Monometallic europium, terbium, and neodymium complexes formed from the bridging ligand 2,3-bis(2-pyridyl)pyrazine: Crystal structure and temperature dependent luminescent properties

Lanthanide complexes of the form Ln(tdh)3dpp (where Ln = Nd(III), Eu(III) or Tb(III); tdh = 1,1,1-trifluoro-5,5- dimethyl-2,4-hexanedione and dpp = 2,3-bis(2-pyridyl)pyrazine) have been structurally characterized. X-ray quality crystals were grown by the slow evaporation of concentrated solutions of the complexes. Each metal is 8-coordinate with 6 oxygens from the tdh ligand, 1-pyridyl nitrogen, and 1-pyrazine nitrogen from the dpp ligand. Luminescent studies show that the Nd complex undergoes non-radiative relaxation through solvent vibrational deactivation. In contrast, the Eu and Tb complexes emit in the visible region of the spectrum when solutions of the complex are excited at 388 nm associated with the pi-pi*/transition of the tdh ligand. Emission lines corresponding to transitions from the D-5(0) and D-5(4) state to the F-7(J) manifold of the Eu(III) and Tb(III), respectively, are observed. The intensity of these emissions decreases as temperature is increased. (C) 2015 Elsevier B.V. All rights reserved.