[Ru(phen)(bpy) ₂ ] ²⁺ -type complexes with a P(O)(OEt) ₂ -substituted phen ligand are efficient photocatalysts for photoreactions proceeding via the electron transfer and energy transfer pathways.

Ru(ii) complexes with phosphonate-substituted phenanthroline ligands exhibited higher efficiency than the benchmark photocatalyst [Ru(bpy)₃]²⁺ in photoredox-catalyzed reactions and could be recycled through water extraction for reuse.

Photoredox-catalyzed phosphonylation of bromo-substituted 1,10-phenanthrolines under visible light irradiation was studied. The reaction was shown to proceed under mild conditions with Eosin Y as a photocatalyst in DMSO under blue light irradiation. It is transition-metal-free and affords the target phosphonate-substituted 1,10-phenanthrolines in moderate yields (26–51%) in 22 to 40 h. The rate and selectivity of the reaction depend largely on the position of the bromine atom, as well as on the nature and position of other substituents in the 1,10-phenanthroline core.