IMPROVED METHODS FOR PHTHALOCYANINE AND NAPHTHALOCYANINE CHROMOPHORE SYNTHESIS

Abstract

It has been demonstrated that the structural characteristics of phthalocyanines (Pcs) are critical to their performance in technological applications such as optical limiting, photodynamic therapy (PDT), organic field-effect transistors (OFETs), and organic photovoltaic (OPV) devices. The work in this thesis describes improved methods of substituted Pc and naphthalocyanine (Nc) synthesis addressing some currently encountered problems including: 1) chromophore aggregation and low solubility; 2) the need for selective synthesis of asymmetric Pcs; (3) a lack of general methods for producing Pc materials with structural diversity.Chapter 1 provides a concise review on three major advantages of using Pcs as OPV materials: near-IR absorption, self-organization in mesophase resulting in conductive columnar aggregates, and self-assembly at the supramolecular level to form complex nanostructures. In addition, Pc-based heteroarrays which have potential use for OPV and Pc-based dye sensitized solar cells (DSSC) are also discussed.Chapter 2 describes the synthesis and structural characterization of dendritic Ncs. As a continuation of previous work regarding non-aggregated Pc dendrimers, the site isolation effect of dendrons on Nc chromophores was studied by UV-vis spectroscopy. It was found that installation of higher generation dendrons not only enhanced the solubility of Nc cores in common organic solvents, but also resulted in non-aggregated Ncs in both solution phase and the solid state.Chapter 3 reports a synthetic strategy employing "click" chemistry to produce a family of structurally diverse Pcs. Octaalkynyl substituted Pcs have been prepared as a platform for the incorporation of various azides as peripheral functionalities. One of the Pc derivatives bearing photo-cross-linkable cinnamate residues has proven useful for the fabrication of robust cross-linked photopatterned and imprinted nanostructures.Chapter 4 discusses the synthesis of asymmetrical Pcs with six solubilizing groups and one hydroxyl group on the periphery through the "ROMP-Capture-Release" method. Further modification of the pendent hydroxyl group with sebacoyl chloride demonstrated that the unmasked hydroxyl site was reactive as a nucleophile, thus opening the possibility for intimately grafting Pcs onto inorganic substrates TiO2.Chapter 5 details the synthesis of asymmetric clickable Pcs bearing six alkyne groups and one hydroxyl group on the periphery. "ROMP-Capture-Release" was initially attempted, but it was found that the alkyne groups had to be TIPS-protected in order to avoid cross-metathesis during the "ROMP" reaction. However, the overall yield and efficiency of the TIPS-involved "ROMP-Capture-Release" route was so low that the large quantity of material required for device fabrication could not be obtained. Therefore, an alternative direct synthesis of the asymmetrical Pc by statistical condensation of two phthalonitriles was finally chosen. Pure asymmetrical hexaalkynyl-monohydroxy Pc was obtained after multi-stage column chromatography. Click reactions of this compound with several azides were also carried out.Chapter 6 summarizes the results presented in Chapters 2-5 and outlooks on some future directions that current research may follow.