Synthesis, characterization, theoretical studies and biological activity of coordination compounds with essential metals containing N4-donor ligand 2,9-di(ethylaminomethyl)-1,10-phenanthroline

The work shows the synthesis and characterization of N4-donor L: 2,9-di(ethylaminomethyl)-1,10-phenanthroline and its coordination compounds with some divalent essential metals (Mn, Fe, Co, Ni Cu and Zn). L was obtained as the hydrochloride derivative H3LCl3. The complexes were synthesized by two routes: 1) using L as hydrochloride for Mn, Fe, Co and Zn complexes and 2) from L as a free base for Cu and Ni ones. [Co(HL)Cl-2]NO3 and [Zn(HL)Cl-2]Cl were crystallized and reveal that L is bound to metallic nuclei by only three nitrogen atoms. Cyclic voltammetry studies showed that L alone is capable of being reduced and in complexes, the potential of the coordinated compound process is lower. DFT calculations explain the observable redox behavior regarding HOMO-LUMO orbital energies. Also, the modeling of protonated species of the ligand L suggests that the tetradentate behavior depends on pH conditions of the synthesis. The antiproliferative activity observed on Entamoeba Histolytica and HeLa human tumor cell cultures confirmed that even if complexes are less active than the first choice drugs (metronidazole and cisplatin respectively), it exists a correlation between the observed cytotoxicity and the compounds redox potential. (C) 2017 Elsevier B.V. All rights reserved.