Synthesis, Photochemistry, and Electrochemistry of Single-Wall Carbon Nanotubes with Pendent Pyridyl Groups and of Their Metal Complexes with Zinc Porphyrin. Comparison with Pyridyl-Bearing Fullerenes Mercedes Alvaro, † Pedro Atienzar, † Pilar de la Cruz, ‡ Juan L. Delgado, ‡ Vincent Troiani, ‡ Hermenegildo Garcia,* ,† Fernando Langa,* ,‡ Amit Palkar, § and Luis Echegoyen* ,§ Contribution from the Instituto de Tecnologı ´a Quı ´mica CSIC-UPV, UniVersidad Polite ´ cnica de Valencia, 46022-Valencia, Spain, Facultad Ciencias del Medio Ambiente, UniVersidad de Castilla-La Mancha, 45071-Toledo, Spain, and Department of Chemistry, Clemson UniVersity, Clemson, South Carolina 29634 Received November 14, 2005; E-mail: hgarcia@qim.upv.es; flanga@amb-to.uclm.es; luis@clemson.edu Abstract: A soluble, functionalized Py-SWNT has been synthesized and characterized by solution 1 H and 13 C NMR, FT-Raman, and electron microscopy. Experimental data indicate that Py-SWNT has short tubes with pentyl esters at the tips and pyridyl isoxazolino units along the walls. The synthesis of Py-SWNT is based on a 1,3-dipolar cycloaddition of a nitrile oxide on the SWNT walls, similar to 1,3-dipolar cycloadditions that are common for fullerene functionalization. The resulting Py-SWNT forms a complex with a zinc porphyrin (ZnPor) in a way similar to that reported for pyridyl-functionalized [60]-fullerenes. Formation of this metal-ligand complex was firmly established by a detailed electrochemical study. However, in contrast to the behavior observed for the ZnPor/Py-C 60 complex, photochemical excitation of the complex between ZnPor/Py-SWNT does not lead to electron transfer with the generation of charge-separated states. Fluorescence and laser flash studies indicate that the main process is energy transfer from the singlet ZnPor excited state to the Py-SWNT with observation of emission from Py-SWNT. Triplet ZnPor excited- state quenching by Py-SWNT is only observed in polar solvents such as DMF, but not in benzonitrile. Introduction The novel and unique electronic properties 1 exhibited by fullerenes and carbon nanotubes make them excellent candidates for the development of optoelectronic and photovoltaic devices. 2 Currently, there is considerable interest in studying the photo- physical properties of single-wall carbon nanotube (SWNT) derivatives obtained by covalent 3 and noncovalent 4 function- alization, with the aim of obtaining photoresponsive materials. 5 The aim of this research is to search for long-lived charge- separated states that could be used in the field of photovoltaics. 6 Many of the photoactive dyads that have been previously studied consist of a metalloporphyrin-fullerene donor-acceptor (D-A) system 7 connected through a spacer. 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