Modulating the spectroscopy and dynamics of a proton-transfer dye by functionalizing with phenyl groups

Area of Science:

• Photophysics and Spectroscopy
• Organic Chemistry
• Materials Science

Background:

• Molecules with excited-state proton transfer (ESPT) are crucial for spectroscopy and photophysics.
• Functionalization with electron donating/accepting groups induces intramolecular charge transfer (ICT), altering properties.
• Coupled ICT and ESPT phenomena are vital for advanced material development.

Purpose of the Study:

• To synthesize and investigate novel benzimidazole derivatives, DP-HPPI and DP-MPPI.
• To explore the photophysical properties, including ICT and ESPT, of these new compounds.
• To understand the influence of solvent environment on proton transfer dynamics.

Main Methods:

• Synthesis of 2-(5,10-diphenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol (DP-HPPI) and its methylated analog DP-MPPI.
• Ultrafast spectroscopic techniques to study charge transfer dynamics.
• Solvent-dependent studies to probe the mechanism of proton transfer.

Main Results:

• Both DP-HPPI and DP-MPPI exhibit ultrafast intramolecular charge transfer (ICT) in solution within 400-700 fs.
• DP-HPPI demonstrates a reversible excited-state proton transfer (ESPT) in dichloromethane.
• ESPT in DP-HPPI is inhibited in acetonitrile due to intermolecular hydrogen bonding.

Conclusions:

• The studied benzimidazole derivatives possess significant ICT capabilities.
• DP-HPPI shows tunable ESPT behavior dependent on the solvent environment.
• These findings are crucial for designing novel proton-transfer materials with tailored spectral and photodynamical properties.