Volume 97, Issue 9 - Special Issue: Quantum Science and Technology; Guest Editors: Russell Boyd and Manuel Yañez Montero

This compilation includes more than 9000 p K a values determined in seven dipolar non-hydrogen-bond-donor solvents {dimethyl sulfoxide, acetonitrile, N,N -dimethylformamide, pyridine, acetone, 4-methyl-1,3-dioxolan-2-one (propylene carbonate), oxolane (tetrahydrofuran)} for close to 5000 acids collected from around 800 original works published during the last 60 years. The data have been critically evaluated on the basis of defined quality criteria and depending on situation, kept as they were originally published, marked as doubtful/unreliable (around 2700 values) or corrected (around 2400 values). To enable automated processing and mining, the data are presented as a set of spreadsheets, together with structural codes (SMILES and InChI strings), compound class qualifiers, and comments. The document contains also comprehensive educational background information on the acid-base processes in non-aqueous media, as well as brief descriptions of the main measurement methods, with focus on the reliability of the data and sources of uncertainty. The full dataset is available at the permanent address https://doi.org/10.5281/zenodo.12608876.

Calculating the wave function and the properties of a molecule in solution is a common procedure today that can be performed with a variety of methods. However, the study of solvated systems did not begin with the establishment of the Schrodinger equation in 1926 and the development of the first methods in computational chemistry. In fact, it took until 1973 to see the first self-consistent field equations that included the electrostatic potential of the solvent. It took another two decades for computational methods and solvent models to become consolidated, with an explosion of applications in the 1990s. This article briefly describes that fascinating story.

We report a local description of extended aromatic systems using Clar formalism embedded in Valence Bond-like calculations. We disclose a new implementation of our HuLiS (Hückel/Lewis) program that considers blocks of electrons in addition to bonds and lone pairs/radical centers. The method is based on the Hückel approximation for both the empirical hamiltonian and the atomic orbital orthogonality constraint.

Quantum mechanics is central to our understanding of chemistry both qualitatively and quantitatively. Modern electronic structure calculations can yield energies and structures of small to medium size molecules to chemical accuracy, thereby providing a computational model for chemistry. A potential energy surface describes the energy of a molecule as a function of its geometric parameters. The features of potential energy surfaces provide the connections between quantum mechanics and the traditional chemical concepts such as structure, bonding and reactivity. This brief perspective presents an overview of tools for exploring potential energy surfaces such as optimizing equilibrium geometries, finding transition states, following reaction paths and simulating molecular dynamics.

The diverse cellular functions of nucleic acids are made possible by enzymes that catalyze cleavage of glycosidic (nucleobase–sugar) and phosphodiester bonds. Despite advancements in experimental biochemical methods, critical information about such enzyme-catalyzed reactions is difficult to obtain from traditional experiments. However, computational quantum mechanical (QM) methods can provide atomic level details of catalytic pathways that are complementary to experimental data. This perspective highlights various QM techniques used to advance our understanding of enzymes that process nucleic acids. First, select DNA glycosylases are discussed to showcase how QM calculations on nucleoside/tide and small molecule complexes uncover roles of active site interactions and the preferred order of reaction steps along DNA repair pathways. Furthermore, the ability of calculations on nucleic acid–enzyme complexes that combine QM methods with molecular mechanics (MM) force fields to challenge traditional views of enzyme function and lead to consensus for mechanistic pathways is illustrated. Subsequently, QM-based studies of select nucleases are discussed to highlight how this methodology can discern the various strategies enzymes use to cleave nucleic acid backbones. Overall, this contribution underscores the value in combining QM-based computational work with experimental studies to uncover enzyme-facilitated nucleic acid chemistry to be harnessed in future medicinal, biotechnological and materials applications.

Density functional theory is used to explore the geometries and properties of 55 heterocyclic carbenes containing N, P, As, Sb, Bi, O, S, Se, Te and Po. Planar and non-planar structures have been systematically evaluated and a variety of measures (including Wiberg bond indices, orbital occupancies, HOMO–LUMO gaps, proton affinities, J( 13 C– 1 H) coupling constants and isodesmic reaction energies) have been considered for all systems. The main conclusions are that the heavier heteroatoms can be effective π-donors towards the carbene carbon if planarity can be attained, and that the cost of attaining this planarity is actually quite low for the majority of the heterocyclic carbenes considered.

The literature on relativistic quantum chemistry is briefly reviewed. The meaning of the main physical terms is qualitatively discussed. The ionization potential and electron affinity of a gold atom are discussed as existing examples on high-accuracy calculations. Very accurate calculations exist for 2-electron atoms. The hyperfine structure in the HD and D 2 molecules was used by Pachucki et al., to obtain an improved deuteron quadrupole moment, Q . The remaining, so far excluded, physical contributions are briefly listed. A short answer to the title question is: ‘Probably yes’. Finally, a comment is made on the possible connection, or lack of one, between parity non-conservation and the handedness of life.

For decades, computational theoretical chemistry has provided critical insights into molecular behavior, often anticipating experimental discoveries. This review surveys twenty notable examples from the past fifteen years in which computational chemistry successfully predicted molecular structures, reaction mechanisms, and material properties before experimental confirmation. By spanning fields such as bioinorganic chemistry, materials science, catalysis, and quantum transport, these case studies illustrate how quantum chemical methods have become essential for multidisciplinary molecular sciences. The impact of theoretical predictions across disciplines shows the indispensable role of computational chemistry in guiding experiments and driving scientific discovery.

Computational methods for predicting product ratios in dynamically controlled reactions with shallow intermediates or bifurcating pathways after an ambimodal transition state are reviewed and benchmarked. The range of methods includes molecular dynamics simulations, machine learning-based models and recent advancements in correlational methods, all of which rely on quantum mechanical computations. Together, these approaches form a computational toolbox that enhances the efficiency and effectiveness of exploring reaction selectivity influenced by dynamic effects.

To celebrate the International Year of Quantum Science and Technology (IYQ), we discuss how the concept of aromaticity emerges from the postulates of quantum mechanics. Based on this discussion, we analyze the case of cyclo [18]carbon, a molecule that was characterized for the first time in 2019 in a scanning tunneling microscope. From the very beginning, this molecule was classified as an aromatic molecule. In the present work, we challenge this classification and provide arguments to classify this molecule as a non-aromatic species.

The integration of quantum theory (QT) into chemistry has significantly enhanced computational accuracy, yet challenges remain in translating quantum mechanical results into intuitive chemical concepts. Traditional atomic and molecular models, while empirically effective, lack direct representation in Hilbert space, leading to ambiguities in chemical interpretation. Here, we present a summary of topological methods as a bridge between QT and chemical reasoning, focusing on the quantum theory of atoms in molecules (QTAIM) and the electron localization function (ELF). These approaches provide rigorous frameworks for defining atomic and bonding regions, enabling additive decompositions of quantum mechanical observables. By analyzing critical points of the electron density and other scalar fields, we demonstrate how the QTAIM and the ELF offer complementary insights into molecular bonding. As a case study, we examine the electronic structure of carbon suboxide (C 3 O 2 ), revealing that a combined QTAIM-ELF approach resolves discrepancies between two bonding descriptions.

Owing to the progress of quantum mechanical (QM) calculations, we have investigated, for the first time, the geometric structure of an ion-pair consisting of the Zr phenoxy-imine (Zr–FI) cation and the borate anion. Further, a number of different structures for ‘Cation & Monomer’, ‘Ion-Pair’, and ‘Ion-Pair & Monomer’ systems have also been studied. The obtained preferred structures of these systems indicate the formation of an octahedral geometry around the Zr-atom. In addition, the counter anion (CA) is preferably located on trans to the Me group of the cation. This allows more space for ethylene insertion to the active Zr-C center, leading to high ethylene polymerization activity. Furthermore, from the calculated interaction energy, we have found weaker interaction between the Zr–FI cation and the CA than in the zirconocene catalysts, making the ion separation easier and facilitating the monomer coordination to the metal. We also investigated the electronic characteristics of the cation–anion interactions and have shown that (i) the molecular orbital interaction, (ii) the charge transfer between the cation and the anion, and (iii) the non-covalent bond interaction are also crucial factors in determining the ion-pair structure. In conclusion, the usefulness and necessity of QM investigation of the ion-pair structures have become evident. Therefore, we assert that while studying the reactivity of catalysts based on their geometric structures, today, one must model at least the ion-pair structure in the QM calculations. Finally, we touch on the brand-new study using the Red Moon simulation, which would become a new possible computational molecular technology (CMT), with the help of thorough research using the QM calculations, an established CMT.

Phosphorus is a crucial biogenic element, yet its astrochemical role remains poorly understood due to its low cosmic abundance and the limited number of detected P-containing molecules in the interstellar medium. Given its significance for prebiotic chemistry, PCO-bearing molecules, such as the phosphorus analogs of isocyanates, are promising candidates for laboratory and interstellar studies. Herein, we present a comprehensive theoretical study on the isomeric landscape of the C 2 H 3 PO system, identifying and characterizing 24 low-lying isomers through high-level quantum chemical calculations. The study employs double-hybrid DFT and coupled-cluster methods to refine energy values and structural parameters, while topological analysis of electronic density characterizes chemical bonding. Vinylphosphinidene oxide (CH 2 CHPO) emerges as the most stable isomer, followed by methylphosphaketene (CH 3 PCO), with oxygen-bound structures playing a crucial role in stability. Comparisons with the C 2 H 3 NO system reveal structural parallels, reinforcing the importance of oxygen-bound species. Cyclic structures were also explored, with three- and four-membered P- and O-heterocycles identified, although they are generally less stable than open-chain isomers. These results provide insights into the chemical behavior and stability of C 2 H 3 PO isomers, which could help future spectroscopic studies and detection efforts in the interstellar medium.