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.