Solution and structural binding studies of phosphate with thiophene-based azamacrocycles

Highlight•Ditopic binding of phosphate to thiophene-based azmamcrocycles is reported.•The formation of phosphate complex is supported by proton and phosphorous NMR.•Phosphate complex is stabilized multiple hydrogen bonds from NH ⋯ O and CH ⋯ O interactions.

Two thiophene-based monocyclic receptors L1 and L2 have been studied for phosphate binding in solutions (D2O and DMSO-d6) by 1H NMR and 31P NMR titrations, and in the solid state by single crystal X-ray analysis. Results from 1H NMR titrations suggest that the ligands bind phosphate anions in a 1:2 binding mode in DMSO-d6, with the binding constants of 5.25 and 4.20 (in log K), respectively. The binding of phosphate to L1 and L2 was further supported by 31P NMR in D2O at pH = 5.2. The crystal structure of the phosphate complex of L1 reveals unambiguous proof for the formation of a ditopic complex via multiple hydrogen bonds from NH ⋯ O and CH ⋯ O interactions.

Graphical abstractTwo monocyclic receptors L1 and L2 bind phosphate in D2O and DMSO-d6, as conformed by 1H NMR and 1P NMR studies. Structural analysis of the phosphate complex of L1 reveals the formation of a ditopic complex stabilized via multiple hydrogen bonds from NH ⋯ O and CH ⋯ O interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide