Comparison of homoleptic and heteroleptic 2,2'-bipyridine and 1,10-phenanthroline ruthenium complexes as chemiluminescence and electrochemiluminescence reagents in aqueous solution.

We have conducted a comprehensive comparative study of Ru(bipy)(3)(2+), Ru(bipy)(2)(phen)(2+), Ru(bipy)(phen)(2)(2+), and Ru(phen)(3)(2+) as chemiluminescence and electrochemiluminescence (ECL) reagents, to address several previous conflicting observations and gain a greater insight into their potential for chemical analysis. Clear trends were observed in many of their spectroscopic and electrochemical properties, but the relative chemiluminescence or ECL intensity with a range of analytes/co-reactants is complicated by the contribution of numerous (sometimes opposing) factors. Significantly, the reversibility of cyclic voltammetric responses for the complexes decreased as the number of phenanthroline ligands was increased, due to the lower stability of their ruthenium(III) form in the aqueous solvent.

Evaluation of tris(4,7-diphenyl-1,10-phenanthrolinedisulfonate)ruthenium(II) as a chemiluminescence reagent.

Previous studies have suggested that tris(4,7-diphenyl-1,10-phenanthrolinedisulfonate)ruthenium(II) (Ru(BPS)(3)(4-)) has great potential as a chemiluminescence reagent in acidic aqueous solution. We have evaluated four different samples of this reagent (two commercially available and two synthesised in our laboratory) in comparison with tris(2,2'-bipyridine)ruthenium(II) (Ru(bipy)(3)(2+)) and tris(1,10-phenanthroline)ruthenium(II) (Ru(phen)(3)(2+)), using a range of structurally diverse analytes. In general, Ru(BPS)(3)(4-) produced more intense chemiluminescence, but the oxidised Ru(BPS)(3)(3-) species is less stable in aqueous solution than Ru(bipy)(3)(3+) and produced a greater blank signal than Ru(bipy)(3)(3+) or Ru(phen)(3)(3+), which had a detrimental effect on sensitivity.