The two independent (O^N^O) and (N^N) coordination sites of a newly synthesized bis 2-(hydroxyphenyl)-1,2,4-triazole platform have been exploited to prepare four monometallic neutral (O^N^O)Pt(II) complexes carrying DMSO, pyridine, triphenylphosphine or N-heterocyclic carbene (NHC) as fourth ligand. Then the second (N^N) coordination site was used to introduce an IR-active rhenium tricarbonyl entity, affording the four corresponding heterobimetallic neutral Pt(II)/Re(I) complexes as well as a cationic Pt(II)/Re(I) derivative. X-ray crystallographic studies showed that distortion of the organic platform occurred to accommodate the coordination geometry of both metal centers. No ligand exchange and no transchelation occurred upon incubation of the Pt(II) complexes in aqueous environment or in the presence of Fe(III), respectively. The ligand and the complexes antiproliferative activity was first screened on the triple negative breast cancer cell line MDA-MB-231. Then the IC50 of the most active candidates was determined on a wider panel of human cancer cells (MDA-MB-231, MCF-7 and A2780) as well as on a non-tumorigenic cell line (MCF-10A). Low micromolar activities were reached for the complexes carrying a DMSO ligand, making them the first examples of highly active though hydrolytically stable Pt(II) complexes. Finally, the characteristic mid-IR signature of the Re(CO)3 fragment in the Pt/Re heterobimetallic complexes was used to quantify their uptake in breast cancer cells.