Two mono- and dinuclear Eu(iii) enantiomeric pairs based on chiral bis-bidentate bridging ligands: synthesis, structures, luminescent and ferroelectric properties

Abstract

Using the enantiomeric bis-bidentate bridging ligands (+)/(-)-2,5-bis(4,5-pinene-2-pyridyl)pyrazine (L(S)/L(R)) and depending on the ratio control of reactants, two mono- and dinuclear Eu(III)-based enantiomeric pairs with the formulae Eu(dbm)(3)L(R/S)·2H(2)O (L(R) in R-1, L(S) in S-1 and dbm = dibenzoylmethanato) and Eu(2)(dbm)(6)L(R/S)·H(2)O (L(R) in R-2 and L(S) in S-2) have been stereoselectively synthesized and structurally characterized. The circular dichroic (CD) spectra confirmed their chiroptical activities and enantiomeric natures. The homochiral dinuclear species represents the first example of a polynuclear lanthanide β-diketonate complexes with circular dichroic and crystallographic evidences. The photoluminescent properties studies revealed that both mono- and dinuclear Eu(iii) complexes exhibited the characteristic red emissions of Eu(III) ions in the solid state (at 77 K and 300 K) and CH(2)Cl(2) solution. Notably, the photophysical properties of the mononuclear enantiomers were superior to the dinuclear species. Interestingly, R-2 displayed a ferroelectric property at room temperature, which was not observed for R-1 due to the lack of crystalline polarity. R/S-2 are the first examples of homochiral polynuclear lanthanide complexes with luminescence and ferroelectric properties, being potential multifunctional materials.

Optical Activity in the Near‐IR Region: The λ=980 nm Multiplet of Chiral Yb3+ Complexes

“…Notwithstanding the almost perfect antiprismatic coordination polyhedron, [38,44] some lanthanide complexes belonging to this series display noticeable chiroptical properties:i nC PL (circularly polarized luminescence), the Eu 3 + and Sm 3 + derivatives feature the highestl uminescence dissymmetry factor g lum values reporteds of ar for these metals (close to the theoretical maximum j g lum j = 2), [35] and also, the Yb 3 + complex displays unusually high NIR ECD signals. The D 4 symmetryo ft he atoms in the first coordination sphere precludes the ability of static coupling to represent as ignificant sourceo fc hiroptical activity.…”

“…ECD) and in emission 38. 44 To apply the above‐summarized Richardon’s treatment to Λ‐Cs‐Yb, we first determined charges and polarizabilities of all the relevant atoms (those with a number label in Figure 2), and the results obtained are shown in Table 1.…”

The crystal structure of aqua-tris (1,3-diphenylpropane-1,3-dionato-κ2 O,O′)-lanthanum(III), C45H35LaO7

“…For the crystal structure of a multinuclear analogue of the title compound, see [9]. Analogous mononuclear coordination compounds have also been reported for praseodymium [10], neodymium [11], samarium [10], europium [12,13], holmium [14] and erbium [10]. In the crystal, three possible hydrogen bonds supported by the coordinated water molecule as donor and lanthanum-coordinated oxygen atoms as acceptors are identified.…”

Same or different – that is the question: identification of crystal forms from crystal structure data

“…In the second example, TEVJIP 55 and TEVJIP01 differ in the way the nitrogen atoms on the central ring are located (Fig. 6a).…”