Two copper complexes from two novel naphthalene-sulfonyl-triazole ligands: Different nuclearity and different DNA binding and cleavage capabilities

Abstract

[EN] Two novel naphthalene-sulfonyl-triazole ligands, 5-amino-N1-(naphthalen-3-ylsulfony1)-1,2,4-triazole (anstrz) and 3,5-diamino-N1-(naphthalen-3-ylsulfony1)-1,2,4-triazole (danstrz), purposely designed to interact with DNA, have been prepared for the first time and then fully characterized by H-1, C-13 NMR and IR spectroscopy, mass spectrometry and elemental analysis. The crystal structures of two copper complexes of these derivatives, i.e. [Cu(anstrz)(4)(NO3)(2)]center dot 4CH(3)OH (1), mononuclear, and [Cu(danstrz)(mu-OAc)(2)](2)center dot 2(danstrz) (OAc = acetato) (2), dinuclear, have been determined by single-crystal X-ray diffraction. In both cases the ligand coordinates in a monodentate fashion via the N4 nitrogen atom of the triazole ring. Compound 2, an example of paddle wheel type copper acetate, presents a Cu - Cu' distance of 2.667(1) angstrom. As a result of strong stacking interactions and intense H-bonds, the structure of 2 constitutes a MOF (metal-organic framework). Besides, this dinuclear compound exhibits a very strong antiferromagnetic coupling (J = -324 cm(-1)) and a silent X-band EPR at room temperature. The affinity toward DNA of 1 and 2 has been examined by fluorescence emission spectroscopy, thermal denaturation and viscosimetry assays. The apparent binding constant (K-app) values of 2.2 x 10(7) M-1 for 1 and 2.6 x 10(7) M-1 for 2 suggest important DNA interaction. The dinuclear compound (2) intercalates and produces a high change in the T-m. Both compounds promote DNA scission in the presence of H2O2/ascorbate (1) or ascorbate (2) through oxidative mechanism. The possible reasons for the higher DNA affinity and the more efficient DNA cleavage displayed by compound 2 in relation to compound 1 are discussed.