Crystal Engineering of Rare Earth Amides:  ³_∞[Tb(Im)₃]@NH₃, a Homoleptic 3D Network Exhibiting Strong Luminescence

Abstract

The solvent-free reaction of terbium metal with an imidazole melt (C 3 H 4 N 2 , ImH) yields single-crystalline ∞ 3 [Tb(Im) 3 ]@NH 3 (Im -) C 3 H 3 N 2 -, imidazolate anion) and hydrogen. Both N atoms of the imidazolate rings coordinate η 1 to terbium cations, thereby forming a homoleptic three-dimensional network. The Tb 3+ ions exhibit complete nitrogen coordination, resulting in trigonal prisms as coordination polyhedra and C.N. ) 6. The network contains cavities large enough to take up NH 3 molecules, the latter formed by the partial decomposition reaction of the amine ligand in the melt reaction. Ammonia can be removed thermally or over time without decomposition of the network. Unsubstituted imidazole can thus be utilized for crystal engineering and the formation of rare earth amide network structures. The compound exhibits an amazingly strong green emission. The emission spectrum shows the typical Tb 3+ f-f transitions; additionally, an efficient ligand f Tb 3+ energy transfer is observed.

Polymorphism of isotypic series of homoleptic 1,2,3-triazolate MOFs [Ln(Tz*)3] containing the heavy lanthanides Gd–Lu: from open to dense frameworks of varying dimensionality

“…This is mainly combined to properties like porosity, luminescence and catalysis, to name a few [4][5][6][7][8]. The usual procedure involves synthesis of the framework from suitable solution.…”

“…As expected, this process also leads to formation of powders only. It has now been successful to resolve and refine the structure of the high temperature phase 3 1 [Ln(Tz*) 3 ] for lanthanides Gd--Lu (1)(2)(3)(4)(5)(6)(7)(8) For all reactions to 0.5 mmol of the lanthanide metal, 1.8 mmol (slight excess regarding a stoichiometric reaction) of 1H-1,2,3-triazole and 10-20 mg Hg were added. The reaction mixture was frozen with liquid nitrogen and degassed three times.…”

Group 3 Elements and Lanthanide Metals

“…observed so far is six in trigonal-prismatic coordination [28] and ranges up to nine [125]. Ln imidazolates can also be porous, as the homoleptic MOF 3 ∞ [Ln(Im) 3 ] (Im = imidazolate anion, C 3 H 3 N 2 -, Ln = Tb, Dy, Yb) shows that were gained from a melt of 1H-imidazole (ImH) upon removal of ammonia from 3 ∞ [Ln(Im) 3 ] • NH 3 [28] or 3 ∞ [Ce(Im) 3 ImH] • ImH by removal of imidazole from the pore system [126]. Other azolates like 1,2,3-triazolate mostly give dense structures such as the two series of polymorphous frameworks of the constitution [132].…”

“…In addition to the structural novelty, the high connectivity of Ln-MOFs results in higher thermal stability compared to transition metal-based frameworks. For Ln imidazolates, a thermal stability of 650 ∘ C was observed, which is remarkable for a porous coordination compound that contains an organic ligand [28], and a thermal endurance of 450 ∘ C and higher is frequently observed. High CN of the metal ions can also be advantageous in another way.…”

Photoluminescence properties of terbium complexes bound to amorphous silica

“…As IPTES ligand can provide, in principle, antenna like sensitivation effect for the lanthanide emission [28], such difference in the average lifetimes can be assigned to the energy matching between the triplet levels of IPTES and the ( 5 D 0 , 5 D 1 ) and 5 D 4 excited levels of europium and terbium, respectively [29]. This observation is reinforced by the presence of a weak IPTES absorption in the europium excitation spectrum (at about 350 nm, Fig.…”