Efficient Inhibition of Telomerase by Nickel-Salophen Complexes.

Four nickel(II)-salophen complexes containing alkyl-imidazolium chains connected at the ortho or meta positions were prepared: N,N'-bis(2-hydroxy-4-methyl-3H-imidazol-1-iumbenzylideneamino) phenylenediamine (1), N, N'-bis(2-hydroxy-3-methyl-3H-imidazol-1-iumbenzylideneamino) phenylenediamine (2), N, N'-bis(2-hydroxy-3-methyl-3H-imidazol-1-iumbenzylideneamino) methyl-3H-imidazol-1-iumphenylenediamine (3), and N,N'bis(2-hydroxy-4-methyl-3H-imidazol-1-iumbenzylideneamino)methyl-3H-imidazol-1-iumphenylenediamine (4). They protect G-quadruplex DNA (G4-DNA) against thermal denaturation and show K-A values in the range of 7.4 x 10(5) to 4 x 10(7) m(-1) for G(4)-DNA models. Complex 4 exhibits an IC50 value of 70 nm for telomerase inhibition.