Os Complexes Research Articles

Estimating the Wavenumber of Terminal Metal-Hydride Stretching Vibrations of Octahedral d6 Transition Metal Complexes.

The wavenumbers of 774 terminal hydride infrared active stretching modes of 478 distinct classes of structures of d6 octahedral complexes of Mn(I), Re(I), Fe(II), Ru(II), Os(II), Co(III), Rh(III), Ir(III), and Pt(IV) were collected from the literature. A fair correlation ( R2 0.95 with standard deviation 31 cm-1) is found for the data with the equation νMHcalc = ν0 + Δν t + Δν n, where ν0 is the base wavenumber for the metal ion in question, Δν t is the parameter of influence of the ligand trans to the hydride, and Δν n is a correction for the charge of the complex [MHL5] n+. The introduction of a cis influence parameter has little effect on the correlation, showing that the trans influence dominates in this case. The equation is useful in identifying anomalous data reported in the literature, validating future assignments of νMH, understanding better metal-hydride bonding, and possibly assisting in identifying superior hydride-based catalysts.

Spray-Coating As a Versatile Tool for Electrode Surface Modification – from Nanostructured Electrodes to Enzyme Based Sensors

Electrochemical biodevices (e.g. biosensors and biofuel cells) do not only rely on the general stability and activity of the utilized biocatalyst but also on the architecture of the entire electrode. In particular, the choice of suitable electrode surface structuring, enzyme immobilization tech­nique, as well as the co-immobilization of electron-transfer mediators is crucial for highly accu­rate sensing systems. Recently, we presented the fabrication of a membrane-free glucose/O2 powered enzymatic biosupercapacitor based on transparent nanostructured indium tin oxide (ITO) electrodes prepared by means of a spray-coating process.1,2 Compared to ITO nanoparticle (NP) based electrodes obtained by drop-casting, the performance and stability of the glucose/oxygen biosupercapacitor was significantly improved by utilizing spray-coated ITO-NP based electrodes. Optimization of the spray-parameters led to a high electrochemically active surface area with substantially increased porosity, thus enhancing the catalytic currents due to higher biocatalyst loading. In this work, we used a specifically designed spray-coating system as a tool for electrode surface modification. The automated process ensures the formation of homogeneous and reproducible electrode surfaces. Moreover, the system cannot only be used for the preparation of nano-struc­tured electrode surfaces, such as ITO-NP based electrodes, but also allows spraying of enzyme and polymer solutions. By layered spraying of glucose oxidizing enzymes, embedded in an Os complex modified polymer onto the porous surface, so prepared electrodes were utilized in a self-powered glucose biosensor operated by charge/discharge of a Nernstian biosupercapacitor. Addi­tional surface modification has been achieved by the development and optimization of meso- and macro-porous ITO-NP based electrodes. A mixture of ITO nanoparticles and spherical, monodis­perse polymer beads acting as template for pore formation was sprayed onto flat electrodes. The polymer beads were removed by calcination of the material which generates macro-pores of the size of the used polymer beads (see sketch). Based on the porous 3D surface structure, an effective wiring of a subsequently immobilized enzyme redox polymer hydrogel is achieved which minimizes limitations caused by a slow electron transfer within the polymer. Our results demonstrate the high versatility of the developed spray-coater not only for surface structuring, but also for whole modification of entire electrode designs with enzymes wired in hydrogels with applications in fuel cells, bio-supercapacitors and self-powered biosensors.

NVM Streaker: a fast and reconfigurable performance simulator for non-volatile memory-based memory architecture

The high density, low power consumption non-volatile memory (NVM) provides a promising DRAM alternative for the in-memory big-data processing applications, e.g., Spark, It is significant to simulate the behaviors when NVMs are deployed into the area of big-data processing before their widespread use in market. However, existing simulation approaches are not applicable for big-data processing due to two reasons. First, some approaches require complicated hardware and/or OS supports. Second, cycle-level or function-level simulations are too time-consuming to simulate the whole software stack of big-data processing. Therefore, the complexity and expensive time cost in NVM simulation have dramatically dragged down the integrated research of big data with NVM. This paper proposes a fast and reconfigurable simulation method, called NVM Streaker, which does not need complex hardware or OS supports. It simulates NVM access costs using disturbed DRAM accesses and commonly configurable hardware parameters. It is fast since we use DRAM accesses and change its access costs to simulate NVM access costs, thus enabling to simulate the whole software stack to run Spark applications. It is reconfigurable since we enable users to configure the disturbed memory access costs, in order to simulate different NVM access costs. The experimental results show that we can simulate Spark applications with almost negligible cost and high efficiency.

Cymene‐Osmium(II) Complexes with Amino‐Phosphane Ligands as Precatalysts for Nitrile Hydration Reactions

AbstractThree different series of half‐sandwich Os(II) complexes, namely [OsCl2(η6‐p‐cymene){PPh2(NR2)}] [R=Me (5a), Et (5b)], [OsCl2(η6‐p‐cymene){PPh(NR2)2}] [R=Me (6a), Et (6b)] and [OsCl2(η6‐p‐cymene){P(NR2)3}] [R=Me (7a), Et (7b)], have been synthesized. These species proved to be catalytically active for the selective hydration of organonitriles, with compound [OsCl2(η6‐p‐cymene){PPh2(NMe2)}] (5a) being the most effective. In addition, the catalytic activity of 5a was found to be superior to those shown by related Ru(II), Ru(IV), Rh(I) and Pt(II) species containing the amino‐phosphane PPh2(NMe2), i. e. compounds [RuCl2(η6‐p‐cymene){PPh2(NMe2)}] (10), [RuCl2(η3:η3‐C10H16){PPh2(NMe2)}] (12), [RhCl(COD){PPh2(NMe2)}] (13) and cis‐[PtCl2{PPh2(NMe2)}2] (15). Details on the synthesis and characterization of complexes 10, 12 and 15 are also included, along with a discussion on the role played by the ligand PPh2(NMe2) during the catalytic reactions. In this sense, the amino‐phosphane does not act as H‐bond acceptor for the water molecule, generating instead in the aqueous reaction medium the cooperative phosphinous acid ligand PPh2(OH).

Corrigendum: Structure and Thermodynamics of Mg:Phosphate Interactions in Water: A Simulation Study.

In the above paper, we computed the binding free energy between Mg2+ and in water from molecular dynamics simulations using the AMOEBA force field. The simulations employed a restraint energy that maintained the Mg2+–phosphate distance within a specific range. The free energy contribution of the restraint was computed analytically [using Eq. (2) in the original manuscript]. The result depends on the concentration of the solutes. Unfortunately, the analytical calculation was done inadvertently at the concentration of the simulations, instead of the standard state concentration. When computing at the correct, 1 M standard state concentration, the restraint free energies change by about 1.3 kcal mol−1. Through Table 1 below, we provide a corrected version of Table 2 in the original text. We take advantage of this note to improve our estimate of another contribution, the correction for the use of a finite PBC simulation box. In the above paper, we used an analytical estimate [given in Eq. (3) in the original manuscript] that represents the leading term in an expansion in powers of the inverse box size. In the corrected Table 1 below (replacing Table 2 in the original text), we have also included the next term, which depends on the cube of the inverse box size. The improved correction was reported by Simonson and Roux (Equation 17 in Ref. 1). Overall, the computed Mg2+: standard free energy is −2.23 kcal mol−1, very close to the experimental value of −1.7 kcal mol−1. The bound state is predominantly Outer Sphere. State Apply restraint Introduce Mg2+ charge Introduce Mg2+ vdW Remove restraint Correct for PBC box Total IS complex 1.18 −428.23 1.01 0.00 0.00 −426.04 OS complex 0.37 −427.48 −0.65 −0.02 0.00 −427.78 unbound Mg 0.00 −426.79 0.00 1.21 −425.58 IS binding 1.18 −0.43 0.00 −1.21 −0.46±1.20 OS binding 0.37 −1.34 −0.02 −1.21 −2.20±1.20 Overall binding −2.23±1.20 The authors apologize for this oversight.

Conceptual Extension of the Degradation–Transformation of N-Heterocyclic Carbenes: Unusual Rearrangements on Osmium

The range of processes of degradation–transformation of NHC ligands in the coordination sphere of a transition metal has been enlarged. The NHC-acyl ligand of the complex Os{κ2-C,C-[C(O)CH2ImMe]}Cl(PiPr3)2 (1) undergoes a complex rearrangement promoted by internal alkynes to give Os{κ2-C,N-[CH2ImMe]}Cl(CO)(PiPr3)2 (2). Mechanistic studies have revealed that the degradation involves a catalytic alkyne-mediated deinsertion of CO from the acyl moiety to afford Os{κ2-C,C-[CH2ImMe]}Cl(CO)(PiPr3)2 (3), followed by a thermally activated stoichiometric 1,2-methylene shift from N to C. The catalytic activity of the alkynes depends upon their substituents, decreasing in the sequence diphenylacetylene > 1-phenyl-1-propyne > 3-hexyne > 2-butyne. Phenylacetylene tautomerizes in the metal coordination sphere to afford the stable vinylidene Os{κ2-C,C-[C(O)CH2ImMe]}Cl(═C═CHPh)(PiPr3)2 (4), which experiences the coupling of the acyl moiety and the vinylidene ligand under a carbon monoxide atmosphere. The addition of HBF4·...

Heterobimetallic Ru-Os complexes function as multichannel sensors for selected anions by taking profit of metal-ligand interaction

In this work we report detailed anion sensing behaviors of a new series of bimetallic Ru(II)-Os(II) complexes derived from an asymmetric heteroditopic bridging ligand (tpy-Hbzim-dipy) consisting of both bipyridine and terpyridine chelating sites covalently connected through phenyl-imidazole spacer. The sensing studies were performed in both organic as well as aqueous medium through multiple optical channels and spectroscopic tools by taking profit of metal ligand interaction in the complexes. The dyads behave as chromogenic and fluorogenic sensors for F−, CN−, AcO− and H2PO4− in acetonitrile without much selectivity. On the other hand, all the four dyads behave as sensors for CN−, SCN−, and S2− in water. Equilibrium/binding constants of the interaction process and detection limits of the complexes towards selected anions were determined from absorption and emission titration data and the values were found to lie in order of 106 M−1 and 10−9 M, respectively. Luminescence lifetimes of the dyads were also modulated to a significant extent by selected anions which in turn justify the utility of the complexes as suitable lifetime-based sensors for selected anions. Finally, test strips were also fabricated based on the metalloreceptors for their probable use as efficient test kits to detect CN−, SCN−, and S2− in pure water for field measurements that do not require any equipment.

How Inert are Osmium−Ligand Bonds? A Combined Thermal, Photochemical and Electrochemical Case Study With a Click Tripodal Ligand

AbstractThe first examples of osmium(II) complexes of the type [Os(L)(dmso)Cl]+ (L=tripodal ligand) are reported. Photoactivation is shown to be a convenient route for performing ligand substitution reactions in such complexes. Photochemical bond activation works where thermal and electrochemical routes fail. Drastic differences are presented in the reactivity of the Os complexes with the pyridine‐containing ligands versus the triazole‐containing ligands. A detailed experimental and theoretical investigation into photochemical bond activation reactions is presented.

Stimuli-Responsive Dual-Color Photon Upconversion: A Singlet-to-Triplet Absorption Sensitizer in a Soft Luminescent Cyclophane.

Reversible emission color switching of triplet-triplet annihilation-based photon upconversion (TTA-UC) is achieved by employing an Os complex sensitizer with singlet-to-triplet (S-T) absorption and an asymmetric luminescent cyclophane with switchable emission characteristics. The cyclophane contains the 9,10-bis(phenylethynyl)anthracene unit as an emitter and can assemble into two different structures, a stable crystalline phase and a metastable supercooled nematic phase. The two structures exhibit green and yellow fluorescence, respectively, and can be accessed by distinct heating/cooling sequences. The hybridization of the cyclophane with the Os complex allows near-infrared-to-visible TTA-UC. The large anti-Stokes shift is possible by the direct S-T excitation, which dispenses with the use of a conventional sequence of singlet-singlet absorption and intersystem crossing. The TTA-UC emission color is successfully switched between green and yellow by thermal stimulation.

Stimuli‐Responsive Dual‐Color Photon Upconversion: A Singlet‐to‐Triplet Absorption Sensitizer in a Soft Luminescent Cyclophane

AbstractReversible emission color switching of triplet–triplet annihilation‐based photon upconversion (TTA‐UC) is achieved by employing an Os complex sensitizer with singlet‐to‐triplet (S‐T) absorption and an asymmetric luminescent cyclophane with switchable emission characteristics. The cyclophane contains the 9,10‐bis(phenylethynyl)anthracene unit as an emitter and can assemble into two different structures, a stable crystalline phase and a metastable supercooled nematic phase. The two structures exhibit green and yellow fluorescence, respectively, and can be accessed by distinct heating/cooling sequences. The hybridization of the cyclophane with the Os complex allows near‐infrared‐to‐visible TTA‐UC. The large anti‐Stokes shift is possible by the direct S‐T excitation, which dispenses with the use of a conventional sequence of singlet–singlet absorption and intersystem crossing. The TTA‐UC emission color is successfully switched between green and yellow by thermal stimulation.

PNP-Pincer Complexes of Osmium: Comparison with Isoelectronic (PCP)Ir and (PNP)Ir+ Units

Several complexes of (tBu4PNP)Os (1) (tBu4PNP = C5NH3-2,6-(CH2PtBu2)2) are reported. 1 is isoelectronic with (tBu4PCP)Ir (2), which has played a leading role in homogeneous catalytic alkane dehydrogenation; the (tBu4PNP)Os complexes were investigated in this context. (tBu4PNP)OsH4 (1-H4) is analogous to (tBu4PCP)IrH4 (2-H4), but while 2-H4 has some character of a dihydrogen dihydride, 1-H4 is unambiguously a tetrahydride. Ethylene reacts with 1-H4 to afford trans-(tBu4PNP)OsH2(C2H4) (1-H2(C2H4)). At 25 °C, 1-H2(C2H4) readily undergoes reversible ethylene insertion into an Os–H bond to yield (tBu4PNP)OsH(C2H5) (1-EtH). DFT calculations indicate that alkane C–H addition to 1 is thermodynamically much more favorable than addition to 2. The favorable thermodynamics of 1-(alkyl)H, however, disfavor reductive elimination and formation of the free Os(0) fragment that is required for a catalytic cycle analogous to that reported for 2. The much greater favorability of C–H or H–H addition to 1 as compared with Ir(I...

Oxidation of olefins catalyzed by half-sandwich osmium(II) arene complexes

Ten complexes [(η6-(arene)OsCl(C5H4N-2-CH=N-C6H5X)]PF6 (with arene = p-cymene (1) or benzene (2); X = 4-F (a), 4-Cl (b), 4-Br (c), 4-I(d) and 4–methyl (e)) were synthesized by reacting the corresponding N,N′-bidentate ligands with the osmium arene dimers [(η6-arene)Os(μ-Cl)Cl]2 in a 2:1 ratio. Complexes 1a-e and 2c-d are new. The compounds were fully characterized via 1H and 13C NMR, IR and UV–Vis spectroscopy, and elemental analyses. The x-ray crystal structure of compound 2e is also reported. The Os(II) complex shows the expected “ piano stool” type geometry. These Os(II) compounds were investigated in the catalytic oxidation of olefins to carbonyl compounds with NaIO4 as terminal oxidant in a H2O/t-BuOH biphasic system. All of the compounds were very effective catalysts for this reaction and gave the corresponding aldehyde in high yields.

Exploiting the benefit of S0→ T1 excitation in triplet-triplet annihilation upconversion to attain large anti-stokes shifts: tuning the triplet state lifetime of a tris(2,2'-bipyridine) osmium(ii) complex.

Os(ii) complexes are particularly interesting for triplet-triplet annihilation (TTA) upconversion, due to the strong direct S0→ T1 photoexcitation, as in this way, energy loss is minimized and large anti-Stokes shift can be achieved for TTA upconversion. However, Os(bpy)3 has an intrinsic short T1 state lifetime (56 ns), which is detrimental for the intermolecular triplet-triplet energy transfer (TTET), one of the crucial steps in TTA upconversion. In order to prolong the triplet state lifetime, we prepared an Os(ii) tris(bpy) complex with a Bodipy moiety attached, so that an extended T1 state lifetime is achieved by excited state electronic configuration mixing or triplet state equilibrium between the coordination center-localized state (3MLCT state) and Bodipy ligand-localized state (3IL state). With steady-state and time-resolved transient absorption/emission spectroscopy, we proved that the 3MLCT is slightly above the 3IL state (by 0.05 eV), and the triplet state lifetime was prolonged by 31-fold (from 56 ns to 1.73 μs). The TTA upconversion quantum yield was increased by 4-fold as compared to that of the unsubstituted Os(ii) complex.

A potential method to improve the in vitro cytotoxicity of half-sandwich Os(ii) complexes against A2780 cells

The [Os(η6-pcym)(dpa)(VP)]PF6 (1-VP) complex contains the histone deacetylase (HDAC) inhibitor valproate (2-propylpentanoate; VP) as a monodentate O-donor ligand and shows ca. 3-fold higher in vitro cytotoxicity against A2780 human ovarian carcinoma cells than its chlorido analogue [Os(η6-pcym)(dpa)Cl]PF6 (1-Cl); pcym = 1-methyl-4-(propan-2-yl)benzene (p-cymene), dpa = 2,2'-dipyridylamine. The complex 1-VP showed promising selectivity towards the A2780 ovarian carcinoma cell line (IC50 = 20.9 μM) over normal human hepatocytes (IC50 > 200.0 μM). Moreover, the complex 1-VP was found to be inactive against MCF-7 (breast adenocarcinoma), PANC-1 (pancreatic adenocarcinoma) and HT-29 (colon carcinoma) up to a concentration of 100 μM. Detailed flow cytometry studies indicated that treatment of A2780 cells with complex 1-VP led to induction of apoptosis, production of reactive oxygen species (ROS) and superoxide (SO) anion radicals, as well as mitochondrial membrane potential depletion and cell cycle perturbations. The microscopic assessment (standard hematoxylin/eosin staining) revealed signs of morphological changes associated with the progression of apoptosis in A2780 cells treated with the IC50 concentration of the complex 1-VP. Consistent with the intracellular production of ROS and SO, the complex 1-VP induced hydroxyl radical formation, as proved by EPR spin trapping experiments. This case study suggests that replacement of the chlorido ligand of half-sandwich Os(ii) complexes by a releasable monodentate biologically active ligand (e.g., VP used in this study) is an effective strategy for the development of novel non-platinum cytotoxic agents.

Half-sandwich Os(ii) and Ru(ii) bathophenanthroline complexes: anticancer drug candidates with unusual potency and a cellular activity profile in highly invasive triple-negative breast cancer cells.

There is an urgent need to discover new, selective compounds to add to the limited arsenal of chemotherapeutics displaying selective toxicity for aggressive triple-negative breast cancer (TNBC) cells. The effect of two, recently developed metal-based half-sandwich complexes [Os(η6-pcym)(bphen)(dca)]PF6 (Os-dca) and [Ru(η6-pcym)(bphen)(dca)]PF6 (Ru-dca) [pcym = 1-methyl-4-(propan-2-yl)benzene (p-cymene); bphen = 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline); dca = dichloroacetate] on triple-negative breast cancer cells MDA-MB-231 is reported. The complexes display selective toxicity in several tumor cells (at submicromolar concentrations), and a prominent effect is observed against highly progressive triple negative breast cancer MDA-MB-231 cells for Os-dca. The lower potency of Ru-dca in comparison with Os-dca is apparently connected with a relatively quick release of the dca ligand due to the hydrolysis of Ru-dca before this complex enters the cells. Remarkably, both Os-dca and Ru-dca reduce successfully metastasis-related properties of the triple-negative breast cancer cells such as migration, invasion, and re-adhesion. The anti-metastatic effects of Os-dca and Ru-dca are associated with their ability to suppress matrix metalloproteinase activity and/or production and reduce the expression of aquaporins. Further detailed mechanistic studies reveal that Os-dca reverses Warburg's effect and oncosis seems to be a prominent mode of cell death that predominates over apoptosis. As such, Os-dca can efficiently overcome the resistance of cancer cells to clinically-used apoptotic inducers cisplatin and carboplatin. The cytostatic and anti-metastatic properties of Os-dca in MDA-MB-231 provide a strong impetus for the development of new metal-based compounds to target hardly treatable human TNBC cells and displaying different modes of action compared to the antitumor metallodrugs in clinical use.

Multiple cluster CH activations and transformations of furan by triosmium carbonyl complexes.

Reaction of Os3(CO)10(NCMe)2 with the triosmium furyne complex Os3(CO)9(μ3,η2-C4H2O)(μ-H)2, 1 yielded the bis-triosmium complex 2 containing a bridging furyenyl ligand by CH activation at the uncoordinated C-C double bond. Heating 2 led to additional CH activation with formation of the first furdiyne C4O ligand in the complex Os3(CO)9(μ-H)2(μ3-η2-2,3-μ3-η2-4,5-C4O)Os3(CO)9(μ-H)2, 3. The furdiyne ligand in 3 was subsequently ring-opened and decarbonylated to yield products 4 and 5 containing novel bridging C3 ligands. Complex 2 also undergoes ring opening to yield an intermediate Os3(CO)9(μ-H)(μ3-η2-μ-η2-CH-C-CH-C[double bond, length as m-dash]O)Os3(CO)10(μ-H), 6 which was also decarbonylated thermally to yield 4 and 5. All products were characterized by a combination of IR, NMR, mass spec and single-crystal X-ray diffraction analyses.

Investigation of anticancer properties of caffeinated complexes via computational chemistry methods

Computational investigations were performed for 1,3,7-trimethylpurine-2,6-dione, 3,7-dimethylpurine-2,6-dione, their Ru(II) and Os(III) complexes. B3LYP/6-311++G(d,p)(LANL2DZ) level was used in numerical calculations. Geometric parameters, IR spectrum, 1H-, 13C and 15N NMR spectrum were examined in detail. Additionally, contour diagram of frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) maps, MEP contour and some quantum chemical descriptors were used in the determination of reactivity rankings and active sites. The electron density on the surface was similar to each other in studied complexes. Quantum chemical descriptors were investigated and the anticancer activity of complexes were more than cisplatin and their ligands. Additionally, molecular docking calculations were performed in water between related complexes and a protein (ID: 3WZE). The most interact complex was found as Os complex. The interaction energy was calculated as 342.9kJ/mol.

Catalytic Nitrogen-to-Ammonia Conversion by Osmium and Ruthenium Complexes.

Despite the critical role Ru and Os complexes have played in the development of transition metal dinitrogen chemistry, they have not been shown to mediate catalytic N2-to-NH3 conversion (N2RR), nor have M-NxHy complexes been derived from protonation of their M-N2 precursors. To help delineate factors for N2RR catalysis, we report on isostructural tris(phosphino)silyl Ru and Os complexes that mediate catalytic N2RR, and compare their activities with an isostructural Fe complex. The Os system is most active, and liberates more than 120 equiv NH3 per Os center in a single batch experiment using Cp*2Co and [H2NPh2][OTf] as reductant and acid source. Isostructural Ru and Fe complexes generate little NH3 under the same conditions. Protonation of Os-N2- affords a structurally characterized Os=NNH2+ hydrazido species that mediates NH3 generation, suggesting it is a plausible intermediate of the catalysis. Inactive Os hydrides are characterized that form during catalysis.

Theoretical study of structure, bonding, and electronic behavior of novel sandwich complexes Os3(C6H6) n (n = 1, 2)

The correlations between structural and electronic properties of the monolayer cluster Os3 and sandwich complexes of Os3(C6H6) n (n = 1, 2) were studied with density functional theory. Every Os adopts η2 fashion to coordinate with C6H6 in Os3(C6H6), while every Os adopts η2 and η1 fashion to coordinate with below and above C6H6 rings in Os3(C6H6)2. η2 fashion is σ donation and π back bond, and η1 fashion belong to σ bond. The first binding energy between Os3 and below C6H6 ring is–114.23 kJ/mol, which is weaker than the second binding energy with–174.16 kJ/mol between Os3(C6H6) and above C6H6 ring. The reason is that the change of spin multiplicity is different, which leads the symmetry of Os3(C6H6)2 to be broken.

Anticancer Ru(η6-p-cymene) complexes of 2-pyridinecarbothioamides: A structure–activity relationship study

Ru(II) and Os(II) complexes of 2-pyridinecarbothioamide ligands were introduced as orally administrable anticancer agents (S.M. Meier, M. Hanif, Z. Adhireksan, V. Pichler, M. Novak, E. Jirkovsky, M.A. Jakupec, V.B. Arion, C.A. Davey, B.K. Keppler, C.G. Hartinger, Chem. Sci., 2013, 4, 1837–1846). In order to identify structure-activity relationships, a series of N-phenyl substituted pyridine-2-carbothiamides (PCAs) were obtained by systematically varying the substituents at the phenyl ring. The PCAs were then converted to their corresponding RuII(η6-p-cymene) complexes and characterized spectroscopically and by X-ray diffraction as well as in terms of stability in water and HCl. The cytotoxic activity of the PCA ligands and their respective organoruthenium compounds was evaluated in a panel of cell lines (HCT116, H460, SiHa and SW480). The lipophilic PCAs 1–4 showed cytotoxicity in the low micromolar range and 6 was the most potent compound of the series with an IC50 value of 1.1μM against HCT116 colon cancer cells. These observations were correlated with calculated octanol/water partition coefficient (clogP) data and quantitative estimated druglikeness. A similar trend as for the PCAs was found in their Ru complexes, where the complexes with more lipophilic ligands proved to be more cytotoxic in all tested cell lines. In general, the PCAs and their organoruthenium derivatives demonstrated excellent drug-likeness and cytotoxicity with IC50 values in the low micromolar range, making them interesting candidates for further development as orally active anticancer agents.