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Keywords = hydrated-cation–π interaction

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17 pages, 2381 KB  
Review
From Na2Cl to CaCl: Progress in the 2D Crystals of Unconventional Stoichiometries in Ambient Conditions
by Mengjiao Wu, Xiaoling Lei and Haiping Fang
Solids 2025, 6(3), 38; https://doi.org/10.3390/solids6030038 - 15 Jul 2025
Viewed by 1012
Abstract
Two-dimensional (2D) crystals which present unconventional stoichiometries on graphene surfaces in ambient conditions, such as Na2Cl, Na3Cl, and CaCl, have attracted significant attention in recent years due to their electronic structures and abnormal cation–anion ratios, which differ from those [...] Read more.
Two-dimensional (2D) crystals which present unconventional stoichiometries on graphene surfaces in ambient conditions, such as Na2Cl, Na3Cl, and CaCl, have attracted significant attention in recent years due to their electronic structures and abnormal cation–anion ratios, which differ from those of conventional three-dimensional crystals. This unconventional crystallization is attributed to the cation–π interaction between ions and the π-conjugated system of the graphene surface. Consequently, their physical and chemical properties—including their electrical, optical, magnetic, and mechanical characteristics—often differ markedly from those of conventional crystals. This review summarizes the recent progress made in the fabrication and analysis of the structures, distinctive features, and applications of these 2D unconventional stoichiometry crystals on graphene surfaces in ambient conditions. Their special properties, including their piezoelectricity, metallicity, heterojunction, and room-temperature ferromagnetism, are given particularly close attention. Finally, some significant prospects and further developments in this exciting interdisciplinary field are proposed. Full article
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14 pages, 2619 KB  
Article
«Green-Ligand» in Metallodrugs Design—Cu(II) Complex with Phytic Acid: Synthetic Approach, EPR-Spectroscopy, and Antimycobacterial Activity
by Kseniya A. Koshenskova, Natalia V. Makarenko, Fedor M. Dolgushin, Dmitriy S. Yambulatov, Olga B. Bekker, Matvey V. Fedin, Sergei A. Dementev, Olesya A. Krumkacheva, Igor L. Eremenko and Irina A. Lutsenko
Molecules 2025, 30(2), 313; https://doi.org/10.3390/molecules30020313 - 15 Jan 2025
Viewed by 1538
Abstract
The interaction of sodium phytate hydrate C6H18O24P6·xNa·yH2O (phytNa) with Cu(OAc)2·H2O and 1,10-phenanthroline (phen) led to the anionic tetranuclear complex [Cu4(H2O)4(phen)4(phyt)]·2Na+ [...] Read more.
The interaction of sodium phytate hydrate C6H18O24P6·xNa·yH2O (phytNa) with Cu(OAc)2·H2O and 1,10-phenanthroline (phen) led to the anionic tetranuclear complex [Cu4(H2O)4(phen)4(phyt)]·2Na+·2NH4+·32H2O (1), the structure of the latter was determined by X-ray diffraction analysis. The phytate 1 is completely deprotonated; six phosphate fragments (with atoms P1–P6) are characterized by different spatial arrangements relative to the cyclohexane ring (1a5e conformation), which determines two different types of coordination to the complexing agents—P1 and P3, P4, and P6 have monodentate, while P2 and P5 are bidentately bound to Cu2+ cations. The molecular structure of the anion complex is stabilized by a set of strong intramolecular hydrogen bonds involving coordinated water molecules. Aromatic systems of phen ligands chelating copper ions participate in strong intramolecular and intermolecular π-π interactions, further contributing to their association. At the supramolecular level, endless stacks are formed, in the voids of which sodium and ammonium cations and water molecules are present. The stability of 1 in the presence of human serum albumin (HSA) was investigated using Electron Paramagnetic Resonance (EPR) spectroscopy. Continuous wave (CW) EPR spectra in water/glycerol frozen solution clearly indicate a presence of an exchange-coupled Cu(II)-Cu(II) dimeric unit, as well as a Cu(II) monomer-like signal arising from spins sufficiently distant from each other, with comparable contributions of two types of signals. In the presence of albumin at a 1:1 ratio (1 to albumin), the EPR spectrum changes significantly, primarily due to the reduced contribution of the S = 1 fraction showing dipole–dipole splitting. The biological activity of 1 in vitro against the non-pathogenic (model for Mycobacterium tuberculosis) strain of Mycolicibacterium smegmatis is comparable to the first-line drug for tuberculosis treatment, rifampicin. Full article
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12 pages, 8437 KB  
Article
Two-Dimensional Graphene-Based Potassium Channels Built at an Oil/Water Interface
by Xiaoyuan Wang, Hanhan Yang, Zhenmei Yu, Zengtao Zhang and Yong Chen
Materials 2023, 16(15), 5393; https://doi.org/10.3390/ma16155393 - 31 Jul 2023
Cited by 2 | Viewed by 1274
Abstract
Graphene-based laminar membranes exhibit remarkable ion sieving properties, but their monovalent ion selectivity is still low and much less than the natural ion channels. Inspired by the elementary structure/function relationships of biological ion channels embedded in biomembranes, a new strategy is proposed herein [...] Read more.
Graphene-based laminar membranes exhibit remarkable ion sieving properties, but their monovalent ion selectivity is still low and much less than the natural ion channels. Inspired by the elementary structure/function relationships of biological ion channels embedded in biomembranes, a new strategy is proposed herein to mimic biological K+ channels by using the graphene laminar membrane (GLM) composed of two-dimensional (2D) angstrom(Å)-scale channels to support a simple model of semi-biomembrane, namely oil/water (O/W) interface. It is found that K+ is strongly preferred over Na+ and Li+ for transferring across the GLM-supported water/1,2-dichloroethane (W/DCE) interface within the same potential window (-0.1-0.6 V), although the monovalent ion selectivity of GLM under the aqueous solution is still low (K+/Na+~1.11 and K+/Li+~1.35). Moreover, the voltammetric responses corresponding to the ion transfer of NH4+ observed at the GLM-supported W/DCE interface also show that NH4+ can often pass through the biological K+ channels due to their comparable hydration–free energies and cation-π interactions. The underlying mechanism of as-observed K+ selective voltammetric responses is discussed and found to be consistent with the energy balance of cationic partial-dehydration (energetic costs) and cation-π interaction (energetic gains) as involved in biological K+ channels. Full article
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15 pages, 4059 KB  
Article
Structure Guiding Supramolecular Assemblies in Metal-Organic Multi-Component Compounds of Mn(II): Experimental and Theoretical Studies
by Manjit K. Bhattacharyya, Kamal K. Dutta, Pranay Sharma, Rosa M. Gomila, Miquel Barceló-Oliver and Antonio Frontera
Crystals 2023, 13(5), 837; https://doi.org/10.3390/cryst13050837 - 18 May 2023
Cited by 7 | Viewed by 1917
Abstract
Two multi-component coordination compounds of Mn(II), viz. [Mn(H2O)6](2-Mepy)2(4-NO2bz)2·2H2O (1) and [Mn(H2O)6][Mn(2,3-PDCH)3]2 (2) (where, 2-Mepy = 2-methylpyridine, 4-NO2bz = [...] Read more.
Two multi-component coordination compounds of Mn(II), viz. [Mn(H2O)6](2-Mepy)2(4-NO2bz)2·2H2O (1) and [Mn(H2O)6][Mn(2,3-PDCH)3]2 (2) (where, 2-Mepy = 2-methylpyridine, 4-NO2bz = 4-nitrobenzoate, 2,3-PDC = 2,3-pyridinedicarboxylate), have been synthesized and characterized using elemental, spectroscopic (FT-IR and electronic), TGA and single-crystal X-ray diffraction analyses. Complex 1 is a co-crystal hydrate of Mn(II) involving uncoordinated 2-Mepy, 4-NO2bz and water molecules; while compound 2 is a multi-component molecular complex salt of Mn(II) comprising cationic [Mn(H2O)6]2+ and anionic [Mn(2,3-PDCH)3]complex moieties. The uncoordinated 2-Mepy and 4-NO2bz moieties of 1 are involved in lone-pair (l.p)-π and C–H⋯π interactions which stabilize the layered assembly of the compound. The crystal structure of compound 2 has been previously reported. However, we have explored the unusual enclathration of complex cationic moieties within the supramolecular host cavities formed by the molecular assembly of complex anionic moieties. The supramolecular assemblies obtained in the crystal structure have been further studied theoretically using DFT calculations, quantum theory of atoms-in-molecules (QTAIM) and non-covalent interaction plot (NCI plot) computational tools. Theoretical studies reveal that the combination of π-staking interactions (l.p-π, π-π and C–H···π) have more structure-guiding roles compared to the H-bonds. The large binding energy of π-stacking interactions in 2 is due to the antiparallel orientation of aromatic rings and their coordination to the metal centers, thereby increasing the contribution of the dipole–dipole interactions. Full article
(This article belongs to the Special Issue Mixed-Metal Coordination Polymers)
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13 pages, 2937 KB  
Article
High-Efficiency Ion Enrichment inside Ultra-Short Carbon Nanotubes
by Yu Qiang, Xueliang Wang, Zhemian Ying, Yuying Zhou, Renduo Liu, Siyan Gao and Long Yan
Nanomaterials 2022, 12(19), 3528; https://doi.org/10.3390/nano12193528 - 9 Oct 2022
Cited by 3 | Viewed by 2718
Abstract
The ion-enrichment inside carbon nanotubes (CNTs) offers the possibility of applications in water purification, ion batteries, memory devices, supercapacitors, field emission and functional hybrid nanostructures. However, the low filling capacity of CNTs in salt solutions due to end caps and blockages remains a [...] Read more.
The ion-enrichment inside carbon nanotubes (CNTs) offers the possibility of applications in water purification, ion batteries, memory devices, supercapacitors, field emission and functional hybrid nanostructures. However, the low filling capacity of CNTs in salt solutions due to end caps and blockages remains a barrier to the practical use of such applications. In this study, we fabricated ultra-short CNTs that were free from end caps and blockages using ball milling and acid pickling. We then compared their ion-enrichment capacity with that of long CNTs. The results showed that the ion-enrichment capacity of ultra-short CNTs was much higher than that of long CNTs. Furthermore, a broad range of ions could be enriched in the ultra-short CNTs including alkali-metal ions (e.g., K+), alkaline-earth-metal ions (e.g., Ca2+) and heavy-metal ions (e.g., Pb2+). The ultra-short CNTs were much more unobstructed than the raw long CNTs, which was due to the increased orifice number per unit mass of CNTs and the decreased difficulty in removing the blockages in the middle section inside the CNTs. Under the hydrated-cation–π interactions, the ultra-short CNTs with few end caps and blockages could highly efficiently enrich ions. Full article
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27 pages, 6076 KB  
Article
Density Functional Method Study on the Cooperativity of Intermolecular H-bonding and π-π+ Stacking Interactions in Thymine-[Cnmim]Br (n = 2, 4, 6, 8, 10) Microhydrates
by Yanni Wang, Chaowu Dai, Wei Huang, Tingting Ni, Jianping Cao, Jiangmei Pang, Huining Wei and Chaojie Wang
Molecules 2022, 27(19), 6242; https://doi.org/10.3390/molecules27196242 - 22 Sep 2022
Cited by 1 | Viewed by 2514
Abstract
The exploration of the ionic liquids’ mechanism of action on nucleobase’s structure and properties is still limited. In this work, the binding model of the 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br, n = 2, 4, 6, 8, 10) ionic liquids to the thymine (T) [...] Read more.
The exploration of the ionic liquids’ mechanism of action on nucleobase’s structure and properties is still limited. In this work, the binding model of the 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br, n = 2, 4, 6, 8, 10) ionic liquids to the thymine (T) was studied in a water environment (PCM) and a microhydrated surroundings (PCM + wH2O). Geometries of the mono-, di-, tri-, and tetra-ionic thymine (T-wH2O-y[Cnmim]+-xBr, w = 5~1 and x + y = 0~4) complexes were optimized at the M06-2X/6-311++G(2d, p) level. The IR and UV-Vis spectra, QTAIM, and NBO analysis for the most stable T-4H2O-Br-1, T-3H2O-[Cnmim]+-Br-1, T-2H2O-[Cnmim]+-2Br-1, and T-1H2O-2[Cnmim]+-2Br-1 hydrates were presented in great detail. The results show that the order of the arrangement stability of thymine with the cations (T-[Cnmim]+) by PCM is stacking > perpendicular > coplanar, and with the anion (T-Br) is front > top. The stability order for the different microhydrates is following T-5H2O-1 < T-4H2O-Br-1 < T-3H2O-[Cnmim]+-Br-1 < T-2H2O-[Cnmim]+-2Br-1 < T-1H2O-2[Cnmim]+-2Br-1. A good linear relationship between binding EB values and the increasing number (x + y) of ions has been found, which indicates that the cooperativity of interactions for the H-bonding and π-π+ stacking is varying incrementally in the growing ionic clusters. The stacking model between thymine and [Cnmim]+ cations is accompanied by weaker hydrogen bonds which are always much less favorable than those in T-xBr complexes; the same trend holds when the clusters in size grow and the length of alkyl chains in the imidazolium cations increase. QTAIM and NBO analytical methods support the existence of mutually reinforcing hydrogen bonds and π-π cooperativity in the systems. Full article
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10 pages, 3795 KB  
Article
Size-Dependent Spontaneous Separation of Colloidal Particles in Sub-Microliter Suspension by Cations
by Shiqi Sheng, Haijun Yang, Yongshun Song, Ruoyang Chen, Shanshan Liang and Haiping Fang
Int. J. Mol. Sci. 2022, 23(15), 8055; https://doi.org/10.3390/ijms23158055 - 22 Jul 2022
Cited by 3 | Viewed by 2253
Abstract
Great efforts have been made to separate micro/nanoparticles in small-volume specimens, but it is a challenge to achieve the simple, maneuverable and low-cost separation of sub-microliter suspension with large separation distances. By simply adding trace amounts of cations (Mg2+/Ca2+/Na [...] Read more.
Great efforts have been made to separate micro/nanoparticles in small-volume specimens, but it is a challenge to achieve the simple, maneuverable and low-cost separation of sub-microliter suspension with large separation distances. By simply adding trace amounts of cations (Mg2+/Ca2+/Na+), we experimentally achieved the size-dependent spontaneous separation of colloidal particles in an evaporating droplet with a volume down to 0.2 μL. The separation distance was at a millimeter level, benefiting the subsequent processing of the specimen. Within only three separating cycles, the mass ratio between particles with diameters of 1.0 μm and 0.1 μm can be effectively increased to 13 times of its initial value. A theoretical analysis indicates that this spontaneous separation is attributed to the size-dependent adsorption between the colloidal particles and the aromatic substrate due to the strong hydrated cation-π interactions. Full article
(This article belongs to the Special Issue Non-covalent Interaction)
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11 pages, 2676 KB  
Article
Mechanism for the Intercalation of Aniline Cations into the Interlayers of Graphite
by Yifan Guo, Ying Li, Wei Wei, Junhua Su, Jinyang Li, Yanlei Shang, Yong Wang, Xiaoling Xu, David Hui and Zuowan Zhou
Nanomaterials 2022, 12(14), 2486; https://doi.org/10.3390/nano12142486 - 20 Jul 2022
Cited by 4 | Viewed by 2802
Abstract
The dynamic behaviors of aniline cation (ANI+) intercalating into graphite interlayers are systematically studied by experimental studies and multiscale simulations. The in situ intercalation polymerization designed by response surface methods implies the importance of ultrasonication for achieving the intercalation of ANI [...] Read more.
The dynamic behaviors of aniline cation (ANI+) intercalating into graphite interlayers are systematically studied by experimental studies and multiscale simulations. The in situ intercalation polymerization designed by response surface methods implies the importance of ultrasonication for achieving the intercalation of ANI+. Molecular dynamics and quantum chemical simulations prove the adsorption of ANI+ onto graphite surfaces by cation–π electrostatic interactions, weakening the π–π interactions between graphene layers. The ultrasonication that follows breaks the hydrated ANI+ clusters into individual ANI+. Thus, the released positive charges of these dissociative cations and reduced steric hindrance significantly improve their intercalation ability. With the initial kinetic energy provided by ultrasonic field, the activated ANI+ are able to intercalate into the interlayer of graphite. This work demonstrates the intercalation behaviors of ANI+, which provides an opportunity for investigations regarding organic-molecule-intercalated graphite compounds. Full article
(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)
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18 pages, 2815 KB  
Article
Sponge-Like Water De-/Ad-Sorption versus Solid-State Structural Transformation and Colour-Changing Behavior of an Entangled 3D Composite Supramolecuar Architecture, [Ni4(dpe)4(btc)2(Hbtc)(H2O)9]·3H2O
by Chih-Chieh Wang, Szu-Yu Ke, Kuan-Ting Chen, Ning-Kuei Sun, Wei-Fang Liu, Mei-Lin Ho, Bing-Jyun Lu, Yi-Ting Hsieh, Yu-Chun Chuang, Gene-Hsiang Lee, Shi-Yi Huang and En-Che Yang
Polymers 2018, 10(9), 1014; https://doi.org/10.3390/polym10091014 - 11 Sep 2018
Cited by 8 | Viewed by 4391
Abstract
An entangled composite compound, [Ni4(dpe)4(btc)2(Hbtc)(H2O)9]·3H2O (1), where H3btc = 1,3,5-benzenetricarboxylic acid and dpe = 1,2-bis(4-pyridyl)ethane, has been synthesized and structurally characterized. Single-crystal structural determination reveals that compound [...] Read more.
An entangled composite compound, [Ni4(dpe)4(btc)2(Hbtc)(H2O)9]·3H2O (1), where H3btc = 1,3,5-benzenetricarboxylic acid and dpe = 1,2-bis(4-pyridyl)ethane, has been synthesized and structurally characterized. Single-crystal structural determination reveals that compound 1 consists of four coordination polymers (CPs), with two two-dimensional (2D) (4,4) layered metal-organic frameworks (MOFs) of [Ni(dpe)(Hbtc)(H2O)] and [Ni(dpe)(btc)(H2O)] anion, and two one-dimensional (1D) polymeric chains of [Ni(dpe)(btc)(H2O)3] anion and [Ni(dpe)(H2O)4]2+ cation, respectively. The three-dimensional (3D) supramolecular architecture of 1 is constructed via the inter-penetration of inter-digited, double-layered, 2D rectangle-grid MOFs by two 1D coordination polymeric chains, and tightly entangled together via the combination of inter-CPs π–π stacking and hydrogen bonding interactions. The ad-/de-sorption isotherms of 1 for water displays a hysteresis profile with a maximum adsorption of 17.66 water molecules of per molecule unit at relative P/P0 < 0.89. The reversible de-/re-hydration processes in 1 monitored by cyclic water de-/ad-sorption TG analysis and PXRD measurements evidence a sponge-like water de-/ad-sorption property associated with a thermal-induced solid-state structural transformation. The magnetic property of 1 suggests that the ferromagnetic coupling might refer to a stronger inter-Ni(II) interaction, which could be along the btc3− or Hbtc2− ligands; the antiferromagnetic coupling corresponding to the weaker inter-Ni(II) interactions, which could be the dpe ligands for the 2D framework. Full article
(This article belongs to the Special Issue Advances in Coordination Polymers)
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