Synthesis of fullerohelicates and fine tuning of the photoinduced processes by changing the number of addends on the fullerene subunits
作者:Michel Holler、François Cardinali、Hind Mamlouk、Jean-François Nierengarten、Jean-Paul Gisselbrecht、Maurice Gross、Yannick Rio、Francesco Barigelletti、Nicola Armaroli
DOI:10.1016/j.tet.2005.07.126
日期:2006.2
Two fullerene-substituted m-phenylene-bis-phenanthroline ligands have been prepared. The synthesis of the first derivative (L1) is based on an esterification reaction between a C-s symmetrical cis-2 fullerene bis-adduct bearing a carboxylic acid function and a bisphenanthroline alcohol (5). The second ligand (L2) has been obtained by reaction of a bis-phenanthroline malonate (9) and C-60 under Bingel conditions. The copper(I) complexes of L1 and L2 have been prepared by treatment with a slight excess of Cu(CH3CN)(4)BF4. NMR spectroscopy and mass spectrometry analysis have unambiguously shown that these complexes are bis-copper(l) helicates substituted with two fullerene moieties. The photophysical properties of the copper(I) complexes Cu-2(L1)(2) and Cu-2(L2)(2) have been investigated. In both systems photoinduced electron transfer from the central metal-complexed unit to the external fullerenes may occur, in principle, by excitation of both moieties. However, this is found to be the case only for the methanofullerene system Cu-2(L2)(2). Unexpectedly, for Cu-2(L1)(2), photoexcitation of the peripheral carbon spheres is followed by regular internal deactivation. Possible reasons for this behavior are examined in light of current theories for photoinduced energy and electron transfer. (c) 2006 Elsevier Ltd. All rights reserved.