Binuclear dichlorido(η 6 ‐ p ‐cymene)ruthenium(II) complexes with bis(nicotinate)‐ and bis(isonicotinate)‐polyethylene glycol ester ligands

Neutral binuclear ruthenium complexes 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 of the general formula [{RuCl 2 (η 6 ‐ p ‐cym)} 2  μ‐(N ∩ N)] (N ∩ N = bis(nicotinate)‐ and bis(isonicotinate)‐polyethylene glycol esters: (3‐py)COO(CH 2 CH 2 O) n CO(3‐py) and (4‐py)COO(CH 2 CH 2 O) n CO(4‐py), n =1–4), as well as mononuclear [RuCl 2 (η 6 ‐ p ‐cym)((3‐py)COO(CH 2 CH 2 OCH 3 )‐ κN )], complex 9 , were synthesized and characterized using elemental analysis and electrospray ionization high‐resolution mass spectrometry , infrared, 1 H NMR and 13 C NMR spectroscopies. Stability of the binuclear complexes in the presence of dimethylsulfoxide was studied. Furthermore, formation of a cationic complex containing bridging pyridine‐based bidentate ligand was monitored using 1 H NMR spectroscopy. Ligand precursors, polyethylene glycol esters of nicotinic ( L1  · 2HCl– L4  · 2HCl and L9  · HCl) and isonicotinic acid dihydrochlorides ( L5  · 2HCl– L8  · 2HCl), binuclear ruthenium(II) complexes 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 and mononuclear complex 9 were tested for in vitro cytotoxicity against 518A2 (melanoma), 8505C (anaplastic thyroid cancer), A253 (head and neck tumour), MCF‐7 (breast tumour) and SW480 (colon carcinoma) cell lines. Copyright © 2014 John Wiley & Sons, Ltd.