title: Coordinative interactions between porphyrins and C60, La@C82, and La2@C80.
abstract: For the first time, a C(60) derivative (1) and two different lanthanum metallofullerene derivatives, La@C(82)Py(2) and La(2)@C(80)Py (3), that feature a pyridyl group as a coordination site for transition-metal ions have been synthesized and integrated as electron acceptors into coordinative electron-donor/electron-acceptor hybrids. Zinc tetraphenylporphyrin (ZnP) served as an excited-state electron donor in this respect. Our investigations, by means of steady-state and time-resolved photophysical techniques found that electron transfer governs the excited-state deactivation in all of these systems, namely 1/ZnP, 2/ZnP, and 3/ZnP, whereas, in the ground state, notable electronic interactions are lacking. Variation of the electron-accepting fullerene or metallofullerene moieties provides the incentive for fine-tuning the binding constants, the charge-separation kinetics, and the charge-recombination kinetics. To this end, the binding constants, which ranged from log K(assoc) =3.94-4.38, are dominated by axial coordination, with minor contributions from the orbital overlap of the curved and planar π systems. The charge-separation and charge-recombination kinetics, which are in the order of 10(10) and 10(8) s(-1) , relate to the reduction potential of the fullerene and metallofullerenes, respectively.
authors.affiliation: Life Science Center of Tsukuba Advanced Research, Alliance, University of Tsukuba, Tsukuba 305-8577, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Marc
authors.initials: M
authors.lastname: Rudolf
authors.forename: Silke
authors.initials: S
authors.lastname: Wolfrum
authors.forename: Shankara Gayathri
authors.initials: SG
authors.lastname: Radhakrishnan
authors.forename: Ryo
authors.initials: R
authors.lastname: Aoyama
authors.forename: Yuya
authors.initials: Y
authors.lastname: Yokosawa
authors.forename: Azusa
authors.initials: A
authors.lastname: Oshima
authors.forename: Takeshi
authors.initials: T
authors.lastname: Akasaka
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nagase
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
mesh_terms: D004579:Electron Transport; D037741:Fullerenes / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*
chemical_list: D037741:Fullerenes; D009942:Organometallic Compounds; D011166:Porphyrins; D007811:Lanthanum; C069837:fullerene C60