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)₃⁴⁻) 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)₃²⁺) and tris(1,10-phenanthroline)ruthenium(II) (Ru(phen)₃²⁺), using a range of structurally diverse analytes. In general, Ru(BPS)₃⁴⁻ produced more intense chemiluminescence, but the oxidised Ru(BPS)₃³⁻ species is less stable in aqueous solution than Ru(bipy)₃³⁺ and produced a greater blank signal than Ru(bipy)₃³⁺ or Ru(phen)₃³⁺, which had a detrimental effect on sensitivity. Although the complex is often depicted with the sulfonate groups of the BPS ligand in the para position on the phenyl rings, NMR characterisation revealed that the commercially available BPS material used in this study was predominantly the meta isomer.