Solid state molecular device based on a rhenium(I) polypyridyl complex immobilized on TiO2 films

Area of Science:

• Photochemistry and Photophysics
• Materials Science
• Molecular Electronics

Background:

• Investigating the behavior of rhenium complexes with ligands like 1,10-phenanthroline (phen) and 4-[trans-(pyridin-4-yl-vinyl)]benzoic acid (stpyCOOH).
• Understanding photoinduced molecular motion and its potential applications in devices.

Purpose of the Study:

• To investigate the photochemical and photophysical properties of fac-[Re(CO)3(phen)(trans-stpyCOOH)](+) in solution and on TiO2 surfaces.
• To explore the photoinduced trans-to-cis isomerization of the stpyCOOH ligand and its effect on electron injection.
• To demonstrate the potential of photoinduced molecular motion for generating electrical current.

Main Methods:

• Spectrophotometry and 1H NMR spectroscopy to determine quantum yields of photoisomerization.
• Adsorption of the rhenium complex onto TiO2 films.
• Monitoring photocurrent generation upon photoirradiation.

Main Results:

• Efficient trans-to-cis photoisomerization of the coordinated stpyCOOH ligand was observed in acetonitrile solution (Φ(NMR) = 0.48 ± 0.04).
• The trans-to-cis isomerization was also achieved on TiO2 surfaces (Φ(UV-vis) = 0.23 ± 0.03) for the first time.
• Photoisomerization on TiO2 surfaces triggered electron injection into the semiconductor, leading to increased photocurrent.

Conclusions:

• Photoinduced trans-to-cis isomerization of immobilized ligands on TiO2 films acts as a trigger for electron injection.
• This system serves as a proof of concept for utilizing photoinduced molecular motion to generate electrical current in molecular machines/devices.