Ruthenium-Nitrosyl Complexes with Glycine, l‑Alanine, l‑Valine, l‑Proline, d‑Proline, l‑Serine, l‑Threonine, and l‑Tyrosine: Synthesis, X‑ray Diffraction Structures, Spectroscopic and Electrochemical Properties, and Antiproliferative Activity

The
reactions of [Ru­(NO)­Cl5]2– with glycine
(Gly), l-alanine (l-Ala), l-valine (l-Val), l-proline (l-Pro), d-proline
(d-Pro), l-serine (l-Ser), l-threonine
(l-Thr), and l-tyrosine (l-Tyr) in n-butanol or n-propanol afforded eight
new complexes (1–8) of the general
formula [RuCl3(AA–H)­(NO)]−, where
AA = Gly, l-Ala, l-Val, l-Pro, d-Pro, l-Ser, l-Thr, and l-Tyr, respectively.
The compounds were characterized by elemental analysis, electrospray
ionization mass spectrometry (ESI-MS), 1H NMR, UV–visible
and ATR IR spectroscopy, cyclic voltammetry, and X-ray crystallography.
X-ray crystallography studies have revealed that in all cases the
same isomer type (from three theoretically possible) was isolated,
namely mer(Cl),trans(NO,O)-[RuCl3(AA–H)­(NO)], as was also recently reported for osmium
analogues with Gly, l-Pro, and d-Pro (see Z. Anorg. Allg. Chem. 2013, 639, 1590–1597). Compounds 1, 4, 5, and 8 were investigated by ESI-MS with regard
to their stability in aqueous solution and reactivity toward sodium
ascorbate. In addition, cell culture experiments in three human cancer
cell lines, namely, A549 (nonsmall cell lung carcinoma), CH1 (ovarian
carcinoma), and SW480 (colon carcinoma), were performed, and the results
are discussed in conjunction with the lipophilicity of compounds.