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

Michiya Fujiki; Laibing Wang; Nanami Ogata; Fumio Asanoma; Asuka Okubo; Shun Okazaki; Hiroki Kamite; Abd Jalil Jalilah

doi:10.3389/fchem.2020.00685

Chirogenesis and Pfeiffer Effect in Optically Inactive Eu^III and Tb^III Tris(β-diketonate) Upon Intermolecular Chirality Transfer From Poly- and Monosaccharide Alkyl Esters and α-Pinene: Emerging Circularly Polarized Luminescence (CPL) and Circular Dichroism (CD)

Front Chem. 2020 Aug 11:8:685. doi: 10.3389/fchem.2020.00685. eCollection 2020.

Authors

Michiya Fujiki¹, Laibing Wang¹, Nanami Ogata¹, Fumio Asanoma¹, Asuka Okubo¹, Shun Okazaki¹, Hiroki Kamite¹, Abd Jalil Jalilah^{1

2

3}

Affiliations

¹ Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Japan.
² School of Materials Engineering, Universiti Malaysia Perlis, Jejawi, Malaysia.
³ Centre of Excellence Frontier Materials Research, Universiti Malaysia Perlis, Kangar, Malaysia.

Abstract

We report emerging circularly polarized luminescence (CPL) at 4f-4f transitions when lanthanide (Eu^III and Tb^III) tris(β-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 β-diketonates. The g _lum value of Eu(fod)₃ in CABu are +0.0671 at 593 nm (⁵ $D_{0} \to^{7}$ F₁) and -0.0059 at 613 nm (⁵ $D_{0} \to^{7}$ 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 $D_{4} \to^{7}$ F₆), +0.0078 at 540 nm (⁵ $D_{4} \to^{7}$ F₅), and -0.0018 at 552 nm (⁵ $D_{4} \to^{7}$ 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 α-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 Eu^III and Tb^III 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 Eu^III and Tb^III in the near-UV region.

Keywords: cellulose; circular dichroism; circularly polarized luminescence; europium; non-covalent interaction; saccharide; terbium; terpene.