Luminescent properties of a 3,5-diphenylpyrazole bridged Pt(ii) dimer.

We report the synthesis, electrochemistry, photophysical properties and electroluminescence of a highly luminescent pyrazolate-bridged platinum(ii) complex. The complex has the general formula of [((N^C^N)Pt)2(µ-pz)][PF6] where N^C^N = 1,3-di(2-pyridyl)benzene and µ-pz = 3,5-diphenylpyrazolate. The X-ray structure shows that the bridging pyrazolate ligand causes a close Pt-Pt interaction of 3.05(7) Å. The emission profile of the complex was determined in solution, glassy 2-methyltetrahydrofurane at 77 K, and the solid state at both room temperature and 77 K. Each emission profile displayed a strong red metal-metal-to-ligand charge transfer while the solution and glassy 2-methyltetrahydrofurane emission profiles also displayed a ligand-centred transition. The absolute quantum yields of the complex in solution and the solid state at room temperate are 86% and 39%, respectively. Light-emitting electrochemical cells (LEECs) of [((N^C^N)Pt)2(µ-pz)][PF6] were fabricated which displayed appreciable electroluminescence, among the brightest and most efficient LEECs from dinuclear compounds to date.

Copper Selective Polymeric Extractant Synthesized by Ring-Opening Metathesis Polymerization.

Novel polymers bearing pendant picolinic acid functionalities have been synthesized by ring-opening metathesis polymerization (ROMP) for applications in separations-based purification protocols. These polymers and their corresponding monomer were shown to be selective for Cu2+ over a variety of other divalent metal cations as inferred from pH dependent studies carried out under both liquid-liquid and solid-liquid extraction conditions. The polymer system of this study also showed high selectivity for Cu2+ over Ni2+ in mock protocols that could be relevant to the purification of Cu radioisotopes. Separation factors as high as 290 were achieved for extractions from solutions containing a 100-fold excess of Ni2+ relative to Cu2+.

Electronic Interactions of n-Doped Perylene Diimide Groups Appended to Polynorbornene Chains: Implications for Electron Transport in Organic Electronics.

A polymer consisting of a polynorbornene backbone with perylene diimide (PDI) pendant groups on each monomeric unit is synthesized via ring opening metathesis polymerization. The PDI pendant groups along the polymer backbone, studied by UV-vis absorption, fluorescence emission, and electron paramagnetic resonance spectroscopy in addition to electrochemical methods, show evidence of molecular aggregation and corresponding electronic coupling with neighboring groups, which forms pathways for efficient electron transport from one group to another in a specific reduced form. When n-doped, the title polymer shows redox conductivity of 5.4 × 10-3 S cm-1 , comparable with crystalline PDI materials, and is therefore a promising material for use in organic electronics.

A Thiophene-Containing Conductive Metallopolymer Using an Fe(II) Bis(terpyridine) Core for Electrochromic Materials.

Three Fe(II) bis(terpyridine)-based complexes with thiophene (Fe(L1)2), bithiophene (Fe(L2)2), and 3,4-ethylenedioxythiophene (Fe(L3)2) side chains were designed and synthesized for the purpose of providing two terminal active sites for electrochemical polymerization. The corresponding metallopolymers (poly-Fe(Ln)2, n = 2 or 3) were synthesized on indium tin oxide (ITO)-coated glass substrates via oxidative electropolymerization of the thiophene-substituted monomers and characterized using electrochemistry, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and atomic force microscopy. The film poly-Fe(L2)2 was further studied for electrochromic (EC) color-switching properties and fabricated into a solid-state EC device. Poly-Fe(L2)2 films exhibit an intense MLCT absorption band at 596 nm (ε = 4.7 × 104 M-1 cm-1) in the UV-vis spectra without any applied voltage. Upon application of low potentials (between 1.1 and 0.4 V vs Fc+/Fc), the obtained electropolymerized film exhibited great contrast with a change of transmittance percentage (ΔT%) of 40% and a high coloration efficiency of 3823 cm2 C-1 with a switching time of 1 s. The film demonstrates commonplace stability and reversibility with a 10% loss in peak current intensity after 200 cyclic voltammetry cycles and almost no loss in change of transmittance (ΔT%) after 900 potential switches between 1.1 and 0.4 V (vs Fc+/Fc) with a time interval of 0.75 s. The electropolymerization of Fe(L2)2 provides convenient and controllable film fabrication. Electrochromic behavior was also achieved in a solid-state device composed of a poly-Fe(L2)2 film and a polymer-supported electrolyte sandwiched between two ITO-coated glass electrodes.

Direct synthesis of CdSe nanocrystals within a conducting metallopolymer: toward improving charge transfer in hybrid nanomaterials.

CdSe nanocrystals with tunable sizes and distributions were synthesized directly from Cd(ii) ions coordinated to the conjugated backbone of a thiophene-based conducting metallopolymer. Using our seeded growth technique, the resulting nanocrystals are in direct electronic communication with the polymer, which leads to effective charge transfer between the donor and acceptor.

Phenyl substitution of cationic bis-cyclometalated iridium(iii) complexes for iTMC-LEECs.

A series of seven cationic bis-cyclometalated iridium(iii) complexes of the form [(C^N)2(N^N)Ir][PF6] has been designed in order to examine the effect of bulky, hydrophobic phenyl substituents on the structure-property relationship of these ionic transition metal complexes (iTMCs) in light-emitting electrochemical cells (LEECs). Capping phenyl substituents on the cyclometalating and ancillary ligands allows for individual tuning of the HOMO and LUMO energy levels, respectively, yielding an emission range from yellow to red. The complexes in this series exhibit increased quantum yields, up to 70% higher than the unoptimized, archetypal [(2-phenylpyridine)2(2,2'-bipyridine)Ir][PF6]. Among these, one complex, C3, was recently reported to produce devices with superior luminance and efficiency. Simultaneous measure of the series of complexes enabled the clear discernment of trends in device performance connected to fundamental structure-property relationships that elucidate the origin of enhanced luminance. In general, phenyl substitution of the 2-phenylpyridine ligands of the parent complex produced higher luminance and faster device response than phenyl substitution of the 2,2'-bipyridine ligand. Overall, complex design and device engineering produce competitive LEECs from simple, single-layer architectures. The synthesis, crystallographic, photophysical, and electrochemical properties of the iTMCs, along with the electroluminescence properties of the LEEC devices are reported herein.

Discerning the Impact of a Lithium Salt Additive in Thin-Film Light-Emitting Electrochemical Cells with Electrochemical Impedance Spectroscopy.

Light-emitting electrochemical cells (LEECs) from small molecules, such as iridium complexes, have great potential as low-cost emissive devices. In these devices, ions rearrange during operation to facilitate carrier injection, bringing about efficient operation from simple, single-layer devices. Prior work has shown that the luminance, efficiency, and responsiveness of iridium LEECs is greatly enhanced by the inclusion of small fractions of lithium salts, but much remains to be understood about the origin of this enhancement. Recent work with planar devices demonstrates that lithium additives in iridium LEECs enhance double-layer formation. However, the quantitative influence of lithium salts on the underlying physics of conventional thin-film, sandwich structure LEECs, which beneficially operate at low voltages and generate higher luminance, has yet to be clarified. Here, we use electrochemical impedance spectroscopy to discern the impact of the lithium salt concentration on double-layer formation within the device and draw correlations with performance metrics, such as current, luminance, and external quantum efficiency.

Influence of Lithium Additives in Small Molecule Light-Emitting Electrochemical Cells.

Light-emitting electrochemical cells (LEECs) utilizing small molecule emitters such as iridium complexes have great potential as low-cost emissive devices. In these devices, ions rearrange during operation to facilitate carrier injection, bringing about efficient operation from simple, single layer devices. Recent work has shown that the luminance, efficiency, and responsiveness of iridium-based LEECs are greatly enhanced by the inclusion of small amounts of lithium salts (≤0.5%/wt) into the active layer. However, the origin of this enhancement has yet to be demonstrated experimentally. Furthermore, although iridium-based devices have been the longstanding leader among small molecule LEECs, fundamental understanding of the ionic distribution in these devices under operation is lacking. Herein, we use scanning Kelvin probe microscopy to measure the in situ potential profiles and electric field distributions of planar iridium-based LEECs and clarify the role of ionic lithium additives. In pristine devices, it is found that ions do not pack densely at the cathode, and ionic redistribution is slow. Inclusion of small amounts of Li[PF6] greatly increases ionic space charge near the cathode that doubles the peak electric fields and enhances electronic injection relative to pristine devices. This study confirms and clarifies a number of longstanding hypotheses regarding iridium LEECs and recent postulates concerning optimization of their operation.

Enhanced Luminance of Electrochemical Cells with a Rationally Designed Ionic Iridium Complex and an Ionic Additive.

Light-emitting electrochemical cells (LEECs) offer the potential for high efficiency operation from an inexpensive device. However, long turn-on times and low luminance under steady-state operation are longstanding LEEC issues. Here, we present a single-layer LEEC with a custom-designed iridium(III) complex and a lithium salt additive for enhanced device performance. These devices display reduced response times, modest lifetimes, and peak luminances as high as 5500 cd/m(2), 80% higher than a comparable device from an unoptimized complex and 50% higher than the salt-free device. Improved device efficiency suggests that salt addition balances space charge effects at the interfaces. Extrapolation suggests favorable half-lives of 120 ± 10 h at 1000 cd/m(2) and 3800 ± 400 h at 100 cd/m(2). Overall, complex design and device engineering produce competitive LEECs from simple, single-layer architectures.

Polymeric Materials for the Separation of f-Elements Utilizing Carbamoylmethylphosphine Oxide Chelating Ligands.

The ability of carbamoylmethylphosphine oxide (CMPO) ligands to selectively chelate actinides has been shown to be enhanced by preorganizing the ligands on molecular scaffolds. To increase the preorganization, a new polymeric material with a polyoxanorbornene backbone and CMPO ligand pendant groups has been synthesized, and the ability of the material to selectively extract actinides utilizing a biphasic extraction strategy has been tested. In liquid-liquid extractions of f-block metals from acidic aqueous media into an organic solution containing chelating materials, the polymeric material exhibited a significantly higher ability to extract Th4+ ions than the monomer, with an order of magnitude greater affinity for the polymeric material in most cases. Due to the unique properties of polymeric materials versus small molecules, additional questions arose as to the effect of molecular weight on extraction efficiency. Extraction and separation efficiencies varied for materials of differing molecular weights, with the largest molecular weight polymer extracting near quantitative amounts of thorium ions, and the smaller molecular weight polymers showing separation factors for Th4+ ions over Ce3+, La3+, and Eu3+ ions ranging from 124 to 328.

Resonance Raman Spectroscopy of the T1 Triplet Excited State of Oligothiophenes.

The characterization of triplet excited states is essential for research on organic photovoltaics and singlet fission. We report resonance Raman spectra of two triplet oligothiophenes with n-alkyl substituents, a tetramer and hexamer. The spectra of the triplets are more complex than the ground state, and we find that density functional theory calculations are a useful starting point for characterizing the bands. The spectra of triplet tetrathiophene and hexathiophene differ significantly from one another. This observation is consistent with a T1 excitation that is delocalized over at least five rings in long oligomers. Bands in the 500-800 cm(-1) region are greatly diminished for an aggregated sample of hexathiophene, likely caused by fast electronic dephasing. These experiments highlight the potential of resonance Raman spectroscopy to unequivocally detect and characterize triplets in thiophene materials. The vibrational spectra can also serve as rigorous standards for evaluating computational methods for excited-state molecules.

Phase and redox shifted four iron/four sulfur clusters: fluorous analogs of metalloenzyme cofactors.

Reactions of (1) [Q]2[Fe4S4(SC(CH3)3)4] and the fluorous thiols HS(CH2)nRf8 (n = 2, 3; Rf8 = (CF2)7CF3)), or (2) [Na]2[Fe4S4(S(CH2)nRf8)4] (n = 2, 3) and [PhCH2P((CH2)3Rf6)3][Br] or [PPN][Cl] (PPN = Ph3P[horiz bar, triple dot above]N[horiz bar, triple dot above]PPh3), give the title compounds [Q]2[Fe4S4(S(CH2)nRf8)4], comprised of a fluorous dianion and in some cases fluorous cations, with (1) Q/n = Ph4P/2 (, 67%), Ph4P/3 (, 67%), Me4N/3 (69%), and Ph3P(CH2)2Rf6/2 (73%) or (2) PhCH2P((CH2)3Rf6)3/2 (, 39%), PhCH2P((CH2)3Rf6)3/3 (, 63%), and PPN/2 (36%). The educt [Ph3P(CH2)2Rf6]2[Fe4S4(SC(CH3)3)4] is in turn prepared from FeCl3, HSC(CH3)3/CH3ONa, and [Ph3P(CH2)2Rf6][I], and the educts [Na]2[Fe4S4(S(CH2)nRf8)4] from [Na]2[Fe4S4(SC(CH3)3)4] and HS(CH2)nRf8. The SCH2(1)H and (13)C NMR signals of these paramagnetic salts appear 8.7-10.3 and 32.3-34.9 ppm downfield from those of the corresponding thiols, but the chemical shifts of other signals are nearly normal. The UV-visible spectra show bands similar to those of non-fluorous analogs (290-298 nm and 406-415 nm; ε = 25 700 and 19 200 M(-1) cm(-1) for ). The singly fluorous salts are soluble in organic solvents of moderate polarity, but not in fluorous solvents. The doubly fluorous salts , are soluble in all fluorous solvents assayed, with partition coefficients of >99.65 : <0.35 (CF3C6F11/toluene) and 93.2-93.1 : 6.9-6.8 (FC-72/THF). Cyclic voltammograms carried out using a platinum working microelectrode show that is 0.08 V thermodynamically easier to reduce than .

Direct insights into metal-induced conductivity enhancement in conducting metallopolymers.

Conducting polymers of a Schiff-base ligand and the corresponding oxo-vanadium(IV) complex have been synthesized, characterized, and studied. The metal-free ligand polymer allows for direct comparison between the properties of the ligand polymer and corresponding conducting metallopolymer. The role of the metal centers in the conducting metallopolymer is elucidated unambiguously.

Incorporation of thieno[3,2-b]thiophene moieties as novel electropolymerizable groups in a conducting metallopolymer and study of the effect on photostability.

A novel nickel(II)-containing conducting metallopolymer utilizing thieno[3,2-b]thiophene moieties as the electropolymerizable groups is synthesized and characterized. A metal-free polymer is also obtained via electropolymerization of the title ligand allowing comparative studies of the electrochemical and spectroscopic properties of the polymer system in the presence and absence of nickel(II) metal ions. Photodegradation of the two polymers is studied along with an analogous system incorporating bithiophene as the electropolymerizable groups. Stability is found to be comparable between the metal-free thieno[3,2-b]thiophene- and bithio-phene-based polymers; however, significant enhancement is observed in the thieno[3,2-b]thiophene-based nickel(II) conducting metallopolymer.

Electrochemical modification of indium tin oxide using di(4-nitrophenyl) iodonium tetrafluoroborate.

Optoelectronic applications often rely on indium tin oxide (ITO) as a transparent electrode material. Improvements in the performance of such devices as photovoltaics and light-emitting diodes often requires robust, controllable modification of the ITO surface to enhance interfacial charge transfer properties. In this work, modifier films were deposited onto ITO by the electrochemical reduction of di(4-nitrophenyl) iodonium tetrafluoroborate (DNP), allowing for control over surface functionalization. The surface coverage could be tuned from submonolayer to multilayer coverage by either varying the DNP concentration or the number of cyclic voltammetry (CV) grafting scans. Modification of ITO with 0.8 mM DNP resulted in near-monolayer surface coverage (4.95 × 10(14) molecules/cm(2)). X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of 4-nitrophenyl (NO2Ph) moieties on the ITO surface through the detection of a NO2 nitrogen signal at 405.6 eV after grafting. Further XPS evidence suggests that the NO2Ph radicals do not bond to the surface indium or tin sites, consistent with modification occurring either through bonding to surface hydroxyl groups or through strong physisorption on ITO. CV in the presence of an electroactive probe and electrochemical impedance spectroscopy (EIS) were used to investigate the electronic effects that modification via DNP has on ITO. Even at submonolayer coverage, the insulating organic films can reduce the current response to ferrocene oxidation and reduction by more than 25% and increase the charge transfer resistance by a factor of 10.

(E)-4-[7-(2,3-Di-hydro-thieno[3,4-b][1,4]dioxin-5-yl)-2,1,3-benzo-thia-diazol-4-yl]-2-[(neo-pentyl-imino)-meth-yl]phenol.

In the title mol-ecule, C24H23N3O3S2, the benzo-thia-diazole ring system is essentially planar, with an r.m.s. deviation of 0.020 (8) Å. The thio-phene and hy-droxy-substitiuted rings form dihedral angles of 23.43 (9) and 35.45 (9)°, respectively, with the benzo-thia-diazole ring system. An intra-molecular O-H⋯N hydrogen bond is observed. In the crystal, weak C-H⋯O hydrogen bonds and π-π stacking inter-actions [centroid-centroid distance = 3.880 (3) Å] link mol-ecules into chains along [100]. In addition, there are short S⋯S contacts [3.532 (3) Å] which link these chains, forming a two-dimensional network parallel to (010).

6-Bromo-N-(6-bromo-pyridin-2-yl)-N-[4-(2,3-di-hydro-thieno[3,4-b][1,4]dioxin-5-yl)phen-yl]pyridin-2-amine.

In the title mol-ecule, C22H15Br2N3O2S, the central benzene ring forms dihedral angles of 12.39 (17), 56.66 (17) and 74.71 (19)°, respectively, with the mean planes of the thio-phene and two pyridine rings. The dioxane ring is in a half-chair conformation. An intra-molecular C-H⋯O hydrogen forms an S(6) ring. The amine N atom is sp (2)-hybridized.

4-(2,3-Di-hydro-thieno[3,4-b][1,4]dioxin-5-yl)aniline.

In the title mol-ecule, C12H11NO2S, the dioxane-type ring adopts a half-chair conformation. The thio-phene ring forms a dihedral angle of 12.53 (6)° with the benzene ring. In the crystal, N-H⋯O, hydrogen bonds link mol-ecules, forming chains along the c-axis direction. A weak intra-molecular C-H⋯O hydrogen bond is observed.

5-Phenyl-1,2,5-di-thia-zepane.

In the title compound, C10H13NS2, the seven-membered ring adopts a chair conformation. The S-S bond length is 2.0406 (5) Šand the C-S-S-C torsion angle is -83.89 (7)°. The amine group is sp (2)-hybridized. In the crystal, mol-ecules are linked into chains along [001] by weak inter-molecular S⋯S contacts of 3.5246 (5) Å.

Molecular sensing and discrimination by a luminescent terbium-phosphine oxide coordination material.

PCM-15 is a robust and recyclable sensor for the effective discrimination of a wide range of small molecules. Sensing is achieved by direct attenuation of the luminescence intensity of Tb(III) ions within the material. A competition study involving trace amounts of NH3 in H2 gas shows that PCM-15 can be used to quantitatively detect trace analytes.