Terpyridine Ruthenium Complexes Research Articles

Modulation of room temperature emission characteristics of heteroleptic ruthenium-terpyridine complexes via aggregation

In this work, we have thoroughly investigated the modulation of room temperature luminescence characteristics of our recently reported stilbene-appended heteroleptic Ru(II)-terpyridine complexes of the type, [(tpy-PhCH3)Ru(tpy-pvp-X)](ClO4)2, wherein X =naphthalene, anthracene, and pyrene moiety via aggregation through the use of appropriate solvent mixtures. Taking profit of the polyaromatic motif, the complexes display both aggregation-induced emission quenching as well as emission augmentation, depending upon nature of the solvent mixtures. By virtue of the presence of stilbene unit, the complexes undergo trans–cis isomerization upon irradiation of light. We have previously investigated the reversible trans–cis isomerization of the non-aggregated form of the complexes upon alternative treatment of visible and UV light. In the present study, we have also undertaken the trans → cis photoisomerization of the aggregated forms of the complexes. The rate constant and quantum yield of photoisomerization in the aggregated form of the complexes are also estimated and compared with their non-aggregated counterparts.

Fabrication of molecular-scale logic devices and implication of artificial neural networks for analysis of anion-responsive behaviors of luminescent ruthenium-terpyridine complex

Anion responsive spectral characteristics of a homoleptic luminescent Ru(II)-terpyridine complex derived from 4′-(p-triphenylphosphoniummethylphenyl)-2,2′:6′,2″-terpyridine bromide (tpy-PhCH2PPh3Br) ligand has been utilized here to mimic the operation of several advanced logic functions. The complex displays remarkable change in absorption and emission spectral profiles in presence of selected anions due to concerted hydrogen bonding followed by anion-induced proton abstraction. Importantly, deprotonation by specific anions followed by restoration to the initial form of the complex is feasible in presence of acid and the process could be recycled. The spectral responsiveness of the complex is employed to mimic various advanced Boolean logic functions, such as IMPLICATION, INHIBIT and combinational logic gates. Execution of exhaustive sensing investigations is often labor-intensive and time-consuming. To address the gap, we employed herein artificial neural network (ANN) models employing three different training algorithms, viz. Bayesian Regularization (BR), Scaled Conjugate Gradient (SCG), and Levenberg-Marquardt (LM) for comprehensive analysis and prediction of the experimental observations. We also compared the outcomes of these models with one another as well as with the experimental data to enable an accurate modeling of the complex’s anion-sensing behavior.

Luminescent Ruthenium-Terpyridine Complexes Coupled with Stilbene-Appended Naphthalene, Anthracene, and Pyrene Motifs Demonstrate Fluoride Ion Sensing and Reversible Trans-Cis Photoisomerization.

A new family of luminescent heteroleptic Ru(II)-terpyridine complexes coupled with stilbene-appended naphthalene, anthracene, and pyrene motifs is reported. Each of the complexes features moderately intense emission at room temperature having a lifetime of 16.7 ns for naphthalene and 11.4 ns for anthracene, while a substantially elevated lifetime of 8.3 μs was observed for the pyrene derivative. All the three complexes display a reversible couple in the positive potential window due to Ru2+/Ru3+ oxidation but multiple reversible and/or quasi-reversible peaks in the negative potential domain because of the reduction of the terpyridine moieties. All the complexes selectively sense F- among the studied anions via the intermediary of different noncovalent interactions. The interaction event is monitored through absorption, emission, and 1H and 19F NMR spectroscopy. Additionally, upon utilizing the stilbene motif, reversible trans-cis isomerization of the complexes has been undertaken upon alternate treatment of visible and UV light so that the complexes can act as potential photomolecular switches. We also carried out the anion sensing characterization of the cis form of the complexes. Theoretical calculation employing density functional theory is also executed for a selective complex (naphthalene derivative) to elucidate different noncovalent interactions that are operative during the complex-fluoride interplay.

Ruthenium terpyridine complexes based on dppz ligands as photodynamic antimicrobial agents against Staphylococcus aureus

A series of ruthenium complexes with dppz ligands were designed and synthesized as antimicrobial photosensitizers against S. aureus. These complexes showed significant antibacterial ability against S. aureus both in vitro and in vivo.

Design of molecular sensors and switches based on luminescent ruthenium-terpyridine complexes bearing active methylene and triphenylphosphonium motifs as anion recognition sites: experimental and DFT/TD-DFT investigation.

Synthesis, characterization and thorough investigation of the photophysical and electrochemical properties of a new category of emissive homo- and heteroleptic Ru(II)-complexes derived from the [4'-(p-triphenylphosphonium methyl phenyl)-2,2':6',2''-terpyridine]bromide (tpy-PhCH2PPh3Br) ligand have been executed in this work. Incorporation of the PhCH2PPh3+Br- group at the terpyridine motif appropriately adjusts the triplet metal-to-ligand charge transfer (3MLCT) and metal-centered (3MC) excited states so that the complexes luminesce at room temperature (RT) having lifetimes within the range of 6.82-9.63 ns. The RT emission characteristics of the complexes get further enhanced via aggregation phenomena through the use of different solvent/non-solvent mixtures (DMSO/H2O and DMSO/PhCH3 mixtures). Temperature dependent emission spectral measurements indicate that the emission intensity, quantum yield and lifetime increase upon dropping down the temperature, thereby designated as the on-state, while the increase of temperature causes a reduction of the said properties, indicating the off-state and the process is fully reversible. Taking advantage of the active methylene group coupled with a phosphonium motif, anion sensing characteristics of the complexes are investigated systematically in DMSO through the use of various optical channels and spectroscopic tools. The complexes are very much sensitive to fluoride and to a lesser extent acetate and dihydrogen phosphate among the studied anions. In essence, the complexes function as sensors for temperature and fluoride ion. Computational investigations were also executed via density functional theory (DFT) and time-dependent (TD)-DFT to obtain a clear understanding of the electronic structures of the metalloreceptors, appropriate assignment of the spectral bands and their mode of interaction with selected anions.

Low-Temperature Observation of the Excited-State Decay of Ruthenium-(Mono-2,2':6',2″-Terpyridine) Ions with Innocent Ligands: DFT Modeling of an 3MLCT-3MC Intersystem Crossing Pathway.

The synthesis, electrochemistry, and photophysical characterization of five 2,2':6',2″-terpyridine ruthenium complexes (Ru-tpy complexes) is reported. The electrochemical and photophysical behavior varied depending on the ligands, i.e., amine (NH3), acetonitrile (AN), and bis(pyrazolyl)methane (bpm), for this series of Ru-tpy complexes. The target [Ru(tpy)(AN)3]2+ and [Ru(tpy)(bpm)(AN)]2+ complexes were found to have low-emission quantum yields in low-temperature observations. To better understand this phenomenon, density functional theory (DFT) calculations were performed to simulate the singlet ground state (S0), Te, and metal-centered excited states (3MC) of these complexes. The calculated energy barriers between Te and the low-lying 3MC state for [Ru(tpy)(AN)3]2+ and [Ru(tpy)(bpm)(AN)]2+ provided clear evidence in support of their emitting state decay behavior. Developing a knowledge of the underlying photophysics of these Ru-tpy complexes will allow new complexes to be designed for use in photophysical and photochemical applications in the future.

Synthesis and Theoretical and Photophysical Study on a Series of Neutral Ruthenium(II) Complexes with Donor–Metal–Accepter Configuration

In order to construct a new type of ruthenium(II) terpyridine complexes with activated triplet metal-centered (3MC) states, as well as stabilized triplet metal-to-ligand charge transfer (3MLCT) states, conducive to fine emissive performances, Ru-1, Ru-2, Ru-3, and Ru-4 were synthesized. Compared with the [Ru(terpyridine)2]2+ prototype (0.25 ns), this series of ruthenium(II) terpyridine complexes exhibit lengthened excited state lifetime (43.3 ns for Ru-1, 52.7 ns for Ru-2, 43.6 ns for Ru-3, and 53.4 ns for Ru-4). Interfragment charge transfer analysis illustrates the electron transfer direction of the four complexes, manifesting their intramolecular charge transfer characteristic. When excited, their lowest-lying triplet states are assigned as 3MLCT based on spin-density surface distribution. The singlet excited states and 3MLCT states were thoroughly studied by UV-visual absorption and nanosecond time-resolved transient absorption spectra, respectively. Photoluminescence spectra revealed their weak broadband near-infrared emission at room temperature and red phosphorescence at 77 K. The low molecular weight and the good thermal stability make Ru-1 and Ru-2 suitable for vaporization coating, while the fine solubility in common organic solvents makes Ru-3 and Ru-4 suitable for solution processing. Furthermore, the intrinsic electroneutrality and favorable energy levels endow them with new potential to be applied in the optoelectronic field.

Cover Feature: Strong Ligand Stabilization Based on π‐Extension in a Series of Ruthenium Terpyridine Water Oxidation Catalysts (Chem. Eur. J. 68/2021)

Water oxidation catalysis on a series of ruthenium(II) terpyridine complexes shows a correlation between catalytic performance and the extension of their π bidentate ligand. Substitution of the Cl− ligand by H2O reveals increased stability of the Ru−Cl bond upon increasing the π-system. Computational studies demonstrated how the greater stability of the Cl− ligand negatively influences O2 evolution despite the reaction energy barriers of water oxidation being identical among all complexes. More information can be found in the Full Paper by S. Gräfe, L. González, S. Rau, et al. (DOI: 10.1002/chem.202102905).

Strong Ligand Stabilization Based on π-Extension in a Series of Ruthenium Terpyridine Water Oxidation Catalysts.

The substitution behavior of the monodentate Cl ligand of a series of ruthenium(II) terpyridine complexes (terpyridine (tpy)=2,2′:6′,2′′‐terpyridine) has been investigated. 1H NMR kinetic experiments of the dissociation of the chloro ligand in D2O for the complexes [Ru(tpy)(bpy)Cl]Cl (1, bpy=2,2’‐bipyridine) and [Ru(tpy)(dppz)Cl]Cl (2, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine) as well as the binuclear complex [Ru(bpy)2(tpphz)Ru(tpy)Cl]Cl3 (3 b, tpphz=tetrapyrido[3,2‐a:2′,3′‐c:3′′,2′′‐h:2′′′,3′′′‐j]phenazine) were conducted, showing increased stability of the chloride ligand for compounds 2 and 3 due to the extended π‐system. Compounds 1–5 (4=[Ru(tbbpy)2(tpphz)Ru(tpy)Cl](PF6)3, 5=[Ru(bpy)2(tpphz)Ru(tpy)(C3H8OS)/(H2O)](PF6)3, tbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) are tested for their ability to run water oxidation catalysis (WOC) using cerium(IV) as sacrificial oxidant. The WOC experiments suggest that the stability of monodentate (chloride) ligand strongly correlates to catalytic performance, which follows the trend 1>2>5≥3>4. This is also substantiated by quantum chemical calculations, which indicate a stronger binding for the chloride ligand based on the extended π‐systems in compounds 2 and 3. Additionally, a theoretical model of the mechanism of the oxygen evolution of compounds 1 and 2 is presented; this suggests no differences in the elementary steps of the catalytic cycle within the bpy to the dppz complex, thus suggesting that differences in the catalytic performance are indeed based on ligand stability. Due to the presence of a photosensitizer and a catalytic unit, binuclear complexes 3 and 4 were tested for photocatalytic water oxidation. The bridging ligand architecture, however, inhibits the effective electron‐transfer cascade that would allow photocatalysis to run efficiently. The findings of this study can elucidate critical factors in catalyst design.

Exploitation of the Second Coordination Sphere to Promote Significant Increase of Room-Temperature Luminescence Lifetime and Anion Sensing in Ruthenium–Terpyridine Complexes

This paper deals with the synthesis, characterization, and photophysical behaviors of three Ru(II)-terpyridine complexes derived from a terpyridyl-imidazole ligand (tpy-HImzPh3Me2), wherein a terpyridine moiety has been coupled with a dimethylbenzil unit through a phenylimidazole spacer. The three complexes display strong emission at RT having excited-state lifetimes in the range of 2.3-43.7 ns, depending upon the co-ligand present and the solvents used. Temperature-dependent emission spectral measurements have demonstrated that the energy separation between emitting metal-to-ligand charge transfer state and non-emitting metal-centered state is increased relative to that of [Ru(tpy)2]2+. In contrast to our previously studied Ru(II) complexes containing similar terpyridyl-imidazole motif but differing by peripheral methyl groups, significant enhancement of RT emission intensity and quantum yield and remarkable increase of emission lifetime occur for the present complexes upon protonation of the imidazole nitrogen(s) with perchloric acid. Additionally, by exploiting imidazole NH motif(s), we have examined their anion recognition behaviors in organic and aqueous media. Interestingly, the complexes are capable of visually recognizing cyanide ions in aqueous medium up to the concentration limit of 10-8 M. Computational studies involving density functional theory (DFT) and time-dependent DFT methods have been carried out to obtain insights into their electronic structures and to help with the assignment of absorption and emission bands.

First-Principles Study on Redox Magnetism and Electrochromism of Cyclometalated Triarylamine-Core Triruthenium Complex

Spin electronic states and optical properties of a circular ruthenium (Ru) terpyridine complex with a triarylamine core (CTTC) are theoretically investigated by first-principles calculations within an all-electron numerical orbital scheme based on spin density functional theory (SDFT), which demonstrate five well-defined redox states for electrochromic functions. Atomic structure of CTTC molecule is obtained by geometric optimization, and its electronic structure with a decreasing semiconductor band-gap exhibits five consecutive single-electron redox states of Ru-coordinated centers. Except for CTTC in (Ru)3+4 redox state exhibiting a net spin of 2.25 (ћ/2), the other redox states are almost zero in total spin. Density distribution and energy-splitting of spin states indicate that the ferromagnetic coupling of Ru cations coordinating with terpyridine/triarylamine ligands originates dominantly from the spin polarization of Ru 4d-orbitals coordinated by N- and C-2p electrons of triarylamine. CTTC molecule in each redox state represents a well-discriminated absorption in visible region, with the highest characteristic peaks locating at 24.2, 20.2, 21.3, and 19.3/21.7 (103 cm−1) and a manifold of peaks at 13.4~25.3 (103 cm−1) for +2~+6 redox states, respectively. Theoretical electronic structure and optics of CTTC complex are used to evaluate the underlying physical mechanism of realizing a multi-color visible electrochromism by four couples of redox pairs, which is suggested to be applied for monitoring electrical information.

A new bis-pyrazolylpyridine ruthenium(III) complex as a potential anticancer drug: in vitro and in vivo activity in murine colon cancer.

We synthesized and characterized the ruthenium(iii) pincer-type complex [RuCl3(H2Lt-Bu] (H2Lt-Bu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine, 1) by elemental analysis, IR and UV-Vis spectroscopy, and the mass spectrometry (MS) method ESI Q-TOF. For comparison reasons, we also studied ruthenium(iii) terpyridine complexes of the general formula [Ru(N-N-N)Cl3], where N-N-N = 4'-chloro-terpyridine (Cl-tpy; 2) or 4'-chlorophenyl-terpyridine (Cl-Ph-tpy; 3). A kinetic study of the substitution reactions of 1-3 with biomolecules showed that the rate constants depend on the properties of the spectator ligand and the nature of the entering nucleophile. The DNA/HSA binding study showed that in comparison to complex 1 (bis-pyrazolylpyridine), the other two (2 and 3) terpyridine complexes had a slightly better binding affinity to calf thymus DNA (CT DNA), while in the case of human serum albumin (HSA), complex 1 exhibited the strongest quenching ability. We demonstrated that 1 possesses significant in vitro cytotoxic activity against mouse colon carcinoma CT26 cells and in vivo antitumor activity in murine heterotopic colon carcinoma. Complex 1 induced G0/G1 cell cycle arrest and apoptotic death in CT26 cells. Additionally, 1 showed antiproliferative activity, as evaluated by the detection of the expression levels of the Ki67 protein. Furthermore, the in vivo results showed that 1 reduced primary tumour growth and the number and growth of lung and liver metastases, significantly prolonging the treated mice's survival rate. This study highlighted that 1 does not show hepato- and nephrotoxicity. Our data demonstrated the considerable antitumor activity of the ruthenium(iii) pincer complex against CT26 tumour cells and implicated further investigations of its role as a potential chemotherapeutic agent for colon carcinoma.

Antitumor Activity of Ruthenium(II) Terpyridine Complexes towards Colon Cancer Cells In Vitro and In Vivo.

Ruthenium complexes have attracted considerable interest as potential antitumor agents. Therefore, antitumor activity and systemic toxicity of ruthenium(II) terpyridine complexes were evaluated in heterotopic mouse colon carcinoma. In the present study, cytotoxic effects of recently synthesized ruthenium(II) terpyridine complexes [Ru(Cl-tpy)(en)Cl][Cl] (en = ethylenediamine, tpy = terpyridine, Ru-1) and [Ru(Cl-tpy)(dach)Cl][Cl] (dach = 1,2-diaminocyclohexane, Ru-2) towards human and murine colon carcinoma cells were tested in vitro and in vivo and compared with oxaliplatin, the most commonly used chemotherapeutic agent against colorectal carcinoma. Ruthenium(II) complexes showed moderate cytotoxicity with IC50 values ranging between 19.1 to 167.3 μM against two human, HCT116 and SW480, and one mouse colon carcinoma cell line, CT26. Both ruthenium(II) terpyridine complexes exerted a moderate apoptotic effect in colon carcinoma cells, but induced significant necrotic death. Additionally, both complexes induced cell cycle disturbances, but these effects were specific for the cell line. Further, Ru-1 significantly reduced the growth of primary heterotopic tumor in mice, similarly to oxaliplatin. Renal damage in Ru-1 treated mice was lower in comparison with oxaliplatin treated mice, as evaluated by serum levels of urea and creatinine and histological evaluation, but Ru-1 induced higher liver damage than oxaliplatin, evaluated by the serum levels of alanine aminotransferase. Additionally, the interaction of these ruthenium(II) terpyridine complexes with the tripeptide glutathione (GSH) was investigated by proton nuclear magnetic resonance (1H NMR) spectroscopy. All reactions led to the formation of monofunctional thiolate adducts [Ru(Cl-tpy)(en)GS-S] (3) and [Ru(Cl-tpy)(dach)GS-S] (4). Our data highlight the significant cytotoxic activity of [Ru(Cl-tpy)(en)Cl][Cl] against human and mouse colon carcinoma cells, as well as in vivo antitumor activity in CT26 tumor-bearing mice similar to standard chemotherapeutic oxaliplatin, accompanied with lower nephrotoxicity in comparison with oxaliplatin.

Synthesis, characterization, and evaluation of biological activities of new 4′‐substituted ruthenium (II) terpyridine complexes: Prospective anti‐inflammatory properties

The synthesis and characterization of Ru (II) terpyridine complexes derived from 4′ functionalized 2,2′:6′,2″‐terpyridine (tpy) ligands are reported. The heteroleptic complexes comprise the synthesized ligands 4′‐(2‐thienyl)‐ 2,2′:6′,2″‐terpyridine) or (4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine and (dimethyl 5‐(pyrimidin‐5‐yl)isophthalate). The new complexes [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl2] (9), [Ru(4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl2] (10), and [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)(NCS)2] (11) were characterized by 1H‐ and 13C‐NMR spectroscopy, C, H, N, and S elemental analysis, UPLC‐ESI‐MS, TGA, FT‐IR, and UV‐Vis spectroscopy. The biological activities of the synthesized ligands and their Ru (II) complexes as anti‐inflammatory, antimicrobial, and anticancer agents were evaluated. Furthermore, the toxicity of the synthesized compounds was studied and compared with the standard drugs, namely, diclofenac potassium and ibuprofen, using hemolysis assay. The results indicated that the ligands and the complex 9 possess superior anti‐inflammatory activities inhibiting albumin denaturation (89.88–100%) compared with the standard drugs (51.5–88.37%) at a concentration of 500 μg g−1. These activities were related to the presence of the chelating N‐atoms in the ligands and the exchangeable chloro‐ groups in the complex. Moreover, the chloro‐ and thiophene groups in complex 9 produce a higher anticancer activity compared with its isothiocyanate derivative in the complex 11 and the 3,4‐dimethoxyphenyl moiety in complex 10. Considering the toxicity results, the synthesized ligands are nontoxic or far less toxic compared with the standard drugs and the metal complexes. Therefore, these newly synthesized compounds are promising anti‐inflammatory agents in addition to their moderate unique broad antimicrobial activity.

Systematic investigation of the antiproliferative activity of a series of ruthenium terpyridine complexes

Due to acquired resistance or limitations of the currently approved drugs against cancer, there is an urgent need for the development of new classes of compounds. Among others, there is an increasing attention towards the use of Ru(II) polypyridyl complexes. Most studies in the literature were made on complexes based on the coordination of N-donating bidentate ligands to the ruthenium core whereas studies on 2,2′:6′, 2″-terpyridine (terpy) coordinating ligands are relatively scare. However, several studies have shown that [Ru(terpy)2]2+ derivatives are able bind to DNA through various binding modes making these compounds potentially suitable as chemotherapeutic agents. Additionally, light irradiation of these compounds was shown to enable DNA cleavage, highlighting their potential use as photosensitizers (PSs) for photodynamic therapy (PDT). In this work, we present the systematic investigation of the potential of 7 complexes of the type [Ru(terpy)(terpy-X)]2+ (X = H (1), Cl (2), Br (3), OMe (4), COOH (5), COOMe (6), NMe2 (7)) as potential chemotherapeutic agents and PDT PSs. Importantly, six of the seven complexes were found to be stable in human plasma as well as photostable in acetonitrile upon continuous light irradiation (480 nm). The determination of the distribution coefficient logP values for the 7 complexes revealed their good water solubility. Complex 7 was found to be cytotoxic in the micromolar range in the dark as well as to have some phototoxicity upon light exposure at 480 nm in non-cancerous retinal pigment epithelium (RPE-1) and cancerous human cervical carcinoma (HeLa) cells. SynopsisThe systematic investigation of the potential of 7 complexes of the type [Ru(terpy)(terpy-X)]2+ (terpy: 2,2′:6′, 2″-terpyridine; X = H (1), Cl (2), Br (3), OMe (4), COOH (5), COOMe (6), NMe2 (7)) as potential chemotherapeutic agents and photosensitizers for photodynamic therapy is presented.

Polymeric binuclear ruthenium complex as efficient electrocatalyst for oxygen evolution reaction

A robust polymeric material constituted by chains of binuclear aqua ruthenium terpyridylphenanthroline complexes connected through benzene ring meta-positions, exhibiting an unusual two electrons and two protons PCET (proton-coupled electron transfer) process and enhanced oxygen evolution reaction (OER) activity, is described. The catalytic active [RuVO] species is generated at potentials more positive than +1.5 V (NHE) in the poly-[{Ru(H2O)(phen)}2(tpy2ph)] film, as confirmed by the rise of the ruthenyl (RuVO) stretching band at 810 cm−1 in the Raman spectrum, and the clear change to a higher activity regime as confirmed by EIS. Faradaic efficiency for OER as high as 39% was achieved at +1.8 V, indicating that poly-[{Ru(H2O)(phen)}2(tpy2ph)] is one of the most active ruthenium terpyridine complexes ever prepared. The synthesis and characterization of the monomeric binuclear [{RuCl(Clphen)}2(tpy2ph)]2+ and its respective [{Ru(H2O)(Clphen)}2(tpy2ph)]4+ aqua complex are also fully described.

Multi-modal surface grafting of [trans-bis(aminodiphenylphosphine) terpyridine-Ru(II)Cl]+Cl− complex onto glassy carbon electrode

The design of a ruthenium-terpyridine complex having 4-aminobenzyl-diphenylphosphine as remote ligands in a trans arrangement ([Ru(trans-PN)2(trpy)Cl]+Cl−, [trans-bis(aminodiphenylphosphine) terpyridine-Ru(II)Cl]+Cl−) is shown to be a highly versatile approach for the immobilization of the organometallics at a carbon surface. Three distinct strategies could be then successfully employed to achieve the grafting of the complex, namely i) the electroreduction of the corresponding in situ produced diazonium cation, ii) the electrooxidation of the aromatic amine moiety in the presence of a base and iii) an anodic electropolymerization in the absence of base. The modified surfaces were characterized by electrochemical or Scanning Electron Microscopy (SEM) studies. The reported approach allows a clean modulation of film thickness and anchoring modes, particularly useful for a given design of ruthenium containing films dedicated to a given application. In this context, the polymer films which contain the largest surface concentration of active ruthenium were employed as immobilized catalyst for oxidation of benzyl alcohol in water, allowing a test of the catalytic activity of the complexes as grafted materials.

Electrografted monolayer based on a naphthalene diimide-ruthenium terpyridine complex dyad: efficient creation of large-area molecular junctions with high current densities.

An electron donor-acceptor dyad has been designed for the creation of large-area molecular junctions (MJ). Diazonium cation electrografting was used to form well controlled monolayers. The robustness of the monolayer enabled the creation of MJs using direct top-coat evaporation with a high yield of operating devices.

Second sphere ligand modifications enable a recyclable catalyst for oxidant-free alcohol oxidation to carboxylates.

Modification of the classic terpyridine pincer ligand with pendent NHR (R = mesityl) groups provides enhanced activity and stability in Ru-catalyzed dehydrogenation catalysis. These second sphere modifications furnish highly active catalysts for the oxidant-free dehydrogenative oxidation of primary alcohols to carboxylates and facilitate catalyst recycling.

Self-assembled supramolecular cages containing dinuclear ruthenium(II) polypyridyl complexes

Four dinuclear ruthenium(II) terpyridine complexes containing terminal pyridyl groups were synthesised for assembly into larger heterometallic supramolecular structures. These 4nm long metalloligands are capable of binding additional metal ions. Combination of tetrakis(acetonitrile)palladium(II) tetrafluoroborate with one of the dinuclear complexes lead to rapid self-assembly of a [Pd2L4]20+ cage, which was characterised using high resolution electrospray mass spectrometry and NMR spectroscopy, including diffusion measurements.