Characterization of excited electronic and vibronic states of platinum metal compounds with chelate ligands by highly frequency-resolved and time-resolved spectra

The lowest excited electronic states of triplet character and related vibronic properties are discussed in detail on the basis of highly frequency-resolved and time-resolved emission and excitation spectra of per-protonated, per-deuterated, and partially deuterated [Pt(bpy)(2)](2+), [Rh(bpy)(3)](3+), [Ru(bpy)(3)](2+), and [Os(bpy)(3)](2+). Emphasis is placed on the use of the enormous amount of information displayed in well-resolved vibrational satellite structures. For comparison, IR data and Raman spectra are also used. In addition, data are given for [Ru(bpz)(3)](2+), [Ru(bpy)(2)(bpz)](2+), [Ru(bpdz)(3)](2+), [Ru(bpy)(2)(bpdz)](2+), [Ru(i-biq)(2)(bpy)](2+), Pt(bhq)(2), Pt(phpy)(2), Pt(3-thpy)(2), Pt(2-thpy)(CO)(Cl), Pt(2-thpy)(2), Pt(qol)(2), Pt(qtl)(2). Trends and effects are also addressed, which are related to the amount of metal d-orbital mixing. In particular, we discuss the role of traps and sites in the context of high-resolution, site-selective, and line-narrowed spectra of chromophores doped into matrices; the interplay between states of ligand-centered (3) pi pi* and (MLCT)-M-3 character; localization versus delocalization behavior; radiative decay properties; zero-field splittings; spin-lattice relaxations via direct and Orbach mechanisms; Arrhenius behavior after time delay; Franck-Condon activities and Huang-Rhys factors; Franck-Condon versus Herzberg Teller activities and tunability of these activities under high magnetic fields; isotope marking and deuteration effects; aggregate formation of [Ru(bpy)(3)](2+); and radiationless energy transfer in neat [Ru(bpy)(3)](PF6)(2). These effects are in part treated in detail, but the aim is to use easy-to-follow descriptions. In particular, it is emphasized throughout this review that chemical tunability opens fascinating possibilities for controlled variation of physical properties.