DNA interaction with Al–N,N′-bis(salicylidene)2,2′-phenylendiamine complex

The Al(III) complex, [Al(salophen)2H2O]NO3, was synthesized and characterized by spectroscopic (NMR and FT-IR) techniques. Then the binding of Schiff base complex of [Al(salophen)]+ type, where salophen denotes N,N′-bis(salicylidene) 2,2-phenylendiamine to calf thymus DNA, has been investigated by spectrophotometric, circular dichroism, spectrofluorometric, melting temperature and viscosimetric techniques. This Al(III) complex showed absorption hyperchromism in the range of 310–390 nm, increase in melting temperature, some structural changes in specific viscosity, when bound to calf thymus DNA. The binding constant has been determined using absorption measurement and found to be 1.82 × 103 M−1 and 1.31 × 103 M−1 in HEPES and Tris–HCl buffers, respectively. Also the fluorescence spectral characteristics and interaction of Al–salophen complex with DNA have been studied. Al–salophen bound to DNA showed a marked increase in the fluorescence intensity along with a bathochromic shift (5 nm). The intersection point of the binding isotherm indicated a binding site size of 12 bp per bound complex molecule in both HEPES and Tris–HCl buffers. The experimental results showed that the Al–salophen complex bound to DNA by non-intercalative mode and major groove binding was the preferred mode of interaction