Modulation of Pt -> Ln Energy Transfer in PtLn(2) (Ln = Nd, Er, Yb) Complexes with 2,2 '-Bipyridyl/2,2 ':6 ' 2 ''-Terpyridyl Ethynyl Ligands

Reaction of (CH3)(3)SiC Cbpy (bpy = 2,2'-bipyridyl), (CH3)(3)SiC CC(6)H(4)tpy (tpy = 2,2':6'2 ''-terpyridyl), or (CH3)(3)SiC CC6H4C Cbpy with Pt(BU2'bpy)Cl-2 in the presence of KF and CuI gave Pt(Bu-2'bpy)(C Cbpy)(2) (1), Pt(Bu-2'bpy)(C CC(6)H(4)tpy)(2) (5), or Pt(Bu-2'bpy)(C CC6H4C Cbpy)(2) (9), respectively. Incorporating Ln(hfac)(3) (Ln = Nd, Er, Yb; hfac = hexafluoroacetylacetonate) units with 1, 5, and 9 through 2,2'-bipyridyl/2,2':6'2 ''-terpyridyl chelation induces isolation of a series of PtLn(2) heterotrinuclear complexes. Upon excitation of the PtLn(2) complexes at 350 nm <= lambda(ex) <= 500 nm, near-infrared (NIR) luminescence from lanthanide ions is indeed lighting up through effective Pt -> Ln energy transfer from (3)[d(Pt) -> pi*(Bu-2'bpy)] metal-to-ligand charge transfer transition excited-state of the Pt(Bu-2'bpy)bis(acetylide) antenna chromophore. By successive insertion of phenylene or ethynyl between acetylide and 2,2'-bipyridyl/2,2':6',2 ''-terpyridyl in the bridging ligands, the rate and efficiency of Pt -> Ln energy transfer are tunable. In contrast with quite effective Pt -> Ln energy transfer in Pt-C Cbpy-Ln (Pt...Ln = 8.6 angstrom) and Pt-C CC(6)H(4)tpy-Ln (Pt...Ln = 14.1 angstrom) arrays, the long-range energy transfer across Pt-C CC6H4C Cbpy-Ln (Pt...Ln = 14.9 angstrom) array becomes less efficient.