Geometric and electronic structure of metal-cage fullerenes, C 59 M (M = Pt, Ir) obtained by laser ablation of electrochemically deposited films Josep M. Poblet,* a Jordi Mu ˜ noz, a Krzysztof Winkler, b,c Mark Cancilla, b Akari Hayashi, b Carlito B. Lebrilla* b and Alan L. Balch* b a Departament de Quimica Fisica i Inorganica, Universitat Rovira i Virgili, Imperial Tarraco 1, 43005 Tarragona, Spain b Department of Chemistry, University of California, Davis, California 95616, USA. E-mail: albalch@udavis.edu c Department of Chemistry, Institute of Chemistry, University of Bialystok, Bialystok, Poland Received (in Bloomington, IN, USA) 4th December 1998, Accepted 9th February 1999 Laser ablation of electrochemically deposited C 60 M n [M = Pt, Ir(CO) 2 ] films produces [C 59 M] + whose electronic and geometric structures have been investigated by density functional theory. A number of clusters based on a fullerene-like cage with heteroatoms incorporated into the cage framework have been observed in mass spectrometric studies. These clusters include examples where boron, 1 nitrogen, 2 silicon, 3 and niobium 4 are incorporated into the cages. The dimer, {C 59 N} 2 , has been prepared via a chemical route and isolated. 5 Recently, Branz et al. reported gas phase studies that generated C 60 M x and C 70 M x by evaporation of the metal into the fullerene vapor. 6 Subsequent photofragmentation of C 60 M x and C 70 M x produced clusters with the compositions, C 5922n M and C 6922n M with M = Fe, Co, Ni, Rh, Ir and n = 0, 1, 2. Here we report complementary studies that show that C 5922n M and C 692n M can be formed by laser ablation of electrochemically deposited films that are believed to contain polymeric, covalently bound chains: …C 60 ML n C 60 ML n C 60 ML n …, where ML n = Ir(CO) 2 or Pt. 7 Fig. 1 shows the results of laser ablation studies of the electrochemically deposited C 60 {Ir(CO) 2 } n film, which was obtained by electrochemical reduction of a toluene–acetonitrile (4 : 1 v/v) solution of C 60 and Ir(CO) 2 Cl(NH 2 C 6 H 4 Me-p) as described previously. 7 The lower trace shows the entire spectrum in the positive ion mode from laser desorption with a 340 nm N 2 laser from a film of C 60 {Ir(CO) 2 } n . The spectrum reveals a strong [C 60 ] + peak at m/z 720 with the usual set of lower mass peaks due to loss of C 2 units from the fullerene. At higher mass the second most intense feature in the spectrum is a multiplet that is indicative of the presence of [C 59 Ir] + . Additionally a feature is seen at m/z 877 that corresponds to the presence of [C 57 Ir] + . Inset 1 shows an expansion of the spectroscopic multiplets for the [C 59 Ir] + and [C 57 Ir] + features and comparison with the calculated spectra based on the natural abundances of isotopes of C and Ir. No other iridium containing peaks are seen in the spectrum, the other peaks in the spectrum between those of [C 57 Ir] + and [C 60 ] + correspond to the fullerene ions, [C 7022n ] + . There is also no evidence in this spectrum for the presence of the [C 60 Ir n ] + ions which were a prominent feature of the mass spectra that were obtained by Branz et al. 6 in their studies of the reactions of C 60 and iridium vapors that led to the prior detection of [C 59 Ir] + . Fig. 2(a) shows the corresponding spectral features for formation of [C 69 Ir] + that was obtained by desorption from a film prepared by electrochemical reduction of a solution of C 70 and Ir(CO) 2 Cl(NH 2 C 6 H 4 Me-p). Fig. 2(b) shows the spectral features for the formation of [C 59 Pt] + which was obtained by desorption from a film of C 60 Pt n prepared by electrochemical reduction of a solution of C 60 and PtCl 2 (pyridine) 2 . In the negative ion mode, the spectra from all three films show only the features due to [C 60 ] 2 and its fragmentation products; no evidence for the existence of [C 59 Ir] 2 , [C 69 Ir] 2 or [C 59 Pt] 2 was seen. We believe that the ions, [C 59 Ir] + , [C 69 Ir] + and [C 59 Pt] + , are formed during the laser ablation process from (h 2 -C 60 )M units that are present in the electrochemically deposited films. In order to understand the electronic and geometrical structures of these heterofullerenes, the optimal geometries have been computed by means of DFT calculations† under the Fig. 1 Mass spectra (positive ion mode) obtained by laser ablation of electrochemically deposited films from C 60 and Ir(CO) 2 Cl(NH 2 C 6 H 4 Me-p). Inserts show expansions of the multiplets observed for [C 59 Ir] + and [C 57 Ir] + and comparisons with the calculated spectra. Fig. 2 Mass spectra (positive ion mode) obtained by laser ablation of electrochemically deposited films from (a) C 70 and Ir- (CO) 2 Cl(NH 2 C 6 H 4 Me-p); and (b) C 60 and PtCl 2 (py) 2 . Chem. Commun., 1999, 493–494 493