The first observation of four-electron reduction in [60]fullerene-metal cluster self-assembled monolayers (SAMs)Electronic supplementary information (ESI) available: CV spectra, half-wave potentials and XPS data. See http://www.rsc.org/suppdata/cc/b2/b209024d/
Abstract:Self-assembled monolayers (SAMs) of a mu 3-eta 2:eta 2:eta 2-C60 triosmium cluster complex Os3(CO)8(CN(CH2)3Si(OEt)3)(mu 3-eta 2:eta 2:eta 2-C60) (2) on ITO or Au surface exhibit ideal, well-defined electrochemical responses and remarkable electrochemical stability being reducible up to tetranionic species in their cyclic voltammograms.
“…The CV of triphosphine-coordinated C 60 −tetrairidium complex 3 reveals four reversible redox couples that each correspond to a one-electron processes with the third and fourth waves overlapped within the CB solvent potential window. The general features of the CV of 3 are similar to those of the previously reported complexes 7 10 and 8 , as listed in Table . All the four-half-wave potentials of 3 , however, appear at much more negative potentials, at least by ca.…”
Section: Resultssupporting
confidence: 83%
“…Cyclic voltammograms (CVs) of 2 , 3 , and 6 are shown in Figure , and that of 5 is shown in Figure . Half-wave potentials ( E 1/2 ) of all the new compounds, together with free C 60 , Os 3 (CO) 8 (PMe 3 )(μ 3 -η 2 :η 2 :η 2 -C 60 ) ( 7 ), Os 3 (CO) 8 (CN(CH 2 ) 3 Si(OEt) 3 )(μ 3 -η 2 :η 2 :η 2 -C 60 ) ( 8 ), and Rh 6 (CO) 5 (dppm) 2 (CNCH 2 Ph)(μ 3 -η 2 :η 2 :η 2 -C 60 ) 2 ( 9 ), are provided in Table . 4 CVs of 2 , 3 , and 6 in chlorobenzene (scan rate = 50 mV/s).…”
Section: Resultsmentioning
confidence: 99%
“…The C 60 −metal π-interaction in the μ 3 -η 2 :η 2 :η 2 -C 60 −metal clusters little perturbs the C 60 hybridization, as evidenced by our earlier studies on the self-assembled monolayers, the photovoltaic cell device application, and the X-ray structural characterization of C 60 −metal cluster π-complexes 3a. Thus, the electronic properties of bisfullerene complexes with a metal cluster spacer are expected to be drastically different from those of organic-based bisfullerenes.…”
Heating a mixture of Ir(4)(CO)(9)(PPh(3))(3) (1) and 2 equiv of C(60) in refluxing chlorobenzene (CB) affords a "butterfly" tetrairidium-C(60) complex Ir(4)(CO)(6){mu(3)-kappa(3)-PPh(2)(o-C(6)H(4))P(o-C(6)H(4))PPh(eta(1)-o-C(6)H(4))}(mu(3)-eta(2):eta(2):eta(2)-C(60)) (3, 36%). Brief thermolysis of 1 in refluxing chlorobenzene (CB) gives a "butterfly" complex Ir(4)(CO)(8){mu-k(2)-PPh(2)(o-C(6)H(4))PPh}{mu(3)-PPh(2)(eta(1):eta(2)-o-C(6)H(4))} (2, 64%) that is both ortho-phosphorylated and ortho-metalated. Interestingly, reaction of 2 with 2 equiv of C(60) in refluxing CB produces 3 (41%) by C(60)-assisted ortho-phosphorylation, indicating that 2 is the reaction intermediate for the final product 3. On the other hand, reaction of Ir(4)(CO)(8)(PMe(3))(4) (4) with excess (4 equiv) C(60) in refluxing 1,2-dichlorobenzene, followed by treatment with CNCH(2)Ph at 70 degrees C, affords a square-planar complex with two C(60) ligands and a face-capping methylidyne ligand, Ir(4)(CO)(3)(mu(4)-CH)(PMe(3))(2)(mu-PMe(2))(CNCH(2)Ph)(mu-eta(2):eta(2)-C(60))(mu(4)-eta(1):eta(1):eta(2):eta(2)-C(60)) (5, 13%) as the major product. Compounds 2, 3, and 5 have been characterized by spectroscopic and microanalytical methods, as well as by single-crystal X-ray diffraction studies. Cyclic voltammetry has been used to examine the electrochemical properties of 2, 3, 5, and a related known "butterfly" complex Ir(4)(CO)(6)(mu-CO){mu(3)-k(2)-PPh(2)(o-C(6)H(4))P(eta(1)-o-C(6)H(4))}(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6). These cyclic voltammetry data suggest that a C(60)-mediated electron transfer to the iridium cluster center takes place for the species 3(3)(-) and 6(2)(-) in compounds 3 and 6. The cyclic voltammogram of 5 exhibits six well-separated reversible, one-electron redox waves due to the strong electronic communication between two C(60) cages through a tetrairidium metal cluster spacer. The electrochemical properties of 3, 5, and 6 have been rationalized by molecular orbital calculations using density functional theory and by charge distribution studies employing the Mulliken and Hirshfeld population analyses.
“…The CV of triphosphine-coordinated C 60 −tetrairidium complex 3 reveals four reversible redox couples that each correspond to a one-electron processes with the third and fourth waves overlapped within the CB solvent potential window. The general features of the CV of 3 are similar to those of the previously reported complexes 7 10 and 8 , as listed in Table . All the four-half-wave potentials of 3 , however, appear at much more negative potentials, at least by ca.…”
Section: Resultssupporting
confidence: 83%
“…Cyclic voltammograms (CVs) of 2 , 3 , and 6 are shown in Figure , and that of 5 is shown in Figure . Half-wave potentials ( E 1/2 ) of all the new compounds, together with free C 60 , Os 3 (CO) 8 (PMe 3 )(μ 3 -η 2 :η 2 :η 2 -C 60 ) ( 7 ), Os 3 (CO) 8 (CN(CH 2 ) 3 Si(OEt) 3 )(μ 3 -η 2 :η 2 :η 2 -C 60 ) ( 8 ), and Rh 6 (CO) 5 (dppm) 2 (CNCH 2 Ph)(μ 3 -η 2 :η 2 :η 2 -C 60 ) 2 ( 9 ), are provided in Table . 4 CVs of 2 , 3 , and 6 in chlorobenzene (scan rate = 50 mV/s).…”
Section: Resultsmentioning
confidence: 99%
“…The C 60 −metal π-interaction in the μ 3 -η 2 :η 2 :η 2 -C 60 −metal clusters little perturbs the C 60 hybridization, as evidenced by our earlier studies on the self-assembled monolayers, the photovoltaic cell device application, and the X-ray structural characterization of C 60 −metal cluster π-complexes 3a. Thus, the electronic properties of bisfullerene complexes with a metal cluster spacer are expected to be drastically different from those of organic-based bisfullerenes.…”
Heating a mixture of Ir(4)(CO)(9)(PPh(3))(3) (1) and 2 equiv of C(60) in refluxing chlorobenzene (CB) affords a "butterfly" tetrairidium-C(60) complex Ir(4)(CO)(6){mu(3)-kappa(3)-PPh(2)(o-C(6)H(4))P(o-C(6)H(4))PPh(eta(1)-o-C(6)H(4))}(mu(3)-eta(2):eta(2):eta(2)-C(60)) (3, 36%). Brief thermolysis of 1 in refluxing chlorobenzene (CB) gives a "butterfly" complex Ir(4)(CO)(8){mu-k(2)-PPh(2)(o-C(6)H(4))PPh}{mu(3)-PPh(2)(eta(1):eta(2)-o-C(6)H(4))} (2, 64%) that is both ortho-phosphorylated and ortho-metalated. Interestingly, reaction of 2 with 2 equiv of C(60) in refluxing CB produces 3 (41%) by C(60)-assisted ortho-phosphorylation, indicating that 2 is the reaction intermediate for the final product 3. On the other hand, reaction of Ir(4)(CO)(8)(PMe(3))(4) (4) with excess (4 equiv) C(60) in refluxing 1,2-dichlorobenzene, followed by treatment with CNCH(2)Ph at 70 degrees C, affords a square-planar complex with two C(60) ligands and a face-capping methylidyne ligand, Ir(4)(CO)(3)(mu(4)-CH)(PMe(3))(2)(mu-PMe(2))(CNCH(2)Ph)(mu-eta(2):eta(2)-C(60))(mu(4)-eta(1):eta(1):eta(2):eta(2)-C(60)) (5, 13%) as the major product. Compounds 2, 3, and 5 have been characterized by spectroscopic and microanalytical methods, as well as by single-crystal X-ray diffraction studies. Cyclic voltammetry has been used to examine the electrochemical properties of 2, 3, 5, and a related known "butterfly" complex Ir(4)(CO)(6)(mu-CO){mu(3)-k(2)-PPh(2)(o-C(6)H(4))P(eta(1)-o-C(6)H(4))}(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6). These cyclic voltammetry data suggest that a C(60)-mediated electron transfer to the iridium cluster center takes place for the species 3(3)(-) and 6(2)(-) in compounds 3 and 6. The cyclic voltammogram of 5 exhibits six well-separated reversible, one-electron redox waves due to the strong electronic communication between two C(60) cages through a tetrairidium metal cluster spacer. The electrochemical properties of 3, 5, and 6 have been rationalized by molecular orbital calculations using density functional theory and by charge distribution studies employing the Mulliken and Hirshfeld population analyses.
“…Furthermore, the electronic communication between C 60 and metal cluster centers can be readily fine-tuned with ligands attached to the metal clusters . The metal-C 60 π-interaction in the C 60 -metal moieties little perturbs the C 60 hybridization as evidenced by earlier studies on self-assembled monolayers and X-ray structural characterization of C 60 -metal π-complexes, − which implies that the electronic properties of bisfullerene complexes with a metal cluster spacer are drastically different from those of organic-based bisfullerenes. In addition, C 60 -metal cluster sandwich compounds should serve as direct models for two carbon nanotubes connected by a heterogeneous inorganic junction .…”
Reaction of Rh(6)(CO)(12)(dppm)(2) (dppm = 1,2-bis(diphenylphosphino)methane) with 1.4 equiv. of C(60) in chlorobenzene at 120 degrees C affords a face-capping C(60) derivative Rh(6)(CO)(9)(dppm)(2)(micro(3)-eta(2),eta(2),eta(2)-C(60)) (1) in 73% yield. Treatment of 1 with excess CNR (10 equiv., R = CH(2)C(6)H(5)) at 80 degrees C provides a bisbenzylisocyanide-substituted compound Rh(6)(CO)(7)(dppm)(2)(CNR)(2)(micro(3)-eta(2),eta(2),eta(2)-C(60)) (2) in 59% yield. Reaction of 1 with excess C(60) (4 equiv.) in refluxing chlorobenzene followed by treatment with 1 equiv. of CNR at room temperature gives a bisfullerene sandwich complex Rh(6)(CO)(5)(dppm)(2)(CNR)(micro(3)-eta(2),eta(2),eta(2)-C(60))(2) (3) in 31% yield. Compounds 1, 2, and 3 have been characterized by spectroscopic and microanalytical methods as well as by X-ray crystallographic studies. Electrochemical properties of 1, 2, and 3 have been examined by cyclic voltammetry. The cyclic voltammograms (CVs) of 1 and 2 show two reversible one-electron redox waves, a reversible one-step two-electron redox wave, and a reversible one-electron redox wave, respectively, within the solvent cutoff window. This observation suggests that compounds 1 and 2 undergo similar C(60)-localized electrochemical pathways up to 1(5)(-) and 2(5)(-). Each redox wave of 2 appears at more negative potentials compared to that of 1 because of the donor effect of the benzylisocyanide ligand. The CV of compound 3 reveals six reversible well-separated redox waves due to strong interfullerene electronic communication via the Rh(6) metal cluster bridge. The electrochemical properties of 1, 2, and 3 have been rationalized by molecular orbital calculations using the density functional theory (DFT) method. In particular, the molecular orbital (MO) calculation reveals significant contribution of the metal cluster center to the unoccupied molecular orbitals in 3, which is consistent with the experimental result of strong interfullerene electronic communication via the Rh(6) metal cluster spacer.
“…Exohedral metallofullerenes have attracted a lot of attention concerning the effects of metal coordination on the chemical and physical properties of C 60 . In particular, the investigation on the C 60 −metal cluster chemistry has unraveled an aspect of C 60 as a versatile, multifunctional ligand exhibiting various σ- and π-type bonding modes. , C 60 −metal cluster complexes have a direct analogy to carbon nanotubes decorated by metal nanoparticles and exhibit very strong electronic communication between C 60 and metal cluster centers that can be fine-tuned with ligands attached on the metal centers. ,3c Furthermore, the electrochemical studies of robust self-assembled monolayers (SAMs) based on C 60 −cluster compounds reveal that the solution electrochemical behavior of C 60 is directly transferred to a two-dimensional surface structure . Our efforts in this field culminate in the recent preparation of the first bisfullerene complex with a Rh 6 cluster bridge, which serves as a direct model for two carbon nanotubes connected by a heterogeneous inorganic junction.…”
The reaction of Ir4(CO)8(PMe3)4 with excess C60 in refluxing 1,2-dichlorobenzene, followed by treatment by CNR (R = CH2C6H5) at 70 degrees C, affords a fullerene-metal sandwich complex Ir4(CO)3(mu4-CH)(PMe3)2(mu-PMe2)(CNR)(mu-eta2,eta2-C60)(mu4-eta1,eta1,eta2,eta2-C60) (1), which exhibits an interesting structural feature of two metal atoms bridging the two C60 centers as well as the first example of a mu4-eta1,eta1,eta2,eta2-C60 bonding mode. Compound 1 has been characterized by NMR spectroscopy, elemental analysis, and X-ray diffraction study. A cyclic voltammetry study reveals strong electronic communication between the two C60 centers in 1, which is due to the presence of a wide channel of two metal centers between the two C60 cages for efficient electronic interaction.
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