Chiral-at-Metal Phosphorescent Square-Planar Pt(II)-Complexes from an Achiral Organometallic Ligand

The
synthesis and characterization of a new kind of cis- and trans-cyclometalated square-planar platinum­(II)
complexes is reported. Uncharged organometallic compounds carrying
one or two of the C∧N-donor ligand LCN were prepared.
Due to the heterobidentate coordination of the achiral chelate ligand,
the formed [PtLCNCl­(SEt2)], cis- and trans-[PtLCN2] complexes are chiral with
the metal serving as the stereo center. The enantiomers of complex trans-[PtLCN2] could be separated and their absolute configuration was determined
by anomalous X-ray diffraction, in accordance with CD spectroscopic
results and TD-DFT calculations. All compounds were fully characterized
by NMR spectroscopy, mass spectrometry and X-ray structure determination.
The photophysical properties of trans-[PtLCN2] have been investigated showing
phosphorescence in solution and in the solid state with a moderate
quantum yield. For the enantiomers, strong circular dichroism (CD)
and circularly polarized luminescence (CPL) effects were observed,
rendering this new structural motif suitable for application in chiroptical
and luminescent materials.