Base- and Metal-Dependent Self-Assembly of Lathanide-Organic Coordination Polymers or Macrocycles with Tetradentate Acylhydrazone-based Ditopic Ligands

Herein, we report a comprehensive study on the lanthanide-directed coordination self-assembly with two bis-tetradentate acylhydrazone ligands H₄ L¹ and H₄ L² . Multifarious outcomes, which are base- and metal-dependent, were revealed by NMR, ESI-TOF-MS and X-ray crystallography. In the absence of base, bent H₄ L¹ was assembled into dinuclear double-strand helicate Ln₂ (H₂ L¹ )₂ by partially-deprotonated assembly with La, Sm or Eu, while trinuclear Ln₃ (H₂ L¹ )₃ with Yb or Lu. For linear H₄ L² , infinite 1D zig-zag metal-organic polymeric chain (Ln₂ H₂ L² )_n was obtained. However, complete deprotonated L¹ and L² assembled into discrete trinuclear Ln₃ (L^{1 /2} )₃ and tetranuclear Ln₄ (L^{1 /2} )₄ macrocyclic structures under the basic condition. For these, there are multiple possible isomers coexisting in the solution which were enumerated and simulated with molecular mechanic modeling. Visible-light sensitized NIR emissions on the Yb complexes have been observed, endowing them potential application in photofunctional materials.

Visible Circularly Polarized Luminescence of Octanuclear Circular Eu(III) Helicate

This work reports on the structural and photophysical characterization of D₄-symmetrical octanuclear circular Ln^III helicates, [(R)- or (S)-ⁱPr-Pybox]₈(Ln^III)₈(THP)₈ (where Ln = Eu and Tb, THP = trianionic tris-β-diketonate, and ⁱPr-Pybox = chiral bis(4-isopropyl-2-oxazolinyl)pyridine). X-ray crystallographic analysis revealed that the octanuclear circular helicate possesses square antiprism architecture and consists of four [(R)- or (S)-ⁱPr-Pybox]₂Ln^III₂(THP)₂ asymmetric units arranged in a closed ring form. Ligand-to-ligand interactions between the THP and the ⁱPr-Pybox ligands have successfully directed formation of enantiopure, homoconfigurational (Δ,Δ,Δ,Δ,Δ,Δ,Δ,Δ)-R and (Λ,Λ,Λ,Λ,Λ,Λ,Λ,Λ)-S isomers. All of the nonacoordinated Ln^III ions are identical and exhibit a distorted capped square antiprism (CSAP) geometry. Upon excitation of the ligand absorption band (λ = 360 nm), the circular helicates display characteristic Eu^III (red, ⁵D₀ → ⁷F_J, J = 0-4) or Tb^III (green, ⁵D₄ → ⁷F_J, J = 6-3) core f-f luminescence. The overall emission quantum yields of the circular Eu^III and Tb^III helicates are 0.145 and 0.0013, respectively, in chloroform. The Eu^III and Tb^III complexes exhibit remarkable circularly polarized luminescence (CPL) activity at their magnetic dipole transition with observed luminescence dissymmetry factors |g_lum| of 1.25 (⁵D₀ → ⁷F₁, λ = 592 nm) and 0.25 (⁵D₄ → ⁷F_5, λ = 541 nm), respectively. Exceptional |g_lum| values of the circular Eu^III helicates highlight the visible intensity difference between left and right circularly polarized emissions of R and S isomers in chloroform and PMMA thin film.

Radii-dependent self-assembly of chiral lanthanide complexes: synthesis, chirality, and single-molecule magnet behavior

A pair of 3-methoxysalicylhydrazone-based homochiral ligands constructed chiral trinuclear and pentanuclear complexes with La^III and Dy^III ions, respectively, which indicates that the radii controlled the self-assembled structures. Chiral transfer during the self-assembly processes was confirmed by crystal structure analysis and CD spectroscopy. Then, magnetic investigations demonstrated that the chiral Dy₅ complexes exhibited typical single-molecule magnet behavior.

Guest Binding Drives Host Redistribution in Libraries of CoII 4 L4 Cages

Two CoII 4 L4 tetrahedral cages prepared from similar building blocks showed contrasting host-guest properties. One cage did not bind guests, whereas the second encapsulated a series of anions, due to electronic and geometric effects. When the building blocks of both cages were present during self-assembly, a library of five CoII LA x LB 4-x cages was formed in a statistical ratio in the absence of guests. Upon incorporation of anions able to interact preferentially with some library members, the products obtained were redistributed in favor of the best anion binders. To quantify the magnitudes of these templation effects, ESI-MS was used to gauge the effect of each template upon library redistribution.

Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex

A new heterotetranuclear complex, [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH, was synthesized via an unsymmetrical single salamo-like ligand H2L: 6-methoxy-6′-ethoxy-2,2′-[ethylenedioxybis(azinomethyl)]diphenol, with Zn(OAc)2·2H2O, Sm(NO3)3·6H2O, and 4,4′-bipyridine by the one-pot method. The [ZnII2–SmIII2] complex was validated via elemental analysis, powder X-ray diffraction (PXRD) analysis, infrared spectroscopy, and ultraviolet–visible (UV–Vis) absorption spectroscopy. The X-ray single crystal diffraction analysis of the [ZnII2–SmIII2] complex was carried out via X-ray single-crystal crystallography. The crystal structure and supramolecular features were discussed. In addition, while studying the fluorescence properties of the [ZnII2–SmIII2] complex, the density functional theory (DFT) calculation of its structure was also performed.

A Series of Lanthanide-Germanate Oxo Clusters Decorated by 1,10-Phenanthroline Chromophores

A series of lanthanide-germanate oxo clusters, [Ln₈(phen)₂Ge₁₂(μ₃-O)₂₄T₁₂(H₂O)₁₆]·2H₂O [Ln = Dy (1a) and Er (1b); T = -CH₂CH₂COO^- group; phen = 1,10-phenanthroline], [Ln₈(phen)₂Ge₁₂(μ₃-O)₂₄T₁₂(H₂O)₁₆]·2phen·16H₂O [Ln = Sm (2a), Eu (2b), and Gd (2c)], and [Ho₈(phen)₂Ge₁₂(μ₃-O)₂₄T₁₂(H₂O)₁₄]·2phen·13H₂O (3), have been hydrothermally synthesized from the reactions of bis(carboxyethylgermanium sesquioxide) and Ln₂O₃ with auxiliary phen chromophores. Compounds 1a and 1b consist of cage clusters [Ln₈(phen)₂Ge₁₂(μ₃-O)₂₄T₁₂(H₂O)₁₆] and free H₂O molecules, where cage clusters are arranged in a CsCl type, while compounds 2a-2c consist of cage clusters [Ln₈(phen)₂Ge₁₂(μ₃-O)₂₄T₁₂(H₂O)₁₆], free phen, and free H₂O molecules, where cage clusters are arranged in a NaCl type. Compound 3 consists of the one-dimensional neutral chain [Ho₈(phen)₂Ge₁₂(μ₃-O)₂₄T₁₂(H₂O)₁₄]_n and free H₂O molecules. These compounds provide the first examples of p-f heterometallic [Ge-O-Ln] oxo clusters decorated by phen chromophores. The photoluminescent and magnetic properties of all compounds have been investigated.