Site-selective DNA photocleavage involving unusual photoinitiated tautomerization of chiral tridentate vanadyl(V) complexes derived from N-salicylidene alpha-amino acids.

The titled vanadyl(V) complexes serve as efficient reagents for cleaving supercoiled plasmid DNA by photoinitiation. Complex 3d, derived from 2-hydroxy-1-naphthaldehyde and l-phenylalanine, exhibits a unique wedge feature, inducing a site-selective photocleavage at the C22-T23 of the bulge backbone for a HIV-27 DNA system at 0.1-5 muM. Transient absorption experiments for 3d indicate the involvement of LMCT with concomitant tautomerization, leading to an o-quinone-methide V-bound hydroxyl species responsible for the cleavage profiles. [structure: see text]