Self-Assembled Aggregates and Molecular Bilayer Films of a Double-Chain Fullerene Lipid: Structure and Electrochemistry

Fullerene Building Blocks with Tailor-Made Solubility and New Insights into Their Hierarchical Self-Assembly

Herein, the synthesis of fullerene derivatives with adjustable polarities and lyotropic aggregation properties is reported. The polarity range spans from superhydrophobic to hydrophilic, while simultaneously providing a further reactive position with a view to graft them onto other materials. The synthetic strategy relies on a selective protection with an isoxazoline moiety. The remaining octahedral positions were further functionalized with the desired groups to tune their solubility, yielding mixed [5:1] hexakisadducts. The subsequent deprotection by clean photolytic reaction led to fullerene pentakisadducts with an incomplete octahedral addition pattern, which are useful forerunners for the synthesis of building blocks. Their hydrophobic/hydrophilic behavior has been characterized both in solution and surface through octanol/water partition coefficients (log P) and contact angle measurements. Furthermore, these derivatives can form supramolecular constructions which have been studied by dynamic light scattering (DLS) and cryo‐TEM.

Efficient synthesis of highly soluble and functionalized fulleropyrrolidines

New functionalized fulleropyrrolidines with high emission and absorption.

Tunable one-, two-, and three-dimensional self-assemblies from an acceptor-donor fullerene-N,N-dimethylaminoazobenzene dyad: interfacial geometry and temporal evolution

Controllable fabrication of spontaneously ordered and varied geometry fullerene C(60) based molecular architecture was achieved upon hierarchical self-assembly of the fullerene-N,N-dimethylaminoazobenzene acceptor-donor hybrid (DPNME). Simple preparation techniques, such as Langmuir-Blodgett (LB), solution-cast, and immersion at the liquid-air and solid-air interfaces, were used without templates as a function of DPNME concentration, media pH, time, and supporting substrate characteristics. The resulting structures depending upon the preparation methods were investigated with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and molecular modeling, which revealed a delicate role of intermolecular donor-acceptor, π-π, and van der Waals interactions between the electron deficient fullerene core and the N,N-dimethylaminoazobenzene electron donor under neutral conditions. Upon protonation, the electrostatics associated with the charged DPNME moiety and the dominant intermolecular fullerene-fullerene interactions guided the self-assembly process. Increased time scales led the molecular subunits to grow by maximizing the most favored orientations and yielded one-dimensional (1D) and two-dimensional (2D) structures in neutral and acidic conditions, respectively, which upon solvent evaporation formed the final multipods or stacked squares upon oriented attachment. For the protonated DPNME, 2D lamellar sheets formed from the bilayers gained cohesive energy, forming ultimately rectangular sheets. Interestingly, the Si(100) supported multilayer DPNME Langmuir films as a function of surface pressure and pH yielded a uniform and directional structure pattern in comparison with the geometry obtained from drop casting methods. This controllable structure architecture of the fullerene-azobenzene hybrid opens up a new alley in fullerene C(60) based self-assembly.

Multifunctional, polymorphic, ionic fullerene supramolecular materials: self-assembly and thermotropic properties

An N-methylfulleropyrrolidine (2) bearing three eicosyloxy chains on the laterally substituted phenyl group can be further functionalized to give the ionic fullerene derivative, i.e., N,N-dimethylfulleropyrrolidinium iodide (1). The spectroscopic, electrochemical, self-assembly, and liquid crystalline properties of 1 have been investigated and compared to its neutral precursor 2. Changes in electronic structure upon ionization are observed in the UV spectra. Additionally, a positive potential shift of electrochemical reductions for 1 compared to those of 2 is noted in both homogeneous solution and film state. Driven by the π-π, van der Waals, and electrostatic interactions, the ionic compound 1 is able to form a variety of functional and polymorphic self-assembled structures both from solution and on substrates, including hierarchically organized flakelike microparticles with high water repellency, doughnut-shaped objects with rough surfaces, and long one-dimensional C(60) nanowires (>1 μm). The thermotropic behavior of 1 has also been investigated, and a smectic liquid crystalline phase was observed at elevated temperatures. Further investigations of the thermotropic behavior of 1 revealed that a deionization back-reaction from 1 to the neutral precursor 2 gradually occurred. The mechanism of this deionization reaction is presented and discussed. These investigations provide insight into the effects of added ionicity to alkylated fullerene derivatives, in particular on their self-assembly features and functionality.