Synthesis, Characterization and Photophysical Properties of a Novel Phthalocyanine-Based Cyclopenta[Hi]Aceanthrylene Derivative

Abstract

The study and understanding of photoinduced energy- and electron-transfer processes in donor-acceptor (D-A) model compounds are of great interest for the preparation of artificial photosynthetic systems which could be used for the development of efficient solar-energy-conversion ensembles.[1] In this context, among the chromophores that have been employed as molecular components in artificial photosynthetic systems, porphyrinoids, the ubiquitous molecular building blocks employed by nature in natural photosynthesis, have been the preferred and obvious choice. Within the large family of porphyrinoid systems, phthalocyanines (Pcs)[2]enjoy a privileged position. These chromophores, which have a two-dimensional 18-π- electron aromatic system isoelectronic with that of porphyrins (Pors), possess in fact unique physicochemical properties which render these macrocycles valuable building blocks in materials science.The benefits resulting from the use of Pcs as molecular building blocks for the construction of artificial photosynthetic systems has led others and us to synthesize and study a wide range of covalent and noncovalent Pc-based D-A systems incorporating electroactive acceptor units of diverse nature and redox character such as fullerenes, carbon nanotubes, perylenediimide, anthraquinone, ferrocene, ruthenium bypyridine complexes, flavin, or Pors.[3] In the search for novel electron-accepting moiety, we have recently started to investigate the use of nonalternant cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs). CP-PAHs have been extensively studied in the past decades owing to their structural similarities to fullerenes, interesting optical properties (relatively small band gaps), and remarkable electron-accepting ability.[4] Within the family of CP-PAHs, cyclopenta[hi]aceanthrylene (CPA), a fragment of the oval-shaped C70 fullerene which presents a LUMO energy level (- 3.69 eV) comparable in energy to those of PCBM-C61 (- 3.7 eV) and perylene bisimide (- 3.83 eV), has been recently used as acceptor unit in blends with P3HT[5] and in donor-acceptor copolymers.[6] We will present here the synthesis, characterization and photophysical study of a novel Pc-based CPA system 1 (Fig. 1). Figure 1. Molecular structure of phthalocyanine-based cyclopenta[hi]-aceantrylene system 1.