Controlling Ligand Excimer Formation with Dipole Changes in Emissive Rare-Earth/Phosphonic Acid Complexes

Area of Science:

• Coordination Chemistry
• Photophysics
• Materials Science

Background:

• Arylvinyl phosphonic acid (AVPA) ligands are utilized in lanthanide complexes.
• Understanding excited-state dynamics is crucial for designing luminescent materials.

Purpose of the Study:

• To investigate how ligand substitution affects excited-state evolution in Eu-AVPA complexes.
• To correlate ground-state and excited-state properties with photophysical outcomes.

Main Methods:

• Computational geometry optimizations (ground and excited states).
• Transient absorption spectroscopy.
• Analysis of optical absorption and emission properties.

Main Results:

• CF3-substituted AVPA ligands exhibit preassociation in the ground state.
• Excimer formation is enhanced in CF3-substituted complexes, evidenced by red-shifted absorption.
• Eu3+ emission is reduced with CF3 substitution due to interligand aggregate formation.

Conclusions:

• Ground-state ligand preassociation influences excited-state dynamics.
• Excited-state geometry evolution, particularly phenyl-phenyl planarity, plays a role in energy flow.
• Ligand design must consider both static and dynamic factors for optimizing energy transfer in rare earth complexes.