As a contribution to the identification of the relevant species for biological activity and the understanding of structure–activity relationships of [VIVO(L-2H)(NN)] antitrypanosomal complexes (NN is a bidentate polypyridyl DNA intercalator; L is a tridentate salicylaldehyde semicarbazone derivative), new [VVO2(L-2H)] complexes and [VIVO(L-2H)(NN)] complexes including bipy or dppz (dipyrido[3,2-a: 2′,3′-c]phenazine) co-ligands are prepared and characterized in the solid state and in solution. Their activity is evaluated on Trypanosoma cruzi. The lipophilicity, as structural descriptor related to bioactivity, of the whole [VIVO(L-2H)(NN)] series is determined. Furthermore, the antiproliferative effect of those new compounds showing activity against T. cruzi is evaluated on the genetically related parasite T. brucei with the aim to develop broad spectrum agents. The new [VIVO(L-2H)(dppz)] complexes are about ten to fifteen times more toxic to T. cruzi than the bipy analogues and show quite good in vitro activity on T. brucei brucei. They are shown to interact with DNA, suggesting that this biomolecule may be the parasite target. The stability of the VIVO-complexes in solution is accessed by several techniques. Globally the data suggest that the relevant species for biological activity are the [VIVO(L-2H)(NN)] compounds, their order of activity being dependent on the NN nature, but not much on the substitution on the salicylaldehyde semicarbazone moiety. A parabolic relationship between biological response and lipophilicity (determined as RM = log [(1 / Rf) − 1] by a TLC method) is obtained. From this correlation an optimum RM value, close to 1.44, was found, which may be used as design guide for future development of antitrypanosomal compounds. Fil: Fernández, Mariana. Universidad de la República; Uruguay Fil: Becco, Lorena. Universidad de la República; Uruguay Fil: Correia, Isabel. Universidade Técnica de Lisboa; Portugal Fil: Benítez, Julio. Universidad de la República; Uruguay Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina Fil: Echeverría, Gustavo Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Medeiros, Andrea. Universidad de la República; Uruguay. Instituto Pasteur de Montevideo; Uruguay Fil: Comini, Marcelo. Instituto Pasteur de Montevideo; Uruguay Fil: Lavaggi, María Laura. Universidad de la República; Uruguay Fil: González, Mercedes. Universidad de la República; Uruguay Fil: Cerecetto, Hugo. Universidad de la República; Uruguay Fil: Moreno, Virtudes. Universidad de Barcelona; España Fil: Costa Pessoa, Joao. Universidade Técnica de Lisboa; Portugal Fil: Garat, Beatriz. Universidad de la República; Uruguay Fil: Gambino, Dinorah. Universidad de la República; Uruguay