Michele Maggini

The Addition of Diazo Compounds to C60 as a Way to the Understanding of the Electronic and Magnetic Properties of Fullerenes

The addition of diazo compounds to fullerene C60 affords mixtures of isomers that, upon heating, converge usually to a single component. A careful structural study of all the adducts is reported. The results allow, to a certain extent, the experimental determination of some properties so far postulated for C60 only on theoretical grounds.

γ(glicydoxypropyl)-trymethoxysilane-based matrices tailored for optical limiting applications

A hybrid organic-inorganic material derived 3- (glycidoxypropyl)-trimethoxysilane (GPTMS) and fullerene derivatives has been developed for optical limiting applications. The control of the final material has been achieved by engineering the matrix-fullerene solid-state system. Different Lewis acids (Zr(OBut)4, Ti(OBut)4, BF3, SiCl4, and TiCl4) have been used as the catalysts of the epoxy ring opening of (GPTMS) and the polyethylene oxide formation, in three different syntheses, to control and optimize the matrix- fullerene interaction and the optical limiting properties. The microstructure of the hybrid matrix has been studied by Fourier Transform Infra-Red Spectroscopy. UV-vis spectra and optical limiting measurements of the doped materials showed that in the Zr(OBut)4, TiCl4, BF3 derived matrices clustering of fulleropyrrolidine molecules is avoided and optical limiting is obtained. In the Ti(OBut)4, SiCl4, and not epoxy catalyzed derived matrices, instead, the aggregation of fulleropyrrolidines degraded the optical limiting properties. The laser damage threshold in the Zr(OBut)4, TiCl4 and especially BF3 derived matrices was larger than in the other matrices. Moreover, a multilayer system has been fabricated to develop an optical limiting device.

Photoinduced electron transfer in fullerenes containing donor-bridge-acceptor dyads

Excited states properties of supramolecular fullerene donor- bridge-acceptor dyads were studied under various conditions. The steady-state emission yields of C60-Fc and Ru-C60 dyads are noticeably quenched relative to ruthenium and fullerene model compounds, respectively. This indicates that intramolecular electron-energy transfer plays a predominant contribution in the deactivation of the photoexcited chromophores, e.g. the singlet excited state of the fullerene core and ruthenium excited MLCT state. Picosecond and nanosecond resolved photolysis show that the photoexcited C60-Fc and Ru-C60 dyads transform rapidly into charge separated states. Characteristic NIR absorption of the fullerene (pi) -radical anions were complimented by a detailed UV/vis analysis and confirm the existence of long-lived radical pairs. The structure, length, and nature of the bridging spacer separating the two reactive centers had a significant impact on the lifetime nd stabilization of the charge separated states.