The biological activities of the hydroxy, amino and carboxy diruthenium compounds 2-4 were discussed elsewhere . While 4 has limited effect on both HFF viability and parasite proliferation at the tested concentrations, 2 and 3 almost completely abolished parasite proliferation at 1 µM but are also toxic to the host cells at this concentration. Methylene hydroxy compound 5 has a strong effect on the parasite proliferation even at 0.1 µM, while being less toxic to the host cells compared to phenol derivative 2. Like their respective diruthenium hydroxy and amine intermediates 2 and 3, both alkyne ester and amide derivatives 6 and 7 greatly impact T. gondii proliferation but affect significantly less the HFF viability. Related to carboxy analogue 4, alkyne amide 8 shows a higher impact on parasite proliferation but also increased toxicity to the host cells. Diruthenium azide analogue 9 efficiently inhibits parasite proliferation even when applied at 0.1 µM but reduces HFF viability up to 64% when applied at 1 µM, while glucose azide derivative 10 exhibits neither antiparasitic activity nor toxicity at both tested concentrations.