Supramolecular architecture in an oxovanadium(V)-schiff base complex: Synthesis, Ab initio structure determination from X-ray powder diffraction, DNA binding and cleavage activity

The synthesis, spectroscopic characterization, X-ray powder structure determination, and thermal behavior of a binuclear bis(mu-oxo)-bridged vanadium(V) complex, [(VO2L2)2], L = N,N'-dimethylenediamine(o-hydroxyl acetophenon), along with its DNA binding ability and photoinduced DNA cleavage activity, have been described. The compound crystallizes in a monoclinic system with a = 7.679(3) angstrom, b = 12.020(5) angstrom, c = 13.882(6) angstrom, beta = 90.799(4)degrees, space group P2(1)/c, and Z = 2. The crystal structure has been solved from laboratory X-ray powder diffraction data using the direct space approach and refined by the Rietveld method. The dimeric complex consists of two edge-sharing vanadium octahedra with each metal center coordinated to one oxo-, one phenolate-, and two bridging-oxygen ligands, and two nitrogen donor atoms. The molecular structure reveals a two-dimensional grid of R-4(4)(24) rings in the (011) plane, which on combination with one-dimensional polymeric chains along the [100] direction, forms a novel three-dimensional supramolecular framework. Thermogravimetric analysis of the complex indicates multiple overlapping decornposition steps in the temperature range 180-800 degrees C with the end product being V2O5. The complex binds to double-stranded DNA giving a K-app value of 1.56 x 10(7) M-1 and displays DNA cleavage activity on UV (300 nm) irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species.