Jackson D. Megiatto

Introduction of useful peripheral functional groups on [2]catenanes by combining Cu(I) template synthesis with “click” chemistry

Two protocols based on Cu(I) template synthesis and “click” reactions for the synthesis of functionalized [2]catenanes are described. A straightforward procedure, involving high dilution conditions at high temperatures (70 °C), affords [2]catenanes bearing two identical peripheral groups in high yields. For the preparation of non-symmetrically functionalized [2]catenanes, a second milder and simpler protocol was developed, generalizing and extending the method. The introduction of peripheral functional groups into the catenane structure opens up possibilities of using [2]catenanes as building blocks for preparation of even more complex structures.

Carbon nanotubes: Nanotubes reveal all in solution

Enhancing the solubility of single-walled carbon nanotubes through non-covalent bonds has led to an improvement in our ability to probe and understand their interactions with electron donors and acceptors.

Photoexcited state properties of H2-porphyrin/C60-based rotaxanes as studied by time-resolved electron paramagnetic resonance spectroscopy.

Light-driven intramolecular electron transfer (ET) and energy transfer (EnT) processes in two rotaxanes, the first containing two free base porphyrins and C(60) fullerene moieties incorporated around a Cu(I)bisphenanthroline core ((H(2)P)(2)-Cu(I)(phen)(2)-C(60)) and a second lacking the fullerene moiety ((H(2)P)(2)-Cu(I)(phen)(2)), were studied by X-band (9.5 GHz) time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The experiments were performed in frozen toluene and ethanol and different phases of the nematic liquid crystal (E-7). It is demonstrated that the ET and EnT processes in the (H(2)P)(2)-Cu(I)(phen)(2)-C(60) rotaxane in different media result in the formation of the same charge-separated state, namely (H(2)P)(2)(•+)-Cu(I)(phen)(2)(•-)-C(60), while photoexcitation of the (H(2)P)(2)-Cu(I)(phen)(2) rotaxane does not induce noticeable transfer processes in these matrices. The results are discussed in terms of the high conformational mobility of the rotaxanes, which enables changes in the molecular topography and resultant modification of the rates and routes of photoinduced processes occurring in these systems. The parameters of the transfer processes are compared with those obtained in our previous study of (ZnP)(2)-Cu(I)(phen)(2)-C(60) and (ZnP)(2)-Cu(I)(phen)(2) rotaxanes under the same experimental conditions.

Chapter 10:Interlocked Artificial Photosynthetic Model Systems Composed of Electron-Donor and [60]Fullerene Units

This chapter summarises the work carried out in the past 15 years on the synthesis and photophysical properties of organic photosynthetic model systems in which electron-donor groups are mechanically linked to fullerenes, usually [60]fullerene (C60), in topologically diverse interlocked architectures. The chapter focuses particularly on rotaxanes, in which a chain with bulky end groups passes through a macrocyclic ring, and catenanes, with two or more interlocked rings. The special techniques used for efficient synthesis of these large supramolecular systems involves molecular recognition and self-assembly based on hydrogen bonding, π–π interactions, and coordination to metal cations, most importantly Cu+. The goal of research in this area has been to manipulate interlocked organic structures through synthesis so as to maximise the lifetimes of charge-separated states produced upon excitation using light corresponding to the solar spectrum. The ways in which interlocked systems can be structurally manipulated using external stimuli so as to alter positions of noncovalently linked electron-donor (D) and electron-acceptor (A) groups will be described, including shuttle motions in D–A rotaxanes. While much of the discussion concerns rotaxanes with a C60 moiety, for which numerous synthetic protocols have been developed, the last section focuses on D–A catenanes containing C60, which are much more challenging synthetic targets. It has recently been demonstrated that photoinduced electron transfer takes place in a zinc(II)porphyrin-C60[2]catenane through an intervening Cu(I) complex that was used to assemble the system, to generate a charge-separated state whose lifetime is in the microsecond time domain.