A comparison of sensitized Ln(III) emission using pyridine- and pyrazine-2,6-dicarboxylates--part II.

The synthesis, X-ray structures and photophysical properties of several new Ln(III) complexes with the dianion of pyrazine-2,6-dicarboxylic acid (H(2)PYZ) that demonstrate excellent stability and solubility in non-aqueous solution are reported, and compared to structurally analogous complexes derived from pyridine-2,6-dicarboxylic acid (H(2)DPA). The Eu(III) and Yb(III) complexes demonstrate efficient metal centered luminescence in the visible and Near Infra-Red (NIR) regions, respectively. Low temperature (77 K) phosphorescence measurements using the corresponding Gd(III) complex has allowed the photophysical properties of the sensitizer to be rationalized, together with corresponding TD-DFT studies for a model complex. Lastly, we have evaluated the sensitization efficiencies for these complexes, and have undertaken femtosecond transient absorption (TA) measurements in order to evaluate the relative importance of the intersystem crossing and energy transfer processes involved with sensitized Ln(III) emission via the antennae effect.