New modulated metallic macrocycles: Electrochemistry and their interaction with calf thymus DNA

New modulated pentacoordinate complexes [C17H34N7O2Cu]ClO4 (5), [C17H34N7O2Co]ClO4 (6), [C17H34N7O2Ni] ClO4 (7) have been synthesized by the interaction of 1,8-dihydro-1,3,6,8,10,13 Cu(II) (2), Co(II) (3), Ni(II) (4) hexaazacyclotetradecane complexes and Hsalea N-(2-hydroxy benzyl)-2-amino-1-ethanol ligand (1). All the complexes have been characterized by infrared, electron paramagnetic resonance, 1H and 13C nuclear magnetic resonance (NMR), 2D correlation spectroscopy NMR and ultraviolet-visible (UV-vis) spectroscopy. In all the complexes, the metal center is encapsulated by the Hsalea ligand in a pentacoordinate environment. Conductance measurements show that the complexes are ionic in nature. UV-vis absorption titration and viscometric studies have been carried out to ascertain the interaction of complexes 5 and 6 with calf thymus DNA (CT DNA). The experimental results suggest that complex 5 binds to CT DNA through partial intercalation of the aromatic ring into the base pair of DNA while complex 6 binds to CT DNA by electrostatic mode. The intrinsic binding constants Kb of complex 5 and 6 were found to be 6.8 × 10−5 M−1 and 1.8 × 10−4 M−1, respectively. The binding of complexes 5 and 6 with CT DNA has also been investigated by cyclic voltammetry.