Qiao-Zhi Li

Boosting Activation of Oxygen Molecules on C60 Fullerene by Boron Doping

The activation of oxygen molecules on boron-doped C60 fullerene (C59 B) and the subsequent water formation reaction are systematically investigated by using hybrid density functional calculations. Results indicate that C59 B shows a favorable ability to activate oxygen molecules both kinetically and thermodynamically. The oxygen molecule is first adsorbed on the boron atom, which is identified to be the most reactive site in C59 B for O2 adsorption because of its high positive charge and spin density. The adsorption structure C59 BO2 can further isomerize to form two products with small reaction barriers. Water formation reactions upon these two structures are energetically favorable and suggest a four-electron mechanism for the oxygen reduction reaction catalyzed by C59 B. This work provides a reliable theoretical insight into the catalytic properties of boron-doped fullerene, which is believed to be helpful to explore fullerene catalysts.

Stabilization of a Chlorinated #4348C66:C2v Cage by Encapsulating Monometal Species: Coordination between Metal and Double Hexagon-Condensed Pentalenes

Carbon cages in endohedral and exohedral fullerene derivatives are usually different. A recent report suggested that chlorofullerene C66Cl10:Cs and endohedral metallofullerene (EMF) Sc2@C66 shared the same cage (#4348)C66:C2v, while it was denied by the definitive characterization of Sc2@C66, which actually possesses the (#4059)C66:C2v isomer. Here, we show that a (#4348)C66:C2v cage with a double hexagon-condensed pentalene (DHCP) moiety, which was captured by exohedral chlorination, is also capable of being stabilized by encapsulating tri- or divalent monometal (M) species. On the basis of density functional theory calculations combined with statistical mechanics analyses, (#4348)C66:C2v-based mono-EMFs M@C2v(4348)-C66 (M = Tb, La, Y, and Yb) were demonstrated to be the most stable and predominant isomers at the fullerene formation temperature region, while another chlorinated cage (#4169)C66:Cs, featured with triple sequentially fused pentagon (TSFP) moiety, is less favorable to be obtained in the form of EMFs, although these two cages can be interconverted by a simple Stone-Wales transformation. The superiority of M@C2v(4348)-C66 over M@Cs(4169)-C66 comes from the stronger interaction of M-DHCP over that of M-TSFP in both ionic and covalent bonding aspects. In addition, size-selective complexation of host [n]cycloparaphenylene ([n]CPP) and Tb@C2v(4348)-C66 was simulated, showing that [10]CPP exhibits the best affinity toward Tb@C66, which provides a new opportunity for isolation and characterization of C66-based mono-EMFs.

Photoreactions of Endohedral Metallofullerene with Siliranes: Electronic Properties of Carbosilylated Lu3N@Ih-C80

Photochemical carbosilylation of Lu3N@Ih-C80 was performed using siliranes (silacyclopropanes) to afford the corresponding [5,6]- and [6,6]-adducts. Electrochemical studies indicated that the redox potentials of the carbosilylated derivatives were shifted cathodically in comparison with those of the [5,6]-pyrrolidino adducts. The electronic effect of the silirane addends on Lu3N@Ih-C80 was verified on the basis of density functional theory calculations.

Epoxy and Oxidoannulene Oxidation Mechanisms of Fused-Pentagon Chlorofullerenes: Oxides Linked by a Pirouette-Type Transition State

Recently, the oxidative functionalization of double-fused-pentagon (DFP)-containing chlorofullerenes #271C50Cl10 and #913C56Cl10 was carried out, resulting in two monoepoxides with the oxygen atom added at the ortho site of pentalene on the DFP moiety. To uncover the reactivity of isolated-pentagon-rule violating fullerenes upon oxidation, two possible formation processes (ozone molecule and oxygen radical served as oxidation reagents) of these two oxides were systematically investigated through density functional theory calculations. For the ozone oxidation, two possible pathways were explored, and the results indicate that the biradical mechanism Pathos-RACDP is kinetically more favorable than Pathos-RABP, where R, A, and P represent reactants, ozonide intermediates, and oxidation products and B, C, and D represent another three oxygen-containing intermediates. The products obtained by ozone oxidation ([6,6]-55-closed epoxides P-C3-C29 for #271C50Cl10 and P-C42-C43 for #913C56Cl10 with oxygen atom added at the shortest and highest HOMO-contribution bonds) are consistent with experimental observations. However, the oxygen radical additions on these two chlorofullerenes favor generation of the [5,6]-66-open oxidoannulene adducts P-C3-C2 and P-C42-C54, respectively. Subsequent analyses of their geometrical features and structural stabilities suggest that these two oxidoannulene adducts are energetically unfavorable and could be converted to more stable epoxides mentioned above by undergoing a pirouette-type transition state. In these two diverse oxidation procedures, the favorable C-C bonds for ozone attacking and C atoms for oxygen-adsorption are rationalized in terms of their bond lengths and HOMO contributions as well as pyramidalization angles.

Magnetic and electronic properties of porphyrin-based molecular nanowires

Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.