In the search of an effective chemotherapy for the treatment of cancer, in this work we describe the synthesis, characterization and biological activity of two new platinum complexes. The general formula is [Pt2(L)(X)4], where L was 1,2,4,5-tetrakis((1H-pyrazol-1-yl)methyl)benzene and X were iodine (1) and chlorine (2). The most probable structure was established through a combination of spectroscopic analysis and density functional theory (DFT) calculations. Studies of interaction of complexes with DNA were carried out, and the results by spectroscopic titrations, thermal denaturation and viscosity, showed noncovalent interactions of complexes with DNA. The comet assay showed damage to cellular DNA. Inhibition assays of thioredoxin reductase (TrxR) were carried out, and the compounds showed notable inhibitory activity on the enzyme in a concentration dependent manner, with IC50 values of 3.9 and 3.5 nM for 1 and 2 respectively. Complex 2 exhibited greater inhibitory effects than complex 1 against all the tumor cell lines, with growth inhibitory effects superior to cisplatin in some cases.