Cerium Photosensitizers: Structure-Function Relationships and Applications in Photocatalytic Aryl Coupling Reactions.

Two complete mixed-ligand series of luminescent CeIII complexes with the general formulas [(Me3Si)2NC(NiPr)2]xCeIII[N(SiMe3)2]3–x (x = 0, 1-N; x = 1, 2-N, x = 2, 3-N; x = 3, 4) and [(Me3Si)2NC(NiPr)2]xCeIII(OAr)3–x (x = 0, 1-OAr; x = 1, 2-OAr, x = 2, 3-OAr; x = 3, 4) were developed, featuring photoluminescence quantum yields up to 0.81(2) and lifetimes to 117(1) ns. Although the 4f → 5d absorptive transitions for these complexes were all found at ca. 420 nm, their emission bands exhibited large Stokes shifts with maxima occurring at 553 nm for 1-N, 518 nm for 2-N, 508 nm for 3-N, and 459 nm for 4, featuring yellow, lime-green, green, and blue light, respectively. Combined time-dependent density functional theory (TD-DFT) calculations and spectroscopic studies suggested that the long-lived 2D excited states of these complexes corresponded to singly occupied 5dz2 orbitals. The observed difference in the Stokes shifts was attributed to the relaxation of excited states through vibrational processes facilitate...