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A new pair of multifunctional Zn(II)–Dy(III) enantiomers based on the chiral Schiff-base ligands [R,R-ZnLDy(H2O)(NO3)3] (1R2R-ZnDy) and [S,S-ZnLDy(H2O)(NO3)3] (1S2S-ZnDy) (H2L = phenol, 2,2′-[[(1R,2R/1S,2S)-1,2-diphenyl-1,2-ethanediyl]bis[(E)-nitrilomethylidyne]]bis[6-methoxy]) was synthesized and characterized. Magnetic studies indicate that 1R2R-ZnDy behaves as a single-molecule magnet. Enantiomers 1R2R-ZnDy and 1S2S-ZnDy show chiroptical activity and circularly polarized luminescence in the N,N-dimethylformamide (DMF) solution. The chiral Zn(II)–Dy(III) complexes display magnetic circular dichroism signals at room temperature. Accordingly, these complexes will inspire intriguing research on single-molecule magnets with circular polarization of luminescence activity and magneto-optic effects, which will give new clues to design multifunctional molecular magnetic materials. [ABSTRACT FROM AUTHOR]

Three types of Eu(III) coordination polymers with different distorted chiral ligands, [Eu(+tfc)3(p-dpeb)]n, [Eu(+pfc)3(p-dpeb)]n, and [Eu(+hfc)3(p-dpeb)]n (+tfc: (+)-3-(trifluoroacetyl)camphorate, +pfc: (+)-3-(pentafluoropropionyl)camphorate, +hfc: (+)-3-(heptafluorobutyryl)camphorate, p-dpeb: 1,4-bis(diphenylphosphorylethynyl)benzene), were prepared for elucidating the relationship between their structural distortions, ligand-to-metal charge transfer (LMCT), and circularly polarized luminescence (CPL) properties. Their strain factors in the ligands were evaluated using crystallographic data obtained by single-crystal X-ray structural analyses. The characteristics of the LMCT excited states were estimated from theoretical calculations. The introduction of a bulky substituent into the chiral ligand afforded a distorted structure of β-diketonates and changed the direction of the transition electric dipole moments, which are related to the magnitude of the CPL intensity. The CPL dissymmetry factor (gCPL) of [Eu(+hfc)3(p-dpeb)]n, with a large distorted structure, was −0.22, while those of [Eu(+tfc)3(p-dpeb)]n and [Eu(+pfc)3(p-dpeb)]n, with small distorted structures, were −0.05 and −0.10, respectively. The controlled steric hindrance of the chiral ligands in Eu(III) coordination polymers is one of the strain factors enhancing their CPL properties. [ABSTRACT FROM AUTHOR]

A series of chiral platina[5]helicenes displaying dual luminescence, i.e., fluorescence between 450 and 600 nm and red/NIR phosphorescence between 700 and 900 nm, has been synthesised, characterised and studied by first-principle calculations. This unusual behavior has been attributed to limited electronic interactions between the d orbitals of the metal and the π-orbitals of the organic ligand on the excited-state. Accordingly, the electron richness of the donor group on the helical ligand does not affect the energy of the phosphorescence process but does play a role on its efficiency. Interestingly, near-infrared circularly polarized luminescence can be obtained for the three complexes with dissymmetry factors up to 3 × 10−3 at 750 nm. [ABSTRACT FROM AUTHOR]

β-Diketones are one of the most widely used ligands for sensitizing the luminescence of lanthanide complexes due to their excellent sensitization abilities. However, the difficulties in introducing chiral groups to take part in the electronic transitions of conjugated systems limit their application in lanthanide circularly polarized luminescence (CPL) materials. In view of the inherent chirality of the helical structure, herein, a pair of homochiral quadruple-stranded helicates, Eu2L4, is assembled based on chiral bis-β-diketonate ligands, wherein the two point chirality centers in the spacer preorganize the helical conformation of the ligand (3S,4S)/(3R,4R)-3,4-bis(4,4′-bis(4,4,4-trifluoro-1,3-dioxobutyl)phenoxyl)-1-benzylpyrrolidine, LSS/LRR. X-ray crystallographic analyses reveal that the R,R configurations of the chiral carbons in the spacer induce the M helical sense of the ligand, while the S,S configurations induce the P helical sense. Through the comprehensive spectral characterization in combination with semiempirical geometry optimization using the Sparkle/RM1 model, it is confirmed that the preorganized ligands successfully control the homochirality of the helicates. Moreover, the mirror-image CD and CPL spectra and NMR measurements confirm the formation of enantiomeric pairs and their diastereopurities in solution. Detailed photophysical and chiroptical characterization studies reveal that the helicates not only exhibit intense circularly polarized luminescence (CPL) with ‖glum‖ values reaching 0.10, but also show a high luminescence quantum yield of 34%. This study effectively combines the helical chirality of the helicates with the excellent sensitization ability of the β-diketones, providing an effective strategy for the syntheses of chiral lanthanide CPL materials. [ABSTRACT FROM AUTHOR]

We studied enantiopure chiral trivalent lanthanide (Ln3+ = La3+, Sm3+, Eu3+, Gd3+, Tm3+, and Yb3+) complexes with two fluorinated achiral tris(β-diketonate) ligands (HFA = hexafluoroacetylacetonate and TTA = 2-thenoyltrifluoroacetonate), incorporating a chiral bis(oxazolinyl)pyridine (PyBox) unit as a neutral ancillary ligand, by the combined use of optical and chiroptical methods, ranging from UV to IR both in absorption and circular dichroism (CD), and including circularly polarized luminescence (CPL). Ultimately, all the spectroscopic information is integrated into a total and a chiroptical super-spectrum, which allows one to characterize a multidimensional chemical space, spanned by the different Ln3+ ions, the acidity and steric demand of the diketone and the chirality of the PyBox ligand. In all cases, the Ln3+ ions endow the systems with peculiar chiroptical properties, either allied to f–f transitions or induced by the metal onto the ligand. In more detail, we found that Sm3+ complexes display interesting CPL features, which partly superimpose and partly integrate the more common Eu3+ properties. Especially, in the context of security tags, the pair Sm/Eu may be a winning choice for chiroptical barcoding. [ABSTRACT FROM AUTHOR]