Frank De Proft

Computing Fukui functions without differentiating with respect to electron number. I. Fundamentals.

By using perturbations in the molecular external potential, the authors deduce the Fukui function from the change in Kohn-Sham orbital energies, avoiding the troublesome differentiation of the density with respect to electron number. Though this paper focuses on the Fukui function, the same general technique can be used to compute the functional derivative of any observable with respect to the external potential. In this paper, the method is used to compute the Fukui function for the beryllium atom and the formaldehyde molecule. The follow-up paper (part II) addresses the problem of computing condensed reactivity indicators.

σ, π aromaticity and anti-aromaticity as retrieved by the linear response kernel

The chemical importance of the linear response kernel from conceptual Density Functional Theory (DFT) is investigated for some σ and π aromatic and anti-aromatic systems. The effect of the ring size is studied by looking at some well known aromatic and anti-aromatic molecules of different sizes, showing that the linear response is capable of correctly classifying and quantifying the aromaticity for five- to eight-membered aromatic and anti-aromatic molecules. The splitting of the linear response in σ and π contributions is introduced and its significance is illustrated using some σ-aromatic molecules. The linear response also correctly predicts the aromatic transition states of the Diels-Alder reaction and the acetylene trimerisation and shows the expected behavior along the reaction coordinate, proving that the method is accurate not only at the minimum of the potential energy surface, but also in non-equilibrium states. Finally, the reason for the close correlation between the linear response and the Para Delocalisation Index (PDI), found in previous and the present study, is proven mathematically. These results show the linear response to be a reliable DFT-index to probe the σ and π aromaticity or anti-aromaticity of a broad range of molecules.

Synthesis of Fused 3-Aminoazepinones via Trapping of a New Class of Cyclic Seven-Membered Allenamides with Furan

Novel tricyclic tetrahydroazepinones were synthesized via an in situ Diels-Alder reaction of furan with cyclic allenamides. These reactive intermediates are the first examples of cyclic seven-membered allenamides and were prepared starting from N-(2-chloroallyl)-2-allylglycine derivatives via ring-closing metathesis followed by dehydrochlorination. The trapping of the intermediate cycloallene with furan occurred endo- and regioselectively and provided a convenient entry into new building blocks for medicinal chemistry. The diastereoselectivity of the cycloaddition was confirmed using quantum chemical computations.

Synthesis and structural characterization of heteroboroxines with MB2O3 core (M = Sb, Bi, Sn).

Reaction of organoantimony and organobismuth oxides (LSbO)(2) and (LBiO)(2) (where L is [2,6-bis(dimethylamino)methyl]phenyl) with four equivalents of the organoboronic acids gave new heteroboroxines LM[(OBR)(2)O] 1a-2c (for M = Sb: R = Ph (1a), 4-CF(3)C(6)H(4) (1b), ferrocenyl (1c); for M = Bi: R = Ph (2a), 4-CF(3)C(6)H(4) (2b), and ferrocenyl (2c)). Analogously, reaction between organotin carbonate L(Ph)Sn(CO(3)) and two equivalents of organoboronic acids yielded compounds L(Ph)Sn[(OBR)(2)O] (where R = Ph (3a), 4-CF(3)C(6)H(4) (3b), and ferrocenyl (3c)). All compounds were characterized by elemental analysis and NMR spectroscopy. Their structure was described both in solution (NMR studies) and in the solid state (X-ray diffraction analyses 1a, 1c, 2b, 3b, and 3c). All compounds contain a central MB(2)O(3) core (M = Sb, Bi, Sn), and the bonding situation within these rings and their potential aromaticity was investigated by the help of computational methods.

A DFT and HF quantum chemical study of the tin nanocluster [(RSn)12O14(OH)6]2+ and its interactions with anions and neutral nucleophiles: confrontation with experimental data

Calculations of traditional wave function and DFT based reactivity descriptors are reported for the nanocluster [(RSn)12O14(OH)6]2+ (R = CH3) in order to get insight into the factors determining the exact nature of its interactions with anions or neutral nucleophiles (F−, Cl−, OH−, H2O, acetone, DMSO). Two levels of calculation (Hartree–Fock and DFT) were used in this study, giving the opportunity to compare the performance of both aproaches. As a whole the HF and DFT results, despite some numerical differences, are qualitatively and in most cases quantitatively similar, since no interchanges in the sequences are found. Calculated charge distributions indicate that the hexacoordinated tin atoms are expected to be harder, the pentacoordinated ones softer. This result is confirmed by the condensed local softness and experimental observations provided by the literature (X-ray, 119Sn NMR), thereby matching predictions made on the basis of the HSAB principle. Molecular electrostatic potential (MEP) calculations further confirm this selectivity, indicating that nucleophiles will approach preferentially the macrocation around the poles rather than at the equator of the cage. Calculated stabilization energies indicate that the charged (F−, Cl− and OH−) and uncharged (DMSO, acetone and water) nucleophiles tested all interact preferentially with the cage pole region around the hexacoordinated tin atoms. This feature appears related to the electrostatic nature of the interaction for the charged nucleophiles and to the tendency, for all the nucleophiles, to form hydrogen bridges with the μ2-OH moieties. The basicity of the three types of oxygen atoms [μ2-OH, μ3-O(I), μ3-O(P)] present in [(RSn)12O14(OH)6)]2+ has been addressed by protonation energy and MEP calculations, taking into account accessibility factors not represented by atomic charges. Summarizing, it turns out that the hardness/softness properties of tin atoms are modulated by their coordination; however, the sole consideration of these quantities is not sufficient to predict in all cases the strength and orientation of the interaction between various nucleophiles and the cluster, since electrostatic interactions and H-bonding play a major role.

Alchemical Derivatives of Atoms: A Walk Through the Periodic Table

Exploring the Chemical Compound Space is at stake when looking for molecules with optimal properties. In order to guide experimentalists to navigate through this unimaginably huge space, theoreticians should look for efficient and cheap algorithms. One of the strategies put forward some years ago was to look for transmutation of molecular structures, thereby changing their nuclear charge content, for which alchemical derivatives are instrumental. A collection of well tested isolated atom alchemical derivatives would be a basic instrument in a navigation toolbox. In this work, isolated atom alchemical derivatives were evaluated with different techniques, from the more accurate numerical differentiation and Coupled Perturbed Kohn–Sham approaches to the \(Z^{-1}\) energy expansion model which upon derivation with respect to Z yields the desired derivatives. For this third approach a systematic, computationally elegant, method is developed to routinely evaluate an optimal set of all expansion coefficients in the energy expansion for a given N. For the lighter elements, \(Z=1-18\), the comparison between the three approaches shows that the order of magnitude and sequences in the different approaches are similar paving the way for a walk through the complete Periodic Table by combining the \(Z^{-1}\) expansion approach with the National Institute of Standards and Technology (NIST) databank atomic energy values at various levels of LDA. A uniform decrease is retrieved not only for the alchemical potential (the electrostatic potential at the origin) but also for the alchemical hardness, with some minor exceptions. The latter values are relatively strongly influenced by relativistic effects for the heavy elements. The uniform decrease of the first derivative is evidenced and quantified. Periodicity shows up in some exploratory calculations on the third derivative (the hyperhardness) which turn out to be strongly basis set dependent. The Periodic Tables generated could be used in a first step in exploring Chemical Compound Space in a systematic, efficient and cheap way. Some possible refinements (atoms-in-molecules corrections) and extensions (inclusion of mixed Z and N derivatives) are touched upon.