Wavelength-Dependent Singlet Oxygen Generation in Luminescent Lanthanide Complexes with a Pyridine-Bis(Carboxamide)-Terthiophene Sensitizer.

Lanthanide ion (LnIII ) complexes, [Ln(3Tcbx)2 ]3+ (LnIII =YbIII , NdIII , ErIII ) are isolated with a new pyridine-bis(carboxamide)-based ligand with a 2,2':5',2''-terthiophene pendant (3TCbx), and their resulting photophysical properties are explored. Upon excitation of the complexes at 490 nm, only LnIII emission is observed with efficiencies of 0.29 % at 976 nm for LnIII =YbIII and 0.16 % at 1053 nm for LnIII =NdIII . ErIII emission is observed but weak. Upon excitation at 400 nm, concurrent 1 O2 formation is seen, with efficiencies of 11 % for the YbIII and NdIII complexes and 13 % for the ErIII complex. Owing to the concurrent generation of 1 O2 , as expected, the efficiency of metal-centered emission decreases to 0.02 % for YbIII and 0.05 % for NdIII . The ability to control 1 O2 generation through the excitation wavelength indicates that the incorporation of 2,2':5',2''-terthiophene results in access to multiple sensitization pathways. These energy pathways are unraveled through transient absorption spectroscopy.