First- and Second-Generation Heterometallic Dendrimers Containing Ferrocenyl–Ruthenium(II)–Arene Motifs: Synthesis, Structure, Electrochemistry, and Preliminary Cell Proliferation Studies

Four
first- and second-generation heterometallic ferrocenyl derived p-cymene-Ru­(II) metallodendrimers, of general formula [DAB-PPI­{(η6-p-cymene)­Ru­((C7H5NO)-κ2-N,O)­PTA­(5-ferrocenylvinyl)}n]­[PF6]n and [DAB-PPI­{(η6-p-cymene)­Ru­((C6H5N2)-κ2-N,N)­Cl­(5-ferrocenylvinyl)}n]­[PF6]n (where n = 4 (G1), 8 (G2), DAB = 1,4-diaminobutane, PPI
= poly­(propyleneimine), PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]­decane)
have been synthesized. All complexes have been characterized using
analytical (i.e., HR-ESI mass spectrometry, HPLC, elemental analysis,
and cyclic voltammetry) and spectroscopic (i.e., 1H and 13C­{1H} NMR and infrared) methods. Electrochemical
studies reveal that the N,O-p-cymene-Ru­(II)-PTA complexes result in two irreversible
redox processes (oxidation of the Fe­(II) and Ru­(II) centers), while
the N,N-p-cymene-Ru­(II)
complexes display one reversible wave (Fe­(II)/Fe­(III) couple). Heterometallic
model complexes have been prepared, and for one of the complexes,
its molecular structure has been determined by single-crystal X-ray
crystallography. In vitro antiproliferation activity
of the dendritic ligands and their complexes were evaluated against
A2780 and A2780cisR human ovarian cancer lines, the SISO human cervix
cancer line, the LCLC-103H human lung cancer line, and the 5637 human
bladder cancer line. Nine of the twelve compounds slowed the growth
of the ovarian cancer cell lines by more than 50% at equi-iron concentrations
of 5 μM.