Manipulating the proton transfer process in molecular complexes: synthesis and spectroscopic studies

Area of Science:

• Supramolecular Chemistry
• Solid-State Chemistry
• Spectroscopy

Background:

• Proton transfer is fundamental to many chemical and biological processes.
• Understanding proton transfer in molecular complexes is key to designing functional materials.
• The influence of substituents on proton transfer dynamics requires further investigation.

Purpose of the Study:

• To investigate the proton transfer process in molecular complexes in both solid and solution phases.
• To elucidate the role of hydrogen bonding and electron-withdrawing groups in governing proton transfer.
• To correlate structural and electronic properties with the observed proton transfer phenomena.

Main Methods:

• Single-crystal X-ray diffraction (SCXRD) for structural analysis of N-H-O bonding.
• Fourier-transform infrared (FTIR) and Raman spectroscopy to determine hydrogen positions.
• UV-Visible spectroscopy to monitor intramolecular charge transfer (ICT) in solution.
• (1)H-NMR spectroscopy to identify and monitor aliphatic hydrogen bonding.

Main Results:

• Proton transfer extent correlates with intramolecular charge transfer (ICT) and constituent species stability.
• Increased nitro groups lead to higher melting points and enhanced ionic character.
• Aliphatic C-H-O hydrogen bonding and solvent nature influence molecular complex identity in solution.
• Conductivity increases with nitro group number, indicating enhanced ionic character.

Conclusions:

• The study provides direct insights into proton transfer mechanisms in molecular complexes.
• Molecular design, particularly the incorporation of nitro groups, effectively modulates ionic character and conductivity.
• Hydrogen bonding interactions play a crucial role in stabilizing the proton transfer process.