Multi-colour circularly polarized luminescence properties of chiral Schiff-base boron difluoride complexes

Abstract

A series of chiral Schiff-base boron difluoride complexes was synthesized and their photophysical properties were examined. These complexes showed multi-colour (blue, yellow and red) photoluminescence in solution and in the...

Circularly Polarized Luminescent Bis(Boron Difluoride) Complexes with Chiral Schiff‐base Ligands

“…In the present work, we newly designed chiral bis(boron difluoride) complexes 1 a – c based on the naphthalene backbone to achieve longer wavelengths and wider color variety in CPL (Figure 1). As a result, these complexes exhibited efficient blue to yellow photoluminescence in dilute solution, and long‐wavelength fluorescence were observed compared to previously reported mononuclear analogues with similar naphthalene backbones [14b] . Notably, a weak CPL with a g lum value of the order of 10 −4 was observed in the solution state, whereas the g lum value increased significantly to the order of 10 −2 in the KBr‐dispersed pellet state.…”

“…In the solution state, the wavelengths of the emission peak maxima ( λ max ) increase in the order of 1 a ( λ max =454 nm)< 1 b ( λ max =478 nm) < 1 c ( λ max =498, 520 nm). Compared to the previously reported mononuclear Schiff‐base boron difluoride complexes, [14b] a longer wavelength of luminescence was achieved on the similar naphthalene backbones. The emission spectra were also recorded in the KBr‐dispersed pellet state, in which the emission wavelengths are bathochromically shifted compared with those of the solution state.…”

“…Chiral Schiff‐base ligands ( R , R )‐ 2 a – c and ( S , S )‐ 2 a – c were prepared by condensation of the corresponding dicarboxyaldehyde with commercially available optically pure ( R )‐ or ( S )‐1‐phenylethylamine in boiling ethanol. The chiral bis(boron difluoride) complexes ( R , R )‐ 1 a – c and ( S , S )‐ 1 a – c were prepared by the reaction of BF 3 ⋅OEt 2 with ( R , R )‐ 2 a – c and ( S , S )‐ 2 a – c in dry 1,2‐dichloroethane (DCE) according to the previous report [14b] . Complexes 1 a – c were successfully characterized by 1 H, 13 C, 19 F, and 11 B nuclear magnetic resonance (NMR) spectroscopy (Figures S1–S12), infra‐red (IR) spectroscopy, high‐resolution mass spectrometry (HRMS), and elemental analysis, respectively.…”

“…Our research group has focused on the development of functional materials based on organo‐ and organometallic complexes with ( N , O )‐chelate Schiff‐base ligands [14] . In the course of these studies, we have investigated the CPL activities of these complexes and recently found that boron difluoride complexes with chiral Schiff‐base ligands can potentially become efficient CPL emitters [14b] . Such complexes are easily synthesized by the two step reactions of the corresponding aldehyde and exhibited intense CPL in the drop cast film state up to the order of g lum =10 −2 .…”

External environment sensitive circularly polarized luminescence properties of a chiral boron difluoride complex

“…19 Boron difluoride complexes, one of the families of organoboron complexes, have been recognized as promising materials for CPL-SOMs due to their ease of preparation and modification. 20 Various CPL-active boron difluoride complexes 21 containing conjugated π-systems including axial chirality, 21 a , c , i helical chirality 21 b , d , h and planar chirality 21 e – g have been reported.…”