Emitting-state properties of square-planar dithiocarbamate complexes of palladium(II) and platinum(II) probed by pressure-dependent luminescence spectroscopy

Abstract

Temperature- and pressure-dependent Raman and luminescence spectra of four crystalline complexes of palladium(II) and platinum(II) with chelating diethyldithiocarbamate (EDTC) and pyrrolidine-N-dithiocarbamate (PDTC) ligands are reported. The crystal structure of [Pd(PDTC)2] was resolved at 120 K. Luminescence band maxima are observed at approximately 14 500 cm–1and 16 000 cm–1for the palladium(II) and platinum(II) complexes, respectively. Pressure leads to blue shifts of the band maxima by +9 and +13 cm–1/kbar for [Pd(EDTC)2] and [Pd(PDTC)2], and +15 cm–1/kbar for [Pt(EDTC)2]. These spin-forbidden d–d luminescence transitions have lifetimes of approximately 600 µs at temperatures below 20 K. Luminescence intensities at room temperature are low, but they increase significantly with external pressure. The experimental results show that strong increases of luminescence intensities caused by pressure are not limited to complexes with monodentate ligands, a result providing insight on the coordinates with emitting-state distortions responsible for this effect.