Synthesis, characterization and antitumor properties of two highly cytotoxic ruthenium(iii) complexes with bulky triazolopyrimidine ligandsElectronic supplementary information (ESI) available: CIF files and crystals packing of both ruthenium(iii) compounds 1,2; CV and EPR spectra; comparison of X-X distances and X-M-X angles in the studied octahedral ruthenium complexes. CCDC 7878211 and 9018532. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt32216a

Two ruthenium( iii ) complexes composed of 5,7-ditertbutyl-1,2,4-triazolo[1,5- a ]pyrimidine (dbtp) ligands were prepared and structurally characterized by X-ray crystallography, IR, UV-Vis, EPR spectroscopies and cyclic voltammetry (CV). The crystal structures of trans -[RuCl 3 (H 2 O)(dbtp) 2 ] 1 and mer -[RuCl 3 (dbtp) 3 ]·0.815OCMe 2 2 showed slightly distorted octahedral geometries with two 1 or three 2 monodentate dbtp ligands bound in a head-to-head orientation. In both complexes, the heterocyclic dbtp ligands were bound to the ruthenium( iii ) ion through the N3 nitrogen atom. A cytotoxicity assay of both ruthenium( iii ) compounds against two human cell lines (A549 - non-small cell lung carcinoma and T47D - breast carcinoma) was performed. The ruthenium( iii ) complexes showed excellent cytotoxicity with IC 50 values in the range of 0.02-2.4 μM against both cancer cell lines. In addition, the in vitro cytotoxic values of the ruthenium( iii ) compounds were 35-times for 1 and 172-times for 2 higher against T47D than the clinically used antitumor drug cisplatin. Both ruthenum( iii ) complexes showed excellent cytotoxicity against two cancer cell lines: A549 - non-small cell lung carcinoma and T47D - breast carcinoma.