Nonconventional Symmetric Double-Side Electrochromic Devices Employing a Nafion Conductive Layer to Unlock Superior Durability.

In this work, we present a methodology to create an effective novel double-sided symmetric architecture of solid-state electrochromic devices. This principally new nonconventional configuration provides access to novel electrochromic systems that could be applicable for the creation of smart double-side signage, smart boards, nonemissive displays, and other smart interactive devices that change their color upon application of a voltage. The proposed configuration is based on the assembly of two identical electrochromic materials facing each other through an opaque optical separator.

Reducing the resistance for the use of electrochemical impedance spectroscopy analysis in materials chemistry.

Electrochemical impedance spectroscopy (EIS) is a highly applicable electrochemical, analytical, and non-invasive technique for materials characterization, which allows the user to evaluate the impact, efficiency, and magnitude of different components within an electrical circuit at a higher resolution than other common electrochemical techniques such as cyclic voltammetry (CV) or chronoamperometry. EIS can be used to study mechanisms of surface reactions, evaluate kinetics and mass transport, and study the level of corrosion on conductive materials, just to name a few. Therefore, this review demonstrates the scope of physical properties of the materials that can be studied using EIS, such as for characterization of supercapacitors, dye-sensitized solar cells (DSSCs), conductive coatings, sensors, self-assembled monolayers (SAMs), and other materials.

Flexible electrochemical aptasensor for cortisol detection in human sweat.

This communication demonstrates an electrochemical DNA aptasensor for the detection of cortisol in human sweat. The aptasensor was fabricated layer-by-layer assembly on stretchable polydimethylsiloxane (PDMS) coated with conductive nanoporous carbon nanotube-cellulose nanocrystals (CNC/CNT) film using a linker to a cortisol specific DNA aptamer. The flexible cortisol aptasensor had a dynamic range of 2.

Post-Synthetic Color Tuning of the Ultra-Effective and Highly Stable Surface-Confined Electrochromic Monolayer: Shades of Green for Camouflage Materials.

We report here on the strategy for the preparation of a series of electrochromic (EC) materials in green shades designed for camouflage purposes. This top-down post-synthetic modification provides access to new EC materials by fine modulation of the color of the surface-confined metalorganic monolayer pre-deposited on indium tin oxide screen-printed supports. Selective on-surface N-quaternization of the outer pyridine unit of the EC metal complex covalently embedded onto an enhanced surface area electrode results in a bathochromic shift of the absorbance signal as well as visual color change from blue to different shades of green.

Multichromic Monolayer Terpyridine-Based Electrochromic Materials.

The article describes novel electrochromic materials (ECMs) that are based on a monolayer consisting of two or three isostructural metal complexes of 4'-(pyridin-4-yl)-2,2':6',2''-terpyridine simultaneously deposited on surface-enhanced support. The support was made by screen printing of indium tin oxide (ITO) nanoparticles on ITO-glass and has a surface area sufficient for a monolayer to give color visible to the naked eye. The ability to separately electrochemically address the oxidation state of the metal centers on the surface (i.

Ligand Impact on Monolayer Electrochromic Material Properties.

In this study, we present a range of efficient highly durable electrochromic materials that demonstrate excellent redox and lifetime stability, sufficient coloration contrast ratios, and the best-in-class electron-transfer constants. The materials were formed by anchoring as little as a monolayer of predefined iron complexes on a surface-enhanced conductive solid support. The thickness of the substrate was optimized to maximize the change in optical density.

Hemoglobin-driven iron-directed assembly of gold nanoparticles.

The ability to form complex 3D architectures using nanoparticles (NPs) as the building blocks and complex macromolecules that direct these assemblies remains a challenging objective for nanotechnology. Here we report results in which the partial substitution of classical Turkevich citrate-capped gold NPs by a novel, heteroaromatic ligand (L) results in NPs able to form coordination-driven assemblies mediated by free or protein-bound iron ions. The morphology of these assemblies can be tuned depending on the source of iron.

Ultrastable Gold Nanoparticles Modified by Bidentate N-Heterocyclic Carbene Ligands.

Highly stable gold nanoparticles (Au NPs) functionalized by bidentate N-heterocyclic carbene (NHC) ligands have been synthesized by top-down and bottom-up approaches. A detailed study of the effect of alkylation, denticity, and method of synthesis has led to the production of NHC-stabilized nanoparticles with higher thermal stability than bi- and tridentate thiol-protected Au NPs and than monodentate NHC-stabilized NPs. Importantly, bidentate NHC-protected NPs also displayed unprecedented stability to external thiol, which has been an unsolved problem to date with all nanoparticles.

Terpyridine-Based Monolayer Electrochromic Materials.

Novel electrochromic (EC) materials were developed and formed by a two-step chemical deposition process. First, a self-assembled monolayer (SAM) of 2,2':6',2″-terpyridin-4'-ylphosphonic acid, L, was deposited on the surface of a nanostructured conductive indium-tin oxide (ITO) screen-printed support by simple submerging of the support into an aqueous solution of L. Further reaction of the SAM with Fe or Ru ions results in the formation of a monolayer of the redox-active metal complex covalently bound to the ITO support (Fe-L/ITO and Ru-L/ITO, respectively).

Simple direct formation of self-assembled N-heterocyclic carbene monolayers on gold and their application in biosensing.

The formation of organic films on gold employing N-heterocyclic carbenes (NHCs) has been previously shown to be a useful strategy for generating stable organic films. However, NHCs or NHC precursors typically require inert atmosphere and harsh conditions for their generation and use. Herein we describe the use of benzimidazolium hydrogen carbonates as bench stable solid precursors for the preparation of NHC films in solution or by vapour-phase deposition from the solid state.

Mechanistic Aspects of Aryl-Halide Oxidative Addition, Coordination Chemistry, and Ring-Walking by Palladium.

This contribution describes the reactivity of a zero-valent palladium phosphine complex with substrates that contain both an aryl halide moiety and an unsaturated carbon-carbon bond. Although η(2) -coordination of the metal center to a C=C or C≡C unit is kinetically favored, aryl halide bond activation is favored thermodynamically. These quantitative transformations proceed under mild reaction conditions in solution or in the solid state.

Highly selective directed arylation reactions via back-to-back dehydrogenative C-H borylation/arylation reactions.

Dimeric rhodium N-heterocyclic carbene complexes are demonstrated to be effective catalyst precursors for directed C-H borylation reactions at room temperature. The reactions are highly selective for mono-borylation and can be combined with a one-pot Suzuki-Miyaura coupling to give C-H arylation products with exclusive selectivity for mono-arylation without the requirement for steric blocking groups.

Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold.

Since the first report of thiol-based self-assembled monolayers (SAMs) 30 years ago, these structures have been examined in a huge variety of applications. The oxidative and thermal instabilities of these systems are widely known, however, and are an impediment to their widespread commercial use. Here, we describe the generation of N-heterocyclic carbene (NHC)-based SAMs on gold that demonstrate considerably greater resistance to heat and chemical reagents than the thiol-based counterparts.

Dioxygen adducts of rhodium N-heterocyclic carbene complexes.

Rhodium complexes functionalized by N-heterocyclic carbene ligands react with dioxygen to form adducts. Depending on the specifics of the ancillary ligands, oxygen binds to Rh either as a peroxide to form a fully oxidized Rh(III) complex, or as singlet dioxygen in a Rh(I) square planar complex. We have shown through analysis of a series of compounds, some previously published and some novel, that the presence of additional ligands that would support the formation of an octahedral geometry, as typically found with Rh(III) complexes, is critical for formation of the peroxide.

Heteroleptic rhodium NHC complexes with pyridine-derived ligands: synthetic accessibility and reactivity towards oxygen.

The synthesis, structure determination and oxidative stability of novel Rh-NHC complexes which feature pyridine-derived ligands have been described. All complexes described herein were synthesized from common dinuclear precursors of general structure [Rh(NHC)(L)Cl](2), where L is a monodentate olefin. We demonstrate that the use of these precursors is critical for the formation of all complexes since related cyclooctadiene containing precursors ([Rh(NHC)(COD)Cl]) were completely unreactive under identical conditions.

Double single-crystal-to-single-crystal transformation and small-molecule activation in rhodium NHC complexes.

Three gases, one crystal: rhodium NHC complexes undergo back-to-back single-crystal-to-single-crystal transformations by selective nonreversible ligand exchange reactions. Slow diffusion of O(2) converts a dinitrogen complex into a dioxygen complex, and CO subsequently replaces O(2).

Long-range through-bond heteronuclear communication in platinum complexes.

Four analogous platinum stilbene- and stilbazole-based complexes exhibit unusual long-range heteronuclear spin-spin coupling in solution. Single crystal analysis and NMR experiments show that the (19)F, (31)P, and (195)Pt nuclei communicate over large distances (0.9-1.

Directing aryl-I versus Aryl-Br bond activation by nickel via a ring walking process.

Activation of a strong aryl-Br bond of a halogenated vinylarene by nickel(0) is demonstrated in the presence of aryl-I containing substrates. eta2-Coordination of Ni(PEt3)2 to the C=C moiety of halogenated vinylarenes is kinetically preferable and is followed by an intramolecular aryl-halide bond activation process. This "ring-walking" process is quantitative and proceeds under mild reaction conditions in solution.

Fluxional behavior of platinum(0) complexes: intra vs intermolecular reaction pathways.

The fluxional behavior of two analogous platinum complexes has been studied in solution by NMR spectroscopy to elucidate the reaction mechanism and to determine the activation parameters. This includes variable temperature NMR spectroscopy, 2D (1)H- (1)H exchange spectroscopy, and spin saturation transfer measurements. A platinum moiety, Pt(PEt 3) 2, translocates between two carbon-carbon double bonds of two vinylpyridine moieties bridged by an arene (i.

Site affinity effects upon charge injection into siloxane-based monolayers.

Submolecular electrical information is successfully derived by applying element-specific, chemically resolved electrical measurements to a covalently bound stilbazole-based monolayer on a silicon substrate. Pronounced affinity effects are found in the response of adjacent atomic sites to external charge injection, accompanied by intramolecular polarization variations. These noncontact electrical read-out capabilities may provide a first entry toward the realization of organic devices based on submolecular electrical units.

Platinum stilbazoles: ring-walking coupled with aryl-halide bond activation.

The reaction between tetrakis(triethylphosphine)platinum(0) and 4-[trans-2-(4-bromophenyl)vinyl]pyridine (1) is examined. Initially, the metal center coordinates to the bridging double bond of 1. Complexes 2 and 3 were fully characterized, and their X-ray crystallography structures are presented.