Heteroleptic Ir(III)N Complexes with Long-Lived Triplet Excited States and in Vitro Photobiological Activities.

A series of cationic heteroleptic iridium(III) complexes bearing tris-diimine ligands [Ir(phen)(R-phen)] (R-phen = phenanthroline (1), 3,8-diphenylphenanthroline (2), 3,8-dipyrenylphenanthroline (3), 3-phenylphenanthroline (4), 3-pyrenylphenanthroline (5), and 3,8-diphenylethynylphenanthroline (6)) were synthesized and characterized. These complexes possessed phen ligand-localized π,π* transitions below 300 nm, and charge transfer (CT) and/or π,π* transitions between 300 and 520 nm. In 1, 2, 4, and 6, the low-energy bands were mixed CT/π,π*.

Synthesis, Characterization and Photobiological Studies of Ru(II) Dyads Derived from α-Oligothiophene Derivatives of 1,10-Phenanthroline.

Three new bis(2,2'-bipyridine)-heteroleptic Ru(II) dyads incorporating thienyl groups (n = 1-3, compounds 1, 2 and 3, respectively) appended to 1,10-phenanthroline were synthesized and characterized to investigate the impact of n on the photophysical and photobiological properties within the series. All three complexes showed unstructured emission near 618 nm from a triplet metal-to-ligand charge transfer ( MLCT) state with a lifetime (τ ) of approximately 1 μs. Transient absorption measurements revealed an additional excited state that was nonemissive and long-lived (τ  = 43 μs for 2 and 27 μs for 3), assigned as a triplet intraligand ( IL) state that was accessible only in 2 and 3.