Toward Opto-Structural Correlation to Investigate Luminescence Thermometry in an Organometallic Eu(II) Complex

Abstract

Lanthanide-based luminescent materials have unique properties and are well-studied for many potential applications. In particular, the characteristic 5d → 4f emission of divalent lanthanide ions such as EuII allows for tunability of the emissive properties via modulation of the coordination environment. We report the synthesis and photoluminescence investigation of pentamethyl­cyclopenta­dienyl­europium­(II) tetrahydroborate bis­(tetrahydrofuran) dimer (1), the first example of an organometallic, discrete molecular EuII band-shift luminescence thermometer. Complex 1 exhibits an absolute sensitivity of 8.2 cm–1 K–1 at 320 K, the highest thus far observed for a lanthanide-based band-shift thermometer. Opto-structural correlation via variable-temperature single-crystal X-ray diffraction and fluorescence spectroscopy allows rationalization of the remarkable thermometric luminescence of complex 1 and reveals the significant potential of molecular EuII compounds in luminescence thermometry.

Lanthanide Luminescence and Thermochromic Emission from Soft-Atom Donor Dichalcogenoimidodiphosphinate Ligands

“…5,6 The recent discovery of luminescence thermometry in an organometallic Eu(II) complex demonstrates that sensitive "band shift thermometry" is accessible for divalent europium. 7 Here, we have identified three more examples of temperature-dependent luminescence in both Eu(II) and Eu(III) systems, as well as room temperature emission in Pr, Nd, Sm, and Tb.…”

“…Time-resolved emission spectra were collected with 5 nm spectral widths using a 1000−2000 μs collection window after excitation to remove residual fluorescence, leaving only phosphorescence from the ligands. Triplet state energies were then determined from the onset of emission, for the gadolinium complexes (7,12), and these data can be found in the Supporting Information (S8).…”

“…The single crystal structures were reported for both sulfur and selenium analogs with the largest lanthanides: Ln[N-(QPPh 2 ) 2 ] 3 for Ln = La and Ce (Q = S, Se), 39 as well as the selenium analog for Nd[N(SePPh 2 ) 2 ] 3 (10) . 19 The structures determined here include Ln[N(SPPh 2 ) 2 ] 3 , for Ln = Eu (3), Pr (4), Nd (5), Sm (6), Gd (7), Tb (8), and Ln[N(SePPh 2 ) 2 ] 3 , for Ln = Pr (9), Sm (11), and Gd (12). These complexes, shown in Figure 2, are homoleptic and isomorphous to those reported previously.…”

“…Here, we report the synthesis and single-crystal structures of three europium-based complexes, Eu[N(SPPh 2 ) 2 ] 2 (THF) 2 (1), the previously reported Eu[N(SePPh 2 ) 2 ] 2 (THF) 2 (2), 19 and Eu[N(SPPh 2 ) 2 ] 3 (3). Using the same sulfur and selenium ligands, complexes were also prepared with a range of lanthanides and single-crystal structures of the corresponding isomorphous compounds: Ln[N(SPPh 2 ) 2 ] 3 (Ln = Pr (4), Nd (5), Sm (6), Gd (7), Tb (8)) and Ln[N(SePPh 2 ) 2 ] 3 (Ln = Pr (9), Sm (11), Gd (12)) are presented. The crystal structure of Nd[N(SePPh 2 ) 2 ] 3 (10) has been previously reported 19 (and related actinide complex Np[N(SePPh 2 ) 2 ] 3 ); 31 here, we investigate its photophysical properties.…”

Solid-state and solution-phase characterization of SmII-aza[2.2.2]cryptate and its methylated analogue

“…Complexes of divalent lanthanide (Ln II ) ions have attracted attention in recent years owing to their interesting luminescence, magnetic, and electrochemical properties. 1–25 One such group of Ln II complexes that have been the subject of extensive investigation with regard to their structural, photophysical, and electrochemical properties is the Ln II -cryptates. 2,26–42 In many studies, cryptands such as 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (222) and 5,6-benzo-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacos-5-ene are used to encapsulate Ln II ions, 26–32,37–42 and reported Ln II -cryptates have luminescence and electrochemical properties that are useful in applications including light-emitting diodes, imaging, and catalysis.…”