Molecular and Polymer Ln2M2 (Ln = Eu, Gd, Tb, Dy; M = Zn, Cd) Complexes with Pentafluorobenzoate Anions: The Role of Temperature and Stacking Effects in the Structure; Magnetic and Luminescent Properties

Varying the temperature of the reaction of [{Cd(pfb)(H2O)4}+n·n(pfb)-], [Ln2(pfb)6(H2O)8]·H2O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)5(phen)]n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb2Cd2(pfb)10(phen)2] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln2Cd2 fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln2Zn2 [Ln2Zn2(pfb)10(phen)2]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd2Zn2(pfb)10(H2O)2(phen)2]·4MeCN (VII). A new molecular EuCd complex [Eu2Cd2(pfb)10(phen)4]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd:Zn:Ln = 1:1:2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions.

A family of planar hexanuclear CoLn clusters with lucanidae-like arrangement and single-molecule magnet behavior

A family of planar hexanuclear CoLn clusters with the hydroxyl and nitrogen rich ligand 2-[bis(pyridin-2-ylmethyl) amino]-2-(hydroxymethyl)propane-1,3-diol (H₃L), formulated as [Co₄Ln₂(μ₃-O)₂(μ-N₃)₂(OH)₂(H₂O)₂(HL)₄]·(CH₃CO₂)₂·20H₂O [Ln = Dy (1), Gd (2), Tb (3), Eu (4) and Ho (5)], have been synthesized and structurally characterized. They are isomorphous and feature a lucanidae-like arrangement. They are the first examples of 3d-4f clusters with the H₃L ligand. In addition, the magnetic properties of 1-5 have been investigated and the single-molecule magnet (SMM) behaviour is observed for 1.

Wide-Range Columnar and Lamellar Photoluminescent Liquid-Crystalline Lanthanide Complexes with Mesogenic 4-Pyridone Derivatives

A series of liquid crystals with various lanthanide ions (Eu^III , Sm^III , and Tb^III ) was designed and prepared starting from the corresponding lanthanide nitrates and N-alkylated 4-pyridone derivatives bearing mesogenic 3,4,5-tris(alkyloxy)benzyl moieties (alkyl=hexyl, octyl, decyl, dodecyl, tetradecyl, or hexadecyl). These new lanthanidomesogens were investigated for their mesogenic properties by a combination of differential scanning calorimetry, polarizing optical microscopy, and temperature-dependent powder X-ray diffraction (XRD). Their thermal stability was assessed by thermogravimetric analysis. All of these complexes show enantiotropic liquid-crystalline behavior with lamellar (SmA) phases in the case of shorter-chain complexes (C₆ and C₈ ) or hexagonal columnar phases (Col_h ) for complexes with longer alkyl chains (C₁₂ , C₁₄ , and C₁₆ ), which were assigned on the basis of their characteristic textures and XRD studies. For complexes with an intermediate number of carbon atoms in the side chains (C₁₀ ), both a lamellar phase at lower temperatures and a Col_h phase at higher temperatures were evidenced. In the solid state, all these complexes show characteristic emissions assigned to the corresponding lanthanide ion. In addition, the luminescence decay curves showed single-exponential decays with characteristic times in the millisecond range (0.75-0.90 ms for Eu^III , 0.045-0.060 ms for Sm^III , and 0.75-1.05 ms for Tb^III ).

Novel mononuclear and 1D-polymeric derivatives of lanthanides and (η6-benzoic acid)tricarbonylchromium: synthesis, structure and magnetism

Novel derivatives of lanthanides and (η⁶-benzoic acid)tricarbonylchromium were synthesized and characterized; complexes of Tb, Dy, Er and Yb exhibit SMM behavior.

Mononuclear and polynuclear complexes ligated by an iminodiacetic acid derivative: synthesis, structure, solution studies and magnetic properties

Two novel families of coordination polymers, [Ln(bzlida)(Hbzlida)]·H₂O (Ln = La, Nd) and [Ln₂(bzlida)₃]·3H₂O (Ln = Nd, Sm, Eu, Gd) were prepared by hydrothermal reaction of Ln₂O₃ with benzyliminodiacetic acid.

A new class of thermotropic lanthanidomesogens: Eu(III) nitrate complexes with mesogenic 4-pyridone ligands

A new class of thermotropic lanthanidomesogens has been designed and prepared. They are based on 4-pyridone ligands that possess mesogenic cyanobiphenyl groups attached to the 4-pyridone unit via a flexible long alkyl spacer and show a very high thermal stability (decomposition temperatures near 300 °C). Depending on the alkyl length spacer, these complexes exhibit a SmA phase with transition temperatures influenced by the number of mesogenic groups employed and the spacer length.

catena-Poly[[(nitrato-κO,O')silver(I)]-μ(3)-4-pyridone-κO:O:O]

In the title complex, [Ag(NO(3))(C(5)H(5)NO)](n), the Ag(I) atom is coordinated by two O atoms from two different 4-pyridone ligands and two O atoms from one nitrate anion, displaying a nearly planar coordination geometry. The O atoms of two 4-pyridone ligands bridge two symmetrically related AgNO(3) units, forming a dimer, with an Ag⋯Ag separation of 3.680 (2) Å. Neighbouring dimers are linked into an infinite chain through weak Ag⋯O inter-actions [2.765 (2) Å], Ag⋯Ag inter-actions [3.1511 (4) Å] and π-π stacking inter-actions [centroid-centroid distance = 3.623 (4) Å]. N-H⋯O and C-H⋯O hydrogen bonds assemble these chains into a three-dimensional network.