Luminescence study of praseodymium complexes with selected phosphonate ligands

Spectroscopic properties of Pr(III) complexes with diethyl(phthalimidomethyl)phosphonate (DPIP) and diethyl(2-oxo-2phenylethyl)phosphonate (DEPP) ligands were studied using absorption and luminescence spectroscopy. Absorption spectra of praseodymium nitrate hexahydrate complexes with phosphonate ligands in acetonitrile solutions were measured and used to calculate oscillator strength values. Luminescence (excitation and emission) spectra of the Pr(III) complexes with DPIP and DEPP were measured in CH3CN, DMSO, methanol and toluene solutions. The sensitized emission of Pr(III), observed from different excited states (3P0 or 1D2), resulted from the intramolecular energy transfer from the ligands to the emissive levels of Pr(III). The Pr(III) complexes with studied ligands were synthesized and their compositions, as Pr(DEPP)2(NO3)3 and Pr(DPIP)3(NO3)3, were confirmed by elemental analyses. Using IR and 31P NMR spectroscopy coordination mode of the ligands were described.

► We studied spectroscopic properties of Pr(III) complexes with P=O ligands.
► Observed emission is a result of energy transfer from the ligands to Pr(III) (LMET).
► The luminescence originates from two excited states of Pr(III), i.e. 3P0 and/or 1D2.
► The Pr(III) emission can be tuned by the use of appropriate ligands enabling LMET.