Maurizio Prato

Manipulating single-wall carbon nanotubes by chemical doping and charge transfer with perylene dyes

Single-wall carbon nanotubes (SWNTs) are emerging as materials with much potential in several disciplines, in particular in electronics and photovoltaics. The combination of SWNTs with electron donors or acceptors generates active materials, which can produce electrical energy when irradiated. However, SWNTs are very elusive species when characterization of their metastable states is required. This problem mainly arises because of the polydispersive nature of SWNT samples and the inevitable presence of SWNTs in bundles of different sizes. Here, we report the complete and thorough characterization of an SWNT radical ion-pair state induced by complexation with a perylene dye, which combines excellent electron-accepting and -conducting features with a five-fused ring π-system. At the same time, the perylene dye enables the dispersion of SWNTs by means of π–π interactions, which gives individual SWNTs in solution. This work clears a path towards electronic and optoelectronic devices in which regulated electrical transport properties are important. Using carbon nanotubes in electronic or photovoltaic devices generates active metastable states. These elusive species are hard to characterize because of the polydisperse and aggregate nature of nanotube bundles. A complete characterization of the radical–ion pair state has now been achieved using a range of techniques.

Two-dimensional vibrational spectroscopy of rotaxane-based molecular machines

It has recently become possible to synthesize mechanical devices the size of a single molecule. Although it is tempting to regard such molecular machines as nanoscale versions of their macroscopic analogs, many notions from macroscopic mechanics no longer apply at a molecular level. For instance, the concept of viscous friction is meaningless for a molecular machine because the size of the solvent molecules that cause the friction is comparable to that of the machine itself. Furthermore, in many cases, the interactions between a molecular machine and its surroundings are comparable to the force driving the machine. As a result, a certain amount of intrinsic randomness exists in the motion of molecular machines, and the details of their mechanics are largely unknown. For a detailed understanding of the mechanical behavior of molecular machines, experiments that probe their motion on an ultrafast time scale, such as two-dimensional (2D) vibrational spectroscopy, are essential. This method uses coupling between vibrational modes in a molecule to investigate the molecular conformation. The coupling shows up as off-diagonal peaks in a 2D graph of the vibrational response of the molecule, analogous to the spin coupling observed in multidimensional NMR spectroscopy. Both spin coupling and vibrational coupling are sensitive probes of the molecular conformation, but 2D vibrational spectroscopy shows orders of magnitude better time resolution than NMR. In this Account, we use 2D vibrational spectroscopy to study molecular machines based on rotaxanes. These devices consist of a linear thread and a macrocycle that is noncovalently locked onto the thread. In the rotaxanes we study, the macrocycle and the thread both contain CO and NH groups. By determining the coupling between the stretching modes of these goups from the cross peaks in the 2D spectrum, we directly and quantitatively probe the relative position and orientation of the macrocycle and the thread for both a small model rotaxane and a rotaxane-based molecular shuttle. Our results demonstrate the feasibility of using time-resolved 2D-IR experiments to measure externally triggered structural changes of molecular devices with subpicosecond time resolution. We can observe each of the elementary events that underlie the mechanical motion separately. With this ability to investigate the nature of the mechanical motions at the molecular level and with unprecedented time resolution, we expect that 2D-IR spectroscopy on molecular machines will lead to new insights into their function.

Chapter 11:Fullerenes for Materials Science

In this chapter, the most important applications of fullerene derivatives in materials science are presented especially to understand the significant contributions of fullerene chemistry to the development of new materials. A general overview of the state-of-the-art in this interesting field is given, including a number of representative and most recent examples of donor–acceptor systems, organic electron devices, superconductors, fullerene aggregates, nonlinear optics applications, liquid crystals and fullerene–inorganic hybrids.

Small reorganization energies in fullerenes

This article highlights the advantages of employing fullerenes as a viable electron accepting building block in novel donor acceptor systems. The selected examples characterize the small reorganization energies of fullerenes in electron transfer reactions and illustrate the continuing interest and potential of fullerenes as multifunctional electron storage moieties in well-ordered multicomponent composites. Furthermore, the importance of C60 as a promising model system for unraveling fundamental aspects of ET theory is emphasized.

Chapter 7:Fullerenes for Material Science

Fullerenes possess intriguing electrochemical,1,2 photophysical,3 optical,4 semiconducting,5 superconducting,6–8 magnetic9–11 and aggregation12 properties. A new research field has emerged in recent years, based on the functionalization and study of new fullerene derivatives, which intends to exploi...