Francisco Martínez-Peña’s research while affiliated with IMDEA Nanoscience and other places
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Tethered ruthenium(II) complexes [Ru(η6:κ1-arene:N)Cl2] (where arene:N is 2-aminobiphenyl (1) and 2-benzylpyridine (2)) can convert into their open-tethered chlorido counterparts [Ru(η6-arene:NH)Cl3], 1·HCl and 2·HCl, at room temperature via solid-state reaction in the presence of HCl vapors. The reaction is accompanied by a change in color, is fully reversible, and crystallinity is maintained in both molecular materials. Organoruthenium tethers are presented as nonporous materials capable of capturing and releasing HCl reversibly in the crystalline solid state.
Five complexes of formula [Ru(η6-C6H5CH2COOH)(XY)Cl]Cl/Na (XY = ethylenediamine (1), o-phenylenediamine (2), phenanthroline (3), and oxalato (4)) and [Ru(η6:κ1-C6H5CH2COO)(tmen)]Cl (tmen = N, N, N', N'-tetramethylethylenediamine, 5C) have been synthesized and fully characterized. Five new X-ray crystal structures ([Ru(η6-C6H5CH2COOH)(μ-Cl)Cl]2, 1, 3, 4, and 5C·PF6) have been determined, which are the first examples of ruthenium(II) structures with phenylacetic acid as arene ligand. Furthermore, 5C·PF6 is the first example of a five-membered tether ring with a Ru(η6:κ1-arene:O) bond. The tether ring in these complexes opens in acidic pH (<5) and closes reversibly in aqueous solution. The chlorido open-form undergoes aquation, and the aqua adduct can be observed (prior to ring closure) by NMR. The speciation has an attractive complexity in the pH range 0-12, showing interconversion of the three species (chlorido, aqua, and closed tether), dependent on the proton concentration and the nature of the XY chelating ligand. The closed tether version of 3, complex 3C, with σ-donor/π-acceptor phenanthroline as chelating ligand, opens up more readily (pH 4), while the tether ring in complex 5C hardly opens even at pH as low as 1. We have determined the p Ka of the pendant carboxylic group and that of the aqua adduct (ca. 3 and ca. 7, respectively), which can be finely tuned by the appropriate choice of XY. Complexes 1 and 2, which predominate in their inactive (closed-tether) form in intracellular conditions, show some cytotoxic activity (IC50 130 and 117 μM, respectively) in A2780 ovarian cancer cells. Complex 1 catalyzes the reduction through transfer hydrogenation of pyruvate to lactate and NAD+ to NADH in the presence of formate as H-source. Co-incubation with sodium formate decreases the IC50 value of 1 in A2780 cancer cells significantly.
The design of organometallic pH-dependent switches to control in-tumor drug activation is presented. In this picture, the middle and background show that inactive ruthenium(II) arene complexes are innocuous (represented in blue), locked away inside boxes, unable to interact with their molecular target. It is shown, however, that protons (represented by the keys) can open the boxes and release the active form of the ruthenium drug (in red, with Ru in metallic grey), which can bind to DNA. The potential of a series of ruthenium(II) complexes to become pH-responsive anticancer drugs is thus demonstrated. More information can be found in the Full Paper by A. M. Pizarro and F. Martínez-Peña (DOI: 10.1002/chem.201701681).
The potential use of organometallic ruthenium complexes as anticancer drugs is well known. Here we show a family of activatable tethered ruthenium(II) arene complexes of general formula [Ru(η⁶:κ¹-C₆H₅(C₆H₄)NH₂)(XY)]n+ (closed tether-ring) bearing different chelating XY ligands (XY = aliphatic diamine, phenylenediamine, oxalato, bis(phosphino)ethane). The activation of these complexes (closed-to-open tether conversion) occurs in methanol and dimethylsulfoxide at different rates, and to different reaction extents at equilibrium. Most importantly, Ru complex activation (cleavage of the Ru-N-tether bond) occurs in aqueous solution when the proton concentration is high (upon N-tether protonation). The activation dynamics can be modulated by rational variation of the XY chelating ligand. The electron-donating capability and steric hindrance of XY have a direct impact on the Ru-N bond reactivity, with XY = N,N'-dimethyl, N,N'-diethyl, and N,N,N',N'-tetramethylethylenediamine affording complexes more prone to activation. Such activation in acidic media is fully reversible, and proton concentration also governs the deactivation rate; i.e., tether ring closure slows down as the pH decreases. Interaction of a closed-tether complex and its open-tether counterpart with 5'-GMP indicates selectivity of the active (open) complex towards nucleobase interaction. This work presents ruthenium tether complexes as exceptional pH-dependent switches with potential exploitation in cancer research.
On-surface synthesis is a promising strategy for engineering heteroatomic covalent nanoarchitectures with prospects in electronics, optoelectronics and photovoltaics. Here we report the thermal tunability of reaction pathways of a molecular precursor in order to select intramolecular versus intermolecular reactions, yielding monomeric or polymeric phthalocyanine derivatives, respectively. Deposition of tetra-aza-porphyrin species bearing ethyl termini on Au(111) held at room temperature results in a close-packed assembly. Upon annealing from room temperature to 275 °C, the molecular precursors undergo a series of covalent reactions via their ethyl termini, giving rise to phthalocyanine tapes. However, deposition of the tetra-aza-porphyrin derivatives on Au(111) held at 300 °C results in the formation and self-assembly of monomeric phthalocyanines. A systematic scanning tunnelling microscopy study of reaction intermediates, combined with density functional calculations, suggests a [2+2] cycloaddition as responsible for the initial linkage between molecular precursors, whereas the monomeric reaction is rationalized as an electrocyclic ring closure.
... [7] Hemilability in this type of complexes -whereby a vacancy in the first coordination sphere of the metal can be purposely created-is particularly attractive for both catalytic and biological applications, since it allows for controlled metalcentred reactivity inside the cell. [6,8] Despite the impact of the arene on the chemistry of halfsandwich metal-arene compounds, versatility on arene functionalisation has been modest. This is particularly critical in the case of osmium complexes, with just a few reported examples different from the well-known [Os(η 6 -p-cymene)XYZ] complexes. ...
... Scrase et al. reported that a L-2,3-diaminopropionic acid ligand coordinated in a tridentate manner to a ruthenium-η 6 -arene moiety was found to be labilized on lowering of pH, leading to partial reactivity of the complex on incubation with a protected methionine ligand at pH 2.5 [12]. Pizarro et al. have shown reversible intramolecular chelation can be achieved in half-sandwich ruthenium complexes utilizing an hemilabile 2-aminobiphenyl arene ligand [13]. The closed form of the complexes, achieved through an arene ligand η 6 :κ 1 -C6H5(C6H4)NH2 coordination mode ( Figure 1D), dominates Examples of metallodrugs previously investigated for their pH-dependent reactivity (A) cis-[PtCl(Me 2 N(CH 2 ) 2 PPh 2 -N,P)(Me 2 N(CH 2 ) 2 PPh 2 -P)]Cl; (B) the general structure of bis(O-alkyldithiocarbonato)platinum(II) complexes; (C) (SP-4-2)-bis(2-aminoethanolato-κ 2 N,O)platinum(II); (D) general structure of [Ru{η 6 :κ 1 -C 6 H 5 (C 6 H 4 )NH 2 }(XY)] 2+ complexes; (E) structure of [Ru(η 6 -C 6 H 5 CH 2 CH 2 NHR)(C 2 O 4 )(H 2 O)] (R = Ms, Tf) complexes. ...
... In the second step, the dimeric [RuCl 2 (p-cymene)] 2 precursor reacts with anilines to form the corresponding [RuCl 2 (p-cymene)(H 2 NAr)] complexes, in which the ruthenium is coordinated to the nitrogen atom [24][25][26][27]. The ruthenium complexes 1-3 were obtained at a 68-72% yield by the reaction of the amino-cavitand and the [RuCl 2 (p-cymene)] 2 precursor (Scheme 2). ...
... In contrast, during the gradually annealing of a SAM, the molecules retain in an aggregated state, restricting the diffusion and promoting intermolecular reactions such as alkenyl-alkenyl dehydrogenative coupling. [13][14] The close-packed pattern and the lower reaction barrier for alkenyl-alkenyl coupling favor the formation of undesired oligomers through random intermolecular polymerization. ...
