Ionothermal synthesis of octahedral lanthanoid coordination networks exhibiting slow magnetization relaxation and efficient photoluminescence.

An ionothermal reaction of lanthanoid salts with tetraethyl-p-xylenediphosphonate (tepxdp) in ionic liquids, such as choline chloride and malonic acid, resulted in the formation of three novel lanthanoid-organic coordination networks with the formula [Ln(H2pxdp)1.5]n {Ln = Tb (1), Dy (2) and Ho(3) and H4pxdp = p-xylenediphosphonic acid}. The structures, photoluminescence and magnetic properties of the three compounds were investigated in detail. Single crystal X-ray diffraction analysis revealed that the three compounds are isostructural and the Ln3+ ions show an unusual six-coordinate environment with the {LnO6} octahedron. In these compounds, each {PO3C} tetrahedron is corner-shared with two {LnO6} octahedra and each {LnO6} octahedron is corner-shared with six {PO3C} tetrahedra, thus forming an inorganic layer in the crystallographic ab plane. The inorganic layers are further connected by a phenyl group, leading to a three-dimensional framework. Compound 1 exhibits the strong and characteristic emission of TbIII with an impressive quantum yield of 46.2%. Detailed magnetic analysis demonstrated that compound 2 displays a slow magnetic relaxation of magnetization with multiple relaxation mechanisms. The anisotropic energy barrier and the pre-exponential factor τ0 are 51.2 K and 3.9 × 10-7 s, respectively, in the presence of a direct-current field of 500 Oe. This work demonstrates a successful strategy to isolate octahedrally coordinated lanthanoid complexes through ionothermal synthesis to exhibit the single-ion-magnet-like behaviour and photoluminescence properties.

Cobalt and copper pyridylmethylphosphonates with two- and three-dimensional structures and field-induced magnetic transitions.

Two novel metal pyridylmethylphosphonates, namely, [Co(4-pmp)] (1) and [Cu(4-pmp)(H2O)] (2), (4-pmpH2 = 4-pyridylmethylphosphonic acid), have been hydrothermally synthesized and characterized by X-ray diffraction, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. In compound 1, each {PO3C} tetrahedron is corner-shared with three {CoNO3} tetrahedra and vice versa, thus forming a one-dimensional (1-D) inorganic chain along the a axis containing 8-membered rings of [(Co-O-P-O)2]. The inorganic chains are further connected by a 4-pmp(2-) ligand, generating a 2-D layered structure. Compound 2 displays a three-dimensional (3-D) framework structure, in which the inorganic layers are pillared by the pyridyl groups of the ligand, generating a 3-D pillared-layered structure. The magnetic properties of 1 and 2 have been studied. Compounds 1 and 2 behave as metamagnets at low temperature. The critical fields are about 70 kOe for 1 and 47 kOe for 2 at 1.8 K.

Ionothermal synthesis, crystal structure, topology and catalytic properties of heterometallic coordination polymers constructed from N-(phosphonomethyl) iminodiacetic acid.

Reactions of rare earth chlorides, N-(phosphonomethyl)iminodiacetic acid (H(4)pmida) and ferrous oxalate dihydrate under ionothermal conditions result in four new isostructural 3d-4f heterometal coordination polymers, [LnFe(III)Fe(6)(Hpmida)(6)]·2H(2)O {Ln = Eu (1), Dy (2), Ho (3) and Y (4)}. All compounds were characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, and X-ray diffraction. The compounds feature a very interesting three dimensional (3-D) structure built up from a secondary building unit, [Fe(2)(Hpmida)(2)](2-) and possess a new topology type and complicated unique tilings. The catalytic properties of compounds 1-4 were investigated showing that these types of compounds are heterogeneous catalysts in the Knöevenagel condensation with high selectivity.

Six new 3d-4f heterometallic coordination polymers constructed from pyrazole-bridged Cu(II)Ln(III) dinuclear units.

Reactions of lanthanide chlorides, copper hydroxycarbonate and 3,5-pyrazole dicarboxylic acid (H3pdc) under hydrothermal conditions result in six new 3d-4f heterometallic coordination polymers with two types of structures. Compounds [CuLn2(pdc)2(Hpdc)(H2O)4]·2H2O (Ln = Tb (1), Dy (2), Er (3), and Y (4) exhibit a layered porous structure, made up of Cu(II)Ln(III) di-nuclear units which are connected by protonated Hpdc(2-) ligand, while the others [Cu3Ln4(pdc)6(H2O)8] (Ln = Eu (5), Gd (6)) display a three-dimensional (3-D) framework structure, in which six Cu(II)Ln(III) di-nuclear units are cross-linked by two coordinated lanthanide atoms. The catalytic properties of 3 are investigated showing its activity and recyclability in the reaction of cyclopropanation of styrene.

Metal monophosphonates M{(2-C5H4NO)CH2PO3}(H2O)2 (M = Co, Ni, Mn, Cd): synthesis, structure, and magnetism.

Four isostructural metal monophosphonates, M{(2-C(5)H(4)NO)CH(2)PO(3)}(H(2)O)(2) with M = Co (1), Ni (2), Mn (3), and Cd (4), were synthesized and structurally characterized. These compounds show a double-chain structure in which the M(2)(µ-O)(2) dimers are connected by O-P-O bridges. The magnetic responses of 1-3 were investigated over a wide range of magnetic fields (up to 10 T) and temperatures (down to 50 mK). Except for 4, which is weakly diamagnetic from 2 K to room temperature, the dominant magnetic interactions are antiferromagnetic. Isothermal magnetic field sweeps at 50 mK provide signatures in the magnetic responses that are associated with antiferromagnetic to field-induced fully polarized (magnetically saturated) transitions. Analysis of the magnetic data indicates that 1 and 2 form magnetic dimer-like clusters with weak dimer-dimer interactions present. Contrastingly, the magnetic interactions present in 3 are significantly weaker, so a definitive description of the magnetism of this compound is elusive.

[Amino-(iminio)meth-yl]phospho-nate.

The title compound, CH(5)N(2)O(3)P, exists as a zwitterion. The N atom of the imino group is protonated and the phospho-nic acid group is deprotonated. The mol-ecular geometry about the central C atom of this zwitterionic species was found to be strictly planar with the sum of the three angles about C being precisely 360°. In the crystal, the mol-ecules are inter-linked by O-H⋯O and N-H⋯O hydrogen-bonding inter-actions, forming a three-dimensional supra-molecular network structure.

Tuning the field-induced magnetic transition in a layered cobalt phosphonate by reversible dehydration-hydration process.

A layered cobalt phosphonate, Co(2-pmp)(H(2)O)(2) (1) (2-pmpH(2) = 2-pyridylmethylphosphonic acid) is reported, which provides the first example of metamagnetic cobalt system that shows reversible changes in both structures and magnetic behaviors upon dehydration-hydration process.

Poly[[diaqua-hemi-µ(4)-oxalato-µ(2)-oxalato-praseodymium(III)] monohydrate].

In the title complex, {[Pr(C(2)O(4))(1.5)(H(2)O)(2)]·H(2)O}(n), the Pr(III) ion, which lies on a crystallographic inversion centre, is coordinated by seven O atoms from four oxalate ligands and two O atoms from two water ligands; further Pr-O coordination from tetra-dentate oxalate ligands forms a three-dimensional structure. The compound crystallized as a monohydrate, the water mol-ecule occupying space in small voids and being secured by O-H⋯O hydrogen bonding as an acceptor from ligand water H atoms and as a donor to oxalate O-acceptor sites.