A novel di-iron ligand complex for water oxidation catalysis and the development of bis-bipyridinium-based gemini surfactants for template-directed self-assembly

This thesis reports the designs and synthetic routes for a variety of organic molecules that served as the starting materials for the construction of supramolecular complexes via non-covalent interactions. The first project involved the development of a rationally designed dinucleating ligand that would form various stable diiron complexes as potential water oxidation catalysts (WOCs). The WOCs can promote the clean production of hydrogen gas, a green and potential fuel to replace traditional carbon-based fuels, by lowering its cost and increasing its efficiency. The second research project focused on synthesizing novel bis-bipyridinium-based gemini amphiphiles that were capable of self-assembling or co-assembling with a template molecule (the neurotransmitter melatonin) to form ?-? donor-acceptor charge-transfer complexes. This research provided fundamental insights into the structure-property relationships between the amphiphiles and their self-assembly processes which are important for developing methodology that uses self-assembly to construct complex stimuli-responsive functional molecular architectures. The target compounds, which include the ligand and gemini amphiphiles were synthesized using a two-step SN2 route. Supramolecular complexes were formed from the combination of two species (1st: the ligand and an iron salt, and 2nd: the amphiphile and the template). The obtained compounds were characterized by various techniques including 1H-NMR, 13C-NMR, 2D-COSY, 2D-HSQC, and TOF-ESI-MS. The synthesis of the ligand was achieved with a yield of 86% for the 1st step and 45% for the second step. The ligand was later used to form diiron complexes which can be great WOCs due to their ability to form high valent intermediates for O-O bond formation. The synthesis of the gemini amphiphiles had a yield of 62% for 1st step and 62 – 79% for the 2nd step. The formation of ?-? donor acceptor charge transfer complexes were verified by UV-Vis, 1H-NMR, 2D-ROESY NMR, and 2D-DOSY NMR. Melatonin demonstrated its ability to serve as “molecular glue” that can minimize the Coulombic repulsion among positive charged tetracationic gemini amphiphiles as they underwent self-assembly. This resulted in 1) the formation of larger aggregates; 2) a more thermodynamically favorable self-assembly process; and 3) an overall increase in the efficiency of the amphiphiles to self-assemble into micellar superstructures at lower concentrations.