Multiply exo-Methylated Corannulenes.

Invited for the cover of this issue are Shinobu Aoyagi (Nagoya City University), Takahiro Sasamori (University of Tsukuba), and Hideki Yorimitsu (Kyoto University). The image depicts multiply exo-methylated corannulenes (flowers) synthesized from corannulene (central large flower) by the reduction with sodium (soil) to form anionic corannulenes and the subsequent methylation with reduction-resistant dimethyl sulfate (butterflies). Read the full text of the article at 10.1002/chem.202301557.

Multiply exo-Methylated Corannulenes.

The curved π-conjugated surface of bowl-shaped corannulene has been multiply methylated to form exo-di-, -tetra-, and -hexamethylated corannulenes. The multimethylations became possible through in-situ iterative reduction/methylation sequences that involve the reduction of corannulenes using sodium to form the anionic corannulene species, and the subsequent SN 2 reaction of the anionic species with reduction-resistant dimethyl sulfate. X-ray diffraction analyses, NMR, MS, UV-Vis measurements, and DFT calculations have revealed the molecular structures of the multimethylated corannulenes and the sequence of the multimethylation. This work has the potential to contribute to the controlled synthesis and characterizations of multifunctionalized fullerenes.

Facile Multiple Alkylations of C60 Fullerene.

The reduction of fullerene (C60) with sodium dispersion in the presence of an excess amount of dipropyl sulfate was found to yield highly propylated fullerene, C60(nC3H7)n (max. n = 24), and C60(nC3H7)20 was predominantly generated as determined by mass spectroscopy.

Anionic Fluorinated Zn-porphyrin Combined with Cationic Endohedral Li-fullerene for Long-Lived Photoinduced Charge Separation with Low Energy Loss.

Here we report an anionic meso-tetrakis(4-carboxymethylthio-2,3,5,6-tetrafluorophenyl) zinc porphyrin (ZnTF4PPTC4-) to form a supramolecular complex with a cationic lithium endohedral [60]fullerene (Li+@C60). The supramolecular ZnTF4PPTC4-/Li+@C60 complex formed by strong electrostatic attraction with a large binding constant generates a long-lived charge-separated (CS) state with low energy loss by photoinduced electron transfer from ZnTF4PPTC4- to Li+@C60. The anionic fluorinated zinc porphyrin with high oxidation potential reduces the energy loss associated with the charge separation and enhances the energy level of the CS state. The energy level of the CS state determined by electrochemical measurements is at 0.94 eV, which is much higher than that of a similar supramolecular complex using an anionic meso-tetrakis(sulfonatophenyl) zinc porphyrin (ZnTPPS4-) at 0.55 eV. Time-resolved transient absorption spectroscopy demonstrates that ZnTF4PPTC4-/Li+@C60 generates a long-lived CS state with a lifetime of 0.29 ms in a binary solvent of acetonitrile and chlorobenzene. The lifetime of the CS state is comparable to that of ZnTPPS4-/Li+@C60 in benzonitrile.

Reversible Color and Shape Changes of Nanostructured Fibers of a Macrocyclic π-Extended Thiophene Hexamer Promoted by Adsorption and Desorption of Organic Vapor.

A phenyl-substituted macrocyclic π-extended thiophene hexamer 1, composed of four thienylene-ethynylene and two thienylene-vinylene units, has a solid-state structure in which π-π, CH-π, and van der Waals interactions occur. Slow addition of acetone to a solution of 1 in CS2 produces a yellow nanostructured fiber 1-A containing a 1:1.5:1 ratio of 1, acetone, and CS2. Over a 2 min period at 25 °C, 1-A gradually changes to an orange fiber 1-B containing a 1:0.5:1 ratio of 1, acetone, and CS2. On exposure to acetone vapor, 1-B regenerates 1-A (vapochromism), and removal of all solvents from 1-A and 1-B generates a red-orange fiber 1-C, which upon brief immersion in acetone/CS2 produces 1-A. Furthermore, 1-C is converted to orange yellow fiber 1-D upon exposure to acetone vapor for 1 s at 25 °C. Analysis of the horizontal and vertical profiles of the X-ray diffraction (XRD) patterns shows that removal of solvent from 1-A reversibly creates 1-B in conjunction with a shape and size change along with arching.

Structure of [60]fullerene with a mobile lithium cation inside.

The structure of crystalline [60]fullerene with a lithium cation inside (Li+@C60) was determined by synchrotron radiation X-ray diffraction measurements to understand the electrostatic and thermal properties of the encapsulated Li+ cation. Although the C60 cages show severe orientation disorder in [Li+@C60](TFPB-)·C4H10O and [Li+@C60](TFSI-)·CH2Cl2, the Li+ cations are rather ordered at specific positions by electrostatic interactions with coordinated anions outside the C60 cage. The Li+@C60 molecules in [Li+@C60](ClO4-) with a rock-salt-type cubic structure are fully disordered with almost uniform spherical shell charge densities even at 100 K by octahedral coordination of ClO4- tetrahedra and show no orientation ordering, unlike [Li+@C60](PF6-) and pristine C60. Single-bonded (Li+@C60-)2 dimers in [Li+@C60-](NiOEP)⋅CH2Cl2 are thermally stable even at 400 K and form Li+-C bonds which are shorter than Li+-C bonds in [Li+@C60](PF6-) and suppress the rotational motion of the Li+ cations.