Enhanced Photocatalytic Activity of α-Methylstyrene Oligomerization through Effective Metal-to-Ligand Charge-Transfer Localization on the Bridging Ligand

A series of Pd complexes containing a visible-light harvesting moiety with various combination of substituents (R, X) were synthesized. The variation of the substituents resulted in significant change in the electrochemical and photophysical properties of the complexes. Additionally, photocatalytic activity drastically increased through the introduction of an electron-donating group on R and an electron-withdrawing group on X, respectively. The molecular orbital analysis based on density functional theory (DFT) calculation suggested that the enhancement of the catalytic activity is due to the effective Metal-to-Ligand Charge-Transfer (MLCT) localization on the bridging ligand.