Photo-luminescent hetero-trinuclear Zn2Ln (Ln=Nd, Yb, Er or Gd) complexes based on the binuclear Zn2L precursor

Transformative 3d-4f coordination cluster carriers

The aim of this perspective is to summarise the use of the reported 3d-4f Coordination Clusters (CCs) in catalytic reactions and to demonstrate the potential of this emerging field. The pioneering work of Shibasaki, Matsunaga and others, demonstrated the use of 3d-4f in situ systems to catalyse asymmetric organic transformations. Our recent studies show that well characterised 3d-4f CCs catalyse numerous organic transformations and useful mechanistic aspects of their catalysis can be obtained. Furthermore, we have shown that by manipulation of the metal ion coordination environment; the nature of the 3d and lanthanide ions and the organic periphery of the ligand can all improve the efficacy of a 3d-4f CC catalyst. All in situ formed and well characterized 3d-4f CCs involved in catalysis are discussed.

Heterometallic ZnII⁻LnIII⁻ZnII Schiff Base Complexes with Linear or Bent Conformation-Synthesis, Crystal Structures, Luminescent and Magnetic Characterization

A series of racemic, heteronuclear complexes [Zn₂Nd(ac)₂(HL)₂]NO₃·3H₂O (1), [Zn₂Sm(ac)₂(HL)₂]NO₃·3CH₃OH·0.3H₂O (2), [Zn₂Ln(ac)₂(HL)₂]NO₃·5.33H₂O (3–5) (where HL is the dideprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)-1,3-diamino-2-propanol, ac = acetate ion, and Ln = Eu (3), Tb (4), Dy (5), respectively) with an achiral multisite coordination Schiff base ligand (H₃L) were synthesized and characterized. The X-ray crystallography revealed that the chirality in complexes is centered at lanthanide(III) ions due to two vicinally located μ-acetato-bridging ligands. The presented crystals have isoskeletal coordination units but they crystallize in monoclinic (1, 2) or trigonal crystal systems (3–5) with slightly different conformation. In 1 and 2 the Zn^II–Ln^III–Zn^II coordination core is linear, whereas in isostructural crystals 3–5 the chiral coordination cores are bent and lie on a two-fold axis. The complexes 1, 3–5 show a blue emission attributed to the emission of the ligand. For Zn^II₂Sm^III complex (2) the characteristic emission bands of f-f* transitions were observed. The magnetic properties for compounds 1, 4 and 5 are characteristic for the paramagnetism of the corresponding lanthanide(III) ions.

Dinucleating Schiff base ligand in Zn/4f coordination chemistry: synthetic challenges and catalytic activity evaluation

Synthetic challenges and catalytic activity evaluation of Zn/(Dy,Y) coordination clusters derived from a dinucleating Schiff base ligand.

New Heterodinuclear Zn/Ln (Ln = Gd, Tb, Er, Yb) Complexes of Hexadentate N,N′-Bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamines: Synthesis and Structure

Two N,N′-bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamine proligands, H2L1 (R = OCH3) and H2L2 (R = OC2H5), and five heterodinuclear ZnII/LnIII complexes, [Zn(L)(µ-CH3COO)Ln(NO3)2], containing [L1]2– and Gd3+, Tb3+, Er3+, or Yb3+ and [L2]2– and Yb3+ have been synthesised and structurally characterised. The complexes are isostructural and crystallise in the P21/n monoclinic space group. Zinc(ii) is coordinated by the inner N2O2 donor set of the ligand and an oxygen of the bridging acetate anion; the lanthanide(iii) ions possess an O9 coordination environment involving the interaction with the ligand’s outer O4 donor set, two bidentate nitrate ions, and the bridging acetate.

Temperature-dependent self-assembly of near-infrared (NIR) luminescent Zn2Ln and Zn2Ln3 (Ln=Nd, Yb or Er) complexes from the flexible Salen-type Schiff-base ligand

Through the self-assembly of the precursor [Zn(L)(MeCN)] (H2L=N,N'-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) with LnCl3·6H2O (Ln=La, Nd, Yb, Er or Gd) and NaN3 in alcohol-containing solutions, two series of mixed anions-induced Zn2Ln-arrayed complexes [Zn2(L)2(MeOH)ClLn(N3)]·Cl (Ln=La, 1; Ln=Nd, 2; Ln=Yb, 3; Ln=Er, 4 or Ln=Gd, 5) and Zn2Ln3-arrayed complexes [Zn2(L)3Cl2(μ2-OH)(μ3-OH)2Ln3(N3)2] (Ln=La, 6; Ln=Nd, 7; Ln=Yb, 8; Ln=Er, 9 or Ln=Gd, 10) are obtained at room temperature or under reflux, respectively. In contrast to Zn2Ln-arrayed complexes with the two Zn2+ ions in the inner cis-N2O2 cores and one Ln3+ ion in the outer O2O2 moieties, the demetalation of partial precursors leads to the selective exchange of Zn2+ centers for the Ln3+ ions for the formation of novel heterometallic Zn2Ln3-arrayed complexes with the Ln3+ ions in both the inner cis-N2O2 core and the outer O2O2 moieties of the ligands. The result of their photophysical properties shows that the characteristic near-infrared (NIR) luminescence of Nd3+ or Yb3+ ion has been sensitized from the excited state (both 1LC and 3LC) of the ligand H2L, while relatively lower quantum yields for Zn2Ln3-arrayed complexes than those for Zn2Ln-arrayed complexes, correspondingly, should be due to the luminescent quenching with the involvement of OH- oscillators around the Ln3+ ions.

Near-infrared (NIR) luminescent hetero-tetranuclear Zn2Ln2 (Ln = Nd, Yb or Er) complexes self-assembled from the benzimidazole-based HL and two rigid 4,4'-bipyridine ligands with different spacers

Through the self-assembly of the benzimidazole-based ligand HL (HL=2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol) with Zn(OAc)2 · 2H2O, Ln(NO3)3·6H2O (Ln=Nd, Yb, Er or Gd) and 4,4'-bipyridine ligand (bpy, 4,4'-bipyridine or bpe, trans-bis(4-pyridyl)ethylene), two series of Zn2Ln2-arrayed complexes [Zn(2)Ln(2)(L)4(bpy)(NO3)6] (Ln=Nd, 1; Yb, 2; Er, 3 or Gd, 4) and [Zn(2)Ln(2)(L)4(bpe)(NO3)6] (Ln=Nd, 5; Yb, 6; Er, 7 or Gd, 8) were obtained, respectively. The result of their photophysical properties shows that the characteristic near-infrared (NIR) luminescence of Nd(3+), Yb(3+) or Er(3+) ion has been sensitized from the excited state (both (1)LC and (3)LC) of the mixed HL and bipyridyl ligands in both complexes 1-3 and 5-7. Moreover, the change from bpy to bpe bridging for the fine-tuning of whole molecular conjugations, attributing to the different crossings of the two benzimidazole-based L(-) ligands, has the important influence on their NIR luminescent properties.