Light Triggers the Antiproliferative Activity of Naphthalimide-Conjugated (η 6 -arene)ruthenium(II) Complexes.

We report the synthesis and characterization of three half-sandwich Ru(II) arene complexes [(η 6 -arene)Ru(N,N')L][PF 6 ] 2 containing arene = p-cymene, N,N' = bipyridine, and L = pyridine meta- with methylenenaphthalimide (C1), methylene(nitro)naphthalimide (C2), or methylene(piperidinyl)naphthalimide (C3). The naphthalimide acts as an antenna for photoactivation. After 3 h of irradiation with blue light, the monodentate pyridyl ligand had almost completely dissociated from complex C3, which contains an electron donor on the naphthalimide ring, whereas only 50% dissociation was observed for C1 and C2. This correlates with the lower wavelength and strong absorption of C3 in this region of the spectrum (λ max = 418 nm) compared with C1 and C2 (λ max = 324 and 323 nm, respectively). All the complexes were relatively non-toxic towards A549 human lung cancer cells in the dark, but only complex C3 exhibited good photocytoxicity towards these cancer cells upon irradiation with blue light (IC 50 = 10.55 ± 0.30 μM). Complex C3 has the potential for use in photoactivated chemotherapy (PACT).