Enhanced TbIII-centered Luminescence due to Elongated Methylene Arms of Tripodal Schiff Base Ligand

LnIII-tripodal Schiff base complex TbIIILtrpn was prepared, in which the three arms of the ligand were extended by one methylene based on the tris(2-aminoethyl)amine in TbIIILtren. TbIIILtrpn showed enhanced TbIII-centered luminescence compared to TbIIILtren. Crystallographic analysis revealed that the symmetry of the seven-coordination environment of the TbIII center in TbIIILtrpn was diminished compared to that in TbIIILtren, resulting in the increased radiative transition rate and/or decreased back energy transfer rate and, thus, the increased luminescence. We report the structual and luminescence studies of a LnIII-tripodal Schiff base complex, LnIIILtrpn, by one-pot reaction with 5-methylsalicylaldehyde, tris(3-aminopropyl)amine, and Ln(CF3SO3)3. The TbIIILtrpn showed enhanced TbIII-centered luminescence due to the lower symmetry of the TbIII center by extension of methylene arm of tripod.