A Novel Series of Viologen-Containing Dendrimers

by Bhattacharya, Papri

This dissertation investigates the synthesis, characterization and electrochemical properties of viologen-containing dendrimers. Additionally, the self-assembled system of resorcinarenes was investigated with paramagnetic guests using EPR and 1H NMR techniques. Chapter one is a brief introduction to the dendrimers and describes its evolution, structural features, synthetic methods and emerging applications to various fields of research such as catalysis, material science, drug delivery and medicine. Chapter two describes the synthesis, characterization and electrochemical properties of a new series of dendrimers. These dendrimers have a viologen unit at the core surrounded by Newkome and Fr¨¦chet dendrons. The potentials of two consecutive one-electron reductions of the viologen core were determined by cyclic voltammetry. The electrochemistry of viologen unit showed a distinct and obvious trend. Newkome and Fr¨¦chet dendrons having different functional groups as repeating units has opposite effect on the half-wave potentials. The overall effect of these two dendrons is reflected by the corresponding reduction potentials. The redox site encapsulation by the Fr¨¦chet and Newkome dendrons is indicated by the attenuation in heterogeneous electron transfer rate constants. Chapter three describes the probing of self-assembled capsule of resorcinarenes with 4-amino tempo and 4-trimethyl-ammonium tempo derivative. EPR spectroscopy and 1H NMR spectroscopy were used to investigate the nature of complexations involved in these systems. We observed a subsequent change in their spectroscopic parameters. Careful investigation of rotational correlation times and NMR line-widths at half height revealed that 4-trimethyl-ammonium tempo has stronger binding affinity with these capsules compared to 4-amino tempo due to favorable cation ¨C¦Ð interactions.