Steric and Electronic Control of Chiral Eu(III) Complexes for Effective Circularly Polarized Luminescence

Abstract

Circularly polarized luminescence (CPL) is characterized by the differential emission of right and left circularly polarized light by a chiral molecule. This mini-review describes the recent developments in chiral trivalent europium (Eu­(III)) complexes with effective CPL. CPL has many potential applications in security tags, lasers, and three-dimensional organic electroluminescence devices, which is one of the most intensely investigated topics in molecular luminophores. Eu­(III) complexes have attracted considerable attention as effective CPL luminophores for the above-mentioned applications. In this review, recent studies on the Eu­(III) CPL, including the steric (dimer, tetramer, aggregates, and coordination polymers) and electronic control (mononuclear) of Eu­(III) complexes for the construction of a luminophore with effective CPL, are discussed. The characteristic CPL applications employing the chiral mononuclear Eu­(III) complexes are also described. Chiral Eu­(III) complexes with well-designed organic ligands can result in the establishment of new research areas in the fields of photochemistry and materials science.

Unusual Magnetic Field Responsive Circularly Polarized Luminescence Probes with Highly Emissive Chiral Europium(III) Complexes

“…This work builds on earlier publications of Riehl and Richardson, both of them studied the induced MCPL under static external magnetic field from naturally optically inactive probes, and lately by Yoshikawa et al [23–25] . As postulated, applying an external magnetic field induced stronger CPL signals and higher g lum values were obtained for EuL2 – 7 with obvious trends in MCPL enhancement, making these Eu III complexes suitable as magneto‐optical probes [26, 27] …”

Pathways to increase the dissymmetry in the interaction of chiral light and chiral molecules

“…40,42 However, the quantum yield of complex 11 is only 3%, illustrating the need to balance both brightness and the emission dissymmetry. 35,43 Such highly dissymmetric emissions were used to produce phosphorescent OLEDs that emit CP light 44,45 and could be of interest for imaging in a biological context 46 , for high information density molecular barcodes or use in security tags. 11,47 Compared to lanthanide f→f transitions, transition metal d→d transitions typically show a lower dissymmetry.…”

The design of responsive luminescent lanthanide probes and sensors

“…Uniquely, it can give information about the local chiral environment. [88][89][90][91][92][93][94][95][96][97][98][99][100][101] Lanthanide complexes act as pure spherical emitters, avoiding the issues associated with anisotropy that may complicate other CPL active systems.…”