Synthesis, Crystal Structures, and Optical and Magnetic Properties of Samarium, Terbium, and Erbium Coordination Entities Containing Mono-Substituted Imine Silsesquioxane Ligands

Abstract

Mono-substituted cage-like silsesquioxanes of the T8-type can play the role of potential ligands in the coordination chemistry. In this paper, we report on imine derivatives as ligands for samarium, terbium, and erbium cations and discuss their efficient synthesis, crystal structures, and magnetic and optical properties. X-ray analysis of the lanthanide coordination entities [MCl3(POSS)3]·2THF [M = Er3+ (3), Tb3+ (4), Sm3+ (5)] showed that all three compounds crystallize in the same space group with similar lattice parameters. All compounds contain an octahedrally coordinated metal atom, and additionally, 3 and 5 structures are strictly isomorphous. However, surprisingly, there are two different molecules in the crystal structure of the terbium coordination entity 4, monomer (sof 65%) and dimer (sof 35%), with one and two metal centers. Absorption measurements of the investigated materials recorded at 300 K showed that regardless of the lanthanide involved, their energy band gap equals 2.7 eV. Moreover, the analogues containing Tb3+ and Sm3+ exhibit luminescence typical of these rare earth ions in the visible and infrared spectral range, while the compound with Er3+ does not generate any emission. Direct current variable-temperature magnetic susceptibility measurements on polycrystalline samples of 3–5 were performed between 1.8 and 300 K. The magnetic properties of 3 and 4 are dominated by the crystal field effect on the Er3+ and Tb3+ ions, respectively, hiding the magnetic influence between the magnetic cations of adjacent molecules. Complex 5 exhibits a nature typical for the paramagnetism of the samarium(III) cation.

Gravity-Driven Separation for Enrichment of Rare Earth Elements Using Lanthanide Binding Peptide-Immobilized Resin

“…These residues are predisposed to form bidentate ligands over monodentate, owing to their enhanced stability due to the ion’s higher oxidation state of the REE ions (>+2) (Figure S4). In addition, we consider the widely accepted coordination numbers for Tb 3+ and Eu 3+ of 8 and 10, respectively. − Peptide1 showcases a spatial organization where the amino acids D4, D8, and E12 are distinctly positioned with notable intervals between them. This assists in their interaction with both Tb 3+ and Eu 3+ with minimal steric/electrostatic hindrance between the ligands.…”

Heteroleptic samarium complexes with high quantum yields for temperature sensing applications

“…This is because the PMMA polymer matrix suppresses the quenching effect by damping some of the vibronic modes. The lifetime of present complexes in solid state is longer than that reported for [Sm (fod) 3 (µ-bpp)Sm(fod) 3 ] (38.74 µs), 31 [Sm(dbm) 3 (tptz)] (20 ± 0.05 µs), 35 [Sm(hfaa) 3 (Pz) 2 ] (39 µs), 32 [Sm(fod) 3 (tppo) 2 ] (38.5 µs), 48 [MCl 3 (POSS) 3 ]•2THF (13.7 µs), 51 [Sm(tta) 3 (PBr)] (39 µs), [Sm(tta) 3 (MP)] (27 µs) and [Sm(tta) 3 (DP)] (18 µs). 52 This divulges that the antenna effect is efficient, and the present complexes have excellent photoluminescence properties.…”

A Brief Review on Selected Applications of Hybrid Materials Based on Functionalized Cage-like Silsesquioxanes

“…Covalently bonded to the silicon core, the side arms are labile groups that enable various chemical reactions to be carried out on them and are effective nano-building blocks for, among others, supramolecular structures [ 7 , 8 , 9 ]. Depending on the number of reactive organic arms attached to the T 8 -type cage, there are mono-, di-, including ortho , meta , para diadducts, and octa-substituted derivatives ( Figure 2 ) [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”