Electrochemical Characterization of Platinum (II) Bipyridine Liquid Crystals
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SubjectScholarship Sewanee 2011; University of the South, Sewanee, Tennessee; Platinum; Electrochemistry; Liquid crystal; Bipyridine complexes
AbstractLiquid crystalline materials composed of a platinum center chelated by a bipyridine ring and additional ligands have been of immense interest in recent years for their interesting photochemical and electrochemical behavior. The selection of ligands has the ability to selectively tune the behavior of the molecule. In this study, platinum bipyridine systems with ester chains in either the 4-4 or the 5-5' positions on the bipryidine and dithiolate or phenyl acetylide ligands were examined with cyclic voltammetry and chronocoulometry. In solution, the dithiolate series exhibited oxidation-reduction behavior independent of the ester chain length, and the presence of two reversible reductions and one irreversible oxidation was consistent with prior studies. The reversible waves have been assigned as pi to pi* transitions on the bipyridine ring and a mixed metal ligand to ligand transition (MMLLCT). Phenyl acetylides were studied in solution and as thin films on ITO-covered glass working electrodes. In solution, the phenyl acetylides had a similar bipyridine pi to pi* transition in addition to MMLLCT. Position of the ester chain influences redox behavior by possibly facilitating oxidation, as the 5-5' system is completely reversible, whereas the 4-4' system is not. The 5-5' phenyl acetylide film on ITO exhibited some color changes unseen in similar films and is currently being studied with chronocoloumetry.
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