Revealing Parallel Inter- and Intra-Ligand Charge Transfer Dynamics in [Ru(L)₂(dppz)]²⁺ Molecular Lightswitch with N...

Area of Science:

• Photochemistry and Photophysics
• Inorganic Chemistry
• Materials Science

Background:

• Charge localization in photoactive metal complexes determines reactivity.
• Precise measurement of charge redistribution in these systems is challenging.
• The [Ru(bpy)2dppz]2+ complex is a well-studied "molecular lightswitch".

Purpose of the Study:

• To track inter- and intra-ligand charge transfer in [Ru(bpy)2dppz]2+.
• To probe real-time electronic structure changes using ultrafast spectroscopy.
• To elucidate the mechanisms of light-driven charge separation.

Main Methods:

• Ultrafast X-ray absorption spectroscopy.
• First principles calculations.
• Probing electronic structure of ligand nitrogen atoms.

Main Results:

• Confirmed localization of excited electron density on phenazine N atoms of dppz.
• Identified two parallel electron transfer pathways.
• Observed sub-70 fs intra-ligand electron transfer (Ru-to-dppz MLCT) and reassigned slower 2 ps inter-ligand electron hopping (Ru-to-bpy MLCT).

Conclusions:

• Charge separation in [Ru(bpy)2dppz]2+ is significantly faster than previously identified.
• Extended azaacene ligand motifs promote competitive charge transfer processes.
• These findings advance understanding of light-driven electron transfer chemistry.