Enantiopure Lanthanide Complexes Incorporating a Tetraazatriphenylene Sensitiser and Three Naphthyl Groups: Exciton Coupling, Intramolecular Energy Transfer, Efficient Singlet Oxygen Formation and Perturbation by DNA Binding

In cationic nine-coordinate chiral terbium and europium complexes incorporating exciton-coupled naphthyl groups and a tetraazatriphenylene sensitising chromophore, efficient intramolecular energy transfer occurs leading to population of the naphthyl triplet state. With the terbium complex, the absolute quantum yield of singlet oxygen formation is 51% (lambda(exc) 355 nm), and for the Eu complex the intensity of metal-based emission increases by up to 350% on binding to poly(dGdC) or calf-thymus DNA, and was greater for the delta-isomer.