Chirogenesis and Pfeiffer Effect in Optically Inactive EuIII and TbIII Tris(?-diketonate) Upon Intermolecular Chirality Transfer From Poly- and Monosaccharide Alkyl Esters and ?-Pinene: Emerging Circularly Polarized Luminescence (CPL) and Circular Dichroism (CD).

ABSTRACT: We report emerging circularly polarized luminescence (CPL) at 4f-4f transitions when lanthanide (EuIII and TbIII) tris(?-diketonate) embedded to cellulose triacetate (CTA), cellulose acetate butyrate (CABu), D-/L-glucose pentamethyl esters ( D-/ L-Glu), and D-/L-arabinose tetramethyl esters ( D-/ L-Ara) are in film states. Herein, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate (fod) and 2,2,6,6-tetramethyl-3,5-heptanedione (dpm) were chosen as the ?-diketonates. The g lum value of Eu(fod)3 in CABu are +0.0671 at 593 nm (5 D0?7 F1) and -0.0059 at 613 nm (5 D0?7 F2), respectively, while those in CTA are +0.0463 and -0.0040 at these transitions, respectively. The g lum value of Tb(fod)3 in CABu are -0.0029 at 490 nm (5 D4?7 F6), +0.0078 at 540 nm (5 D4?7 F5), and -0.0018 at 552 nm (5 D4?7 F5), respectively, while those in CTA are -0.0053, +0.0037, and -0.0059 at these transitions, respectively. D-/ L-Glu and D-/ L-Ara induced weaker g lum values at 4f-4f transitions of Eu(fod)3, Tb(fod)3, and Tb(dpm)3. For comparison, Tb(dpm)3 in ?-pinene showed clear CPL characteristics, though Eu(dpm)3 did not. A surplus charge neutralization hypothesis was applied to the origin of attractive intermolecular interactions between the ligands and saccharides. This idea was supported from the concomitant opposite tendency in upfield 19F-NMR and downfield 1H-NMR chemical shifts of Eu(fod)3 and the opposite Mulliken charges between F-C bonds (fod) and H-C bonds (CTA and D-/ L-Glu). An analysis of CPL excitation (CPLE) and CPL spectra suggests that (+)- and (-)-sign CPL signals of EuIII and TbIII at different 4f-4f transitions in the visible region are the same with the (+)-and (-)-sign exhibited by CPLE bands at high energy levels of EuIII and TbIII in the near-UV region.

SUBMITTER: Fujiki M 

PROVIDER: S-EPMC7438854 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature