Search

The most polar bond in chemistry is that between a fluorine and an alkalimetal atom. Inspired by our recent finding that other polar bonds (C&bond;M and H&bond;M) have important covalent contributions (i.e., stabilization due to bond overlap), we herein address the question if covalency is also essential in the F&bond;M bond. Thus, we have theoretically studied the alkalimetal fluoride monomers, FM, and (distorted) cubic tetramers, (FM)4, with M = Li, Na, K, and Rb, using density functional theory at the BP86/TZ2P level. Our objective is to determine how the structure and thermochemistry (e.g., F&bond;M bond lengths and strengths, oligomerization energies, etc.) of alkalimetal fluorides depend on the metal atom, and to understand the emerging trends in terms of quantitative Kohn–Sham molecular orbital theory. The analyses confirm the extreme polarity of the F&bond;M bond (dipole moment, Voronoi deformation density and Hirshfeld atomic charges), and they reveal that bond overlap-derived stabilization (ca. -6, -6, and -2 kcal/mol) contributes only little to the bond strength (-136, -112, and -114 kcal/mol) and the trend therein along Li, Na, and K. According to this and other criteria, the F&bond;M bond is not only strongly polar, but also has a truly ionic bonding mechanism. Interestingly, the polarity is reduced on tetramerization. For the lithium and sodium fluoride tetramers, the F4 tetrahedron is larger than and surrounds the M4 cluster (i.e., F&bond;F ≫ M&bond;M). But in the potassium and rubidium fluoride tetramers, the F4 tetrahedron is smaller than and inside the M4 cluster (i.e., F&bond;F < M&bond;M). © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 238–250, 2007 [ABSTRACT FROM AUTHOR]

The symmetry-decomposed Voronoi deformation density (VDD) charge analysis is an insightful and robust computational tool to aid the understanding of chemical bonding throughout all fields of chemistry. This method quantifies the atomic charge flow associated with chemical-bond formation and enables decomposition of this charge flow into contributions of (1) orbital interaction types, that is, Pauli repulsive or bonding orbital interactions; (2) per irreducible representation (irrep) of any point-group symmetry of interacting closed-shell molecular fragments; and now also (3) interacting open-shell (i.e., radical) molecular fragments. The symmetry-decomposed VDD charge analysis augments the symmetry-decomposed energy decomposition analysis (EDA) so that the charge flow associated with Pauli repulsion and orbital interactions can be quantified both per atom and per irrep, for example, for σ, π, and δ electrons. This provides detailed insights into fundamental aspects of chemical bonding that are not accessible from EDA., (© 2023 The Authors. Journal of Computational Chemistry published by Wiley Periodicals LLC.)

Principles are presented for the design of functional near-infrared (NIR) organic dye molecules composed of simple donor (D), spacer (π), and acceptor (A) building blocks in a D-π-A fashion. Quantitative Kohn-Sham molecular orbital analysis enables accurate fine-tuning of the electronic properties of the π-conjugated aromatic cores by effecting their size, including silaaromatics, adding donor and acceptor substituents, and manipulating the D-π-A torsional angle. The trends in HOMO-LUMO gaps of the model dyes correlate with the excitation energies computed with time-dependent density functional theory at CAMY-B3LYP. Design principles could be developed from these analyses, which led to a proof-of-concept linear D-π-A with a strong excited-state intramolecular charge transfer and a NIR absorption at 879 nm. © 2018 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc., (© 2018 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.)

Selenium based diaryl dichalcogenides are compounds that are receiving attention in organic synthesis as eco-friendly oxidation agents as well as in pharmaceutical chemistry, where, together with tellurium-based derivatives, are appealing drugs mainly for their antioxidant properties. A benchmark study to establish optimal density functional theory (DFT) methods for the description of their molecular and electronic structure as well as for their energetics is presented here. Structural features, such as the orientation of the phenyl rings, as well as energetic aspects, i.e., the chalcogen-chalcogen bond strength, are discussed, with the aim of applying the novel insights to quantum mechanics-based investigations of their reactivity and to facilitate drug design. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

We have carried out an extensive exploration of gas-phase alkyl cation affinities (ACA) of archetypal anionic and neutral bases across the periodic system using zeroth order regular approximation-relativistic density functional theory at BP86/QZ4P//BP86/TZ2P. ACA values were computed for the methyl, ethyl, i-propyl and t-butyl cations and compared with the corresponding proton affinities (PA). One purpose of this work is to provide an intrinsically consistent set of values of the 298 K ACA of all anionic (XH (n-1)(-)) and neutral bases (XH(n)) constituted by maingroup-element hydrides of groups 14-17 and the noble gases (group 18) along the periods 1-6. Another purpose is to determine and rationalize the trend in affinity for a cation as the latter varies from proton to t-butyl cation. This undertaking is supported by quantitative bond energy decomposition analyses. Correlations are established between PA and ACA values., (Copyright © 2010 Wiley Periodicals, Inc.)

We present the Voronoi Deformation Density (VDD) method for computing atomic charges. The VDD method does not explicitly use the basis functions but calculates the amount of electronic density that flows to or from a certain atom due to bond formation by spatial integration of the deformation density over the atomic Voronoi cell. We compare our method to the well-known Mulliken, Hirshfeld, Bader, and Weinhold [Natural Population Analysis (NPA)] charges for a variety of biological, organic, and inorganic molecules. The Mulliken charges are (again) shown to be useless due to heavy basis set dependency, and the Bader charges (and often also the NPA charges) are not realistic, yielding too extreme values that suggest much ionic character even in the case of covalent bonds. The Hirshfeld and VDD charges, which prove to be numerically very similar, are to be recommended because they yield chemically meaningful charges. We stress the need to use spatial integration over an atomic domain to get rid of basis set dependency, and the need to integrate the deformation density in order to obtain a realistic picture of the charge rearrangement upon bonding. An asset of the VDD charges is the transparency of the approach owing to the simple geometric partitioning of space. The deformation density based charges prove to conform to chemical experience., (Copyright 2003 Wiley Periodicals, Inc.)