Energy transfer dynamics in multichromophoric arrays engineered from phosphorescent Pt(II)/Ru(II)/Os(II) centers linked to a central truxene platform.

A rigid star-shaped tetrachromophoric trimetallic complex engineered from a 5,5',10,10',15,15'-hexabutyltruxene platform functionalized in the 2,7,12 positions with three different metal centers, namely, a terpyridine-Pt(II) ethynylene unit and Ru(II) and Os(II) bipyridine centers, was synthesized in a controlled fashion and characterized by (1)H NMR and mass spectrometry. The protocol was devised in such a way that key mono and dinuclear model complexes and two reference truxene ligands could also be prepared. Room temperature (RT) optical absorption and RT and 77 K luminescence studies were performed on the truxene ligands, the trimetallic species, the various mono- and binuclear complexes and precursors lacking the truxene fragment; RT nanosecond transient absorption measurements were also carried out in particular cases.

A pre-organised truxene platform for phosphorescent [Ru(bpy)2] and [Os(bpy)2] metal centres: a clear-cut switch from Förster- to Dexter-type energy-transfer mechanism.

We report on the synthesis, optical properties and energy-transfer features of a series of transition-metal-containing complexes and dyads, based on a pre-organised truxene scaffold. In this series, the [Ru(bpy)(3)](2+) and [Os(bpy)(3)](2+) photoactive terminals are coupled to the bridging aromatic truxene core through rigid ethynyl linkers. The photoinduced energy-transfer processes taking place from the Ru- to the Os-based levels, and from the truxene bridging ligand to the terminal-metal chromophores are studied and the pathways and mechanisms are discussed.

Excited-state dynamics in a dyad comprising terpyridine-platinum(II) ethynylene linked to pyrrolidino-[60]fullerene.

A hybrid [Pt((t)Bu(3)terpy)(C[triple bond]C-Ph-C(60))](+) complex (Pt-Fu) wherein a phosphorescent platinum center is linked to fullerene has been prepared using a copper(I)-promoted cross-coupling reaction. The electrochemical and spectroscopic properties were understood in light of the properties of the isolated building blocks and references compounds, Pt and Fu. In particular, in Pt-Fu, the electrochemical studies revealed that the first reduction process is fullerene-based and that the lowest-energy Pt(+)-Fu(-) charge-separated (CS) state lies in the range 2.

Energy transfer processes in electronically coupled porphyrin hetero-dyads connected at the beta position.

Energy transfer in a series of hetero-dyads of zinc porphyrin and free-base porphyrin connected at the beta position by pi conjugated bridges has been determined. The dyads have been characterized and compared with the homo dyads, excellent models for the donor and the acceptor porphyrins in the electronically conjugated system. The homo dyads provide reliable parameters for the determination of the energy transfer rate calculated according to the Förster theory.

Spectroscopy and electrochemical properties of a homologous series of acetylacetonato and hexafluoroacetylacetonato cyclopalladated and cycloplatinated complexes.

A photophysical, electrochemical and computational study has been performed on a homologous series of cyclometallated Pd(II) (1a-f) and Pt(II) (2a-f) complexes of general formula [(C,N)M(O,O)]; (H(C,N) = azobenzene, 2-phenylpyridine, benzo[h]quinoline; M = Pd, Pt; H(O,O) = acetylacetone, hexafluoroacetylacetone). Experimental and computational data have shown the strong influence exerted by electronegativity of the ancillary ligand on the frontier orbitals of the complexes, such an effect being enhanced for the Pt(II) species.