Van der Waals Complexes

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Van der Waals complexes are weakly bound molecular assemblies formed through van der Waals forces, which include dipole-dipole interactions, induced dipole interactions, and London dispersion forces. These complexes typically involve non-covalent interactions between neutral molecules or atoms, resulting in transient structures that are significant in fields such as physical chemistry and molecular physics.

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Al4 2; the anion–π interactions and aromaticity in the presence of counter ions.

by Cina Foroutan-Nejad

The influence of presence of counter ions and π-complexation with benzene on the bonding and magnetic properties of Al4 2, the most studied all-metal cluster, is studied here. It is shown that complexation by either counter ions or... more

Fig. 2 The linear correlation between the atomic charges and the delocalization indices for Aly?~ salts. 6(1,2) and 6(1, 3), respectively, denote vicinal and para delocalization indices. bond length increase, compared with the free Al,?~. Variations of 1, 2 and 1, 3 delocalization ind ices of Al,?~ at the geometry of MgAly are still negligible (1.7% for 1, 2 and 1.2% for 1, 3 delocalization indices). This suggests that the influence of the polarization-charge transfer and e ectron sharing on the electron delocalization is considerably more prominent than the geo- metry alternation. The 1,2 and finely correlated with the atomic ,3 delocalization indices are charges, Fig. 2; this suggests that in this group of molecules, t he influence of atomic charge

Fig. 3 The linear correlation between bond length variation and various types of the bond magnetizability, e.g. total magnetizability, o- and m-magnetizability, for Al,’~ in the geometries of its salts.

Fig.4 The correlation between the atomic charges and various types of the bond magnetizability, e.g. total magnetizability, o- and m-magnetizability, for Aly?~ salts. Only the n-bond magnetizability shows a linear correlation. Taking the aforementioned facts into account, it seems that here, the electron sharing and atomic charges are the major effective factors on the magnitude of the magnetizability. Separating the o- and m-contributions to the total magnetiz- ability shows that the 72°" of the molecule is correlated by both the (1,2) delocalization indices and atomic charges with linear correlations with reasonable correlation coeffi- cients. On the other hand, the magnitude of the a is neither correlated with atomic charges nor delocalization indices, see Fig. 4.

Fig.5 The structures of T-shaped and PPS complexes of benzene-Al4M. The QTAIM atomic charges for every atomic basin are presented in the figure.

Table 1 The magnetic/electronic properties of Al,~ salts with alkaline metals and alkaline earth metals. y(Al)'"™, 7(Al|Al’), 7-- (AD and 7. (AI|Al’) are the isotropic intra-atomic, isotropic bond, out-of-plane inter-atomic and out-of-plane bond magnetizabilities for Al atomic basins in the Al,?~ in cgs—-ppm units respectively. The amount of the total magnetizabilities as well as the magnetizabilities of the 1- and o-frameworks of the Al, moiety, Aly?~ (m) and Al,?~ (o), are separately presented. The g(Al) represents the charge of atoms in molecules and 6(AI|Al’) is the delocalization index between two atoms in atomic units. The 1,2 (vicinal) and 1,3 (para) delocalization indices are presented in regular and italics fonts, respectively indices between the Al atoms and doubly charged cations are close to the range of covalent interactions.’ As a rough assumption, one may state that as the delocalization between the Al atoms and the counter ions increases, the delocalization between Al atoms decreases. However, the correlation between these two factors is not quite straightforward and this simple rule breaks in some cases.

“ The percent localization is defined as (Q) = (A(Q)/N(Q)).100, where AQ) and N(Q) represent the localization index and population of the atomic basin respectively. In an ionic system (Q) approaches 100% but in covalent systems it decreases considerably. ’ Delocalization index between each Li atoms and its two neighbouring Al atoms. Table 2 The percent localizations, /(Al)“, of the Al atoms and counter ions and delocalization indices between metallic cations and Al atoms, 6(M"* |Al) in atomic units

Table 4 The binding energies, BE, (bold numbers are the ZPVE corrected values), charge of Al, salts, g¢]M"* + Al,?-), benzene moiety, g(Bz), the counter ions, g(M"~), and the distance between the Al, framework and benzene, R, in benzene-Aly?~ complexes. In mn complexes (PPS complexes) R represents the distance between geometric centres of two rings. In CH complexes (T-shaped complexes) R represents the distance between the ring centre of the Aly ring and the closest hydrogen atom in benzene. Q-, is the quadrupole moment of the molecules derived from QTAIM computations and w(M"* + Al,’ ) is the polarizabilty of the Aly salts as is derived from DFT computations

Table 5 The magnetic/electronic properties of benzene—Al, complexes. 7(Q)'"™, 7(Q|Q’), x-- (Q)'™"™ and y-- (Q\Q’) are the isotropic inter-atomi isotropic bond, out-of-plane intar-atomic and out-of-plane bond magnetizabilities for Al atoms in Al, frameworks and C atoms in benzene, Bz, i cgs—ppm units, respectively. The 6(Q\Q”) is the delocalization index between adjacent atoms in the Al, frameworks and C atoms in the benzer molecules in atomic units. The 1,2 (vicinal) and 1,3 (para) delocalization indices in the Al, framework are presented in regular and italics font respectively. PDI, para delocalization index, values for the benzene molecules are also represented. PDI is the average of the delocalization inde between para carbon atoms in the benzene rings

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Van der Waals Complexes

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