• Synthesis of five diorganotin(IV) complexes. • Structural characterization by FT-IR, 1H, 13C NMR spectroscopy and mass spectrometery. • Single crystal X-ray analysis confirms the solid state molecular structure of complexes with seven coordinated tin center and pentagonal bipyramidal geometry. • DNA interaction study through UV-Vis spectroscopy, viscometery and cyclic voltametery • Antioxidant activity and cytotoxicity against human breast cancer cell line MDA-MB-231 Five new organotin(IV) complexes, Me 2 SnL (1), n -Bu 2 SnL (2), tert -Bu 2 SnL (3), Ph 2 SnL (4) and n -Oct 2 SnL (5), have been synthesized from the reaction of R 2 SnCl2 (R= Me, Bu, tert -Bu, Ph, Oct) with N'-(3-ethoxy-2-hydroxybenzylidene)formohydrazide (H 2 L). The structural elucidation of synthesized compounds was done by FT-IR, 1H-NMR, 13C-NMR spectroscopy and single-crystal X-ray analysis. Crystallographic data of complex (1) showed seven coordinated central tin atom with distorted pentagonal bipyramidal geometry. Where in solution the Sn atom of synthesized complexes exhibit five coordination, confirmed from 1H-NMR. The results from DNA interaction studies via UV-visible spectroscopy, viscosity, cyclic voltammetry, and differential pulse voltammetry (DPV) suggested an intercalative mode of interaction between the synthesized compounds and SS-DNA. Furthermore, the complexes interact more significantly than ligand. Electrochemical and thermodynamic parameters, including diffusion coefficient, ∆H, ∆G, and ∆S, were calculated using cyclic voltammetry data. The linear plot of peak current (I) vs. square root of the scan rate (υ1/2) indicated the electrochemical processes to be diffusion controlled. The DPPH free radical scavenging assay results showed that complex (4) is an active antioxidant. In-vitro cytotoxicity of the synthesized compounds was determined on human breast cancer cell line MDA-MB-231 using tetrazolium-based MTT assay, and complexes (2) , (3) and (4) showed significant cytotoxic activity. The structure-activity relationships may be utilised to direct the optimization of the activity of agents from this class of compounds by comparing the specifics of the compound structures, their DNA binding, and toxicity. DNA binding interaction of the new diorganotin(IV) complexes was studied by UV-Visible spectrophotometry, viscometry and electrochemical techniques. The antioxidant activity and cytotoxicity against human breast cancer cell line MDA-MB-231 was also determined. [Display omitted] [ABSTRACT FROM AUTHOR]