A new approach to the effects of isocyanide (CN-R) ligands on the luminescence properties of cycloplatinated(ii) complexes

Abstract

The present investigation highlights the effects of the presence of isocyanide ligands on the emission properties of cycloplatinated(II) compounds. The new complexes with a general formula of [Pt(ppy)(Me)(CN-R)] (ppy = deprotonated 2-phenylpyridine and R = benzyl (1), 2-naphthyl (2), tert-butyl (3)) were produced using a quite simple method. Then, the resulting complexes were accurately identified employing multinuclear 1D and 2D NMR spectroscopy and two of them (1 and 3) were further authenticated by single crystal X-ray crystallography. The optical properties of 1–3 were investigated by UV-visible and photoluminescence spectroscopy. The obtained photophysical data were supported by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The concurrent presence of Me and isocyanide ligands as two strong carbon σ-donor ancillary ligands in the structure of these cycloplatinated(II) complexes was probably responsible for the strong luminescence observed at room temperature. This was confirmed by the obtained relatively high quantum yield values (0.41, 0.56 and 0.40 for 1, 2 and 3, respectively). The luminescence investigation of the complexes under different conditions indicates that R substituents in the structures of isocyanide ligands have a remarkable influence on the emission properties.