Electrochemisty and electrogenerated chemiluminescence of Ru(phen)₂dppz(BF₄)₂ both free and intercalated into DNA

Abstract

Ruthenium (II) bisphenanthroline dipyridophenazine, Ru(phen)2dppz2+, exhibits first oxidation and reduction voltammetric responses which correlate well with the UVvis spectroscopy and are typical to the compound class. The complex proves energy sufficient for electrogenerated chemiluminescence (ECL), and does so in aqueous media with co-reactants, also similar to its phenanthroline and bipyridine analogues. However, this behavior is curious since this compound’s aqueous photoluminescence (PL) is undetectable but exhibits ‘light switch’ behavior upon intercalation into both calf thymus DNA and other polynucleotides in that the PL greatly increases. The ECL of both the free and intercalated complex is presented as well as scanning electrochemical microscopy (SECM) studies to understand the complex’s kinetic behavior in water upon oxidation. In an effort to understand the SECM results, the program COMSOL Multiphysics is used to model the EC’ (catalytic) following reaction. The simulation results are validated using the ferrocyanide/cysteine system, which is known to exhibit the EC’ mechanism.