Luminescent water-soluble cycloplatinated complexes: Structural, photophysical, electrochemical and chiroptical properties

The luminescent square-planar Pt(II) complexes of the type [Pt(C^N)(N^N)]+X-, where (C^N) is the cyclometallated 2-phenylpyridine ligand, (N^N) a chiral diamine and BF4−or CH3COO−as counterion (X−) have been synthesized. The chiral diamine Campy has been used, resulting in a mixture of regioisomers. The complexes were characterized and their structures in solution were determined by a combination of different spectroscopic and chiroptical techniques (NMR, UV–Vis, ECD, IR, VCD and CPL) associated with electrochemical, DFT and TDDFT studies. Remarkably, the acetate derivatives proved to be soluble and stable in water for at least a month. The electrochemical behaviour of the [Pt(C^N)(N^N)]BF4was investigated and the LUMO energies estimated. The photophysical properties of the new compounds were deeply investigated in water or dimethyl sulfoxide solution by UV–Vis, steady state emission and time-correlated single-photon counting spectroscopy.