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she worked for a couple of months on luminescent logic gates with A. P. de Silva in Belfast (1995). She then moved to Strasbourg and obtained a PhD under the supervision of Jean-Paul Collin and Jean-Pierre Sauvage, working on iridium bis-terpyridine complexes as photosynthetic model systems (2000). She is currently working as a postdoctoral researcher in the group of Roeland J. M. Nolte in Nijmegen (the Netherlands).

Abstract:Fullerene derivatives in which an oligophenylenevinylene (OPV) group is attached to C 60 through a pyrrolidine ring have been prepared by 1,3-dipolar cycloaddition of the azomethine ylides generated in situ from the corresponding aldehydes and sarcosine. Electrochemical and photophysical studies have revealed that ground-state electronic interactions between the covalently bonded OPV moiety and the fullerene sphere are small. The photophysical investigations have also shown that both in dichloromethane and benzonitrile solution an efficient singlet-singlet OPV f C 60 photoinduced energy-transfer process takes place, and occurrence of electron transfer, if any, is by far negligible relative to energy transfer. The C 60 -OPV derivatives have been incorporated in photovoltaic devices, and a photocurrent could be observed showing that photoinduced electron transfer does take place under these conditions. However, the efficiency of the devices is limited by the fact that photoinduced electron transfer from the OPV moiety to the C 60 sphere must compete with an efficient energy transfer. The latter process, as studied in solution, leads to the population of the fullerene lowest singlet excited state, found to lie slightly lower in energy than the charge-separated state expected to yield electron/hole pairs. Thus, only a small part of the absorbed light is able to contribute effectively to the photocurrent.

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A new synthetic procedure has been developed which makes possible the preparation of IrLL‘3+ complexes (L, L‘ = terpyridine derivative) in good yields. In a first step, IrLCl3 is obtained under relatively mild conditions as an intermediate. Subsequent reaction with L‘ (a few minutes in refluxing ethylene glycol) affords IrLL‘3+. The electrochemical behavior and ground- and excited-state spectroscopic properties of four IrLL‘3+ complexes in nitrile solvents are reported. The X-ray structure of one of these complexes is also described. The complexes have been designed keeping in mind their incorporation in linearly arranged multicomponent arrays, according to a templating strategy based on the assembly of tpy-type ligands by the Ir(III) center. The complexes feature a high-lying level for the luminescent excited state (>2.5 eV), with a satisfactory room-temperature luminescence intensity (φem ≈ 10-2) and lifetime on the microsecond time scale. These favorable properties indicate that the Ir(III)-tpy center will not be the final recipient of the energy-harvesting processes in multipartite systems built around them. Temperature-dependent studies of the luminescence properties in the 95−298 K range indicate that the higher-lying levels of these complexes are not efficient pathways for deactivation of the luminescent states. For these reasons, it is concluded that the studied Ir-tpy-type complexes are well suited (i) to play the role of photoactive center and to gather photo- and electroactive units or (ii) to act as electron relays in linearly arranged multicomponent arrays.

Five supramolecuiar systems containing the Ru(ttp)22+ photosensitizer (P) covalently linked to an electron acceptor (A), MV2+, and/or an electron donor (D), PTZ or DPAA, have been synthesized; ttp is 4'-p-tolyl-2,2':6',2"-terpyridine, MV2+ is methyl viologen, PTZ is phenotiazine, and DPAA is di-p-anisylamine. In the D-P-A triads the electron donor and acceptor groups are linked in opposite positions with respect to the photosensitizer. The spectroscopic properties (room-temperature absorption spectra, emission spectra and lifetimes in the 90-200 K temperature range, and transient absorption spectra and lifetimes at 150 K) and the (room-temperature) electrochemical behavior of the supramolecuiar systems and of their components have been investigated. At 90 K, where the solvent is frozen, no quenching of the photosensitizer luminescence is observed for all the supramolecuiar systems. At 150 K, where the solvent is fluid, the results obtained were as follows. In the PTZ-Ru(ttp)22+ dyad, neither quenching of the photosensitizer luminescence nor formation of oxidized donor are observed. In the DPAA-Ru(ttp)22+ dyad, luminescence quenching and transient formation of the oxidized donor take place. For the Ru(ttp)22+-MV2+ dyad, transient formation of the reduced acceptor is observed, but the lifetime of the photosensitizer luminescence increases, indicating that charge recombination leads back to the excited photosensitizer. The PTZ-Ru(ttp)22+-MV2+ triad behaves as the Ru(ttp)22+-MV2+ dyad. For the DPAA-Ru(ttp)22+-MV2+ triad, strong luminescence quenching is observed, and transient absorption spectroscopy shows that charge separation is followed by a very fast charge recombination reaction ( < 100 ns). Thermodynamic and kinetic aspects of the photoinduced electron-transfer processes are discussed.