Koji Harano

A 3 nm-sized cage-shaped Hg6L4 complex with large openings was quantitatively formed from trismonodentate ligand (L) and Hg2+ ions in a self-assembled manner. The cage complex shows reversible interconversion with a capsule-shaped Hg6L8 complex in response to the ratio of ligand to Hg2+. This structural switching is coupled with reversible ON/OFF switching of fluorescence between fluorescent Hg6L8 capsule and nonfluorescent Hg6L4 cage.

Amphiphiles are used for a variety of applications in our daily life and in industrial processes. They typically possess hydrophobic and hydrophilic moieties within the molecule, thereby performing a myriad of functions through the formation of two- and three-dimensional assemblies in water, such as Gibbs monolayers and micelles. However, these functions are often inseparable because they emerge from the same structural feature of the molecule, and are difficult to control because the structural

Abstract Molecular crystals consist of an array of periodically arranged molecules in a three-dimensional space. Although nowadays we can routinely obtain crystal structures at the atomic level, the picture of how individual molecules gather together in an orderly manner and grow into crystals of visible size is still unresolved. Over the last decade, we focused on the mechanism of crystal nucleation, which is the initial step of crystallization—it plays a critical role in determining the crysta

Whereas a statistical average of molecular ensembles has been the conventional source of information on molecular structures, atomic resolution movies of single organic molecules obtained by single-molecule real-time transmission electron microscopy have recently emerged as a new tool to study the time evolution of the structures of individual molecules. The present work describes a proof-of-principle study of the determination of the conformation of each C-C bond in single perfluoroalkyl fuller

Many chemical reactions, such as multistep catalytic cycles, are cascade reactions in which a series of transient intermediates appear and disappear stochastically over an extended period. The mechanisms of such reactions are challenging to study, even in ultrafast pump-probe experiments. The dimerization of a van der Waals dimer of [60]fullerene producing a short carbon nanotube is a typical cascade reaction and is probably the most frequently studied in carbon materials chemistry. As many as 2

Cyclodextrins (CDs) are doughnut-shaped cyclic oligosaccharides having a cavity and two rims. Inclusion binding in the cavity has long served as a classic model of molecular recognition, and rim binding has been neglected. We found that CDs recognize guests by size-sensitive binding using the two rims in addition to the cavity, using single-molecule electron microscopy and a library of graphitic cones as a solid-state substrate for complexation. For example, with its cavity and rim binding abili

Carbon fiber (CF) obtained by pyrolysis of polyacrylonitrile (PAN-CF) surpasses metals in properties suitable for diverse applications such as aircraft manufacture and power turbine blades. PAN-CF obtained by pyrolysis at 1200-1400 °C shows a remarkably high tensile strength of 7 GPa, much higher than pitch-based CF (pb-CF) consisting of piles of pure graphene networks. However, little information has been available on the atomistic structure of PAN-CF and on how it forms during pyrolysis. We py

Abstract Real-time imaging of the dynamics of single molecules and molecular assemblies with atomic-resolution electron microscopy is an emerging experimental methodology to obtain single-molecule-level information on molecular motions and reactions. The central idea of the methodology is to capture single molecules and molecular assemblies in solution with a chemical fishhook and bring them into the nm-scale view field of the electron microscope. We report herein the installation of aromatic gr

Delivery of siRNA is a key technique in alternative gene therapy, where the siRNA cargo must be effectively loaded onto a tailor-designed carrier molecule and smoothly unloaded precisely upon arrival at the target cells or organs. Any toxicity issues also need to be mitigated by suitable choice of the carrier molecule. A water-soluble cationic fullerene, tetra(piperazino)[60]fullerene epoxide (TPFE), was previously shown to be nontoxic and effective for lung-targeted in vivo siRNA delivery by wa

We prepared self-assembled vesicles comprising layers of fullerene, alkyl chains, triazole, oligo(ethylene oxide) chains, biotin and avidin molecules. High-resolution scanning electron microscopy using a superhydrophilic indium-tin oxide substrate was found to be useful for nanometer-level structural analysis of the vesicles and individual avidin molecules whose structures are difficult to analyze.