Mononuclear Rare-Earth Metalloligands Exploiting a Divergent Ligand

Rare-earth tris-diketonato [RE(dike)3pyterpy] metalloligands can be prepared reacting at room temperature [RE(dike)3dme] (dme = 1,2-dimethoxyethane; dike = tta with Htta = 2-thenoyltrifluoroacetone and RE = La, 1; Y, 2; Eu, 3; Dy, 4; or dike = hfac with Hhfac hexafluoroacetylacetone, and RE = Eu, 5; Tb, 6; Yb 7) with 4'-(4‴-pyridil)-2,2':6',2″-terpyridine (pyterpy). The molecular structures of 1, 5, 6, and 7 have been studied through single-crystal X-ray diffraction showing mononuclear neutral complexes with the rare-earth ion in coordination number nine and with a muffin-like coordination geometry. [RE(tta)3pyterpy] promptly reacts with [M(tta)2dme] with formation of [Mpyterpy2][RE(tta)4]2 (M = Zn, RE = Y, 8; M = Co, RE = Dy, 9). Consistently, [Zn(hfac)2dme] reacts at room temperature with 2 equiv of pyterpy yielding [Znpyterpy2][hfac]2 10 that easily can be transformed by reaction with 2 equiv of [Eu(hfac)3] in [Znpyterpy2][Eu(hfac)4]2 11 that has been structurally characterized. Finally, 1, 2, 3, 5, and 7 metalloligands react at room temperature in few minutes with [PtCl(μ-Cl)PPh3]2 yielding the heterometallic molecular complexes [RE(dike)3pyterpyPtCl2PPh3] (dike = tta, RE = La, 12; Y, 13; Eu; 14; dike = hfac, RE = Eu, 15; Yb, 16).

Stoichiometrically Controlled Assembly of Lanthanide Molecular Complexes of the Heteroditopic Divergent Ligand 4'-(4-Pyridyl)-2,2':6',2″-terpyridine N-Oxide in Hypodentate or Bridging Coordination Modes. Structural, Magnetic, and Photoluminescence Studies

Mononuclear rare-earth tris-β-diketonato complexes RE(tta)₃dme [RE = Y (1), La (2), Dy (3), or Eu (4); Htta = 2-thenoylacetone; dme = 1,2-dimethoxyethane] react cleanly at room temperature in a 1:1 molar ratio with the heteroditopic divergent ligand 4'-(4-pyridyl)-2,2':6',2″-terpyridine N-oxide (pyterpyNO) to yield RE₂(tta)₆(pyterpyNO)_n, where n = 2 for RE = Y (5), Dy (6), or Eu (7) and n = 3 for RE = La (8). The crystal structure of 5 revealed a dinuclear compound with two pyterpyNO's bridging through the oxygen atom in a hypodentate mode leaving the terpyridine moieties uncoordinated. Using a metal:pyterpyNO molar ratio of 2 for RE = Y (9), Dy (10), or Eu (11), it was possible to isolate the molecular complexes RE₄(tta)₁₂(pyterpyNO)₂, while using a 5:3 molar ratio, the product La₅(tta)₁₂(pyterpyNO)₃ (12) can be obtained. ⁸⁹Y nuclear magnetic resonance spectroscopy revealed two different yttrium centers at room temperature for 9. An X-ray diffraction study of 10 showed a symmetrical tetranuclear structure resulting from the coordination of two Dy(tta)₃ fragments to the two hypodentate terpyridines of the dinuclear unit and presenting two different coordination sites for metals with coordination numbers of 8 and 9. Magnetic studies of 6 and 10 revealed the presence of an antiferromagnetic interaction between the two Dy(III) atoms bound by the NO bridges. These compounds displayed a slow relaxing magnetization through Orbach (6) and Raman (10) processes in the absence of an applied magnetic field; the rate increased upon application of a 1 kOe field. 7 and 11 showed a bright red emission typical of Eu³⁺. The two complexes have similar emission properties mainly determined by the employed β-diketonato ligands.

Terpyridine-Based 3D Metal-Organic-Frameworks: A Structure-Property Correlation

Design, synthesis, and applications of metal-organic frameworks (MOFs) are among the most salient fields of research in modern inorganic and materials chemistry. As the structure and physical properties of MOFs are mostly dependent on the organic linkers or ligands, the choice of ligand system is of utmost importance in the design of MOFs. One such crucial organic linker/ligand is terpyridine (tpy), which can adopt various coordination modes to generate an enormous number of metal-organic frameworks. These frameworks generally carry physicochemical characteristics induced by the π-electron-rich (basically N-electron-rich moiety) terpyridines. In this minireview, the construction of 3D MOFs associated with symmetrical terpyridines is discussed. These ligands can be easily derivatized at the lateral phenyl (4'-phenyl) position and incorporate additional organic functionalities. These functionalities lead to some different binding modes and form higher dimensional (3D) frameworks. Therefore, these 3D MOFs can carry multiple features along with the characteristics of terpyridines. Some properties of these MOFs, like photophysical, chemical selectivity, photocatalytic degradation, proton conductivity, and magnetism, etc. have also been discussed and correlated with their frameworks.

Functionalised Terpyridines and Their Metal Complexes—Solid-State Interactions

Analysis of the weak interactions within the crystal structures of 33 complexes of various 4′-aromatic derivatives of 2,2′:6′,2″-terpyridine (tpy) shows that interactions that exceed dispersion are dominated, as expected, by cation⋯anion contacts but are associated with both ligand–ligand and ligand–solvent contacts, sometimes multicentred, in generally complicated arrays, probably largely determined by dispersion interactions between stacked aromatic units. With V(V) as the coordinating cation, there is evidence that the polarisation of the ligand results in an interaction exceeding dispersion at a carbon bound to nitrogen with oxygen or fluorine, an interaction unseen in the structures of M(II) (M = Fe, Co, Ni, Cu, Zn, Ru and Cd) complexes, except when 1,2,3-trimethoxyphenyl substituents are present in the 4′-tpy.