Estudo das ligações de halogênio em compostos de coordenação contendo ligantes piridínicos empregando superfícies de Hirshfeld e gráficos de impressão digital

Abstract

Supramolecular chemistry is based on the study of structures held together by noncovalent bonds and their resulting properties since applications are directly related to the technological advancements necessary for the development of a nation such as the self-assembly process in inorganic structures, molecular recognition, devices for drug delivery and others. The halogen bond (LX) is a non-covalent bond with a strength comparable to stronger interactions; therefore, it is essential since it can direct several properties, such as luminescence, color, and catalytic activity solubility, among others. Hirshfeld analysis tools are free, easy to use, and can, in some instances, replace more elaborate and expensive theoretical calculations in the study of supramolecular characteristics of inorganic crystalline solids. These calculations allow us to obtain qualitative and quantitative data on the individual contributions of each non-covalent bond in a crystalline lattice and enable the comparison of results for different structures. This work involved searching the Cambridge Structural Database (CSD) for structures of the type [MY2(o-Xpy)2], [MY2(m-Xpy)2] e [MY2(p-Xpy)2], where M = Zn2+, Co2+ or Cu2+, Y = Cl–, Br– or I– and Py = monosubstituted pyridine ligand in ortho-, meta- or para- by X, this being = Cl–, Br– or I–. The result returned 33 structures and, among these, 21 of them containing zinc(II) or cobalt(II) had their Hirshfeld surfaces and 2D fingerprint graphics generated using the CrystalExplorer17® software for the analysis of non-covalent bonds, with a focus in comparing the data for the LX observed in these complexes. The results showed a direct relationship of increased polarizability of the LX-donor halogen on the strength of this interaction. The same was not observed for the nature of the LX-receptor halogen, indicating the relevance of the donor atom in interactions of this type. The work showed that Hirshfeld’s tools are sufficient for the analysis and correlation of data between different structures regarding comparing the strengths of non-covalent bonds in complexes such as those analyzed in this work, indicating that this analysis in these cases can replace more expensive and elaborate theoretical calculations. The data show that coordination compounds containing ligands such as those present in the complexes analyzed in this work are interesting for the maintenance of supramolecular structures through strong non-covalent interactions, such as LX and, in addition, hydrogen bonds and ··· interactions. Consequently, the results of this work will be used to guide future research projects in our group.