Bingel–Hirsch Reaction on Sc₂@C₆₆: A Highly Regioselective Bond Neighboring to Unsaturated Linear Triquinanes

The dispersion-corrected density functional theory (M06-2X) was adopted to investigate the kinetically driven Bingel–Hirsch and thermodynamically controlled Prato reactions on Sc₂@<i>C</i>_2<i>v</i>(4059)-C₆₆ which possesses the unconventional unsaturated linear triquinanes (ULTs), respectively. The mechanism differences of these two reactions on Sc₂@C₆₆ could lead to their different functionalization performances. The investigations on Bingel–Hirsch addition suggest that this process prefers to occur on the C–C bond (9–8) next to other than those (such as 9–10) on the ULT moieties, resulting in a highly regioselective product. The most favorable addition site (atom C₉) for the bromomalonate anion is the only one that connects two equivalent [5,5] C–C bonds (10–11 and 31–30) among all possible atoms. In addition, solvent effect for this reaction was evaluated, and the results suggest that <i>ortho</i>-dichlorobenzene (ODCB) is more feasible than toluene for Sc₂@C₆₆. However, the Prato reaction for this system turned out to show poor regioselectivity to the best reactive bond 10–11

Encapsulation of Monometal Uranium into Fullerenes C_2<i>n</i> (2<i>n</i> = 70–74): Important Ionic U⁴⁺C_2<i>n</i>^4– Characters and Covalent U‑Cage Bonding Interactions

By using density functional theory calculations combined with statistical thermodynamic analyses, the stabilization performance of a series of fullerene cages C2n (2n = 70–74) via encapsulating monometal uranium was systematically and thoroughly investigated. Results indicate that fullerene cages D5h(8149)-C70 and D3h(14246)-C74 obeying the isolated pentagon rule and C2(10612)-C72 featured with one pentalene moiety were the most promising candidates to encage uranium. Subsequent Mulliken spin density distribution and frontier molecular orbital analyses suggest that four formal electron transfer occurs from monometal U to above the carbon cages. There also exists a high degree of covalent character between the atom U and fullerenes C2n based on Mayer bond order and quantum theory of atoms in molecule (QTAIM) analyses, indicative of the cooperative stabilization by both ionic and covalent bonding interactions. In addition, investigations on the above-mentioned U@C2n isomers and other favorable candidates (U@Cs(8094)-C70, U@C1(10610)-C72, U@C1(13393)-C74, and U@C1(14049)-C74) reveal that these isomers could be closely linked via simple C2 addition and Stone–Wales transformation. These results will provide a systematic understanding on U-based endohedral metallofullerenes (EMFs) and also might be helpful for further exploration of EMF growth mechanisms

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 Path_os-RACDP is kinetically more favorable than Path_os-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

Stabilization of a Chlorinated ^#4348C₆₆:<i>C</i>_2<i>v</i> 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:<i>C</i>_<i>s</i> and endohedral metallofullerene (EMF) Sc₂@C₆₆ shared the same cage ^#4348C₆₆:<i>C</i>_2<i>v</i>, while it was denied by the definitive characterization of Sc₂@C₆₆, which actually possesses the ^#4059C₆₆:<i>C</i>_2<i>v</i> isomer. Here, we show that a ^#4348C₆₆:<i>C</i>_2<i>v</i> 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, ^#4348C₆₆:<i>C</i>_2<i>v</i>-based mono-EMFs M@<i>C</i>_2<i>v</i>(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 ^#4169C₆₆:<i>C</i>_<i>s</i>, 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@<i>C</i>_2<i>v</i>(4348)-C₆₆ over M@<i>C</i>_<i>s</i>(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 [<i>n</i>]­cycloparaphenylene ([<i>n</i>]­CPP) and Tb@<i>C</i>_2<i>v</i>(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

Mechanism and Kinetics-Guided Discovery of Nanometal Scissors to Cut Phosphoester Bonds

Nanomaterials (NMs) that catalytically cut phosphoester bonds are of interest in pure chemistry and importance in developing frontier technologies toward gene editing, disease therapy, and environment recovery. However, a universal theory guiding the discovery of such NM catalysts is still lacking. As a result, the current research of these catalysts is mainly limited to NMs consisting of high-valent metal ions. In this work, the mechanisms and kinetics, activity descriptor, and theoretical models for predicting the catalytic activities of arbitrary metal and metal-oxide NMs in the hydrolysis of organophosphates have been studied by density functional theory calculations as well as experiments. The results will provide a systematic understanding of the previously reported NM catalysts, and they will provide theoretical guidelines for further optimization and screening of these catalysts. Using the model, the catalytic activity of Ru nanoparticles, which have high chemical stability and biocompatibility, will be discovered, opening the door to developing the catalysts based on noble metals. The results are expected to inspire the research of new NM catalysts with potential in various frontier biochemical and biomedical applications

Mechanism and Kinetics-Guided Discovery of Nanometal Scissors to Cut Phosphoester Bonds

Nanomaterials (NMs) that catalytically cut phosphoester bonds are of interest in pure chemistry and importance in developing frontier technologies toward gene editing, disease therapy, and environment recovery. However, a universal theory guiding the discovery of such NM catalysts is still lacking. As a result, the current research of these catalysts is mainly limited to NMs consisting of high-valent metal ions. In this work, the mechanisms and kinetics, activity descriptor, and theoretical models for predicting the catalytic activities of arbitrary metal and metal-oxide NMs in the hydrolysis of organophosphates have been studied by density functional theory calculations as well as experiments. The results will provide a systematic understanding of the previously reported NM catalysts, and they will provide theoretical guidelines for further optimization and screening of these catalysts. Using the model, the catalytic activity of Ru nanoparticles, which have high chemical stability and biocompatibility, will be discovered, opening the door to developing the catalysts based on noble metals. The results are expected to inspire the research of new NM catalysts with potential in various frontier biochemical and biomedical applications