Implementation of Quantum Level Addressability and Geometric Phase Manipulation in Aligned Endohedral Fullerene Qudits

Endohedral nitrogen fullerenes have been proposed as building blocks for quantum information processing due to their long spin coherence time. However, addressability of the individual electron spin levels in such a multiplet system of 4S3/2 has never been achieved because of the molecular isotropy and transition degeneracy among the Zeeman levels. Herein, by molecular engineering, we lifted the degeneracy by zero-field splitting effects and made the multiple transitions addressable by a liquid-crystal-assisted method. The endohedral nitrogen fullerene derivatives with rigid addends of spiro structure and large aspect ratios of regioselective bis-addition improve the ordering of the spin ensemble. These samples empower endohedral-fullerene-based qudits, in which the transitions between the 4 electron spin levels were respectively addressed and coherently manipulated. The quantum geometric phase manipulation, which has long been proposed for the advantages in error tolerance and gating speed, was implemented in a pure electron spin system using molecules for the first time.

Covalent Inter-Synthetic-Carbon-Allotrope Hybrids

Inter-synthetic-carbon-allotrope (SCA) architectures are constructed by hybridizing different types of carbon allotropes such as 0D-fullerene, 1D-carbon nanotubes (CNTs), and 2D-graphene. Also hybridizations of different fullerene families (e.g., empty fullerene, heterofullerenes, and endohedral fullerenes as well as their isomers) are considered as inter-SCA architectures and represent an emerging class of nanofunctional materials. Such highly integrated hybrids are quite promising, since they hold the potential of combining unique properties of each building block. For instance, hybridization of 2D-graphene, a synthetic carbon allotrope with outstanding chemical/physical properties, with 0D-fullerenes leads to materials with both outstanding solid state properties (e.g., electron mobility, flexibility, transparency, and mechanical stability) and distinct molecular properties (spatially resolved and tailor-made exohedral cage functionalization and endohedral guest encapsulation). Therefore, such integrated hybrids have potential as multifunctional nanocarbon materials applicable, for example, in energy storage, electronic devices, solar cells, or advanced sensors. Recognizing these significant advantages, a series of methods and techniques has been developed to synthesize such integrated hybrids. Based on in-depth understanding of fullerene chemistry, interfullerene hybrids where multiple fullerenes are linked together have been synthesized and fully characterized. However, due to the difficulty in functionalizing graphene or CNTs as a result of their poor dispersibility and weak reactivity the corresponding hybrids including these macromolecular forms are less explored. Furthermore, few approaches toward such systems reported so far inevitably involve some drawbacks such as low degree of addition and low production ability. This Account presents the concepts and strategies of our studies on the construction of inter-SCA hybrids. We first emphasize on our efficient "reductive functionalization route" as a versatile strategy for graphene/CNT functionalization. In sharp contrast to previous approaches, our strategy enables unprecedented functionalization of graphene/CNT without damaging their structures. As a consequence, the door for cross-dimensional architectures via hybridizing graphene/CNT with fullerenes has been opened. We will then summarize the diverse inter-SCA hybrids that we recently synthesized, ranging from interfullerene hybrids to those of cross-dimensional graphene/CNT-(endo)fullerenes hybrids as well as CNTs networks. For interfullerene hybrids, different types of fullerenes including empty fullerenes, heterofullerenes, and endohedral fullerenes have been employed. Finally, the prospects on the future challenges on inter-SCA hybrids are envisioned. This Account will provide fundamental insight into construction of inter-SCA hybrids and stimulate further efforts toward research on this emerging topic.

The first molecular dumbbell consisting of an endohedral Sc3N@C80 and an empty C60-fullerene building block

An unprecedented hybrid dumbbell consisting of a metallofullerene and an empty fullerene was afforded via simple click reaction of suitable precursor derivatives of Sc₃N@C₈₀ and a C₆₀ hexakisadduct.