Structural Chemistry最新文献

Mirra Efimovna Dyatkina (1915–1972), an outstanding quantum chemist, was one of several scientists who started systematic quantum chemical studies of molecular structure in the USSR. She obtained principal results in the theory of directed valences, in building quantum chemical descriptions of semiquinones and metalloketils, in studying conjugated systems with heteroatoms. She developed ideas about multiple bonds in complex compounds and a theory of increasing the multiplicity of bonds in uranyls, vanadyls and other similar compounds. One of the first calculations of the spin density in organic radicals was also performed by M.E. Dyatkina. Most often M.E. Dyatkina is mentioned together with her teacher and senior colleague Yakov Kivovich Syrkin (1894–1974). Indeed, she shared with him both the honor of pioneering work in a new field of science and the honor of being the Galilei of the 20th century who suffered for this novel science in the USSR. Her contemporaries were well acquainted with her work. Her younger colleague I.D. Morozova recalled Charles Coulson, Per-Olov Löwdin, Frank Harris, Enrico Clementi who were looking forward to her arrival at the conference and greeted her with deep respect. Apart from several obituaries, no historical, scientific or memoir articles about M.E. Dyatkina were published after her death. Therefore, she is hardly remembered today, although her contemporaries all over the world were well acquainted with her works. This article is intended to correct this injustice, briefly describing the biography and main scientific results of M.E. Dyatkina.

James D. Watson, arguably the most famous scientist of the second half of the 20th century, passed away on November 6, 2025. He was the co-discoverer (with Francis Crick) of the double helix structure of DNA, which is widely considered the greatest biological discovery of the 20th century. He wrote the epoch-making book on the discovery’s story, pioneered methods in textbook writing, initiated and managed the US Human Genome Project; and developed Cold Spring Harbor Laboratory into a leading international biomedical research center. In the last phase of his life, he lost the respect of the research community due to his racist statements.

Attempts are made to unravel the ground state H-X-H bond angles in group-15 hydrides (XH(_3), where X=N, P, As and Sb) via high level quantum chemical calculations. The energy differences between s and p valence orbitals of the central atoms and their linear combinations demonstrate a systematic increase of p and decrease of s orbital character in the involved hybrid orbital as one descends through group-15. This parameter quantitatively indicates the deterioration of s-p orbital overlapping and reveals a systematic decrease in the H-X-H angles from NH(_3) to SbH(_3), and thus corroborates the existing experimental observations.

The crystal and molecular structures of the following acetylpyrenes (AcPYs ), and benzoylpyrenes (BzPYs) have been determined by X-ray crystallography: 1-acetylpyrene, 2-acetylpyrene, 1,3-diacetylpyrene, 1,6-diacetylpyrene, 1,8-diacetylpyrene, 2,7-diacetylpyrene, 1-benzoylpyrene (1-BzPY), 1,3-dibenzoylpyrene, 1,6-dibenzoylpyrene, 1,8-dibenzoylpyrene (1,8-Bz₂PY), 1-(4-fluorobenzoyl)pyrene, and 1,6-bis(4’-fluorobenzoyl)pyrene . Special attention was drawn to the stereodescriptors E, Z, P and M in the conformations of AcPYs and BzPYs. Geometrical parameters of the molecular structures of the AcPYs and BzPYs. and of previously reported crystal structures, including 1,3,6-tribenzoylpyrene and 1,3,6,8-tetrabenzoylpyrene are provided. Two cases of crystal dynamic isomerism, as distinct from polymorphism, have been revealed: 1E-BzPY/1/Z-BzPY and 1Z8E-Bz₂PY/1Z8Z-Bz₂PY. Most of the crystal structures of AcPYs and BzPYs under study adopt the more stable Z-conformations of the acetyl and benzoyl groups vis-à-vis the pyrene ring. The deviation from planarity of the carbonyl groups from the plane of the pyrene ring system is higher in AcPYs, as compared with BzPYs. The rich stereochemistry of the crystal structures of acetylpyrenes and benzoylpyrenes, as manifested in the E-, Z-, M- and P-stereodescriptors is noted.

We celebrate the 2025 Nobel Prize in Chemistry for the development of metal–organic frameworks and recall prior related discoveries in supramolecular chemistry and Nadrian Seeman’s oeuvre who built extended structures of DNA molecules with large cavities.

Albrecht Dürer began the mathematical study of pentagonal tilings five hundred years ago with the publication in 1525 of his textbook of mathematics Underweysung der Messung. A century later Johannes Kepler produced more elaborate and intricate pentagonal tilings. In the 20th century Maurits Escher made pentagonal tilings into art. Escher’s art–science interactions with Roger Penrose made the latter keep thinking about tilings; he made pentagonal tilings tile the plane aperiodically in 1974. And Alan Mackay built on and extended Penrose’s work to predict the existence of quasicrystals in 1981.

The lower bound of structure determinants connecting given structural units into the connected structure, referred to as implicit hierarchical depth (IHD) of the structure, is dependent on the rank of the symmetry group of the structure, the number of orbits occupied by the structural units, and on their site-symmetry groups. The equation relating the IHD of a crystal structure and crystallographic data is given herein in a general form. A crystal structure tends to, but not always, acquires the most parsimonic arrangement of the structural units in terms of IHD because of geometric limitations and contacts formed parallel to the process of crystallization and hence redundant for crystal structure formation. The code was developed and written in the GAP environment to estimate the values of IHD for 1731 Wyckoff positions of space groups. Some applications of IHD to reticular chemistry are discussed using molecular crystals, but not only them, as examples.

Four new alkali uranyl molybdates have been prepared using a reactive flux technique. [Rb₂Na₂][(UO₂)₆(MoO₄)₈](H₂O) (1) is monoclinic, I2/m, a = 14.3760(3), b = 13.9903(3), c = 23.0921(7)Å, β = 107.957(3)º, V = 4418.2(2)ų; [Rb₄Na₂][(UO₂)₃(MoO₄)₄(Mo₂O₈)] (2) is triclinic, P-1, a = 7.5329(2), b = 7.9131(2), c = 13.3491(4)Å, α = 76.608(2), β = 83.667(2), γ = 82.048(2)º, V = 764.11(4)ų; Rb₁₀[(UO₂)₈O₈(Mo₅O₂₀)] (3) is triclinic, P-1, a = 16.9823(4), b = 17.8883(4), c = 20.4050(4)Å, α = 108.619(2), β = 93.689(2), γ = 91.436(2)º, V = 5855.3(2)ų; while [Cs₇Rb₇][(UO₂)₁₆O₁₃(MoO₅)₅](H₂O)₅ (4) is monoclinic, C2, a = 33.8722(9), b = 33.8486(8), c = 7.4245(2)Å, β = 90.021(2)º, V = 8512.4(4)ų. 1, 2, and 4 correspond to three novel architectures; the layers in 4 are characterized by a particularly complex topology. Topological analysis of known uranyl molybdates has been performed, which demonstrates that all their structures can be described as modular, i.e. constructed of some “basic” structural units of lower dimensionality.

A mathematical model is presented which creates four novel classes of m-fold cyclic twins in two dimensions, in addition to one class previously known. Each member of a class is characterized by four integer parameters: the twin modulus m, naturally describing the rotational symmetry of the twin, and three more parameters, (mu ), (nu ), and (sigma ), respectively, related to the properties of an integer inclination sequence fundamental for the generation of the cyclic twins by an m-fold composition of discrete circle involute spirals. A selection of the most interesting cases is depicted for each class, and a number of potential applications are discussed.

The current paper discusses the enthalpy of formation of triglycine. Upon asking “What is the enthalpy of formation of triglycine?”, we find that there are two non-isomeric species that are generally referred to as “triglycine”: glycylglycylglycine and nitrilotriacetic acid. In the current paper the enthalpies of formation of these two species termed "triglycines" are discussed and related to each other. In addition, a similar analysis is carried out for the related “diglycines”.