Structural Chemistry最新文献

We explore intriguing parallels between the work Alan Mackay and the mathematician B. N. Delone.

Toxic insecticide vapours such as allethrin and permethrin pose significant threats to the environment. The current work brings us closer to insights on the detection of allethrin and permethrin using a new two-dimensional (2D) beta arsenic antimonene (β-AsSb) nanosheet as a vapour sensor. The structural stability of the buckled β-AsSb nanosheet is confirmed and exhibits an energy band gap of 2.304 eV. We used a semiconductor β-AsSb nanosheet as a base material to adsorb allethrin and permethrin. The variations in the electronic properties of β-AsSb nanosheet are tracked based on the charge transfer, projected density of states spectrum, charge density difference and electron localisation function results. Moreover, both allethrin and permethrin are physically adsorbed on β-AsSb nanosheet, as observed from the adsorption energy results. The adsorption/desorption of allethrin and permethrin on β-AsSb nanosheet makes it a suitable sensing element for allethrin and permethrin molecules.

Fivefold symmetry is incompatible with the translational periodicity of two-dimensional crystalline lattices. Nonetheless, aperiodic tilings, such as those introduced by Penrose and anticipated in Islamic geometric art, have demonstrated that local fivefold symmetry and long-range order can coexist without periodic repetition. Inspired by these mathematical constructs, recent advances in surface science have enabled the study of molecular self-assembly in two dimensions using molecules with intrinsic fivefold symmetry. In particular, penta-substituted derivatives of corannulene—rigid, bowl-shaped molecules resembling hard pentagons—exhibit intriguing self-assembly behavior on metal surfaces. Scanning tunneling microscopy (STM) reveals that these molecules organize into dense monolayers with stripe and rotator packing motifs reminiscent of theoretically predicted pentagonal tilings. Subtle variations in chirality and substitution patterns lead to diverse plane group symmetries (pm, p1, p2gg), domain boundaries, and packing densities. The balance between molecular geometry, chirality, and substrate interactions governs the emergence of ordered phases. These findings deepen our understanding of symmetry frustration, quasiperiodicity, and the transition between local and global order in molecular monolayers, with implications for the design of functional nanostructured materials.

Pyrochlore oxides are progressively becoming potential candidates for thermoelectric power generation and solar energy owing to their unique electronic structures that are advantageous for optoelectronic and thermoelectric characteristics. The spintronic, optoelectronic and thermoelectric properties of novel pyrochlore oxides including RE₂Th₂O₇ (RE = Nd, Pr) are analyzed to evaluate their potential for industrial applications. All Calculations are performed using ab-initio calculations based on density functional theory (DFT) approach. Nd₂Th₂O₇ and Pr₂Th₂O₇ are direct bandgap semiconductors with energy bandgaps of 2.88 and 2.79 eV, respectively, in both spin channels. Their paramagnetic behavior is analyzed, and magnetic moments can be deduced by examining band patterns perceived in energy band structures of RE₂Th₂O₇ (RE = Nd, Pr) associated electronic states in spin up and spin down channels. Significant values of magnetic moments (({mu }_{B})) for Nd₂Th₂O₇ and Pr₂Th₂O₇ are 12.0 and 7.001, respectively. RE₂Th₂O₇ (RE = Nd, Pr) show a significant absorption of incident photons in the near-UV constituency in both spin channels. The optical reflectivity spectra (R(omega )) for RE₂Th₂O₇ (RE = Nd, Pr) exhibit a lower reflectance value of about 20% within presented energy range. The positive values of Seebeck coefficient ((S)) indicate p-type semiconducting behavior of RE₂Th₂O₇ (RE = Nd, Pr). Nd₂Th₂O₇ is promising candidate for thermoelectric device applications as its ZT value is 0.99.

Intermolecular interactions play a pivotal role in chemical processes such as catalysis, crystal formation, and drug-protein complexation. The Quantum Theory of Atoms in Molecules (QTAIM) provides a robust framework for analyzing these interactions through topological descriptors of electron density. However, the computational cost of obtaining accurate electron density distributions for large systems remains a challenge. This study critically evaluates the promolecular approximation (Independent Atom Model, IAM) as a cost-effective alternative for QTAIM analysis, focusing on its ability to describe various non-covalent interactions, including hydrogen bonds, halogen bonds, π…π stacking, and dispersion interactions. By comparing promolecular and density functional theory (DFT) results across diverse molecular systems, we demonstrate that the IAM model reliably reproduces trends in QTAIM descriptors, particularly for weaker and medium-strength interactions. However, in the case of some types of non-directional interactions, the molecular graph is often incorrectly predicted. Furthermore, we propose a semi-quantitative model to estimate intermolecular binding energies using promolecular-derived descriptors, showcasing the potential of IAM for large-scale applications in supramolecular chemistry and materials science.

Conventional nitrogen bases such as ammonia, methanimine, hydrogen cyanide, and pyridine become very strong acids upon complexation with diborane(4), a very efficient electron donor whose structure was elucidated, among others, by Pople. The present study uses G4 high-level ab initio calculations and different chemical bonding tools to delve into the reasons why this fact occurs. We observe that the acidity of B₂H₄–N-Base complexes, in terms of the ionization constant, increases from 38 to 58 orders of magnitude compared to the corresponding free N-Bases, thus switching from different degrees of basicity to super acidic forms. Even though the formation of the complex involves breaking one of the characteristic (3c,2e) bonds of diborane(4), the neutral adduct is more stabilized the stronger the N-Base. The deprotonation of the N-Base significantly alters the structural and electronic landscape of the complex; in fact, the bridged B₂H₄ moiety is preserved for complexes with hydrogen cyanide and pyridine but fully rearranged with ammonia and methanimine. These latter rearrangements result in anionic global minima [BH₃–BHNH₂]⁻ and [BH₃–BHN=CH₂]⁻, whose very strong B-N bonds contribute substantially to their overall stabilization and are ultimately responsible for the huge acidity enhancement observed. In all cases, the estimated acidity is equal to or higher than that of phosphoric acid, but in particular, hydrogen cyanide becomes a stronger acid than perchloric acid, which is among the strongest superacids in the gas phase.

The stability in the series of half-sandwich 5-(η⁵-cyclopentadienyl)-5-metalla-1,3,2,4-dithiadiazoles incorporating a first-row transition metal was investigated in function of the electron configuration of the M^III metal centre, at the DFT/B3LYP level of theory. Taking 5-(η⁵-cyclopentadienyl)-5-cobalta-1,3,2,4-dithiadiazole or CpCoS₂N₂, the only known and experimentally available compound in the series, as a reference, calculated electronic, thermodynamic, and geometric properties were combined with molecular orbital (MO) diagrams to investigate the relative stabilities of the systems. The results indicate that the stability of CpCoS₂N₂ is linked to a small (positive or even negative) charge on the metal, the occupation of the bonding MO involved in back donation, and the absence of electrons in high-lying antibonding MOs. Moving away from Co in either direction within the period leads to a decreased stability, except for CpVS₂N₂, which exhibits numerous stabilizing features similar to CpCoS₂N₂.

Compound (I), tris(ethane-1,2-diol)-zinc(II) 2,2',3,3',5,5',6,6'-octafluoro[1,1'-biphenyl]-4,4'-dicarboxylate, which has been published previously as VOGROB, displays an unusually large number of molecular and crystallographic characteristics, none of which is unique per se; what, in fact, is interesting and important about this substance is that so many of them are observed in a single crystalline object. For example, the use of ethylene glycol as a bidentate ligand to transition metal cations is far from common — a search of the Cambridge Structural Database (CSD) for examples of any metal ligated by ethylene glycol produces only 125 hits, of which 12 crystallize in Sohncke space groups and all but one, (I), crystallize with Z’ = 1.0. Other interesting oddities of (I) are detailed below, and these are extremely rare, to put it conservatively; among them are questions of chirality and crystallization behavior.

Graphical Abstract

Proteins/polypeptides are a large class of organic/biochemical/biomedical related molecules most simply and most generally described by the generic structure NH₂CH(R¹)CONHCH(R²)CONHCH(R³),,, NHCH(R^{some large number})COOH, or more properly as the corresponding zwitterion. In these species, R¹, R², R^{some large number} are arbitrarily chosen from a well-defined collection of some 20 affixed groups. The archetypal example is polyglycine, the related “shorter” glycine, diglycine … hexaglycine. For these species, all of these R groups are H and much of their understanding has come from calorimetric determinations of their enthalpies of formation, and more recently high-level quantum chemical calculations. In the current study, we ask the question given as the title of this paper “If polyglycine is the polymer, then what is the monomeric repeating unit)?” Three natural choices are given, − CH₂–CO–NH − , − NH–CH₂ − CO–, or − CH₂–NH–CO − . From the analysis of the energetics of the related dimer, 2,5-diketopierazine, we demonstrate that these choices are in fact equivalent.

Piroctone olamine, an antifungal agent used in anti-dandruff cosmetics, was studied to characterize its structure and physicochemical properties, along with its complex with 2-amino-1-ethanol. Using DFT methods, geometry optimization and calculations of thermodynamic, electronic, and reactivity parameters were performed. Spectroscopic techniques (FTIR, Raman, UV–Vis, and spectrofluorimetry) supported experimental data interpretation. Molecular docking and dynamics simulations revealed stable piroctone-protein interactions, indicating potential pharmacological relevance beyond antifungal activity. This research enhances understanding of 1-hydroxy-2-pyridinone derivatives and their broader therapeutic potential.