant enzymes or other fungi and often conjugated to more polar substances, like sugars. The formed—often less toxic—metabolites [...] Read more.

Mycotoxins are toxic secondary metabolites produced by filamentous microfungi on almost every agricultural commodity worldwide. After the infection of crop plants, mycotoxins are modified by plant enzymes or other fungi and often conjugated to more polar substances, like sugars. The formed—often less toxic—metabolites are stored in the vacuole in soluble form or bound to macromolecules. As these substances are usually not detected during routine analysis and no maximum limits are in force, they are called modified mycotoxins. While, in most cases, modified mycotoxins have lower intrinsic toxicity, they might be reactivated during mammalian metabolism. In particular, the polar group might be cleaved off (e.g., by intestinal bacteria), releasing the native mycotoxin. This review aims to provide an overview of the critical issues related to modified mycotoxins. The main conclusion is that analytical aspects, toxicological evaluation, and exposure assessment merit more investigation. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

21 pages, 6813 KiB

Open AccessReview

Atomic Details of Biomineralization Proteins Inspiring Protein Design and Reengineering for Functional Biominerals

by Luigi Franklin Di Costanzo

Chemistry 2022, 4(3), 827-847; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry4030059 - 15 Aug 2022

Cited by 2 | Viewed by 3166

Abstract

Biominerals are extraordinary materials that provide organisms with a variety of functions to support life. The synthesis of biominerals and organization at the macroscopic level is a consequence of the interactions of these materials with proteins. The association of biominerals and proteins is [...] Read more.

Biominerals are extraordinary materials that provide organisms with a variety of functions to support life. The synthesis of biominerals and organization at the macroscopic level is a consequence of the interactions of these materials with proteins. The association of biominerals and proteins is very ancient and has sparked a wealth of research across biological, medical and material sciences. Calcium carbonate, hydroxyapatite, and silica represent widespread natural biominerals. The atomic details of the interface between macromolecules and these biominerals is very intriguing from a chemical perspective, considering the association of chemical entities that are structurally different. With this review I provide an overview of the available structural studies of biomineralization proteins, explored from the Protein Data Bank (wwPDB) archive and scientific literature, and of how these studies are inspiring the design and engineering of proteins able to synthesize novel biominerals. The progression of this review from classical template proteins to silica polymerization seeks to benefit researchers involved in various interdisciplinary aspects of a biomineralization project, who need background information and a quick update on advances in the field. Lessons learned from structural studies are exemplary and will guide new projects for the imaging of new hybrid biomineral/protein superstructures at the atomic level. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

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