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

Abstract

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 <i>n</i>-butanol or <i>n</i>-propanol afforded eight new complexes (<b>1</b>–<b>8</b>) 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 <i>mer</i>(Cl),<i>trans</i>(NO,O)-[RuCl₃(AA–H)­(NO)], as was also recently reported for osmium analogues with Gly, l-Pro, and d-Pro (see <i>Z. Anorg. Allg. Chem.</i> <b>2013</b>, <i>639</i>, 1590–1597). Compounds <b>1</b>, <b>4</b>, <b>5</b>, and <b>8</b> 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