New Amphiphilic Polypyridyl Ruthenium（Ⅱ） Sensitizer and Its Application in Dye-Sensitized Solar Cells

Amphiphilic polypyridyl mthenium（Ⅱ） complex cis-di（isothiocyanato）（4,4＇-di-tert-butyl-2,2＇-bipyridyl）（4,4＇- dicarboxy-2,2＇-bipyridyl）ruthenium（Ⅱ）（K005） has been synthesized and characterized by cyclic voltammetry, ^1H NMR, UV-Vis, and FT-IR spectroscopies. The sensitizer sensitizes TiO2 over a notably broad spectral range due to its intense metal-to-ligand charge-transfer （MLCT） bands at 537 and 418 nm. The photophysical and photochemical studies of K005 were contrasted with those of cis-Ru（dcbpy）2（NCS）2, known as the N3 dye, and the amphiphilic ruthenium（Ⅱ） dye Z907. A reversible couple at E1/2=0.725 V vs. saturated calomel electrode （SCE） with a separation of 0.08 V between the anodic and cathodic peaks, was observed due to the Ru^Ⅱ/Ⅲ couple by cyclic voltammetry. Furthermore, this amphiphilic ruthenium complex was successfully used as sensitizers for dye-sensitized solar cells with the efficiency of 3.72% at the 100 mW·cm^-2 irradiance of air mass 1.5 simulated sunlight without optimization of TiO2 films and the electrolyte.     

Anion Sensing in Aqueous Media by Photo-active Transition-Metal Bipyridyl Rotaxanes

A chloride anion templation methodology is utilized in the construction of novel transition-metal rhenium(I) and ruthenium(II) bipyridyl appended [2]rotaxanes. (1) H?NMR spectroscopic titrations reveal the ability of the rotaxanes to selectively bind chloride over the more basic oxoanions, with the ruthenium(II) bipyridyl appended rotaxane strongly binding chloride in 30?% water. Photophysical investigations demonstrate the ability of the rotaxanes to sense anions in aqueous media, with chloride being selectively complexed, in general agreement with NMR spectroscopy determined anion binding data.     

Transition Metal Self-assembly of Dithiocarbamate Based Anion Receptors

Abstract

Novel macrocyclic and acyclic transition metal dithiocarbamate based anion receptors, prepared via metal mediated self-assembly, strongly bind anions, and in the case of L² electrochemically recognise carboxylate, chloride and dihydrogen phosphate.     

Transition metal-directed self-assembly of calix[4]arene based dithiocarbamate ligands

The transition metal-directed self-assembly of dithiocarbamate ligand functionalized upper and lower rim calix[4]arenes affords novel dimeric bimetallic bis(calix[4]arene) species as determined by a combination of analytical methods including X-ray crystallography. An exception is a zinc(II) dithiocarbamate upper rim calix[4]arene assembly which is monomeric in nature. Electrochemical investigations reveal the bimetallic copper(II) bis(calix[4]arene) systems can electrochemically sense dihydrogen phosphate and carboxylate anions via significant cathodic perturbations of the respective copper(II)/(III) dithiocarbamate oxidation wave.     

Structural organization of a {ruthenium[tris(bipyridyl)]} complex by strong π–π stacking of a tethered 1,8-naphthalimide synthon: Impact on electrochemical and spectral properties

The new ligand N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide has been prepared by the reaction of 1,8-naphthalimide, 5-(bromomethyl)-2,2′-bipyridine and potassium carbonate in refluxing acetone. Reaction of this ligand and bis(bipyridyl)ruthenium(II) dichloride in refluxing ethanol followed by anion exchange with ammonium hexafluorophosphate produces {ruthenium[bis(bipyridyl)][N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide]}(PF₆)₂ (1). In both the solid state (X-ray analysis) and in solution (shown by PGSE-NMR analysis), the 1,8-naphthalimide synthon organizes the cationic metal units into dimers with a strong, directionally oriented (head to tail) π–π stacking interaction. UV–VIS, fluorescence spectroscopy and electrochemical studies indicate that even with the strong interactions of the 1,8-naphthalimide groups, it does not have a significant influence on the properties of the [Ru(bipy)₃]²⁺ core.     

Electrocatalytic oxidation of alcohols on carbon electrodes modified by functionalized polypyrrole–RuO2 films

The electrocatalytic activity of several types of polypyrrole films bearing cationic pendant group [tris(bipyridyl)ruthenium(II) complexes, viologen, ammonium] and containing dispersed microparticles of RuO₂ towards the oxidation of alcohols to aldehydes or ketones has been investigated. Best results are obtained with polypyrrole films substituted by a tris(bipyridyl)ruthenium(II) complex, the latter acting as an electron relay for the electrogeneration of the strong oxidizing species RuO₄²⁻. The influence of several parameters such as base, supporting electrolyte, electrolysis potential and catalyst amount on the efficiency of the electrocatalysis has been examined. Under optimum conditions a maximum turnover of 10 900 was reached. In all cases the lifetime of these electrode materials was limited by the slow release of the RuO₄²⁻ species.     

Transition metal and organometallic anion complexation agents

Anions are ubiquitous species, and therefore, their sensing is of considerable interest. Anion receptors containing electrochemically active groups such as ferrocene or cobaltocenium, or optically active groups such as ruthenium(II) bipyridyl derivatives, allow the binding of anions to be detected by a physical response at the metal centre. These systems have been incorporated into various acyclic, macrocyclic and calix[4]arene frameworks, many of which include an amide hydrogen-bonding group. Anions may be recognised in a range of environmental conditions, with some receptors even being active in aqueous solution. The incorporation of new transition metal and organometallic systems has led to the development of several new strategies in anion recognition.     

The anion binding properties of neutral receptors bearing nitro group,phenanthroline or ruthenium(II) metal

A series of neutral cyclohexadiamine anion receptors containing nitro, phenanthroline or ruthenium(II) have been designed and synthesized. Their u.v.–vis spectroscopy investigations reveal that the receptor bearing nitro group displays the strongest affinities for F⁻, AcO⁻, H₂PO ₄ ⁻ and can be used as an efficient detection tool for the above anions. Results indicate that the anion affinities can be enhanced through appending nitro group and ruthenium(II) metal compared with phenanthroline moiety.     

A New Luminescent Ruthenium(II) Polypyridine‐derived Dipicolylamine Complex as a Sensor for Cu2+ Ions

A chemo‐sensor [Ru(bpy)₂(bpy‐DPF)](PF₆)₂ ( 1 ) (bpy=2,2′‐bipyridine, bpy‐DPF=2,2′‐bipyridyl‐4,4′‐bis(N,N‐di(2‐picolyl))formylamide) for Cu²⁺ using di(2‐picolyl)amine (DPA) as the recognition group and a ruthenium(II) complex as the reporting group was synthesized and characterized successfully. It demonstrates a high selectivity and efficient signaling behavior only for Cu²⁺ with obvious red‐shifted MLCT (metal‐to‐ligand charge transfer transitions) absorptions and dramatic fluorescence quenching compared with Zn²⁺ and other metal ions.     

Diorganotin(IV) dithiocarbamate complexes as chromogenic sensors of anion binding

One dinuclear chlorodiphenyltin (IV) dithiocarbamate complex (1) and four mononuclear complexes of general formula Ph₂Sn(S₂CNR)Cl (2, 3, 5, and 6) have been synthesized and characterized both in solid-state and solution. X-ray structures for complexes 1, 3 and 6 demonstrated a five-coordination geometry around of tin atoms, in which dithiocarbamate ligand chelates asymmetrically the metal center. As shown by ¹¹⁹Sn NMR spectroscopy, five-coordination geometry observed in the solid-state remains in solution. The stability of these chlorodiphenyltin(IV) dithiocarbamate complexes in the presence of biologically relevant anions such as acetate, dicarboxylates of general formula ^?OOC-(CH₂)_n-COO^? (n = 2–8), dihydrogenphosphate, hydrogensulfate, and halides has been examined in acetonitrile solutions. For all of these organotin(IV) complexes the displacement of the coordinated ligands (i.e., chloride and dithiocarbamate) from the organotin(IV) moiety occurred in the presence of monoanions like acetate, dihydrogenphosphate, hydrogensulfate and fluoride. A stepwise mechanism for ligand exchange is proposed based on UV–Vis, ¹H, ¹³C and ¹¹⁹Sn spectroscopic data, as well as mass spectrometry. From UV–Vis titration experiments it was found that dicarboxylates with small spacers like malonate and succinate, acted differently in the exchange of the dithiocarbamate group in comparison to other monoanionic O donor ligands or dicarboxylates with longer chains, perhaps by following an intramolecular displacement of the coordinated ligand.The lability of these organotin(IV) dithiocarbamate compounds in solution hampers their use as stably host for anions, however, by taking advantage of the intrinsic chromogenic properties of free dithiocarbamate anions, or by attaching dithiocarbamate groups to well-known fluorescent moieties such as antracene, these complexes can sense the presence of O-donor anions at very low concentrations by displacement of the metal-coordinated dithiocarbamate.     

Streptavidin reduces oxygen quenching of biotinylated ruthenium(II) and palladium(II) complexes

Transition metal complexes such as biotinylated ruthenium(II) tris(bipyridyl) and palladium(II) porphyrin show an increase in luminescence intensity and lifetime upon binding to streptavidin in aqueous solution. Here we show that this increase of luminescence lifetime and intensity are caused by the shielding of the transition metal complexes from dissolved oxygen through streptavidin rather than by hydrophobicity effects as recently claimed.     

Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

The reaction of 2,2′:4,4′′:4′,4′′′‐quaterpyridyl (qtpy), with d⁶ ruthenium(II) (Ru^II), and rhenium(I) (Re^I) metal centers has been investigated. The pendant pyridyl groups on the products have also been methylated to produce a second series of complexes containing coordinated Meqtpy²⁺. The absorption spectra of the complexes are dominated by intraligand and charge‐transfer bands. The ruthenium(II) complexes display broad unstructured luminescence consistent with emission from a Ru(d)→diimine(π*) manifold in acetonitrile solutions. In aqueous solutions, their emissions are weaker and the lifetimes are shorter. This effect is particularly acute for complexes incorporating coordinated dipyridylpyrazine, dppz, ligands. Although the emission of the ruthenium(II) complexes containing Meqtpy²⁺ is generally shorter than their qtpy analogs, it is notable that solvent‐dependent effects are much less intense. The rhenium(I) complexes also display broad unstructured luminescence but, compared with the ruthenium(II) systems, they have a relatively short lifetime in acetonitrile. Electrochemical studies reveal that all of the Ru^II complexes display chemically reversible metal‐based oxidations. Re^I complexes only display irreversible metal‐based oxidations. In most cases, the reduction processes were not fully chemically reversible. The electrochemical and optical studies reveal that the nature of the lowest excited state of these complexes—particularly, the systems incorporating dppz—is highly dependent on the nature of the coordinated ligands. Calculations indicate that, although the excited state of most of the complexes is centered on the qtpy or Meqtpy²⁺ ligands, the excited state of the complexes containing dppz ligands is switched away from the dppz by qtpy methylation. A crystallographic study on one of the dicationic ruthenium(II) structures reveals that it forms an inclusion complex with benzene.     

Alternating π‐conjugated copolymer of dithiafulvene with 2,2′‐bipyridyl units

A π‐conjugated polymer containing a dithiafulvene unit and a bipyridyl unit was prepared by cycloaddition polymerization of aldothioketene derived from 5,5′‐diethynyl‐2,2′‐bipyridine. Ultraviolet–visible (UV–vis) absorption spectra showed that the π‐conjugation system of the polymer expanded more effectively than that of a benzene analogue of poly(dithiafulvene) obtained from 1,4‐diethynylbenzene. Cyclic voltammetry measurements indicated that the dithiafulvene–bipyridyl polymer was a weaker electron‐donor polymer than the benzene analogue. These results supported the idea that the incorporation of the electron‐accepting bipyridyl moiety into conjugated poly(dithiafulvene) induced an intramolecular charge‐transfer (CT) effect between the units. Treatment of the dithiafulvene–bipyridyl polymer with bis(2,2′‐bipyridyl)dichlororuthenium (II) [Ru(bpy)₂Cl₂] afforded a ruthenium–polymer complex. A cyclic voltammogram of the complex showed broad redox peaks, which indicated electronic interaction between the dithiafulvene and tris(bipyridyl) ruthenium complex. The dithiafulvene–bipyridyl polymer formed CT complexes with 7,7,8,8‐tetracycanoquinodimethane (TCNQ) in dimethyl sulfoxide. The UV–vis absorption indicated that the resulting CT complex contained anion radical of TCNQ and partially charge‐transferred TCNQ. The polymer showed an unusually high electrical conductivity of 3.1 × 10^?4 S/cm in its nondoped state due to the effective donor–acceptor interaction between the bipyridine unit and the dithiafulvene unit. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4083–4090, 2001     

Facile Fabrication of Solid‐state Electrochemiluminescence Sensor via Non‐covalent π‐π Stacking and Covalent Bonding on Graphite Electrode

Herein, a facile and efficient method was developed for fabrication of solid‐state electrochemiluminescence (ECL) sensor via non‐covalent π‐π stacking and covalent bonding on the graphite electrode (GE) surface. The electrode was firstly modified with 1‐aminopyrene via π‐π stacking between GE surface and the pyrene moiety. Thereafter a stable and efficient solid‐state ECL sensor was fabricated by covalent immobilization of ruthenium(II) onto the GE surface via amidation reaction between the 1‐aminopyrene and bis(2,2′‐bipyridyl)(4‐methyl‐4′‐carboxypropyl‐2,2′‐bipyridyl) ruthenium(II) bishexafluorophosphate. The sensor has been investigated using tripropylamine and tetracycline as representative analytes, and low detection limits of 0.7 nM and 3.5 nM (S/N=3) were reached, respectively.     

Oxygen quenching of tris(2,2′-bipyridine) ruthenium(II) complexes in thin organic films

A study is presented of the quenching, by oxygen, of the luminescence of tris(2,2′-bipyridine) ruthenium(II) complexes immobilized in thin, transparent, polymer-based films. The film media consist of a water-insoluble linear polymer plasticized with a trialkylphosphate ester, in which the complex ruthenium cations are solubilized by ion pairing with organophilic anions such as tetraphenylborate.

Luminescence lifetimes were studied in relation oxygen concentration in a gas stream contiguous with the film medium, film thickness and concentration of the metal complex within the film medium. It is shown that the microheterogeneous environment of the luminescent complex, which has recently been implicated in the non-linear quenching responses of polymer-immobilized, transition metal complex oxygen sensors, may arise simply as a consequence of the limited solubility of the complex in the film medium. When solubility is limited, the partial precipitation of the complex results in a colloidal of luminescent particles which exhibit non- uniform susceptibilities to quenching by oxygen. Good solubility, and therefore linear quenching characteristics, are promoted by methyl substitution of the bipyridyl ligand and by use of a plasticizer (tributylphosphate) with marked cation solvating powers.     

The Effect of Heavy Atoms on Photoinduced Electron Injection from Nonthermalized and Thermalized Donor States of MII–Polypyridyl (M=Ru/Os) Complexes to Nanoparticulate TiO2 Surfaces: An Ultrafast Time‐Resolved Absorption Study

We have synthesized ruthenium(II)– and osmium(II)–polypyridyl complexes ([M(bpy)₂ L ]²⁺, in which M=Os^II or Ru^II, bpy=2,2′‐bipyridyl, and L =4‐(2,2′‐bipyridinyl‐4‐yl)benzene‐1,2‐diol) and studied the interfacial electron‐transfer process on a TiO₂ nanoparticle surface using femtosecond transient‐absorption spectroscopy. Ruthenium(II)‐ and osmium(II)‐based dyes have a similar molecular structure; nevertheless, we have observed quite different interfacial electron‐transfer dynamics (both forward and backward). In the case of the Ru^II/TiO₂ system, single‐exponential electron injection takes place from photoexcited nonthermalized metal‐to‐ligand charge transfer (MLCT) states. However, in the case of the Os^II/TiO₂ system, electron injection takes place biexponentially from both nonthermalized and thermalized MLCT states (mainly ³MLCT states). Larger spin–orbit coupling for the heavier transition‐metal osmium, relative to that of ruthenium, accounts for the more efficient population of the ³MLCT states in the Os^II‐based dye during the electron‐injection process that yields biexponential dynamics. Our results tend to suggest that appropriately designed Os^II–polypyridyl dye can be a better sensitizer molecule relative to its Ru^II analogue not only due to much broader absorption in the visible region of the solar‐emission spectrum, but also on account of slower charge recombination.     

Theoretical studies on the interaction of anionic collectors with Cu+, Cu2+, Zn2+ and Pb2+ ions

 The influence of collector structure on interaction with metal cations was modelled by computational ab initio methods. The interaction energies were calculated between metal ions (Cu⁺, Cu²⁺, Zn²⁺ and Pb²⁺) and selected collector anions: ethyl xanthate, ethyl trithiocarbonate, dithiobutyric acid, ethyl dithiocarbamate, diethyl dithiocarbamate, diethylphosphinecarbodithioic acid and diethoxyphosphinecar bodithioic acid. The strongest interaction was found with diethyl dithiocarbamate. The results give qualitative information on the effect of the collector structure on the initial adsorption steps on sulphide mineral flotation. Received: 25 September / Accepted: 11 October 2001 / Published online: 22 March 2002     

Spectral, analytical, thermal, and antimicrobial studies of novel sodium 2-[4(2-hydroxy-3-izopropylaminopropoxy)phenyl]acetamide (atenolol) dithiocarbamate and its divalent transition metal complexes

Atenolol dithiocarbamate (ADTC) and its complexes with Cu(II), Co(II), Ni(II), Zn(II), and Cd(II) have been synthesized. These newly synthesized products have been characterized by elemental analyses (C, H, N, and S), thermal (thermogravimetry (TG) and differential thermal analyses (DTA)) as well as by spectral (UV, IR, and NMR (¹H)) studies. The stability constants (β) of metal complexes of ADTC have been determined by UV-Vis data in solutions in DMSO. The antimicrobial activities of the metal complexes have been screened in vitro against ten bacteria. The text was submitted by the authors in English.     

Side‐chain functionalized polymers containing bipyridine coordination sites: Polymerization and metal‐coordination studies

Monomers containing (trisbipyridine) ruthenium(II), (bisbipyridine) palladium(II), and heteroleptic ruthenium complexes were synthesized and polymerized via ruthenium‐catalyzed ring‐opening metathesis polymerization in nonpolar solvents. The solubility of the resulting polyelectrolytes in nonpolar solutions could be tuned by alkyl functionalization of the ligands around the metal centers. These polymers are the first polynorbornenes containing a 2,2′‐bipyridine‐based metal complex at each repeating unit and might be used in numerous applications, including luminescent and electroluminescent materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2973–2984, 2004     

Iodide Recognition and Sensing in Water by a Halogen‐Bonding Ruthenium(II)‐Based Rotaxane

The synthesis and anion‐recognition properties of the first halogen‐bonding rotaxane host to sense anions in water is described. The rotaxane features a halogen‐bonding axle component, which is stoppered with water‐solubilizing permethylated β‐cyclodextrin motifs, and a luminescent tris(bipyridine)ruthenium(II)‐based macrocycle component. ¹H NMR anion‐binding titrations in D₂O reveal the halogen‐bonding rotaxane to bind iodide with high affinity and with selectively over the smaller halide anions and sulfate. The binding affinity trend was explained through molecular dynamics simulations and free‐energy calculations. Photo‐physical investigations demonstrate the ability of the interlocked halogen‐bonding host to sense iodide in water, through enhancement of the macrocycle component’s Ru^II metal–ligand charge transfer (MLCT) emission.