Noncovalent Interactions at Lanthanide Complexes

Lanthanide complexes have attracted a widespread attention due to their structural diversity, as well as multifunctional and tunable properties. The development of lanthanide based functional materials has often relied on the design of the secondary coordination sphere of the corresponding lanthanide complexes. For instance, usually simple lanthanide salts (solvento complexes) do not catalyze effectively organic reactions or provide low yield of the expected product, whereas the presence of a suitable organic ligand with a noncovalent bond donor or acceptor centre (secondary coordination sphere) modifies the symmetry around the metal centre in lanthanide complexes which then successfully can act as catalysts in both homogenous and heterogenous catalysis. In this minireview, we discuss several relevant examples, based on X-ray crystal structure analyses, in which the hydrogen, halogen, chalcogen, pnictogen, tetrel and rare-earth bonds, as well as cation-π, anion-π, lone pair-π, π-π and pancake interactions, are used as a synthon in the decoration of the secondary coordination sphere of lanthanide complexes.

Magnetic Behavior of Luminescent Dinuclear Dysprosium and Terbium Complexes Derived from Phenoxyacetic Acid and 2,2’-Bipyridine

Two dinuclear lanthanide complexes [Dy2(L1)6(L2)2]·2EtOH (1) and [Tb2(L1)6(L2)2]·2EtOH (2) (HL1 = phenoxyacetic acid and L2 = 2,2’-bipyridine) were synthesized and the crystal structures were determined. In both complexes, the lanthanide centers are nine-coordinated and have a muffin geometry. Detailed magnetic study reveals the presence of field-induced single molecule magnet (SMM) behavior for complex 1, whereas complex 2 is non-SMM in nature. Further magnetic study with 1’, yttrium doped magnetically diluted sample of 1, disclosed the presence of Orbach and Raman relaxation processes with effective energy barrier, ∆E = 16.26 cm−1 and relaxation time, τo = 2.42 × 10−8 s. Luminescence spectra for complexes 1 and 2 in acetonitrile were studied which show characteristic emission peaks for DyIII and TbIII ions, respectively.

Structural diversity and photo-physical and magnetic properties of dimeric to 1D polymeric coordination polymers of lighter lanthanide(iii) dinitrobenzoates

Single crystal diffraction studies reveal the formation of the following 10 new complexes of lighter Ln(iii) ions with general formulas {[Ln(μ2-L1)3·(H2O)2]·H2O}n (Ln = Nd (1) and Eu (2)), [Nd(μ2-L2)2·(CH3COO)·(H2O)2]n (3), [Ln2(μ2-L2)5·(L2)·(H2O)4]n (Ln = Sm (4), Ce (5), and Pr (6)), [La2(μ2-L2)6·(H2O)3·(DMF)]n (7) (DMF = dimethylformamide), [Ln(μ2-L2)2·(L2)·(H2O)3]2 (Ln = Eu (8) and Gd (9)) and [Gd(L2)·(CH3COO)2·(H2O)2]2 (10), where L1 and L2 are anions of 3,5- and 2,4-dinitrobenzoic acid, respectively. Complexes 1-7 are 1D coordination polymers, while 8-10 are dinuclear complexes. The luminescence properties of Nd(iii) and Eu(iii) analogues displayed metal-centred emission with L1 exhibiting weak but more efficient sensitization than L2. A study of the magnetic properties of the compounds clearly demonstrated the field-induced single ion magnet behaviour of the Nd(iii) compounds 1 and 3. Their behaviour has been compared to previously reported analogous Nd(iii) complexes and the role of the lattice solvent and polymorphism on the magnetic behaviour has been evaluated.

A multi-responsive luminescent sensor for organic small-molecule pollutants and metal ions based on a 4d–4f metal–organic framework

A multi-responsive luminescent sensor for organic small-molecule pollutants and metal ions based on a metal–organic framework is reported.

Four new lanthanide–organic frameworks: selective luminescent sensing and magnetic properties

Four new isostructural lanthanide–organic frameworks have been synthesized, which show 2D layer-by-layer structures, and exhibit highly selective and efficient luminescence sensing for Fe³⁺ and Cr⁶⁺ ions in aqueous solution.

Solvents and auxiliary ligands co-regulate three antiferromagnetic Co(ii) MOFs based on a semi-rigid carboxylate ligand

Three new Co(ii)-based coordination polymers have been synthesized by a semi-rigid asymmetry ligand 3-(4′-carboxyphenoxy)phthalic acid. The effects of solvents and auxiliary ligands are investigated in details. Moreover, the magnetism of all the CPs are also discussed.

Three novel 1D lanthanide-carboxylate polymeric complexes: syntheses, crystal structures and magnetic analyses

Three novel one-dimensional (1D) lanthanide coordination complexes involving the 4-methyl-3-nitrobenzoic acid (HL) ligand, with the general formulae [Gd(L)3(H2O)(CH3OH)] (1), [Gd(L)3(H2O)2]·(4,4'-bpy)·CH3OH (2), [Dy(L)3(H2O)(CH3OH)] (3), have been synthesized by solvothermal reactions. These complexes have been structurally characterized by single-crystal X-ray diffraction, IR, PXRD, TGA, and elemental analysis. Complexes 1 and 3 are isostructural except for the distinction of the metal ion. Magnetic measurements indicate that complexes 1-3 show antiferromagnetic behaviors. Complex 3 behaves with slow relaxation of the magnetization, where the frequency-dependent out-of-phase signals are noticed. However, the characteristic maxima were not reached above 2 K under zero direct current (DC) fields. When a DC field of 5000 Oe was employed, the frequency dependent peaks of alternating current (AC) signals were obtained.

Solvothermal synthesis, crystal structure, and properties of lanthanide-organic frameworks based on thiophene-2,5-dicarboxylic acid

A series of lanthanide-organic framework coordination polymers, {[La(2)(TDC)(2)(NO(3))(H(2)O)(4)](OH)·5H(2)O}(n) (1) and [Ln(TDC)(NO(3))(H(2)O)](n) (TDC = thiophene- 2, 5- dicarboxylic acid; Ln = Nd(2), Sm(3), Eu(4), Gd(5), Tb(6), Dy(7), Ho(8), Er(9), Yb(10)) have been synthesized by solvothermal reaction and characterized by elemental analysis, FT-IR, TG analysis, single-crystal X-ray diffraction and power X-ray diffraction. The single-crystal X-ray diffraction analysis results show that 1 displays a 3-D porous framework with (3,7)-connected {4(10).6(11)}{4(3)} topology. The compounds 2-10 crystallized in the same P2(1)/c space group and exhibits a (3,6)-connected {4.6(2)}(2){4(2).6(10).8(3)} topology, Right-handed and left-handed helical chains coexist in the 2-D layer structure. The luminescence properties of 2-10 and the magnetic properties of 5,7,8,9 were investigated.