Sensitized EuIII luminescence through energy transfer from PtM2 (M = Ag or Au) alkynyl chromophores in PtM2Eu2 heteropentanuclear complexes

Using phosphorescent PtM2 (M Ag or Au) heterotrinuclear complexes with ethynyl-functionalized 2,2':6',2 ''-terpyridyl ligands as precursors, PtM2Eu2 heteropentanuclear complexes were synthesized with 2,2':6',2 ''-terpyridyl bound to a Eu-III ion. Upon excitation of the PtM2 chromophore at 390 nm <= lambda(ex) <= 450 nm, the PtM2Eu2 complexes exhibit intense Eu-based luminescence sensitized through intramolecular d -> f energy transfer, and the phosphorescence due to the PtM2 chromophore is largely quenched. By the successive insertion of phenylene and ethynyl between acetylide and 2,2':6',2 ''-terpyridyl in the bridging ligands, the rate and efficiency of d -> f energy transfer are tunable. In contrast with the quite effective d -> f energy transfer in the Pt-C CC(6)H(4)tpy-Eu arrays, the long-range energy transfer across Pt-C CC6H4C CC(6)H(4)tpy-Eu arrays becomes less efficient.