Study of new functional organic materials based on pi-conjugated oligomers and [60]fullerene

Zhou, Ningzhang (2008) Study of new functional organic materials based on pi-conjugated oligomers and [60]fullerene. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

In recent years, monodisperse and structurally defined π-conjugated oligomers have attracted great attention of materials chemists, owing to their fascinating applications as novel nanoscale building blocks for various molecular based electronic, photonic, and optoelectronic devices. To date, the molecular architectures of functional π-oligomers have evolved beyond the realm of simple one-dimensional (1D) linear conjugation and started to enlist some unique two-dimensional (2D) and three-dimensional (3D) structures. Such progress has opened a new avenue to develop and explore esoteric molecular materials with appealing and unprecedented molecular properties and functions, which can be of great use in various device fabrications, for instance, highly efficient organic light-emitting diodes (OLEDs), field- effect transistors (FETs), photovoltaic (PV) or solar cells, chemical and biological sensors, and so on. -- The work of this thesis is primarily dedicated to exploring a class of new hybrid organic materials based on π-conjugated oligomers and Buckminster[60]fullerene (C₆₀), and the detailed studies of which are divided into three major projects. The first project investigates a series of dumbbell shaped C₆₀-π-C₆₀ triads, in which the π units are designed to be linear or cruciform shaped OPE/OPV co-oligomers. The second project deals with a series of bifullerene endcapped oligoynes, and the third project embarks on a group of novel H-shaped OPE/OPV co-oligomers. The chemical synthesis of these conjugated oligomers and C₆₀ derivatives has been implemented on the basis of various classical and modern organic synthetic methodologies, such as Arbuzov reaction, Horner-Wittig reaction, Sonogashira coupling and Hay coupling. In particular, an in situ ethynylation protocol has been extensively employed in the synthesis of numerous C₆₀ derivatives throughout this thesis work. Subsequent to the synthesis, the compounds obtained are subjected to comprehensive property characterizations using UV-Vis absorption and fluorescence spectroscopy to disclose their π-electronic characteristic, cyclic voltammetry (CV) to probe their redox behavior, differential scanning calorimetry (DSC) to probe their solid-state reactivity, and atomic force microscopy (AFM) to reveal their surface morphologic features at the microscopic level. -- In this thesis, a number of efficient synthetic strategies for novel 1D and 2D conjugated OPE/OPV co-oligomers, linear and star-shaped phenylene-oligoynes, and related multiple C₆₀ adducts have been successfully established. Insight into the essential structure-property relationships of these novel π-conjugated molecular systems has been gained by comparative studies. Finally, some of the molecules are found to display appealing molecular properties and functions that portend practical uses in organic photovoltaic and nonlinear optical materials as well as molecular sensing devices.

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