On the recognition of chloride, bromide and nitrate anions by anthracene–squaramide conjugated compounds: a computational perspective?

New Journal of Chemistry Pub Date: 2020-09-21 DOI: 10.1039/D0NJ03685D

Abstract

Anion recognition is widely used in several biological fields. Squaramide derived compounds appear as potential structures to recognize anions. Here, the bond mechanisms between the chloride (Cl?), bromide (Br?) and nitrate (NO3?) anions and anthracene–squaramide conjugated compounds are elucidated considering the influence of the: (i) number, (ii) nature, and (iii) position of the substituents: trifluoromethyl (–CF3) and nitro (–NO2). Energy decomposition analysis (EDA) shows that the interactions between Cl?, Br? and NO3? and anthracene–squaramide have an attractive interaction energy supported predominantly by electrostatic energy followed by orbital contribution. Molecular electrostatic potential (MEP) surfaces imply electrostatic interactions between Cl?, Br? and the oxygen atom from NO3? and the hydrogen atoms from N–H and C–H bonds present in the squaramide structure, and an aryl group, respectively. Cl? interacts with the receptors more strongly than Br?. The NO3? recognition is less attractive than those presented by Cl? and Br?, in agreement with the hardness–softness features of these anions. Importantly, one and, mostly, two group substitutions, –H → –CF3 or –NO2, favor the recognition of Cl?, Br? and NO3? due to the increase of the polarization in the receptor–NH?anion interaction. The –NO2 group promotes a larger effect relative to the –CF3 ligand. The –NO2 ligand positioned at the largest distance conceivable to the benzene–NH group promotes the lowest interference in the N–H?Cl? interaction. These results provide information to design receptors with a larger capability to recognize anions.

Graphical abstract: On the recognition of chloride, bromide and nitrate anions by anthracene–squaramide conjugated compounds: a computational perspective
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