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

Abstract

What prompted you to investigate this topic/problem? Small organic CPL-active molecules (CPL-SOMs) have attracted considerable attention in the last decade for their potential application in next-generation optical devices. Our group is investigating CPL-SOMs with chiral Schiff-base ligands, and recently reported that boron difluoride complexes exhibit efficient and tunable CPL properties. [1,2] These findings prompted us to clarify two questions: (1) How do the molecular structures affect the CPL properties; (2) How does molecular alignment affect their CPL properties. The second of these questions is discussed in this work.

Luminescent solvent-free liquids based on Schiff-base boron difluoride complexes with polyethylene glycol chains

“…As part of our research for the creation of highly fluorescent materials, we recently reported that mono- 14,18,19 and dinuclear 20 boron difluoride complexes exhibited efficient photoluminescence even in the aggregated state. Furthermore, we have achieved lowering the melting point of a boron difluoride complex by introducing polyethylene glycol (PEG) chains into the aromatic rings of Schiff-base ligands, and have succeeded in demonstrating CPL in the solvent-free liquid state.…”

Circularly polarized phosphorescence with a large dissymmetry factor from a helical platinum(ii) complex

“…[1][2][3] Square planar platinum(II) complexes are widely known for their highly efficient phosphorescent emission, and CPP materials have been created by introducing chiral ligands. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] Several chiral platinum(II) complexes have been reported to show CPP with large dissymmetry factors (g lum = 2DI/I = 2(I L À I R )/(I L + I R )) 18 in the aggregated state. 7,8,12,16 In particular, the co-assembly of achiral and chiral platinum complexes reported by You and coworkers showed a considerably large g lum value of 0.064 from a magnetically-allowed metal-metal-to-ligand charge transfer (MMLCT) transition.…”

“…8 However, in the solution-dispersed state, the CPP intensities are low for most of the platinum(II) complexes, usually on the order of 10 À3 . 6,9,[12][13][14][15] This is because platinum complexes usually exhibit magnetically-forbidden metal-to-ligand charge transfer (MLCT)derived phosphorescence.…”

“…The most successful example was reported by Autschbach, Crassous and coworkers in which a platinum(II) complex with a [6]helicene framework exhibited CPP of the order of 10 À2 in the solutiondispersed state at room temperature. 4,27 Our research group has been investigating the photophysical properties of chiral transition metal complexes and recently found that Schiff-base platinum(II) complexes with a distorted square planar coordination platform exhibit tunable CPP properties in solution, 11,13,14 in the polymer-dispersed state, 10 and in the solvent-free liquid state. 12 In the present study, we designed a novel chiral platinum complex 1 with a Schiff-base [4]helicene ligand and the photophysical properties of the complex were compared with its analogue 2 (Scheme 1).…”

“…In this reaction, trans-isomers were not observed in the reaction mixture and cis-isomers were selectively obtained. The newly synthesized complexes 1 and 2 were successfully characterized by infra-red (IR) spectroscopy, 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy (Fig. S4 and S5, ESI †), gradient correlation spectroscopy (gCOSY) (Fig.…”