Lanthanide Contraction in Action: Structural Variations in 13 Lanthanide(III) Thiophene-2,5-dicarboxylate Coordination Polymers (Ln = La-Lu, Except Pm and Tm) Featuring Magnetocaloric Effect, Slow Magnetic Relaxation, and Luminescence-Lifetime-based Thermometry

Thirteen new three-dimensional lanthanide(III)-2,5-thiophenedicarboxylate coordination polymers (Ln-CPs) with general formulas of [Ln(2)(2,5-TDA)(3)(DMA)(2)(H2O)] (n) (Ln-CPs 1-4) and [Ln(2)(2,5-TDA)(3)(DMA)(2)](n)(Ln-CPs 5-13) (where 2,5-TDA(2-) = 2,5-thiophedicarboxylate dianion, DMA = N,N'-dimethylacetamide, and Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Yb (12) Lu (13)) have been synthesized solvothermally under two different temperature conditions in a DMA-H2O mixed solvent system. A structural analysis discloses that the four Ln-CPs 1-4 crystallize in the orthorhombic space group Pna2(1), whereas the eight Ln-CPs 5-8 and 10-13 crystallize in the triclinic (P) over bar1 space group and Ln-CP 9 (Dy) adopts the monoclinic P2/c space group. The distinct crystal structures and coordination features indicate that lanthanide contraction, ancillary DMA molecules, and different coordination modes identified for 2,5-TDA2- play deciding roles in the self-assembly of Ln-CPs 1-13. The Ln(III) centers in compounds 1-13 exhibit three different coordination numbers, 9 (only 1; around La1), 8 (1-8 and 10-12), and 7 (4, 8, 9 and 11-13) with monocapped-square-antiprismatic, bicapped-trigonal-prismatic, and monocapped-trigonal-prismatic geometries, respectively. The title compounds display distinct 3D coordination frameworks with dinuclear (La2O15; for 1 and Ln(2)O(14); for 2-4) SBUs and tetranuclear [Ln(4)O(28)] SBUs (for compounds 5-13). Variable-temperature magnetic susceptibility measurements were investigated for Ln-CPs 7-11 with an applied dc field of 1 kOe. The weak antiferromagnetic interaction and small ligand/metal mass ratio make Ln-CP 7 (Gd) a good candidate for low-temperature magnetic refrigeration with an impressive -Delta S-m(max) = 31.0 J kg(-1) K-1 (63.6 mJ cm(-3) K-1) at T = 2 K and Delta H = 7 T. Furthermore, the frequency and temperature dependences of the alternating current (ac) susceptibilities have been studied to explore the magnetic dynamics of Ln-CPs 8-10. Importantly, for compound 9 (Dy), the chi(m)' and chi(m)'' curves and Cole-Cole plots at 2-6 K suggest the existence of slow magnetic relaxation behavior. Luminescence thermometry studies have been performed at 298-373 K for Ln-CPs 6 and 8. The Eu analogue (6) features a weak temperature dependence of luminescence lifetime (relative sensitivities of 0.43% K-1 and 0.34% K-1 at 298 and 373 K, respectively), whereas the Tb analogue (8) is a good lifetime-based luminescent thermometer with a constant relative sensitivity value of 1.35% K-1 in the investigated temperature range.