Site-Selective DNA Photocleavage Involving Unusual Photoinitiated Tautomerization of Chiral Tridentate Vanadyl(V) Complexes Derived from N-Salicylidene £\-Amino Acids

(Chemical equation presented) 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 μM. 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.