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)] BF4 was 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.