Stability of spherical molecular complexes: a theoretical study of self-assembled M 12 L 24 nanoballs
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ORIGINAL RESEARCH
Stability of spherical molecular complexes: a theoretical study of self-assembled M12 L24 nanoballs 1 · S. E. Perez-Figueroa 1 · Roxana M. del Castillo2 · Ana Mart´ınez1 · Luis E. Sansores1 · ´ ´ Jorge Gutierrez-Flores 1 Estrella Ramos
Received: 11 August 2020 / Accepted: 10 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Supramolecular coordination complexes have become of great interest due to their broad spectrum of applicability, mainly in the area of biomedicine. Understanding the role played by the metal center and the weak interactions in the formation and stabilization of these compounds allow us to have a better design of these molecules and therefore a better guide for the examination of novel applications. In this work, we investigate the effect of noncovalent interactions and the presence of metal centers in the stabilization of Tominaga’s M12 L24 nanoballs. We considered bis(4-pyridyl)-substituted bent frameworks involving two acetylenes spacers as the ligand (L), using –H, –CH3 , and a cyanophenyl group as substituents, and two different metal cations: Pd2+ and Ni2+ . We found that the bond distance between the metal and the ligand was smaller for the nickel complexes than for the palladium compounds. This is related to the dissociation energies (Ni2+ systems are more stable than Pd2+ compounds). Furthermore, nanoballs with the largest ligand’s substituent are significantly more stable than those with the smallest ligand’s substituents. Analyzing the frontier states and the Independent Gradient Model isosurfaces, we found that noncovalent interactions contribute to the stabilization of the complexes. Through the charge distribution, we observed that the metal also polarizes the density of the coordination bond. With these results we can conclude that metal centers and noncovalent interactions play an important role in the stabilization of nanoballs. Keywords Supramolecular coordination complexes · Nanoballs · Noncovalent interactions · Coordinate bonds · DFT
Introduction A supramolecular assembly is a system conformed by two or more chemical species interacting through noncovalent bonds [1]. Molecules are self-assembled in order to form an entity of higher complexity [2]. Supramolecular coordination complexes are those that have metal centers that self-assembled with organic ligands [3]. There is a Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11224-020-01639-0) contains supplementary material, which is available to authorized users. Estrella Ramos
[email protected] 1
Instituto de Investigaciones en Materiales, Universidad Nacional Aut´onoma de M´exico, Circuito Exterior s/n, Ciudad Universitaria, Coyoac´an, 04510, CDMX, Mexico
2
Departamento de F´ısica, Facultad de Ciencias, Universidad Nacional Aut´onoma de M´exico, Circuito Exterior s/n, Ciudad Universitaria, Coyoac´an, 04510, CDMX, Mexico
large number of possible structures and compositions of supramolecular coordina
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