Supramolecular phosphate transfer catalysis by pillar[5]arene

Area of Science:

• Supramolecular Chemistry
• Physical Organic Chemistry
• Catalysis

Background:

• Dinitrophenylphosphate monoester (DNPP) is a substrate susceptible to hydrolysis.
• Pillararenes are macrocyclic hosts capable of forming inclusion complexes.
• Cationic pillararenes offer unique binding properties due to their charged nature.

Purpose of the Study:

• To investigate the kinetic hydrolysis of DNPP catalyzed by a cationic pillararene, P5A.
• To elucidate the supramolecular interactions between DNPP and P5A.
• To characterize the structure of the formed complexes and understand the catalytic mechanism.

Main Methods:

• Kinetic studies were performed to measure hydrolysis rate constants.
• Nuclear Magnetic Resonance (NMR) spectroscopy was used to study complex formation.
• Molecular Dynamics (MD) calculations were employed for structural characterization of complexes.

Main Results:

• NMR confirmed the formation of supramolecular complexes between DNPP and P5A, with proton shifts indicating inclusion within the pillararene cavity.
• MD simulations characterized the 1:1 and 1:2 complexes.
• The presence of P5A increased both the acidity of DNPP and its hydrolysis rate constants.

Conclusions:

• Supramolecular complexation between DNPP and P5A enhances DNPP hydrolysis.
• Catalysis arises from electrostatic stabilization of the transition state and destabilization of the DNPP dianion via steric hindrance of water hydrogen bonding.
• Cationic pillararenes can act as effective catalysts for phosphate ester hydrolysis.