We demonstrate the on-surface formation of homogeneous and uniform electrochromic films via ultrasonic spray coating. This fully automated process is capable of fabricating metallo-organic films on transparent conducting oxides (TCOs) on glass or flexible poly(ethylene terephthalate) (PET) with surface areas of up to 36 cm2 and film thicknesses of half a micron. The assembly process involves alternatingly spray-coating dilute solutions of structurally well-defined iron polypyridyl ([Fe(mbpy-py)3]2+) complexes and bis(benzonitrile)palladium dichloride (Pd(PhCN)2Cl2) onto conductive substrates, where the latter palladium salt was used as the inorganic cross-linker. The on-surface self-assembled three-dimensional networks are intensely colored and were subsequently integrated into laminated electrochromic devices (ECDs) containing a lithium-based gel electrolyte. The ECDs retain their intense color in the ground state, having a ΔT max of 40–49% at λmax ≈ 600 nm, and can be operated for up to 1500 redox cycles. The fluorine-doped tin oxide counter electrode coated with poly(3,4-ethylene-dioxythiophene)polystyrene sulfonate (PEDOT:PSS) as a charge-storage layer resulted in these stable devices. A significant decrease in the potential window of ΔE ≈ 2.5 V was achieved by using a metal grid on PET as the counter electrode. The operation of the electrochromic films is diffusion-controlled, and the diffusion coefficients (D f) reflect their molecular densities. During these studies, we found that ClO4 – is a suitable counterion of the lithium-based electrolytes for optimal ECD performance.
Dissolving a monomer in an UV-curable liquid electrolyte, followed by exposure to UV light, results in a solid electrolyte matrix. [28,29] Frisbie and co-workers and others formed solid-state electrolytes by dissolving viologen derivatives with a copolymer and ionic liquids. [30-36] Such methods require the EC monomers to have good solubility in liquid-gel electrolytes. ECDs, based on solid polymer electrolytes (SPEs), have a long switching time and relatively low redox stability. [19,26-36] These problems might be due to the low ionic conductivities created by a large interfacial resistance at the electrode or the electrolyte's interface as well as poor contact with the electrodes. [37] In order to advance the application of these ECDs, it is necessary to optimize the working electrode-electrolyte combination to form structurally simplified and highly stable ECDs. Here, we demonstrated solid-state multicolor ECDs based on metallo-organic coatings and a layered architecture. Spraycoated layers of electrochromic metal complexes (1, 2) [38] on transparent conducting metal oxides (TCOs) were covered by dropcasting an electrolyte salt embedded in a UV-cured matrix (Figures 1 and 2). [28,29] These ECDs are thermally robust (100 °C, 24 h), have a redox stability of ≈4500 cycles, and switching times of t = 0.4-2.8 s. The device performance does not require a dedicated ion-storage layer, which is common for analogous devices that use a liquid gel-type electrolyte. [38] The multicolor ECDs reported here are formed by using a mixture of two isostructural iron and osmium complexes in one coating. The solid-polymer electrolyte-based architecture offers a new generation of thermally and electrochemically stable devices based on metallo-organic assemblies.
Geometrically constrained, square pyramidal phosphoranide was synthesized, and its reactivity study showed that it is both a nucleophile and reductant.
In this study, the precise positioning and alignment of arrays of two different guest molecules in a crystalline host matrix has been engineered and resulted in new optically active materials. Sub-nm differences in the diameters of two types of 1D channels are sufficient for size-selective inclusion of dyes. Energy transport occurs between the arrays of different dyes that are included in parallel-positioned nanochannels by Förster resonance energy transfer (FRET). The color of individual micro-sized crystals are dependent on their relative position under polarized light. This angular-dependent behavior is a result of the geometrically constrained orientation of the dyes by the crystallographic packing of the host matrix and is concentration dependent.
Paramagnetic metal complexes gained a lot of attention due to their participation in a number of important chemical reactions. In most cases, these complexes are dominated by 17-e metalloradicals that are associatively activated with highly reactive paramagnetic 19-e species. Molybdenum paramagnetic complexes are among the most investigated ones. While some examples of persistent 17-e Mo-centered radicals have been reported, in contrast, 19-e Mo-centered radicals are illusive species and as such could rarely be detected. In this work, the photodissociation of the [Cp(CO) 3 Mo] 2 dimer ( 1 ) in the presence of phosphines was revisited. As a result, the first persistent, formally 19-e Mo radical with significant electron density on the Mo center (22%), Cp(CO) 3 Mo • PPh 2 ( o -C 2 B 10 H 11 ) ( 5b ), was generated and characterized by EPR spectroscopy and MS as well as studied by DFT calculations. The stabilization of 5b was likely achieved due to a unique electron-withdrawing effect of the o -carboranyl substituent at the phosphorus center.
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