Porphyrins/fullerene supramolecular assembl

In a supramolecular approach to fullerene-porphyrin hybrids, the assembly of a rigidly connected dyad, in which a zinc tetraphenylporphyrin, Zn(TPP), is noncovalently linked to a C60 derivative via axial pyridine coordination to the metal, was reported [219-222]. Photo excitation of the dyad Zn-complex led to electron transfer with very long lifetimes of the charge-separated pairs, as revealed by optical spectroscopy and confirmed by time-resolved electron paramagnetic resonance spectroscopy. Accordingly, two different solvent-dependent pathways can be considered for the electron-transfer processes. Either the excitation of the porphyrin chromophore is followed by fast intramolecular electron transfer inside the complex, or alternatively the free porphyrin is excited undergoing intermolecular electron transfer when the acceptor molecules ap-... 

The metastable, 2-D packing motif presented by some Pcs adsorbed on Ag(l 11) has also prompted the utilization of such ensembles as templates for the organization of complementary guest molecules such as fullerenes [193] or corannulenes [194], giving rise to the formation of two-component, 2-D architectures. More recently, a similar approach has been used to prepare a surface-supported, three-component system. In fact, the immersion of an Au substrate into a solution containing both a ZnPc and a Zn porphyrin led to the formation of a highly ordered, 2-D arrangement of both Pc and porphyrin which can act as a bimolecular chessboard toward the supramolecular assembly of a third component (i.e., C6o fullerene) which is selectively trapped in the open spaces (Fig. 25) [195],... 

FIGURE 2.2 Supramolecular nanostructures for light driven energy and electron transfer. This research is focused on rational design and study of self-assembled porphyrin, fullerene, and carbon nanotube bearing supramolecular complexes and nanostructures. 

X. Zhou, S.W. Kang, S. Kumar, R.R. Kulkarni, S.Z.D. Cheng, Q. Li, Self-assembly of porphyrin and fullerene supramolecular complex into highly ordered nanostructure by simple thermal annealing. Chem. Mater. 20, 3551-3553 (2008)... 

Supramolecular assemblies including CNTs have proven difficult due to challenges associated with dispersing SWNTs in neat solvents and to the difficulty in controlling molecular orientation. In one example of supramolecular assembly, a direct current (DC) electric field was employed to induce surfactant (tetraoctlyammonium bromide) or polymer (Nafion) capped SWNTs to assemble into linear bundles. On the basis of the knowledge that fullerenes can experience charge-transfer interactions with porphyrins to form supramolecular assemblies, Kamat and coworkers determined that protonated porphyrins yielded ordered... 

Supramolecular assemblies of metalloporphyrins and fullerenes have been also investigated by some of the authors of this book [37]. In an extensive work concerning the NEXAFS and XPS investigation of zinc diethinyl porphyrins vapour deposited on a Cu(l 11) surface and its interaction with increasing amounts of Ceo, a tilting of the macrocycle on the substrate surface, from flat geometry to standing... 

Fukuzumi S, Saito K, Ohkubo K, Khoury T, Kashiwagi Y, Absalom MA, Gadde S, D Souza F, Araki Y, Ito O, Crossley MJ (2011) Multiple photosynthetic reaction centres composed of supramolecular assemblies of zinc porphyrin dendrimers with a fullerene acceptor. Chem Commun 47(28) 7980-7982... 

In addition to metal coordination bonds, hydrogen bondings, electrostatics, and 7T-7T interactions, the attractive interaction between the curved r-surface of a fullerene and the flat rr-surface of a porphyrin was recently reported [8,9]. When the fullerene and the porphyrin were linked covalently in the single molecule (see 6), the two functions interacted with each other to form a supramolecular assembly in the solid state. In contrast to this divergent system, macrocycle 7 was prepared from the fused zinc porphyrins for the convergent interaction with specific guests. Since 7 had space to accommodate two fuUerenes, this kind of interaction operated well in the supramolecular assembly and moleciflar recognition systems. 

Hydrogen bonding is also important to construct supramolecular architectures of porphyrins, which is well summarized in the review by Satake and Kobuke [14]. For example, self-assembly of a porphyrin-fullerene dyad through Watson-Click hydrogen bonding offers a good model of photoin-duced electron transfer in supramolecular assembly (Fig. 9) [25]. Shirakawa... 

Hasobe, T. Hattori, S. Kamat, P. V. Urano, Y Umezawa, N. Nagano, T. Fukuzumi, S. Organization of supramolecular assemblies of fullerene, porphyrin and fluorescein dye derivatives on Ti02 nanoparticles for light energy conversion. Chem. Phys. 2005,319,243-252. 

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