Unusual C2h -Symmetric trans-1-(Bis-pyrrolidine)-tetra-malonate Hexa-Adducts of C60 : The Unexpected Regio- and Stereocontrol Mediated by Malonate-Pyrrolidine Interaction

Regioswitchable Bingel Bis-Functionalization of Fullerene C70 via Supramolecular Masks

Isomer-pure functionalized fullerenes are required to boost the development of fullerene chemistry in any field, but their multiple functionalization renders a mixture of regioisomers that are very difficult to purify by chromatography. For the specific case of C70, its nonspherical geometry makes its regioselective functionalization more challenging than that of spherical C60. In this work, the supramolecular mask approach is applied for the first time to C70, which is encapsulated in two different nanocapsules to achieve the Bingel bis-cyclopropanation at α-bonds of opposite poles. Based on the tetragonal prismatic geometry imposed by the smaller supramolecular mask tested, the obtained major bis-adduct is completely reversed (major 5 o'clock) compared to bare C70 functionalization (major 2 o'clock). Moreover, by further restricting the accessibility of C70 using a three-shell Matryoshka mask and dibenzyl-bromomalonate, a single regiospecific 2 o'clock bis-isomer is obtained, owing to the perfect complementarity of the mask and the addend steric properties. The outcome of the reactions is fully explained at the molecular level by means of a thorough molecular dynamics (MD) study of the accessibility of the α-bonds to produce the different bis-adducts.

Diversity of Metal—Fullerene Framework Structures Regulated by Metal Salts

Taking into account the diversity of fullerene ligands and metal salts, metal–fullerene frameworks (MFFs) present a variety of structures. Currently, the structural control of MFFs mainly relies on the design and synthesis of fullerene ligands, while the influence of metal building units on the structures has been rarely studied. The present work represents a systematical investigation of fullerene-linked supramolecular architectures incorporating different metal salts. Treatment of a bidentate N,N-donors fullerene ligand (L1) with six metal salts ([Zn(NO₃)₂·6H₂O, Cd(NO₃)₂·4H₂O, Cu(NO₃)₂·3H₂O, Cu(OAc)₂·H₂O, FeCl₂·4H₂O and FeCl₃·6H₂O]) produced six one-dimensional MFFs, i.e., ZnL1(NO₃)₂(H₂O)₂ (1), CdL1(NO₃)₂ (2), Cu(L1)(H₂O)₂(NO₃)₂ (3), CuL1(OAc)(CH₃O) (4), FeL1Cl₂ (5) and FeL1Cl₂(FeCl₄) (6). Compounds 1–3, built with nitrates with different metal centers (M(NO₃)₂, M = Zn, Cd, Cu), present a 1D stair-like, 1D zigzag, and 1D linear chain structure, respectively. Compound 4, synthesized with another Cu(II) salt, Cu(OAc)₂, displays a dinuclear Cu-Cu connected 1D stair-like chain structure, rather than the single Cu linked 1D linear chain obtained from Cu(NO₃)₂. Compounds 5 and 6, assembled from iron chloride of different oxidation states (Fe(II)Cl₂ and Fe(III)Cl₃) reveal a 1D zigzag and a 1D stair-like chain structure, respectively. The results demonstrate the significant influences of metal salts on the structures of metal–fullerene frameworks.