Diana Sandrini

Luminescence of ortho-metallated platinum(II) complexes

Abstract The absorption spectra, emission spectra, and emission lifetimes of Pt(Phpy)2, Pt(Thpy)2, and Pt(Bhq)2 complexes (Phpy−, Thpy−, and Bhq− are the ortho C-deprotonated forms of 2-phenylpyridine, 2-(2-thienyl)-pyridine, and benzo(h)quinoline) have been studied and compared with those of the C-protonated neutral ligands. For all complexes examined the low-energy absorption bands in the near UV and visible region are assigned to metal-to-ligand charge-transfer transitions. The strong and structured luminescence emissions observed in the 500–600 nm region (lifetime in the microsecond range at 77 K) are assigned to metal-to-ligand charge-transfer excited states.

Spectroscopic behavior of a new family of mixed-ligand iridium(III) complexes

Abstract We report the results concerning the absorption spectra, luminescence spectra and luminescence lifetimes of the complexes [(η 5 -Me 5 C 5 )Ir(bpy)Cl]Cl ( 1 ), [(η 5 -Me 5 C 5 )Ir(phen)Cl]Cl ( 2 ), [(η 5 -Me 5 C 5 )Ir(bpy)H]BPh 4 ( 3 ) and [(η 5 -Me 5 C 5 )Ir(phen)H]BPh 4 ( 4 ) (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline and η 5 -Me 5 C 5 = pentamethylcyclopentadienyl = Cp*). For all complexes examined the low energy absorption band is assigned to metal-to-ligand charge-transfer transitions involving the diimine ligands. For the hydrido complexes 2 and 4 the luminescence observed both at 77 K and at room temperature is assigned to metal-to-ligand charge-transfer transitions involving the diimine ligands. The chloride complexes 1 and 3 were not found to emit.

On the Orbital Nature of the Luminescent Excited State of Orthometalated Transition Metal Complexes

The study of the photochemical and photophysical properties of transition metal complexes is of great interest for theoretical reasons (i.e., for a better understanding of the “excited state dimension” of chemistry) as well as for practical applications (luminescent materials, photocatalytic processes etc.). In the last few years the attention of numerous research groups has been focussed on the search and characterization of transition metal complexes that can play the role of light absorption sensitizers (LAS) and/or light emission sensitizers (LES) for the interconversion between light energy and chemical energy via electron transfer reactions involving electronically excited states (Balzani 1983). To perform systematic experiments in this field as well as to arrive at practical devices we need a series of compounds covering a broad range of excited state energies, lifetimes, and oxidation-reduction potentials. The family of Ru(II)-polypyridine compounds, having as a prototype the famous \({\text{R}\text{u} (\text{b}\text{p}\text{y})_3}^{2+}\) complex, has proved to be very interesting for these purposes, and some hundreds Ru(II)-polypyridine compounds have been synthetized and studied in the last few years (Kalyanasundaram; Juris). Polypyridine complexes of Cr(III) (Jamieson), Rh(III) (De Armond), Ir(III) (Watts), and Os(II) (Sutin) have also been studied, but an ideal LAS and/or LES has not yet been found (Balzani 1986).

Reactivity of trans-β-styrylnaphthalene photosensitized by tris(2,2'-bipyridine) chromium (III)

Abstract On photosensitization by tris(2,2′-bipyridine)chromium(III), trans -β-styrylnaphthalene undergoes geometrical isomerization and (in the presence of dioxygen) oxidation to benzaldehyde and naphthaldehyde. Whereas oxidation seems to be due to attack by singlet oxygen, isomerization originates from a cationic radical of the olefin, formed in an electron transfer to be excited complex. The reactivity of such a radical is compared with those of triplet excited states and anionic radicals of stilbene derivatives.

Rates of virtually self-exchange energy transfer processes of ruthenium(II) polypyridine complexes

Abstract The rate constants of electronic energy transfer from the lowest excited state of Ru(bpy) 2 (L) 2+ or Ru(bpy)(L) 2 2+ 10 Ru(L) 3 2+ (b

Non-adiabatic electronic energy transfer from the (3CTRu(bpy)2(CN)2 excited state to Cr(III) complexes

Abstract The quenching of the luminescence lifetime of cis-Ru(bpy)2(CN)2 (bpy = 2,2′-bipyridine) by complexes of the cis- and trans-Cr(en)2(XY)+ families (en = ethylenediamine; X and Y = F, Cl, Br, NCS, ONO) has been studied in aqueous solution and the results obtained have been discussed together with those previously reported for the quenching of the Ru(bpy)32+ luminescene by the same Cr(III) complexes. Experimental results and theoretical considerations show that the quenching process occurs by exchange electronic energy transfer. Since in all cases the process is sufficiently exoergonic to make up for the small intrinsic barriers, the lowest diffusion values of the quenching constants indicate a non-adiabatic behavior. The degree of adiabaticity of the energy transfer process is larger for the neutral Ru(bpy)2(CN)2 donor than for the positively charged Ru(bpy)32+ donor. The X and Y ligands can be ordered in the following adiabaticity series: ONO−, F−