Research

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11 pages, 5751 KiB

Open AccessArticle

Fabrication of Phosphorus-Doped Cobalt Silicate with Improved Electrochemical Properties

by Jie Ji, Yunfeng Zhao, Yifu Zhang, Xueying Dong, Changgong Meng and Xiaoyang Liu

Molecules 2021, 26(20), 6240; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26206240 - 15 Oct 2021

Cited by 4 | Viewed by 1473

The development of electrode materials for supercapacitors (SCs) is greatly desired, and this still poses an immense challenge for researchers. Cobalt silicate (Co₂SiO₄, denoted as CoSi) with a high theoretical capacity is deemed to be one of the sustainable [...] Read more.

The development of electrode materials for supercapacitors (SCs) is greatly desired, and this still poses an immense challenge for researchers. Cobalt silicate (Co₂SiO₄, denoted as CoSi) with a high theoretical capacity is deemed to be one of the sustainable electrode materials for SCs. However, its achieved electrochemical properties are still not satisfying. Herein, the phosphorus (P)-doped cobalt silicate, denoted as PCoSi, is synthesized by a calcining strategy. The PCoSi exhibits 1D nanobelts with a specific surface area of 46 m²∙g⁻¹, and it can significantly improve the electrochemical properties of CoSi. As a supercapacitor’s (SC’s) electrode, the specific capacitance of PCoSi attains 434 F∙g⁻¹ at 0.5 A∙g⁻¹, which is much higher than the value of CoSi (244 F∙g⁻¹ at 0.5 A∙g⁻¹). The synergy between the composition and structure endows PCoSi with attractive electrochemical properties. This work provides a novel strategy to improve the electrochemical performances of transition metal silicates. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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31 pages, 10620 KiB

Open AccessArticle

Synthesis, Characterization, and Non-Covalent Interactions of Palladium(II)-Amino Acid Complexes

by David B. Hobart, Jr., Michael A. G. Berg, Hannah M. Rogers and Joseph S. Merola

Molecules 2021, 26(14), 4331; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26144331 - 17 Jul 2021

Cited by 3 | Viewed by 2042

Abstract

The reaction of palladium(II) acetate with acyclic amino acids in acetone/water yields square planar bis-chelated palladium amino acid complexes that exhibit interesting non-covalent interactions. In all cases, complexes were examined by multiple spectroscopic techniques, especially HRMS (high resolution mass spectrometry), IR (infrared spectroscopy), [...] Read more.

The reaction of palladium(II) acetate with acyclic amino acids in acetone/water yields square planar bis-chelated palladium amino acid complexes that exhibit interesting non-covalent interactions. In all cases, complexes were examined by multiple spectroscopic techniques, especially HRMS (high resolution mass spectrometry), IR (infrared spectroscopy), and ¹H NMR (nuclear magnetic resonance) spectroscopy. In some cases, suitable crystals for single crystal X-ray diffraction were able to be grown and the molecular structure was obtained. The molecular geometries of the products are discussed. Except for the alanine complex, all complexes incorporate water molecules into the extended lattice and exhibit N-H···O and/or O···(HOH)···O hydrogen bonding interactions. The non-covalent interactions are discussed in terms of the extended lattice structures exhibited by the structures. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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12 pages, 3633 KiB

Open AccessArticle

Pressure-Dependent Structure of Methanol–Water Mixtures up to 1.2 GPa: Neutron Diffraction Experiments and Molecular Dynamics Simulations

by László Temleitner, Takanori Hattori, Jun Abe, Yoichi Nakajima and László Pusztai

Molecules 2021, 26(5), 1218; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26051218 - 25 Feb 2021

Cited by 2 | Viewed by 1643

Abstract

Total scattering structure factors of per-deuterated methanol and heavy water, CD₃OD and D₂O, have been determined across the entire composition range as a function of pressure up to 1.2 GPa, by neutron diffraction. The largest variations due to increasing [...] Read more.

Total scattering structure factors of per-deuterated methanol and heavy water, CD₃OD and D₂O, have been determined across the entire composition range as a function of pressure up to 1.2 GPa, by neutron diffraction. The largest variations due to increasing pressure were observed below a scattering variable value of 5 Å⁻¹, mostly as shifts in terms of the positions of the first and second maxima. Molecular dynamics computer simulations, using combinations of all-atom potentials for methanol and various water force fields, were conducted at the experimental pressures with the aim of interpreting neutron diffraction results. The peak-position shifts mentioned above could be qualitatively reproduced by simulations, although in terms of peak intensities, the accord between neutron diffraction and molecular dynamics was much less satisfactory. However, bearing in mind that increasing pressure must have a profound effect on repulsive forces between neighboring molecules, the agreement between experiment and computer simulation can certainly be termed as satisfactory. In order to reveal the influence of changing pressure on local intermolecular structure in these “simplest of complex” hydrogen-bonded liquid mixtures, simulated structures were analyzed in terms of hydrogen bond-related partial radial distribution functions and size distributions of hydrogen-bonded cyclic entities. Distinct differences between pressure-dependent structures of water-rich and methanol-rich composition regions were revealed. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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13 pages, 2644 KiB

Open AccessFeature PaperArticle

The Importance of Strain (Preorganization) in Beryllium Bonds

by Ibon Alkorta, José Elguero, Josep M. Oliva-Enrich, Manuel Yáñez, Otilia Mó and M. Merced Montero-Campillo

Molecules 2020, 25(24), 5876; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25245876 - 11 Dec 2020

Cited by 3 | Viewed by 1939

Abstract

In order to explore the angular strain role on the ability of Be to form strong beryllium bonds, a theoretical study of the complexes of four beryllium derivatives of orthocloso-carboranes with eight molecules (CO, N₂, NCH, CNH, OH₂ [...] Read more.

In order to explore the angular strain role on the ability of Be to form strong beryllium bonds, a theoretical study of the complexes of four beryllium derivatives of orthocloso-carboranes with eight molecules (CO, N₂, NCH, CNH, OH₂, SH₂, NH₃, and PH₃) acting as Lewis bases has been carried out at the G4 computational level. The results for these complexes, which contain besides Be other electron-deficient elements, such as B, have been compared with the analogous ones formed by three beryllium salts (BeCl₂, CO₃Be and SO₄Be) with the same set of Lewis bases. The results show the presence of large and positive values of the electrostatic potential associated to the beryllium atoms in the isolated four beryllium derivatives of ortho-carboranes, evidencing an intrinsically strong acidic nature. In addition, the LUMO orbital in these systems is also associated to the beryllium atom. These features led to short intermolecular distances and large dissociation energies in the complexes of the beryllium derivatives of ortho-carboranes with the Lewis bases. Notably, as a consequence of the special framework provided by the ortho-carboranes, some of these dissociation energies are larger than the corresponding beryllium bonds in the already strongly bound SO₄Be complexes, in particular for N₂ and CO bases. The localized molecular orbital energy decomposition analysis (LMOEDA) shows that among the attractive terms associated with the dissociation energy, the electrostatic term is the most important one, except for the complexes with the two previously mentioned weakest bases (N₂ and CO), where the polarization term dominates. Hence, these results contribute to further confirm the importance of bending on the beryllium environment leading to strong interactions through the formation of beryllium bonds. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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8 pages, 2063 KiB

Open AccessCommunication

Strong Affinity of Triazolium-Appended Dipyrromethenes (TADs) for BF₄⁻

by Charles Guérin, Zhan Zhang, Ludivine Jean-Gérard, Stephan Steinmann, Carine Michel and Bruno Andrioletti

Molecules 2020, 25(19), 4555; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25194555 - 05 Oct 2020

Cited by 2 | Viewed by 1919

Abstract

Because BF₄⁻ is a labile, non- or weakly coordinating anion, it is generally chosen by chemists who do not want the anion to interfere with the associated cation. Herein, we demonstrate that BF₄⁻ actually strongly binds to triazole-appended dipyrromethenes [...] Read more.

Because BF₄⁻ is a labile, non- or weakly coordinating anion, it is generally chosen by chemists who do not want the anion to interfere with the associated cation. Herein, we demonstrate that BF₄⁻ actually strongly binds to triazole-appended dipyrromethenes (TADs). In particular, HETCOR NMR experiments and DFT calculations were used to rationalize the results observed with anion titrations. Hence, special care should be taken when considering that BF₄⁻ is innocent. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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20 pages, 3823 KiB

Open AccessFeature PaperArticle

Exploring the Polymorphism of Drostanolone Propionate

by Gheorghe Borodi, Alexandru Turza and Attila Bende

Molecules 2020, 25(6), 1436; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25061436 - 21 Mar 2020

Cited by 10 | Viewed by 6448

Abstract

2α-Methyl-4,5α-dihydrotestosterone 17β-propionate, known as drostanolone propionate or masteron, is a synthetic anabolic-androgenic steroid derived from dihydrotestosterone. The crystal structures of two polymorphs of drostanolone propionate have been determined by single crystal X-ray diffraction and both crystallizes in the monoclinic crystal system. One is [...] Read more.

2α-Methyl-4,5α-dihydrotestosterone 17β-propionate, known as drostanolone propionate or masteron, is a synthetic anabolic-androgenic steroid derived from dihydrotestosterone. The crystal structures of two polymorphs of drostanolone propionate have been determined by single crystal X-ray diffraction and both crystallizes in the monoclinic crystal system. One is belonging to the P2₁ space group, Z = 2, and has one molecule in the asymmetric unit while the second belongs to the I2 space group, Z = 4, and contains two molecules in the asymmetric unit. Another polymorph has been investigated by an X-ray powder diffraction method and solved by Parallel tempering/Monte Carlo technique and refined with the Rietveld method. This polymorph crystallizes in the orthorhombic P2₁2₁2₁ space group, Z = 4 having one molecule in the asymmetric unit. The structural configuration analysis shows that the A, B, and C steroid rings exist as chair geometry, while ring D adopts a C13 distorted envelope configuration in all structures. For all polymorphs, the lattice energy has been computed by CLP (Coulomb-London-Pauli), and tight-binding density functional theory methods. Local electron correlation methods were used to estimate the role of electron correlation in the magnitude of the dimer energies. The nature of the intermolecular interactions has been analyzed by the SAPT0 energy decomposition methods as well as by Hirshfeld surfaces. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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13 pages, 1645 KiB

Open AccessArticle

Isostructural Inorganic–Organic Piperazine-1,4-diium Chlorido- and Bromidoantimonate(III) Monohydrates: Octahedral Distortions and Hydrogen Bonds

by Maciej Bujak and Dawid Siodłak

Molecules 2020, 25(6), 1361; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25061361 - 17 Mar 2020

Cited by 3 | Viewed by 2187

Abstract

Halogenidoantimonate(III) monohydrates of the (C₄H₁₂N₂)[SbX₅]·H₂O (X = Cl, 1 or Br, 2) formula, crystallizing in the same monoclinic space group of P2₁/n, are isostructural, with an isostructurality [...] Read more.

Halogenidoantimonate(III) monohydrates of the (C₄H₁₂N₂)[SbX₅]·H₂O (X = Cl, 1 or Br, 2) formula, crystallizing in the same monoclinic space group of P2₁/n, are isostructural, with an isostructurality index close to 99%. The single crystal X-ray diffraction data do not show any indication of phase transition in cooling these crystals from room temperature to 85 K. Both hybrid crystals are built up from [SbX₆]^3– octahedra that are joined together by a common edge forming isolated bioctahedral [Sb₂X₁₀]^4– units, piperazine-1,4-diium (C₄H₁₂N₂)²⁺ cations and water of crystallization molecules. These structural components are joined together by related but somewhat different O/N/C–H···X and N–H···O hydrogen bonded systems. The evolution of structural parameters, notably the secondary Sb–X bonds along with the associated X/Sb–Sb/X–X/Sb angles and O/N/C–H···X hydrogen bonds, as a function of ligand exchange and temperature, along with their influence on the irregularity of [SbX₆]^3– octahedra, was determined. The comparison of packing features and hydrogen bond parameters, additionally supported by the Hirshfeld surface analysis and data retrieved from the Cambridge Structural Database, demonstrates the hierarchy and importance of hydrogen bond interactions that influence the irregularity of single [SbX₆]^3– units. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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Review

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24 pages, 3543 KiB

Open AccessFeature PaperReview

Hydrogen-Mediated Noncovalent Interactions in Solids: What Can NMR Crystallography Tell About?

by Ioana Georgeta Grosu, Xenia Filip, Maria O. Miclăuș and Claudiu Filip

Molecules 2020, 25(16), 3757; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25163757 - 18 Aug 2020

Cited by 8 | Viewed by 3011

Abstract

Hydrogen atoms play a crucial role in the aggregation of organic (bio)molecules through diverse number of noncovalent interactions that they mediate, such as electrostatic in proton transfer systems, hydrogen bonding, and CH–π interactions, to mention only the most prominent. To identify and adequately [...] Read more.

Hydrogen atoms play a crucial role in the aggregation of organic (bio)molecules through diverse number of noncovalent interactions that they mediate, such as electrostatic in proton transfer systems, hydrogen bonding, and CH–π interactions, to mention only the most prominent. To identify and adequately describe such low-energy interactions, increasingly sensitive methods have been developed over time, among which quantum chemical computations have witnessed impressive advances in recent years. For reaching the present state-of-the-art, computations had to rely on a pool of relevant experimental data, needed at least for validation, if not also for other purposes. In the case of molecular crystals, the best illustration for the synergy between computations and experiment is given by the so-called NMR crystallography approach. Originally designed to increase the confidence level in crystal structure determination of organic compounds from powders, NMR crystallography is able now to offer also a wealth of information regarding the noncovalent interactions that drive molecules to pack in a given crystalline pattern or another. This is particularly true for the noncovalent interactions which depend on the exact location of labile hydrogen atoms in the system: in such cases, NMR crystallography represents a valuable characterization tool, in some cases complementing even the standard single-crystal X-ray diffraction technique. A concise introduction in the field is made in this mini-review, which is aimed at providing a comprehensive picture with respect to the current accuracy level reached by NMR crystallography in the characterization of hydrogen-mediated noncovalent interactions in organic solids. Different types of practical applications are illustrated with the example of molecular crystals studied by our research group, but references to other representative developments reported in the literature are also made. By summarizing the major concepts and methodological progresses, the present work is also intended to be a guide to the practical potential of this relatively recent analytical tool for the scientists working in areas where crystal engineering represents the main approach for rational design of novel materials. Full article

(This article belongs to the Special Issue Non-Covalent Interaction in Solids and Large Clusters)

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