Eu3+ substitutional defects and their effect on the luminescence spectral and decay dynamics of sal-type one dimensional rare earth coordination polymers and trinuclear complexes

Abstract

Two series of one dimensional coordination polymers, {Na[Ln(sal)4]}n (Ln=Eu, Tb, Er, Y) and {Na[Ln(msal)4]}n (Ln=Er) and a new series of trinuclear complexes Na[Ln2(nsal)7(CH3OH)2] (Ln=Pr, Eu, Er) have been synthesized, structurally characterized and their luminescence and decay dynamical properties studied. This in order to explore the potential of sal-type ligands to yield compounds with various dimensionalities and probe the impact of defect sites on their unique photoluminescence behaviour. The Eu3+ compounds, {Na[Eu(sal)4]}n and Na[Eu2(nsal)7(CH3OH)2] are bright red luminophores having Eu3+ (5D0) emission spectra dominated by the 5D0→7F2 transition. Eu3+ substitutional defects, possibly arising from the swapping of Na+ with Eu3+ ions and the replacement of sal- with methanol, are evident from luminescence and decay dynamical data on both complexes. Decay data also indicate that energy migration on the Eu3+ sub-lattice in one dimensional chains of {Na[Eu(sal)4]}n is multidimensional and dynamic but is less efficient than energy migration in Na[Eu2(nsal)7(CH3OH)2] which features a H-bonded network of trinuclear molecules. The results of this comparative exploration of structure and luminescence can be manipulated to direct dimensionality in crystal engineering of these compounds.