Photophysical Studies of Lanthanide Terpyridine Complexes

Indianapolis, IN

The McMillin group is investigating the photophysical behavior of lanthanide complexes. The bound ligands act as antenna chromophores that sensitize emission from the Laporte-forbidden f-f excited states of the central metal. These antenna chromophores may be tuned by changing the substituent group on the terpyrdine ligand. The complexes that were used have the formula (X-T)La(NO₃)₃, where X-T denotes a tridentate, 4'-substituted 2,2':6,2"-terpyrdine ligand. With this design, it is possible to change the substituent X as well as the metal center. When the metal ion is La(III), Lu(III), or Gd(III), one can monitor the flow of energy amidst ligand-based orbitals. On the other hand, incorporating Eu(III) or Tb(III) introduces f-f states into the picture. Two terpyridine ligands of interest are 4'-(pyrrolidin-1-yl)-2,2':6',2"-terpyridine (pyrr-T) and 4'-(pyren-1-yl)-2,2':6',2"-terpyrdine (pyre-T) due to the existence of novel, low-lying intraligand-charge-transfer (ILCT) states. The presentation focuses on understanding the results of absorbance, emission, and emission lifetime studies.