Unpredictable Dynamic Behaviour of Ruthenium Chelate Pyrrole Derivatives

Reaction of [Ru(H)2(CO)(PPh3)3] 1 with an equimolar amount of pyrrole-2-carboxylic acid (H2L1) leads to the homoleptic chelate derivative k2(O,O)-[RuH(CO)(HL1)(PPh3)2] 2. Prolonged acetonitrile refluxing promotes an unusual k2(O,O)- -> k2(N,O)- dynamic chelate conversion, forming a neutral, stable, air- and moisture- insensitive, solvento-species k2(N,O)-[Ru(MeCN)(CO)(L1)(PPh3)2] 3. Analogously, reaction of 1 with the pyrrole-2-carboxyaldehyde (HL2) affords k2(N,O)-[RuH(CO)(HL2)(PPh3)2] 4, 5, as a couple of functional isomers. Optimized reaction conditions such as temperature and solvent polarity allow the isolation of dominant configurations. Structure 5 is a pyrrolide Ru-carbaldehyde, obtained from cyclization of the pendant CHO function, whereas species 4 can be viewed as an ethanoyl-conjugated Ru-pyrrole. Derivatives 3-5 were characterized by single crystal X-ray diffraction, ESI-Ms, IR, and NMR spectroscopy, indicating distinct features for the Ru-bonded pyrrolyl groups. DFT computational results, coplanarity, bond equalization, and electron delocalization along the fused five-membered rings support aromatic features. In accordance with the antisymbiotic trans-influence, both the isolated isomers 4 and 5 disclose CO ligands opposite to N- or O-anionic groups. The quantitative Mayer bond order evidences a stabilizing backbonding effect. Antibacterial and antifungal trials on Gram-positive (Staphylococcus aureus), Gram-negative (Escherichia coli), and Candida albicans were further carried out

Ru-Controlled Thymine Tautomerization Frozen by a k1(O)-, k2(N,O)-Metallacycle: An Experimental and Theoretical Approach

The reaction of mer-(Ru(H)2(CO)(PPh3)3) (1) with one equivalent of thymine acetic acid (THAcH) unexpectedly produces the macrocyclic dimer k1(O), k2(N,O)-(Ru(CO)(PPh3)2THAc)2 (4) and, concomitantly, the doubly coordinated species k1(O), k2(O,O)-(Ru(CO)(PPh3)2THAc) (5). The reaction promptly forms a complicated mixture of Ru-coordinated mononuclear species. With the aim of shedding some light in this context, two plausible reaction paths were proposed by attributing the isolated or spectroscopically intercepted intermediates on the basis of DFT-calculated energetic considerations. The cleavage of the sterically demanding equatorial phosphine in the mer-species releases enough energy to enable self-aggregation, producing the stable, symmetric 14-membered binuclear macrocycle of 4. The k1-acetate iminol (C=N-OH) unit of the mer-tautomer k1(O)-(Ru(CO)(PPh3)2(THAc)) (2) likely exhibits a stronger nucleophilic aptitude than the prevalent N(H)-C(O) amido species, thus accomplishing extra stabilization through concomitant k2(N,O)-thymine heteroleptic side-chelation. Furthermore, both the ESI-Ms and IR simulation spectra validated the related dimeric arrangement in solution, in agreement with the X-ray determination of the structure. The latter showed tautomerization to the iminol form. The 1H NMR spectra in chlorinated solvents of the kinetic mixture showed the simultaneous presence of 4 and the doubly coordinated 5, in rather similar amounts. THAcH added in excess preferentially reacts with 2 or trans-k2(O,O)-(RuH(CO)(PPh3)2THAc) (3) rather than attacking the starting Complex 1, promptly forming the species of 5. The proposed reaction paths were inferred by spectroscopically monitoring the intermediate species, for which the results were strongly dependent on the of conditions the reaction (stoichiometry, solvent polarity, time, and the concentration of the mixture). The selected mechanism proved to be more reliable, due to the final dimeric product stereochemistry

Synthesis and Antiproliferative Insights of Lipophilic Ru(II)-Hydroxy Stearic Acid Hybrid Species

Metallodrugs represent a combination of multifunctionalities that are present concomitantly and can act differently on diverse biotargets. Their efficacy is often related to the lipophilic features exhibited both by long carbo-chains and the phosphine ligands. Three Ru(II) complexes containing hydroxy stearic acids (HSAs) were successfully synthesized in order to evaluate possible synergistic effects between the known antitumor activity of HSA bio-ligands and the metal center. HSAs were reacted with [Ru(H)2CO(PPh3)3] selectively affording O,O-carboxy bidentate complexes. The organometallic species were fully characterized spectroscopically using ESI-MS, IR, UV-Vis, and NMR techniques. The structure of the compound Ru-12-HSA was also determined using single crystal X-ray diffraction. The biological potency of ruthenium complexes (Ru-7-HSA, Ru-9-HSA, and Ru-12-HSA) was studied on human primary cell lines (HT29, HeLa, and IGROV1). To obtain detailed information about anticancer properties, tests for cytotoxicity, cell proliferation, and DNA damage were performed. The results demonstrate that the new ruthenium complexes, Ru-7-HSA and Ru-9-HSA, possess biological activity. Furthermore, we observed that the Ru-9-HSA complex shows increased antitumor activity on colon cancer cells, HT29

Design, synthesis and characterization of novel heterobimetallic ruthenium(II)-gold(I) complexes as potential anticancer derivatives

Resumen del trabajo presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.Peer reviewe

Assessing land take and its effects on dune carbon pools. An insight into the Mediterranean coastline

In the Mediterranean sandy coasts urban growth largely occurs to sustain sea-side tourism, causing a severe loss of natural coastal dune habitats and the related ecosystem services. During the last half-century coastal dunes integrity has been widely altered by land use change; however, procedures and study cases assessing how in particular their carbon storage and sequestration capacity are affected by land take over this period are still scarse. To fill such knowledge gap, we investigated to which extent urban growth has altered soil carbon sink in a representative sector of the Mediterranean dune system, from 1954 to 2006. Specifically, we propose a procedure that combining experimental data of soil carbon stocks and multi-temporal cover maps allows assessing C stock variation over time. Based on field data we quantified soil carbon storage provided by the main dune habitat types of the Adriatic coast (Beach with Pioneer annual Vegetation, Herbaceous Dune Vegetation and Mediterranean Macchia). Using detailed multi-temporal land cover maps (1954, 1986 and 2006) we quantified the fraction of natural dune habitats replaced by urban areas over time, by means of transition matrices. Then, by combining carbon stocks values with the results of transition matrices, we estimated the C stock loss for natural dunes due to land take. Results show that natural dune habitats have an important role as soil carbon sinks and land take has depleted them with different rates, causing a total net loss of 117 t of soil C in the first time step and a total net loss of 70 t of soil C in the second time step (â\u88¼40% of soil C stock in the last 53 years). Our work underlines the fragility of natural coastal dunes, which during the last decades have become a privileged destination for touristic and recreational activities, thus been progressively replaced by artificial areas, with a direct impact on their carbon storage capacity and the other precious services they provide. By combining ecosystem services measurements with multi-temporal mapping techniques, we enhanced our understanding of transformation processes on coastal dunes, offering as well new insights for dune management