Synthesis and Characterization of a Tripodal Amide Ligand and Its Binding with Anions of Different Dimensionality

Synthesis and crystal structure of a tren-based amide, L1,N,N‘,N‘‘-tris[(2-amino-ethyl)-3-nitro-benzamide] is reported.
The crystallographic results show intramolecular hydrogen bonding and aromatic π···π stacking among tripodal
arms which prevent opening of the receptor cavity. Intermolecular hydrogen bonding in L1 generates the sheetlike
network in the solid state. The structural aspects of binding halides (1 and 2), nitrate (3), perchlorate (4), and
hexafluorosilicate (5) with the protonated L1 are examined crystallographically. Protonation at the apical nitrogen of
L1 in the presence of anions shows a structural transformation from sheet to bilayer network. Anion binding with
multiple receptor units is observed via amide N−H···anion and aryl C−H···anion hydrogen-bonding interactions in
all the complexes. The aryl group having nitro functionality that contributes to anion binding in complexes 1−5
through CH···anion interactions (either para or meta to nitro C−H) is noteworthy. These studies also show higher
anion coordination of chloride (8) and hexafluorosilicate (14) with L1H+.