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

The luminescent square-planar Pt(II) complexes of type [Pt(C^N)(N^N)]+X- have been synthesised, where (C^N) is cyclometallated 2-phenylpyridine ligand, (N^N) a chiral diamine and BF4- or CH3COO- as counterion (X-). The chiral diamine Campy has been used, resulting in a mixture of regioisomers. The complexes were characterised 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)]BF4 was investigated and the LUMO energies were 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.