Synthesis and Characterization of an Isomorphous Lanthanide-Thiophenemonocarboxylate Series (Ln = La–Lu, except Pm) Amenable to Color Tuning

Abstract

A series of 14 lanthanide compounds bearing 2-thiophenecarboxylate (TC) have been prepared under aqueous conditions and structurally characterized. Single crystal X-ray diffraction studies reveal a full isomorphous series across the 4f block of the general formula [(Ln­(TC)3(H2O)2)·(HPy·TC)] n , (Ln = La (La-1) – Lu (Lu-1), excluding Pm), with observable contraction of the cell volume and average metal–oxygen bond distances occurring when moving from lanthanum to lutetium. The 8-coordinate Ln metal centers are bound to two water molecules as well as six oxygen atoms from one bidentate and four bridging TC units that link LnO8 structural units into 1D chains. One lattice stabilizing pyridinium and one outer coordination sphere TC anion are present per formula unit. Reaction optimization provided moderate to high yields of the title products; a lanthanum byproduct [La­(TC)3(HTC)2] n (La-2) was formed by performing the reaction at reduced temperature, or alternatively, successive grinding of La-1 in ethanol resulted in partial conversion to La-2. Solid-state fluorescence studies show ligand sensitized metal-based emission for Eu­(III), Tb­(III), and Dy­(III) in the visible region, and Nd­(III) and Er­(III) in the NIR. Color tuning was easily achieved by varying europium:terbium metal ratios in the reaction mixtures.

Similarities of Coordination Polymer and Dimeric Complex of Europium(III) with Joint and Separate Terpyridine and Benzoate

“…The quantum yield is high, being 61.1(1.4) % (λ ex = 360 nm, λ em = 570–820 nm), determined at room temperature for excitation through the ligand system, as shown for terpyridine‐based ligands. [ 5–8,13 ] The emission lifetime is mainly based on the transitions of Eu 3+ in 1 being 1.493(1) ms (λ ex = 360 nm, λ em = 624 nm), and is typical for trivalent europium [ 34–37 ] and coordination compounds with terpyridine and its derivatives. [ 5,6,8,13,15,38 ] Upon cooling to 77 K the emission lifetime of 1 rises to 1.649(1) ms, as the thermal quenching of the luminescence decreases.…”

Photoluminescence of Visible and NIR‐Emitting Lanthanide‐Doped Bismuth‐Organic Materials

“…[13,19] Nanopure water ( 0.05 mS; Millipore, USA) was used in all experiments. The hostmaterial is built from abismuth metal centerb ound to one terpyridine ligand and three thiophenecarboxylates.…”

“…Bi 2 O 3 (Acros Organics, 99.9 %), Pr(NO 3 ) 3 ⋅ 6 H 2 O (Strem Chemicals, 99.9 %), Nd(NO 3 ) 3 ⋅ 6 H 2 O (Strem Chemicals, 99.9 %), Sm(NO 3 ) 3 ⋅ 6 H 2 O (Strem Chemicals, 99.9 %), Eu(NO 3 ) 3 ⋅ 6 H 2 O (BeanTown Chemical, 99.9 %), Gd(NO 3 ) 3 ⋅ 6 H 2 O (Rare Earth Products, 99.99 %), Tb(NO 3 ) 3 ⋅ 6 H 2 O (Strem Chemicals, 99.9 %), Dy(NO 3 ) 3 ⋅ 6 H 2 O (Strem Chemicals, 99.9 %), Er(NO 3 ) 3 ⋅ 5 H 2 O (Strem Chemicals, 99.9 %), Yb(NO 3 ) 3 ⋅ 5 H 2 O (Strem Chemicals, 99.9 %), 2‐thiophenecarboxylic acid (Acros Organics, 99 %), and 2,2′:6′,2“‐terpyridine (Acros Organics, 96 %) were used as received. [(Eu(TC) 3 (H 2 O) 2 ) ⋅ (HPy ⋅ TC)] n and [Eu 2 (terpy) 2 (TC) 4 ( μ ‐TC) 2 (H 2 O) 2 ] ⋅ 0.43 H 2 O, used in comparative quantum yield studies, were prepared according to previously reported methods . Nanopure water (≤0.05 μS; Millipore, USA) was used in all experiments.…”

Probing Optical Anisotropy and Polymorph‐Dependent Photoluminescence in [Ln2] Complexes by Hyperspectral Imaging on Single Crystals

“…Moreover, the isostructural nature of this specific complex enables the investigation of the influence of molecular packing on PL not only in homo‐ ([Eu 2 ], [Tb 2 ]), but also in heterometallic ([Eu−Tb]) structures. The latter allows to probe energy transfer between two different Ln 3+ centers, which has been shown as highly suitable for example for color tuning of phosphors …”