Neutral and cationic multinuclear half-sandwich rhodium and iridium complexes coordinated to poly(propyleneimine) dendritic scaffolds: Synthesis and cytotoxicity

The development of multinuclear pentamethylcyclopentadienyl (Cp*) rhodium and iridium complexes from first- and second-generation 2-iminopyridyl and salicylaldimine based poly(propyleneimine) dendrimer scaffolds of the type, DAB-(NH2)n (n = 4 or 8, DAB = diaminobutane) has been accomplished. Eight compounds were synthesised, viz. (Cp*MCl)4Gn (1–8), by first reacting DAB-(NH2)n with either 2-pyridinecarboxaldehyde or salicylaldehyde and subsequently metallating the Schiff-base dendrimers with [Cp*MCl2]2 (where M = Rh, Ir). Related mononuclear complexes [Cp*MCl(L)] (L = iminopyridyl or salicylaldimine) (9–12) were obtained in a similar manner. The molecular structures of 9–12 have been determined by single-crystal X-ray diffraction analysis and the in vitro anticancer activities of 1–12 were evaluated against the A2780 and A2780cisR human ovarian carcinoma cell lines.

Graphical abstractSeveral multinuclear neutral and cationic rhodium(III) and iridium(III) complexes containing N,N and N,O Schiff-base ligands based on a poly(propyleneimine) dendritic scaffold were synthesized. These metallodendrimers showed moderate to high antiproliferative activity in human ovarian cancer cell lines.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Polynuclear rhodium and iridium metallodendrimers have been prepared. ► Neutral Rh(III) and Ir(III) dendrimers were synthesized containing salicylaldimine ligands. ► Cationic Rh(III) and Ir(III) dendrimers were synthesized containing iminopyridyl ligands. ► The anticancer activity of the metallodendrimers was evaluated. ► A clear correlation between the dendrimer size and its cytotoxicity is observed.