Tb³⁺→Eu³⁺ Energy Transfer in Mixed-Lanthanide-Organic Frameworks

Abstract

In this work, we report a theoretical and experimental investigation of the energy transfer mechanism in two isotypical 2D coordination polymers, ∞ [(Tb 1−x Eu x )(DPA)(HDPA)], where H 2 DPA is pyridine 2,6-dicarboxylic acid and x = 0.05 or 0.50. Emission spectra of ∞ [(Tb 0.95 Eu 0.05 )(DPA)(HDPA)] and ∞ [(Tb 0.5 Eu 0.5 )(DPA)-(HDPA)], (1) and (2), show that the high quenching effect on Tb 3+ emission caused by Eu 3+ ion indicates an efficient Tb 3+ →Eu 3+ energy transfer (ET). The k ET of Tb 3+ → Eu 3+ ET and rise rates (k r ) of Eu 3+ as a function of temperature for (1) are on the same order of magnitude, indicating that the sensitization of the Eu 3+ 5 D 0 level is highly fed by ET from the 5 D 4 level of Tb 3+ ion. The η ET and R 0 values vary in the 67− 79% and 7.15 to 7.93 Å ranges. Hence, Tb 3+ is enabled to transfer efficiently to Eu 3+ that can occupy the possible sites at 6.32 and 6.75 Å. For (2), the ET processes occur on average with η ET and R 0 of 97% and 31 Å, respectively. Consequently, Tb 3+ ion is enabled to transfer energy to Eu 3+ localized at different layers. The theoretical model developed by Malta was implemented aiming to insert more insights about the dominant mechanisms involved in the ET between lanthanides ions. Calculated single Tb 3+ → Eu 3+ ETs are three orders of magnitude inferior to those experimentally; however, it can be explained by the theoretical model that does not consider the role of phonon assistance in the Ln 3+ → Ln 3+ ET processes. In addition, the Tb 3+ → Eu 3+ ET processes are predominantly governed by dipole−dipole (d−d) and dipole−quadrupole (d−q) mechanisms.

Color and Brightness Tuning in Heteronuclear Lanthanide Terephthalate Coordination Polymers

“…This is in agreement with what has already been suggested previously. [36] These results are also interesting as far as technological applications are concerned. Indeed, they suggest that it is possible to synthesize heteronuclear compounds containing only a few percent of Eu 3+ or Tb 3+ ions and exhibiting luminescence almost as bright as that exhibited by the corresponding homonuclear compound (see Table 4).…”

“…[33,34] However, these smart luminescence properties have not been studied in detail, and up to date, only a few reported works deal with heteronuclear lanthanide containing coordination polymers. [29,31,32,[35][36][37] In this paper, the spectroscopic and colorimetric properties of heteronuclear lanthanide terephthalate coordination polymers are deciphered with the aim of gaining easy tuning of the color and brightness of the lanthanide-centered emission by adjusting the intermetallic distances. 4 ] ϱ .…”

Interpretation of europium(III) spectra

“…has been studied in glasses [444,445], inorganic compounds [446][447][448], solid molecular compounds (including metal-organic frameworks) [449,450], and in solution [451][452][453][454][455][456][457][458][459][460][461][462].…”

Recent advances in lanthanide spectroscopy in Brazil

“…Other lanthanide systems based on crystals [152][153][154][155], silica [156], kaolinite [157], PMMA [158], alumina [159,160], and poly-β-hydroxybutyrate (PHB) [161] have been discussed. The preparation of glasses containing lanthanides and their luminescence properties have been discussed in the literature for several different systems and discussed in the frame of a wide range of applications [10,20,26 …”

“…Rodrigues et al [20] have carried out an experimental and theoretical investigation of a Ln-based MOF (Ln ¼ Eu 3 þ and Tb 3 þ ), where ion-to-ion (Tb 3 þ -Eu 3 þ ) ET takes place. In this system (Fig.…”