In the present work an in depth deep electronic study of multicenter XBs (FX)n/NH3 (X = Cl, Br and n = 1–5) is conducted. The ways in which X∙∙∙X lateral contacts affect the electrostatic or covalent nature of the X∙∙∙N interactions are explored at the CCSD(T)/aug-cc-pVTZ level and in the framework of the quantum theory of atoms in molecules (QTAIM). Calculations show that relatively strong XBs have been found with interaction energies lying between −41 and −90 kJ mol−1 for chlorine complexes, and between −56 and −113 kJ mol−1 for bromine complexes. QTAIM parameters reveal that in these complexes: (i) local (kinetics and potential) energy densities measure the ability that the system has to concentrate electron charge density at the intermolecular X∙∙∙N region; (ii) the delocalization indices [δ(A,B)] and the exchange contribution [VEX(X,N)] of the interacting quantum atoms (IQA) scheme, could constitute a quantitative measure of the covalence of these molecular interactions; (iii) both classical electrostatic and quantum exchange show high values, indicating that strong ionic and covalent contributions are not mutually exclusive.
In supramolecular chemistry, the rational design of self‐assembled systems remains a challenge. Herein, hydrogen‐bonded rosettes of melamine and ammeline have been theoretically examined by using dispersion‐corrected density functional theory (DFT‐D). Our bonding analyses, based on quantitative Kohn–Sham molecular orbital theory and corresponding energy decomposition analyses (EDA), show that ammeline is a much better building block than melamine for the fabrication of cyclic complexes based on hydrogen bonds. This superior capacity is explained by both stronger hydrogen bonding and the occurrence of a strong synergy.
Ion recognition is still an emerging topic in supramolecular chemistry and has aroused great attention in the last few years. In this work, we have examined the assemblies of selected hexameric rosettes of melamine and ammeline and their capacities to host halide and alkali ions in the gas phase and in water. Using relativistic dispersion-corrected density functional theory (DFT-D), we first studied the stability and the effect of introducing monovalent anions (Cl − , Br − , and I − ) and cations (Na + , K + , and Rb + ) in the center of the rosette's cavity. Finally, we explored the interactions in two stacked rosettes with an interlayer ion. Our computations reveal that aminesubstituted triazines are promising candidates for anion and cation recognition either in self-assembled monolayers or pillar array structures. The anion recognition process is governed by both the electrostatic and charge-transfer (donor−acceptor) interactions, while the cation recognition is governed by electrostatic and polarization. In addition, melamine and ammeline could constitute a potent mixture for dual-ion recognition strategies.
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