Synthesis and characterization of new metal complexes containing Triazino[5,6-b]indole moiety: In vitro DNA and HSA binding studies

The present study reports the synthesis, structural characterization of Ni(II) (1,3) and Cu(II) (2,4) metal complexes of Schiff-base (L) derived from 5H-[1,2,4]triazino[5,6-b]indol-3-amine and salicylaldehyde moiety. The coordination sphere of Cu(II)/Ni(II) was completed by tethering secondary ligand 2,2'-Bipyridine and 1,10 phenanthroline to obtain the final complexes 1-4 , respectively. The spectral analysis of complexes 1 and 3 suggested square planar geometry while complexes 2 and 4 acquire the octahedral geometry around the metal centers. In vitro DNA binding profiles of the newly synthesized metal complexes 1-4 with calf thymus DNA (CT DNA) were explored by employing electronic absorption titrations and fluorescence spectral studies. The results revealed that complexes 1-4 bind to DNA through electrostatic surface binding mode along with partial intercalation in the minor groove. Moreover, complexes 3 and 4 have stronger DNA binding propensity with higher intrinsic binding constant K-b values of 1.9 x 10(4) and 4.8 x 10(4) M-1 , respectively. Additionally, HSA binding studies of ligand L and metal complexes 1-4 support the static quenching mechanism and alterations in the microenvironment around Trp-214 residues causing conformational distortions in the HSA secondary structure. Furthermore, molecular docking studies of complexes 3 and 4 with DNA and HSA confirms that both specifically binds in G-C rich regions of the DNA minor groove and subdomain IIA pocket of HSA near the Trp-214 residue. (C) 2021 Elsevier B.V. All rights reserved.