1,3-Thiazole as Suitable Antenna Ligand for Lanthanide Photoluminescence in [LnCl₃(thz)₄]·0.5thz, Ln = Sm, Eu, Gd, Tb, Dy

Abstract

The series of luminescent monomeric lanthanide thiazole complexes [LnCl3(thz)4]⋅0.5thz (Ln = Sm, Eu, Gd, Tb, Dy; thz=1,3-thiazole) has been synthesised and characterised by powder and singlecrystal X-ray diffraction, IR and photoluminescence spectroscopy, DTA/TG as well as elemental analysis. The colourless compounds exhibit photoluminescence in the visible region with varying quantum efficiencies up to QY = 48% for [TbCl3(thz)4]⋅0.5thz. Both, the lanthanide ions as well as the thiazole ligand contribute to the luminescence. Excitation can be achieved via intra-4 f transitions and by exciting the ligand, emission is observed mainly from the lanthanide ions again by 4 f transitions. Thiazole can transfer energy to the lanthanide ions, which further feeds the lanthanide emission by an efficient antenna effect even at room temperature. The lanthanide ions show pentagonalbipyramidal coordination by three chloride anions and four N atoms of 1,3-thiazole, which leads to a strong 5D0 →7F4 transition for europium. Significant differences arise as compared to thiophene complexes because no sulphur atom is involved in the metal coordination, as the thiazole ligand is solely coordinated via its nitrogen function.

50 Jahre “Chemie in unserer Zeit”

“…The latter consist of five chloride anions and three thiazole‐N atoms and are connected to linear chains along the a axis by shared edges by double‐bridging chloride anions [… Ln Cl(μ‐Cl) 2 (thz) 3 Ln Cl(μ‐Cl) 2 (thz) 3 …], as shown in Figure 3. Thiazole coordinates with its nitrogen atom only, no sulfur coordination is observed, which is in accordance to the known complexes [ Ln Cl 3 (thz) 4 ] · 0.5thz 9. and [Pr 4 Cl 10 (OH) 2 (thz) 8 (H 2 O) 2 ][Pr 2 Cl 6 (thz) 8 ] 8.…”

“…Through the series of lanthanides, from praseodymium on, a trend to smaller complexes is observed. Tetrameric and dimeric units were already reported for [Pr 4 Cl 10 (OH) 2 (thz) 8 (H 2 O) 2 ][Pr 2 Cl 6 (thz) 8 ],8 followed by monomeric complexes of heavier lanthanides in [ Ln Cl 3 (thz) 4 ] · 0.5thz ( Ln = Sm, Eu, Gd, Tb, Dy) 9. Combinations of lanthanide trichlorides with thiazole can lead to photoluminescence properties, in which the 1, 3‐thiazole functions as suitable sensitizer.…”

Near-Infrared Luminescence and Inner Filter Effects of Lanthanide Coordination Polymers with 1,2-Di(4-pyridyl)ethylene

“…The compounds show the typical colors of the corresponding lanthanide ions and are air- and moisture-sensitive, but stable to dry oxygen (vide infra). The solvents react as Lewis bases that break up the lanthanide chloride structures, forming luminescent solvate complexes of the type [LnCl 3 (py) 4 ] with Ln = Y, La, Er, Yb or [La 2 (μ 2 -Cl) 2 Cl 4 (py) 8 ] for pyridine and [LnCl 3 (thz) 4 ]·0.5­(thz), Ln = Sm, Eu, Gd, Tb, Dy for thiazole. With increasing reaction temperature and increasing excess of the connecting linker, substitution of the terminal pyridine or thiazole ligands with dpe molecules can be achieved.…”

“…Presence and origin of short-lived aggregation-induced bands of dpe in the coordination polymers remain unknown, as we want to avoid speculation. In contrast, complexes with the ligands pyridine and thiazole [LnCl 3 (py) 4 ]·0.5­(py) with Ln = Eu, Tb or [LnCl 3 (thz) 4 ]·0.5­(thz) with Ln = Sm, Eu, Gd, Tb, Dy show the typical 4f transitions and sensitization by ligand triplet states. Therefore, the dpe ligand is no suitable sensitizer for Ln emission in the visible range and even suppresses Ln 3+ luminescence potentially sensitized by the coligands thz and py in the coordination polymers with Sm ( 5 ), Tb ( 7 ), and Dy ( 8 ).…”

Thiazole and the Diazines Pyrazine and Pyrimidine as Sensitizers for Lanthanide Luminescence from VIS to NIR

“…At lower temperatures, thz forms pyz-and pym-free complexes, as reported before. [15,16] For reactions of lanthanide trichlorides in thiazole with pyrazine, the complexes [Ln 2 Cl 6 (pyz)(thz) 6 ]•2thz [Ln = Tb (1), Er (2)] were obtained and the crystal structure determined by Xray single crystal diffraction. In addition, for larger ionic radii, also a coordination polymer was obtained, and the structure determined for 1 ϱ [Pr 2 Cl 6 (pyz)(thz) 6 ] (3) on single crystals.…”