Effect of Aza Substitution on the Photophysical and Electrochemical Properties of Porphycenes:  Characterization of the Near-IR-Absorbing Photosensitizers 2,7,12,17-Tetrakis(p-substituted phenyl)-3,6,13,16-tetraazaporphycenes

Noemí Rubio, David Sánchez-García, Ana Jiménez-Banzo, Óscar Rey, José I. Borrell, Jordi Teixidó, and Santi Nonell*
Grup d'Enginyeria Molecular, Institut Qumic de Sarri, Universitat Ramon Llull, Via Augusta 390, 08017 Barcelona, Spain
J. Phys. Chem. A, 2006, 110 (10), pp 3480–3487
DOI: 10.1021/jp056494+
Publication Date (Web): February 23, 2006
Copyright © 2006 American Chemical Society
*

 To whom correspondence should be addressed. E-mail:  s.nonell@ iqs.url.edu. Tel:  (+34) 93 267 2000. Fax:  (+34) 93 205 6266.

Abstract

The need for new photodynamic-therapy photosensitizers has stimulated the search of new families of compounds absorbing strongly in the 700−900 nm range, the region where tissue is most transparent to radiation capable to induce the photodynamic effect. Using computational chemistry techniques, 3,6,13,16-tetraazaporphycenes were previously identified as interesting target candidates. This work reports on the photophysical and electrochemical properties of selected members of this new family of macrocycles. Compared to porphycenes, the tetra-aza counterparts show stronger absorption in the near-infrared, lower-lying singlet and triplet excited states, and substantially larger internal conversion quantum yield (ΦIC = 0.93). Energy transfer to oxygen is observed, which results in the formation of the cytotoxic species singlet oxygen. The process is found to be reversible, consistent with a triplet-energy value close to that of singlet oxygen.

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History

  • Published In Issue March 16, 2006
  • Received November 9, 2005
    Revised December 22, 2005

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