Influence of the variation of the co-ligands on the electronic transitions and emission properties of [Pt(I)(CH3)3(iPr-DAB)], [Pt(CH3)4(α-diimine)] and [Pt(SnPh3)2(CH3)2(iPr-DAB)]: an experimental and theoretical study

Abstract

This paper reports the results of a combined spectroscopic (UV/Vis, resonance Raman, emission) and theoretical study of [Pt(I)(CH₃)₃(iPr-DAB)] (iPr-DAB = N,N′-diisopropyl-1,4-diaza-1,3-butadiene), [Pt(CH₃)₄(R-DAB)] (R = alkyl or aryl), [Pt(CH₃)₄(α-diimine)] (α-diimine = pyridine-2-carbaldehyde-N-tert-butylimine or 3,4,7,8-tetramethyl-1,10-phenanthroline), and [Pt(SnPh₃)₂(CH₃)₂(iPr-DAB)]. The difference in character between the halide-to-ligand charge transfer (XLCT; X = I) transition of [Pt(I)(CH₃)₃(iPr-DAB)] and the sigma-bond-to-ligand charge transfer (SBLCT) transitions of the other complexes, is clearly established by resonance Raman (rR) spectroscopy. DFT MO calculations confirm the assignment of the frontier orbitals and lowest-energy electronic transitions, and support the interpretation of the rR spectra. All complexes emit at low temperatures, with excited state lifetimes strongly depending on the character and reactivity of the lowest excited state.