Anion binding studies of tris(2-aminoethyl)amine based amide receptors with nitro functionalized aryl substitutions: a positional isomeric effect

Ravikumar, I. ; Lakshminarayanan, P. S. ; Ghosh, Pradyut (2010) Anion binding studies of tris(2-aminoethyl)amine based amide receptors with nitro functionalized aryl substitutions: a positional isomeric effect Inorganica Chimica Acta, 363 (12). pp. 2886-2895. ISSN 0020-1693

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.ica.2010.02.030

Abstract

Syntheses and crystal structures of tren-based amide, L1, N,N′,N″-tris[(2-amino-ethyl)-4-nitro-benzamide] and L2, N,N′,N″-tris[(2-amino-ethyl)-2-nitro-benzamide] are reported and compared with previously published tripodal amide receptor L3, N,N′,N″-tris[(2-amino-ethyl)-3-nitro-benzamide]. The crystallographic results show intramolecular and intermolecular hydrogen-bonding interactions between two arms of the tripodal receptor and two other adjacent molecules in cases of L1 and L2 whereas in addition to the above interactions an aromatic π···π stacking among tripodal arms is also observed in L3. Receptors L1, L2 and L3 having electron withdrawing –NO2 substituted (para, ortho and meta, respectively) phenyl moieties are explored toward their solution state anion binding properties and selectivity studies. The substantial changes in chemical shifts are observed for the amide protons (–NH) and aromatic protons (–CH) with F and Cl in cases of L1 and L3, and only with F for L2, indicating the participation of –NH and –CH protons in the solution state binding events. Binding constants for the above cases are calculated by 1H NMR titration upon monitoring the –NH signal. Receptor L2 shows exclusive selectivity toward F in dimethyl sulfoxide (DMSO). The structural aspects of binding I, ClO4 and SiF62− with the monoprotonated L1, L1H+·I·DMF (1), L1H+·ClO4·DMF (2) and L1H+·0.5SiF62−·H2O (3), respectively are examined crystallographically. Anion binding with multiple receptor units is observed via amide N–H···anion as well as aryl C–H···anion hydrogen-bonding interactions in all the complexes as observed in cases of previously reported crystal structures of anionic complexes of protonated L3. The aryl group having nitro functionality that contributes to solution state anion binding with the neutral receptor and solid state coordination in complexes 1–3 through CH···anion interactions is noteworthy.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Anion Recognition; Neutral Receptor; Amide; Hydrogen Bonds; X-Ray Crystallography; Supramolecular Chemistry
ID Code:102150
Deposited On:23 Jan 2017 12:03
Last Modified:23 Jan 2017 12:03

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