The chelating ability of quinoxaline cores and the redox activity of organosulfide bridges in layered covalent organic frameworks (COFs) offer dual active sites for reversible lithium (Li)‐storage. The designed COFs combining these properties feature disulfide and polysulfide‐bridged networks showcasing an intriguing Li‐storage mechanism, which can be considered as a lithium–organosulfide (Li–OrS) battery. The experimental–computational elucidation of three quinoxaline COFs containing systematically enhanced sulfur atoms in sulfide bridging demonstrates fast kinetics during Li interactions with the quinoxaline core. Meanwhile, bilateral covalent bonding of sulfide bridges to the quinoxaline core enables a redox‐mediated reversible cleavage of the sulfursulfur bond and the formation of covalently anchored lithium–sulfide chains or clusters during Li‐interactions, accompanied by a marked reduction of Li–polysulfide (Li–PS) dissolution into the electrolyte, a frequent drawback of lithium–sulfur (Li–S) batteries. The electrochemical behavior of model compounds mimicking the sulfide linkages of the COFs and operando Raman studies on the framework structure unravels the reversibility of the profound Li‐ion–organosulfide interactions. Thus, integrating redox‐active organic‐framework materials with covalently anchored sulfides enables a stable Li–OrS battery mechanism which shows benefits over a typical Li–S battery.

The development of compartments for the design of cascade reactions in a local space requires a selective spatiotemporal control. The combination of enzyme-loaded polymersomes with enzymelike units shows a great potential in further refining the diffusion barrier and the type of reactions in nanoreactors. Herein, pH-responsive and ferrocene-containing block copolymers were synthesized to realize pH-stable and multiresponsive polymersomes. Permeable membrane, peroxidase-like behavior induced by the redox-responsive ferrocene moieties and release properties were validated using cyclovoltammetry, dye TMB assay, and rupture of host–guest interactions with β-cyclodextrin, respectively. Due to the incorporation of different block copolymers, the membrane permeability of glucose oxidase-loaded polymersomes was changed by increasing extracellular glucose concentration and in TMB assay, allowing for the chemoenzymatic cascade reaction. This study presents a potent synthetic, multiresponsive nanoreactor platform with tunable (e.g., redox-responsive) membrane properties for potential application in therapeutics.

A bispyridylamine-based hanging unit within the ligand framework of a newly synthesized iron porphyrin complex (Py 2 XPFe) can act, on the one hand, as a hydrogen bonding site to facilitate proton transfer in catalysis and, on the other hand, as coordination site for a second Lewis acidic metal center. The bispyridylamine group in close proximity of the iron porphyrin center is able to mediate electrocatalytic CO 2 reduction in anhydrous MeCN. The hydrogen bonding interactions within the hanging group affect the kinetics of catalysis likely through stabilization of the [Fe I (CO 2 H)] À intermediate, increasing the overall rate of catalysis when compared to the non-functionalized analog, TMPFe (TMP = tetramesitylporphyrin). The rate constants (k app ) of the reduction reaction were calculated using the FOWA method which resulted in a higher TOF max for the complex Py 2 XPFe compared with TMPFe in neat MeCN (1.7 × 10 2 vs. 1.1 × 10 1 s À 1 ). The addition of weak Brønsted acids to the reaction mixture (TFE or PhOH) shows an increase in the rate of catalysis for both complexes, yet the Py 2 XPFe analog displays higher TOF max at each relative acid concentration, suggesting the hanging group beneficially impacts the rate of catalysis in the presence of these proton sources. The addition of Lewis acidic Sc 3 + to Py 2 XPFe also results in an increase in current density of the CO 2 reduction reaction. Resonance Raman as well as 1 H-NMR spectroscopy indicates coordination to the pyridine substituents.

The iron-based porphyrin complex containing a bispyridine-based hanging unit termed Py 2 XPFe was previously used as an effective catalyst for the reduction of protons to molecular hydrogen in solution. Here, the molecular compound was immobilized on a modified gold electrode surface and investigated by spectroelectrochemical methods under catalytic conditions. Immobilization of the Py 2 XPFe was facilitated using a pyridine-based amine linker molecule grafted to the gold electrode by electrochemical amine oxidation. The linker molecule denoted in this report as Pyr-1 allows for effective coordination of the iron porphyrin compound to the modified gold surface through axial coordination of the pyridine component to the Fe center. Resonance Raman spectroelectrochemistry was performed on the immobilized catalyst in pH 7 buffer at increasing cathodic potentials. This facilitates the electrochemical hydrogen evolution reaction (HER) while concurrently allowing for the observation of the v 4 , v 3 , and v 2 porphyrin marker bands, which are sensitive to oxidation and spin state changes at the metal center. The observed changes in these bands at decreasing potential indicate that the immobilized Py 2 XPFe exists in the formal highspin Fe III state before being reduced to the low-spin Fe II state resulting from axial interaction with the linker moiety. This Fe II state likely acts as the precatalyst for the HER reaction. Surfaced enhanced Raman spectroelectrochemistry was also conducted on the system as the gold electrode provides a sufficient surface enhancement effect so as to observe the bonding nature of the pyridine substituents within the second coordination sphere. As the potential is lowered cathodically, the pyridine ring breathing modes at 999 cm −1 are shown to increase in intensity due to protonation, which reach an intensity saturated limit whereat HER is conducted. This suggests that in pH 7 buffer, the increase in cathodic potentials facilitates protonation of the pyridine-based second coordination sphere. The extent to which protonation occurs can be viewed as a function of decreasing potential due to an increase in proton flux at the immobilized catalyst which, at the required onset potential for catalysis, aids in the reduction of protons to molecular hydrogen.

The catalytic activity of two iron-based porphyrin complexes containing pyridine-functionalized second coordination spheres, referred to as Py2XPFe and CuPy2XPFe have been investigated for the hydrogen evolution reaction (HER) and compared with the unsubstituted analog TMPFe in MeCN. The CuPy2XPFe incorporates a second metal center within the pyridine residues and represents a heterodinuclear system, while the structurally analogous Py2XPFe lacks an additional metal in the second coordination sphere. Both the Py2XFe and CuPy2XPFe complexes are observed to activate the weak acid, acetic acid (AcOH) at the FeII/I couple rather than at the more energy intensive FeI/0 couple observed for the TMPFe species at low acid concentrations. The ability of the monometallic Py2XPFe complex to activate the weak proton source at the FeII/I couple manifests as an ECEC(E) type electrochemical mechanism, rather than an EECC(E) type mechanism as observed for the unsubstituted TMPFe. The CuPy2XPFe displays improved reactivity compared with the Py2XPFe and TMPFe under the same substrate conditions; however the mechanistic nuances into the bimetallic CuPy2XPFe system are currently unclear. The concentration of AcOH was incrementally increased and the rate constants of the initial protonation step i.e. formation of a hydridic species (k1,app), as well as of the protonation of the hydric species to produce dihydrogen (k2,app) were calculated using the Foot-of-the-wave and KS zone rate equation methodologies, respectively. The kinetic analysis indicates that the activation of protons through the ECEC(E) type mechanism results in a system in which k1,app < k2,app. As both the monometallic Py2XPFe and bimetallic CuPy2XPFe activate the AcOH at less cathodic potentials than the TMPFe under identical conditions, the overpotential (TOF/2) for these complexes is thus dramatically lower. The reactivity difference of the Py2XPFe when compared to the TMPFe due to the hanging groups influence is postulated to be either a result of the pyridine residues acting as hydrogen bonding promoters to the active site or aiding to stabilize a catalytic intermediate species during catalysis. Interestingly, a mechanistic change for the TMPFe is also observed at higher AcOH concentrations, underlying perhaps an increased HER reactivity of iron-porphyrins in MeCN.

The electrochemistry of several ruthenium porphyrin nitrosyl chloride complexes [Ru(por)(NO)Cl] have been examined in tetrahydrofuran (THF). The complexes undergo one‐electron irreversible reductions, which result in diffusion‐limited substitutions of the chloride ligands for THF. This chloride metathesis is reversible in the presence of added NBu4Cl, and equilibrium constants and rate constants for chloride loss have been estimated. These parameters correlate with the NO stretching frequencies of the parent complexes, with more electron‐donating porphyrin ligands favoring chloride loss from the reduced complexes. The [Ru(por)(NO)(THF)] products of the reductions can be detected by IR, EPR, and visible spectroscopies. These species undergo three further reductions, with good reversibility at scan rates >0.40 V s−1. The [Ru(por) (NO)(THF)]+/0 couples have also been determined, and the rate constants and equilibrium constants for recombination with chloride have been estimated. One‐electron reductions of the [Ru(por)(NO)Cl] complexes result in approximately 1018 enhancement of the rates of chloride loss.

The structure of bis(cobaltocenium) tetrachloridocobaltate(II) dichloromethane 1.2-solvate, [Co(C5H5)2]2[CoCl4]·1.2CH2Cl2, has been determined at 100 K. The title compound crystallizes in the space groupP-1 and is an example of an unusualZ′ = 5 structure. The asymmetric unit contains ten cobaltocenium ions, five tetrachloridocobaltate(II) ions and six molecules of dichloromethane,i.e.5{[Cp2Co]2[CoCl4]}·6CH2Cl2. All the cobaltocenium ions are determined to be in the eclipsed conformation with respect to the cyclopentadienyl rings.

Graphene oxide (GO) and reduced graphene oxide (rGO) have outstanding qualities that could be exploited as reinforcement and antibacterial agents in a plethora of biomedical applications. In this contribution, it is reported the deployment of a polyacrylamide GO-hydrogel composite (GO@pAAm) which was photo-converted and structured by ultra-short laser irradiation using a direct laser writing (DLW) approach. The materials were characterized by Fourier Transform Infrared spectroscopy, scanning electron microscopy and confocal microscopy. The laser structure generates a multi-photo-induced effect: surface foaming and patterning, microdomains with enhanced selective water-swelling and effective GO photo-reduction. A first laser scan seems likely to induce the photo-reduction of GO and subsequent laser pulses trigger the structure/foaming. The photo-reduction of GO is evidenced by Raman spectroscopy by the relatively changing intensities of the D to G signals. Macroscopically by an increase in conductivity (decrease in sheet resistance from RS-GO@pAAm = 304 ± 20 kΩ sq-1 to RS-rGO@pAAm-DLW = 27 ± 8 kΩ sq-1) suggesting a reduction of the material measured by 4-Point-Probe.