| dc.description.abstract | During the past four decades, the field of molecular electronics relied on the design of molecules capable of fulfilling the roles of electronic components such as wires, diodes, and rectifiers. The work described in this thesis involved developing a synthetic strategy to build linear 6,6′-biazulenic -linkers asymmetrically terminated with mercapto and cyano groups along their molecular axes as well as probing electronic coupling of the azulenic sub-units of several asymmetrically substituted 6,6′-biazulene derivatives by cyclic voltammetry and infrared spectroscopy. Chapter I discusses self-assembled monolayers of organic molecules chemisorbed to Au(111) surfaces through thiolate junctions, with special emphasis on the thiolate-gold coordination and factors affecting monolayer formation. Thin film characterization methods employed in this thesis, including reflection-absorption infrared spectroscopy (RAIRS) and optical ellipsometry, are also discussed. An example of how RAIRS selection rules are used to characterize orientation and packing of self-assembled monolayers with respect to gold surfaces is provided. Chapter II offers background on the reactivity and physicochemical properties of azulene followed by a discussion of silicon-based electronic components and their possible molecular counterparts. Applications of azulenic and biazulenic derivatives as potential wires and diodes are considered, particularly those featuring asymmetrically substituted 6,6′-biazulenic motifs. An overview of self-assembly of 6,6′-biazulenic derivatives through isocyano and thiolate junctions on Au(111) surfaces is provided, focusing on using RAIRS and ellipsometry to investigate packing within these monolayer films and orientation of their molecular constituents with respect to the gold surface. Chapter III describes a synthetic approach to asymmetrically functionalize the 6,6′-biazulenic scaffold with cyano (-CN) and mercapto (-SH) groups at the 2 and 2′ positions of the 6,6′-biazulenic scaffold. Spectroscopic characterization of the asymmetrically substituted 6,6′-biazulenic precursors is discussed, as well as the changes in electronic absorption caused by different functionalities along the molecular axis of the biazulenic scaffold. The extent of electronic coupling between the azulenic sub-units of the 6,6′-biazulenic π-linker is also explored through cyclic voltammetry and infrared spectroscopy. Experiments on the self-assembly of the -SH and -CN functionalized 6,6′-biazulene on Au(111) are outlined and discussed. However, attempts at gathering IR spectroscopic and ellipsometric evidence of monolayer formation were unsuccessful. Several experimental suggestions are offered for future work on self-assembly of the aforementioned π-linker. The final chapter of this thesis summarizes key conclusions and offers future work suggestions pertaining to the new 6,6′-biazulenic π-linker described in Chapter III towards a better understanding of its applicability in the field of molecular electronics. The experimental suggestions include several changes to the conditions for monolayer formation, conductivity measurements to be performed with conductive atomic force microscopy, and probing electron transport dynamics using Auger electron spectroscopy. Additionally, several synthetic alternatives to the synthesis used in chapter III are explored with the goal of improving atom economy and increasing overall yields. | |
