Molecular Details of Acetate Binding to a New Diamine Receptor by NMR and FT-IR Analyses.

Molecular Details of Acetate Binding to a New Diamine Receptor by NMR and FT-IR Analyses.

J Phys Chem A. 2016 Mar 31;

Authors: Banerji B, Chatterjee M, Pal U, Maiti NC

Abstract
Acetate anion plays an important role in several biochemical functions such as enzyme reaction, antibody response and action of receptor molecules. This investigation reports the synthesis and molecular details of a unique receptor, 2-Amino-N-(2-amino-benzyl)-benzamide (R) that senses selectively acetate via simultaneous involvement of one aromatic amine group and an amide proton of the receptor molecule. Solution state NMR, steady state fluorescence and FT-IR examinations established that the acetate anion binds to the receptor with 1:1 ratio with high specificity. The binding was stabilized by two H-bonds formation between the oxygen atoms of acetate anion and two H-atoms, one from amide group and the other from the amine group of the receptor. The binding interaction caused significant changes in the chemical shift of the receptor protons and the evaluated affinity constant, from the NMR measurements was found to be 1.87×104 M-1. DFT analysis further showed a significant rotation of one of the two aromatic rings leading to formation of a ten member ring involving the acetate anion, amide proton and the one amine group attached to aromatic ring. The H-bond patterns observed in the crystal structure were significantly changed due to complex formation. However, the changes in the geometrical arrangement in the complex caused a small but a significant increase of the fluorescence emission. Acetate geometry and unique positioning of the amide and amine groups of the receptor render the recognition feasible and DFT analysis estimated ~30 kJ M-1 stabilization due to 1:1 complexation. Such positioning and geometrical arrangement may make the receptor very specific to bind acetate anion and as such became a very relevant molecule in detection and function of the acetate anion present in complex biochemical systems.

PMID: 27029209 [PubMed - as supplied by publisher]

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