Synthesis & Development of Symmetric and Asymmetric Silicon Phthalocyanines Functionalized for Click-Chemistry

Abstract

Although organic field-effect transistors (OFETs) are still advancing flexible and affordable electronics, their wider application is still constrained by their instability, processing difficulties, and ideal charge transfer properties, among other challenges. Because of their environmental stability, customizable optoelectronic characteristics, and two axial coordination sites that allow structural manipulation without affecting the phthalocyanine core, silicon phthalocyanines (SiPcs) present a viable platform to overcome these constraints. The design, synthesis, and characterisation of several axially substituted SiPc compounds intended to improve solution processability, provide clickable functionality, and modify solid-state organization for OFET applications are presented in this thesis. Optimized techniques were used to create symmetrical and asymmetrical SiPcs with benzyloxy-alkyne or thienyl-alkyne axial ligands, with a focus on regulating axial substitution patterns. The effects of axial ligand identity on solubility, aggregation behavior, frontier orbital energies, and redox stability were assessed through extensive structural, optical, and electrochemical characterization, including NMR spectroscopy, mass spectrometry, UV-vis absorption, and cyclic voltammetry. Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions were carried out on one of the SiPc derivatives isolated to demonstrate the functional utility of the designed ligands. This established a basis for future polymer-SiPc covalent hybrid systems achieved via click chemistry and supports their compatibility with post-synthetic modification. The promise of these materials as n-type semiconductors is demonstrated by preliminary OFET device integration, where axial asymmetry and alkyne-based substituents provide chemical diversification. All in all, this work develops a modular design approach for SiPc-based organic semiconductors, offering fresh perspectives on how axial functionalization controls structure-property relationships and facilitating the creation of covalently linked polymer-SiPc architectures for stable, high-performance OFETs in the future.