Protonation and electronic structure of 2,6-dichlorophenolindophenolate during reduction. A theoretical study...

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Biophysical Chemistry

Background:

• 2,6-dichlorophenolindophenolate (DCIP) is a redox indicator crucial in biological systems.
• Understanding protonation is key to elucidating DCIP's reduction mechanisms.
• Previous studies have not fully explored the solvent effects on DCIP protonation.

Purpose of the Study:

• To investigate the protonation sites and mechanisms in the reduction of DCIP.
• To analyze the electronic structure of DCIP anions and radical anions.
• To examine the influence of solvent (methanol, water, oxonium cation) on DCIP protonation.

Main Methods:

• Density Functional Theory (DFT) for electronic structure calculations.
• Molecular Dynamics (MD) simulations to model solvent interactions.
• Quantum Theory of Atoms in Molecules (QTAIM) for electronic structure analysis.

Main Results:

• Oxygen and nitrogen atoms are identified as primary proton acceptor sites.
• Proton acceptor site preference is dependent on the total charge of the DCIP species.
• MD simulations revealed hydrogen bonding interactions with water and methanol, and proton transfer with oxonium cations.
• Calculated pKa values indicate the imino group of DCIPH- is a weaker acid than water.

Conclusions:

• The study elucidates the key protonation sites in DCIP reduction based on charge.
• Solvent interactions significantly influence proton transfer dynamics.
• Computational methods provide valuable insights into the redox chemistry of DCIP.