A series of 12 dinuclear complexes [Ln2Cl6(μ‐4,4′‐bipy)(py)6], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, (1–12, respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4′‐bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl3 and 4,4‐bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln‐N‐MOFs ${\hbox{}{{\hfill 2\atop \hfill \infty }}}$[Ln2Cl6(4,4′‐bipy)3]⋅2(4,4′‐bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, (1, 4–8) were determined, showing an antenna effect through a ligand–metal energy transfer. The highest efficiency of luminescence is observed for the terbium‐based compound 7 displaying a high quantum yield (QY of 86 %). Excitation with UV light reveals typical emission colors of lanthanide‐dependent intra 4f–4f‐transition emissions in the visible range (TbIII: green, EuIII: red, SmIII: salmon red, DyIII: yellow). For the GdIII‐ and YIII‐containing compounds 6 and 1, blue emission based on triplet phosphorescence is observed. Furthermore, ligand‐to‐metal charge‐transfer (LMCT) states, based on the interaction of Cl− with EuIII, were observed for the EuIII compound 5 including energy‐transfer processes to the EuIII ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln‐independent quantum yields in the related MOFs.

C-dots (3-5 nm in diameter) obtained by most simple heating of polyols (glycerol, diethylene glycol and PEG 400) show intense blue and green emission (50% quantum yield). Upon modification with TbCl3/EuCl3, energy transfer from the C-dots to the rare-earth metal results in line-type Tb(3+) (green)/Eu(3+) (red) emission with quantum yields up to 85%.

Y3Al5O12:Ce3+ nanoparticles were prepared by a two-step approach (mean size: 40 nm; quantum yield: 51%) and embedded in polyester.

The reaction of manganese(ii) bromide and the crown ether 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] under mild conditions (80-130 °C) resulted in the formation of three different coordination compounds: MnBr2(18-crown-6) (), Mn3Br6(18-crown-6)2 () and Mn3Br6(18-crown-6) (). In general, the local coordination and the crystal structure of all compounds are driven by the mismatch between the small radius of the Mn(2+) cation (83 pm) and the ring opening of 18-crown-6 as a chelating ligand (about 300 pm). This improper situation leads to different types of coordination and bonding. MnBr2(18-crown-6) represents a molecular compound with Mn(2+) coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3Br6(18-crown-6)2 falls into a [MnBr(18-crown-6)](+) cation - with Mn(2+) coordinated by six oxygen atoms and Br - and a [MnBr(18-crown-6)MnBr4](-) anion. In this anion, Mn(2+) is coordinated by five oxygen atoms of the crown ether as well as by two bromine atoms, one of them bridging to an isolated (MnBr4) tetrahedron. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged [Mn2(18-crown-6)(MnBr6)] chain. Herein, 18-crown-6 is exocyclically coordinated by two Mn(2+) cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3Br6(18-crown-6)) and 98% (Mn3Br6(18-crown-6)2). The excellent quantum yield of Mn3Br6(18-crown-6)2 and its differentiation from MnBr2(18-crown-6) and Mn3Br6(18-crown-6) can be directly correlated to the local coordination.

The series of one-dimensional coordination polymers ϱ 1 [LnCl 3 (bipy)(py) 2 ]·py [bipy = 4,4Ј-bipyridine, py = pyridine; Ln = Gd, Tb, Dy, Ho, Er, Yb] as well as ϱ 1 [Lu 2 Cl 5 (bipy) 2 (py) 4 ]ϱ 1 [LuCl 4 (bipy)] were synthesized by the reactions of anhydrous LnCl 3 with bipy and py. The formation of extended zigzag chains and saltlike band structures with cationic and anionic strands is observed. Pyridine and 4,4Ј-bipyridine ligands serve as suitable antennas for lanthanide-based luminescence in the visible and near-infrared range through effective sensitization by the ligands followed by emission

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.

Eu3+-modified carbon dots (C-dots), 3–5 nm in diameter, were prepared, functionalized, and stabilized via a one-pot polyol synthesis. The role of Eu2+/Eu3+, the influence of O2 (oxidation) and H2O (hydrolysis), as well as the impact of the heating procedure (conventional resistance heating and microwave (MW) heating) were explored. With the reducing conditions of the polyol at the elevated temperature of synthesis (200–230 °C), first of all, Eu2+ was obtained resulting in the blue emission of the C-dots. Subsequent to O2-driven oxidation, Eu3+-modified, red-emitting C-dots were realized. However, the Eu3+ emission is rapidly quenched by water for C-dots prepared via conventional resistance heating. In contrast to the hydroxyl functionalization of conventionally-heated C-dots, MW-heating results in a carboxylate functionalization of the C-dots. Carboxylate-coordinated Eu3+, however, turned out as highly stable even in water. Based on this fundamental understanding of synthesis and material, in sum, a one-pot polyol approach is established that results in H2O-dispersable C-dots with intense red Eu3+-line-type emission.

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