Abstract
Distinct circularly polarized luminescence (CPL) activity was observed in chiral (C∧N∧N)Pt(II) [(C∧N∧N) = 4,5-pinene-6′-phenyl-2,2′-bipyridine] complexes with bis- or triphenylphosphine ligands. Compared to the pseudo-square-planar geometry of chiral (C∧N∧N)Pt(II) complexes with chloride, phenylacetylene (PPV) and 2,6-dimethylphenyl isocyanide (Dmpi) ligands, the coordination configuration around the Pt(II) nucleus of chiral (C∧N∧N)Pt(II) complexes with bulk phosphine ligands is far more distorted. The geometry is straightforwardly confirmed by X-ray crystallography. The phosphines' participation enhanced the CPL signal of Pt(II) complexes profoundly, with the dissymmetry factor (glum) up to 10−3. The distorted structures and enhanced chiroptical signals were further confirmed by time-dependent density functional theory (TD-DFT) calculations.
Highlights
The precursors mononuclear complexes (–)-(C∧N∧N)PtCl and (+)-(C∧N∧N)PtCl were prepared according to previous procedures (Zhang et al, 2014, 2015b)
The bond angles around the metal nucleus of chiral Pt(II) complexes coordinated with bis- or triphenylphosphine ligands are further away from linearity than those of the reference mononuclear compounds (Table 2), which is consistent with the results of the crystal structures
We introduced bulky bis- or triphenylphosphine ligands into the phosphorescent pinene-containing (C∧N∧N)Pt(II) complexes and their structures were determined by single-crystal X-ray analysis
Summary
Polarized luminescence (CPL) materials have attracted considerable attention because of their enormous potential in 3D displays (Zinna et al, 2015; Song F. et al, 2018; Zhang et al, 2020), quantum information (Wagenknecht et al, 2010), chiroptical sensors (Carr et al, 2012; Guo et al, 2019; Wu et al, 2019), photodetectors (Yang et al, 2013; Chen C. et al, 2019) and anti-counterfeiting security (Yang et al, 2020; Yu et al, 2020) These phosphorescent transition metal complexes, which have remarkable metal-center chirality, tunable emission properties, and unusually high phosphorescence efficiency, are receiving increasing interests in recent years (Han et al, 2018).
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