title: Donor-acceptor conjugates of lanthanum endohedral metallofullerene and pi-extended tetrathiafulvalene.
abstract: Stable donor-acceptor conjugates (2, 3) involving an endohedral metallofullerene, La(2)@I(h)-C(80), and pi-extended tetrathiafulvalene (exTTF) have been synthesized by highly regioselective 1,3-dipolar cycloadditions of exTTF-containing azomethine ylides to the endofullerene, yielding exclusively [5,6] metallofulleropyrrolidines with C(1) symmetry in high yields (68-77%). The cyclic voltammograms (CVs) of the conjugates reveal the redox active character of the system due to the presence of both donor and acceptor groups, that is, exTTF and La(2)@I(h)-C(80), respectively. Furthermore, the electrochemically reversible character of the endofullerene confirms the presence of the [5,6] adduct. Despite the relatively close proximity between the exTTF and the endohedral metallofullerene (EMF), only a weak electronic interaction was observed in the ground state, as evidenced by absorption spectroscopy and CV measurements of 2 and 3. On the other hand, in the excited state the fast formation of a radical ion-pair state (i.e., 6.0 x 10(10) s(-1)), that is, the reduction of the electron accepting La(2)@C(80) and the oxidation of exTTF, evolves with lifetimes as long as several ns (3.0 x 10(8) s(-1)) in toluene. Transient absorption spectroscopy experiments confirmed these observations.
authors.affiliation: Departamento de Química Orgánica I, Facultad de Química, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Takano
authors.forename: M Angeles
authors.initials: MA
authors.lastname: Herranz
authors.forename: Nazario
authors.initials: N
authors.lastname: Martín
authors.forename: Shankara Gayathri
authors.initials: SG
authors.lastname: Radhakrishnan
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nagase
authors.forename: Takeshi
authors.initials: T
authors.lastname: Akasaka
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D004563:Electrochemistry; D037741:Fullerenes / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010782:Photolysis; D013057:Spectrum Analysis; D013882:Thiosemicarbazones / Q000737:chemistry
chemical_list: D001391:Azo Compounds; D037741:Fullerenes; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D013882:Thiosemicarbazones; C512188:azomethine; D007811:Lanthanum; C063887:tetrathiafulvalene