Synthesis, structure, photophysics and electrochemiluminescence of Re(i) tricarbonyl complexes with cationic 2,2-bipyridyl ligands

Two water soluble Re(i) tricarbonyl diimine complexes containing cationic 2,2'-bipyridyl ligands [Re(L1)(CO)(3)(AN)](2+) (1) and [Re(L2)(CO)(3)(AN)](3+) (2) (L1 and L2: a cationic 2,2'-bipyridyl ligand, AN: acetonitrile) were synthesized and characterized. Their photophysical, electrochemical and electrochemiluminescent properties were investigated. The crystal structures of the two complexes have also been determined. Electrochemiluminescence (ECL) of the two complexes 1 and 2 have been studied in aqueous buffer solution in the presence of co-reactant tri-n-propylamine (TPrA) or 2-(dibutylamino)ethanol (DBAE) at a Au working electrode. The ECL behavior of the complexes was also studied in the presence of several surfactants such as Triton X-100 and Zonyl FSN. The ECL signals of the rhenium(i) complex were enhanced about 190-fold and 70-fold at a Au electrode in the presence of Triton X-100 for the [Re(L1)(CO)(3)(AN)](2+)/TPrA and [Re(L1)(CO)(3)(AN)](2+)/DBAE systems, respectively.