Synthesis and characterization of the new ligand, 1,2,4-triazino[5,6-b]indol-3-ylimino methyl naphthalene-2-ol and its Ni(II) and Cu(II) complexes: comparative studies of their in vitro DNA and HSA Binding

A new ligand 1,2,4-triazino[5,6-b]indol-3-ylimino methyl naphthalene-2-ol ( HL ) was derived from 5H-[1,2,4]triazino[5,6-b]indol-3-amine and 2-hydroxy-1-naphthaldehyde. The metal complexes of the type [Ni(L)(Bipy)]1/2SO 4 ( 1 ), [Cu(L)(Bipy)(H 2 O) 2 ]1/2SO 4 ( 2 ), [Ni(L)(Phen)]1/2SO 4 ( 3 ) and [Cu(L)(Phen)(H 2 O) 2 ]1/2SO 4 ( 4 ) were synthesized. The ligand ( HL ) and complexes 1 – 4 were thoroughly characterized by elemental analysis and spectroscopic methods (FT-IR, ToF-MS, 1 H NMR, 13 C NMR), molar conductance and magnetic moment determination. The Ni(II) complexes 1 and 3 adopt the square planar geometry and Cu(II) complexes 2 and 4 acquire distorted octahedral arrangement. In vitro DNA binding behavior of ligand ( HL ) and metal complexes 1 – 4 was explored by fluorescence spectral and ethidium bromide studies. The outcomes reveal that the complexes interact with DNA via non-covalent groove binding and electrostatic interactions. The higher binding constant (K) values of 4.35 × 10 4 and 9.12 × 10 4 M −1 for complexes 2 and 4 indicate stronger binding ability with DNA. Moreover, in vitro human serum albumin (HSA) binding experiment with HL and complexes 1 – 4 reveals conformational modulations in the Trp-214 microenvironments in the subdomain IIA pocket. Graphical abstract