Highly optically-diluted lanthanide coordination polymers with unexpected strong luminescence

Abstract

A series of lanthanide coordination polymers with the general chemical formula [Ln₂(dcpa)₃(H₂O)]_∞ (Ln = La–Er except Pm, plus Y; H₂dcpa = 4,5-dichloro-phthalic acid) has been obtained by micro-wave assisted synthesis. Isostructural hetero-lanthanide molecular alloys in which the emissive ions are highly diluted with non-emitting ions have also been prepared. These compounds exhibit unexpectedly high luminescence intensities. Based on photo-physics measurements and theoretical calculations this strong luminescence was attributed to unusually low non-radiative vibrational de-excitation. Intermetallic Tb³⁺ → Eu³⁺ energy transfers have also been estimated in the frame of Förster's mechanism. This study opens the way to the design of a series of compounds, with strong and highly tunable luminescence in the visible domain, which is of interest for material traceability.