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

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Analytical Chemistry

Background:

• Phosphate anion recognition is crucial in biological and chemical systems.
• Developing selective receptors for phosphate binding remains a significant challenge.
• Thiophene-based receptors offer unique electronic and structural properties for molecular recognition.

Purpose of the Study:

• To synthesize and characterize two novel thiophene-based monocyclic receptors, L1 and L2.
• To investigate the binding behavior of L1 and L2 towards phosphate anions in solution and solid states.
• To elucidate the binding mode and strength of phosphate-receptor interactions.

Main Methods:

• Solution-state studies using proton nuclear magnetic resonance (1H NMR) and phosphorus-31 nuclear magnetic resonance (31P NMR) titrations.
• Solid-state characterization via single-crystal X-ray diffraction analysis.
• Computational modeling to support experimental findings (optional, if applicable based on abstract).

Main Results:

• 1H NMR titrations indicated a 1:2 binding mode of ligands to phosphate anions in DMSO-d, with high binding constants (log K of 5.25 for L1 and 4.20 for L2).
• 31P NMR in D2O confirmed phosphate binding to L1 and L2 at pH 5.2.
• X-ray crystallography of the L1-phosphate complex provided definitive evidence for ditopic complex formation through multiple hydrogen bonds (NH···O and CH···O).

Conclusions:

• The synthesized thiophene-based receptors L1 and L2 exhibit efficient binding towards phosphate anions.
• The ditopic binding mode, facilitated by hydrogen bonding, is key to the observed recognition.
• These receptors demonstrate potential for applications in sensing and separation of phosphate species.