Synthesis, structure, DNA binding and photonuclease activity of a nickel(II) complex with a N,N′-Bis(salicylidene)-9-(3,4-diaminophenyl)acridine ligand

A new class of salen functionalized novel ligand N,N′-Bis(salicylidene)-9-(3,4-diaminophenyl)acridine, H2daasal (two potential intercalators, salen and acridine, which are linked together via C–C bond) and its metal complex [Ni(daasal)] have been synthesized and characterized by X-ray diffraction, elemental analysis, UV–Vis, IR, 1H NMR, MALDI-TOF mass spectrometry and cyclic voltammetry methods. From the crystal structure, the salphen moiety is not coplanar with the acridine ring, having a dihedral angle of 68° and 76° in both H2daasal and [Ni(daasal)], respectively. [Ni(daasal)] shows a reversible oxidation cyclic voltammetric response near 1.03 V versus SCE in CH3CN (0.1 M TBAP) assignable to the Ni(II)/Ni(III) couple. The interaction of these compounds with calf-thymus (CT) DNA was examined using spectroscopic and viscosity measurements. These studies reveal that both compounds bind to CT DNA via an intercalative mode. Molecular-modeling studies also support an intercalative mode of binding to the model duplex d(CGCAATTGCG)2 possibly from the major groove with a slight preference for GC rich region. Additionally, [Ni(daasal)] promotes the cleavage of plasmid pBR322 DNA upon irradiation under terminal oxidant Oxone.

A new [Ni(daasal)] was synthesized and structurally characterized. It was binding strongly to CT DNA via intercalation than its free ligand, confirmed by spectroscopic techniques. It promotes cleavage of plasmid pBR322 DNA upon irradiation in presence of KHSO5. Molecular modelling studies support intercalative interactions, possibly through major groove with a slight preference for the GC than the AT rich sequence.Figure optionsDownload as PowerPoint slideHighlights
► A new [Ni(daasal)] with bifunctional intercalator (H2daasal) was synthesized.
► Effect of central Ni(II) ion on DNA binding and photocleavage were studied in detail.
► It binds to CT DNA by intercalation at major groove with a fondness for GC than AT.
► It promotes DNA cleavage on irradiation in presence of KHSO5 in aerobic conditions.