Heteronuclear lanthanide-based coordination polymers exhibiting tunable multiple emission spectra

Abstract

Reactions in water at room temperature between lanthanide ions and 5-hydroxy-1,3-benzene-di-carboxylic acid hereafter referred to as H₂(hip) lead to a new family of lanthanide-based hetero-nuclear compounds with the general chemical formula [Ln_2−2xLn_2x′(hip)₂(H₂O)₁₀,(hip),4H₂O]_∞ where Ln and Ln′ = Pr–Lu or Y and where 0 ≤ x ≤ 1. The physico-chemical properties of this family have been characterized by PXRD, TDXD, TG/TD, EDS, SEM, ⁸⁹Y solid state NMR spectroscopy and optical spectroscopy. The luminescent properties of these compounds are studied in detail. This study reveals that the competition between intermetallic energy transfer and photo-induced electron transfer gives rise to complex multiple emission spectra. It is therefore possible, for some Ln/Ln′ compositions, to obtain green, yellow or red emission by tuning the excitation wavelength over a 50 nm range. From a global point of view, this study shows that this series of compounds could be of great interest as far as luminescent coordination polymers usable as taggants for the fight against counterfeiting are aimed.