Co‐crystallization of a cyanide‐bridged tetranuclear complex Co2Fe2 with 4‐cyanophenol (CP) gave a hydrogen bonding donor–acceptor system, Co2Fe2(bpy*)4(CN)6(tp*)2(PF6)2⋅2 CP⋅8 BN (1). 1 exhibited a ...three‐step phase transition between HT, IM1, IM2, and LT phases upon temperature variation. Variable temperature magnetic measurements and structural analyses revealed that the three‐step spin transition is caused by electron‐transfer‐coupled spin transitions (ETCSTs) accompanied with alteration of the hydrogen bonding interactions.
Waltzing along: A three‐step spin transition is observed in a hydrogen bonding donor–acceptor system composed of a spin‐transition‐active square complex Co2Fe2 and aromatic hydrogen bonded donor molecules. The stabilization of the intermediate phases is caused by a dynamic alteration of hydrogen bonding interactions coupled to spin‐transition behavior.
TONs of copper fun: There is considerable interest in developing catalysts to harness the abundant natural supply of methane for various industrial applications. Two tricopper complexes capable of ...mediating efficient oxidation of methane to methanol under ambient conditions were tested: a biomimetic tricopper complex (see figure) and a tricopper‐peptide species derived from the particulate methane monooxygenase (pMMO) protein.
We report an electrocatalyst, Co bases (metallic Co and Co(OH)
) with fluoride-incorporated CoO coating on the surface of (CoO-F/Co), was synthesized by the electro-deposition method. The porous ...network architecture of CoO-F/Co on the glassy carbon electrode exhibited an ultra-low overpotential of 15 mV, achieving the geometric current density of 10 mA cm
in 1.0 M KOH, which were comparable with the HER performance of numerous reported noble metal electrocatalysts. It is demonstrated that fluoride incorporation improved the electrodeposition particle size, electronic density, conductivity and hydrophilicity of CoO-F/Co the HER performance.
We undertake silver cyanide (AgCN) powder for its catalytic epoxidation of cyclohexene or styrene in CH3CN with variable substrate‐to‐solvent volume ratios using H2O2(aq) at 60 °C. The reaction ...mixtures can facilely separate into organic and aqueous layers. Cyclohexene oxide can be produced in the organic layer with 100 % selectivity from the substrate cyclohexene, while styrene oxide was identified with 80 % selectivity against benzaldehyde in styrene oxidation. After reactions, we can recycle the AgCN particles with comparable bulk property clarified via XRD, XPS, XAS, FT‐IR, and 13C‐SS NMR spectroscopy. Using H218O2 as the oxidant, both epoxide products and acetamide are highly enriched with 18O‐atom, indicating that the π bond‐activation is essential for forming the cyclohexene/styrene oxides in the organic and acetamide in the aqueous layers. The oxidation of cyclohexene/styrene catalyzed by AgCN powder through surface activation by H2O2(aq) and assisted by the non‐innocent CH3CN‐originated acetamide can achieve highly selective π‐bond activation with high reactivity.
An AgCN nanocatalyst with high reusability is developed for epoxidation of cyclohexene and styrene using H2O2(aq) in CH3CN at 60 °C. 100 % cyclohexene oxide and 80 % styrene oxide selectivity in the organic layers can be achieved. Electrophilic adsorbed oxygen and hydroxide species are evidenced to be essential for the heterogeneous olefin epoxidation.
Electrochemical study of {Fe(NO)2}10 DNIC (2‐AMP)Fe(NO)2 (1) (2‐AMP = 2‐aminomethylpyridine) in CH3CN/Na2SO4 aqueous solution (1 M) revealing reversible one‐electron redox couples implicated that ...DNIC 1 may facilitate versatile chemical reactions associated with two‐electron HER (hydrogen evolution reaction) processes. The three‐component photocatalytic HER system is composed of MeOH‐H2O solution (1:1 volume ratio, pH = 11.0) of molecular catalyst DNIC 1 (1.6 μM), photosensitizer fluorescein (Fl) (1.5 mM) and sacrificial electron donor triethylamine (0.36 M) was developed. The reductive quenching rate (R1) (electron transfer from Et3N to Fl) and the oxidative quenching rate (R2) (electron transfer from Fl− to DNIC 1) were calculated as 2.11 × 107 s−1 and 3.984 × 104 s−1, respectively. The faster electron transfer from Fl− to DNIC 1, compared to the electron‐transfer rate (R3) from DNIC 1− to H2O, rationalized the accumulation of the transient‐stable DNIC 1−, degrading to DNIC 1−‐transformed photocatalytic active particles (Fe3O4 major). The three‐component photocatalytic system composed of MeOH‐H2O solution of the isolated particles (2 mg), Fl (1.5 mM), and Et3N (0.36 M) was also employed for photocatalytic HER reaching TON 13456 μmolH2/gcatalyst, TOF 2691 hr−1μmolH2/gcatalyst and the apparent quantum yield 3.71% under radiation (480 nm). That is, for the photocatalytic HER device constructed via a combination of DNIC 1, Fluorescein, and triethylamine, both the homogeneous catalytic HER triggered by {Fe(NO)2}10‐reduced DNIC 1− and the heterogeneous catalytic HER promoted by DNIC 1−‐transformed particles operated concomitantly to drive this photocatalytic HER.
The photocatalytic HER system composed of catalyst (2‐AMP)Fe(NO)2 (2‐AMP = 2‐aminomethylpyridine), fluorescein, and triethylamine was developed to drive water reduction under irradiation (>420 nm).
Copper( i ) N-heterocyclic carbene has a good activity towards aryl halides and was used as a model complex to study the catalytic cycle of Cu( i ) to catalyze the cross C–S coupling reaction because ...the N-heterocyclic carbene has a strong electron donating property, and ligand dissociation can be avoided. Free radical scavenger cumene does not retard the yield of the reaction indicating that the catalytic reaction goes through a non free radical path. Switching the solvent from toluene to DMF lowered the yield of the reaction. DFT calculation shows that the activation of aryl halide is the rate determining step, and the activation energy is higher for the reaction in DMF than in toluene. A plausible catalytic cycle is proposed with the support of DFT calculation.
Nitric oxide (NO) is an endogenous gasotransmitter regulating alternative physiological processes in the cardiovascular system. To achieve translational application of NO, continued efforts are made ...on the development of orally active NO prodrugs for long-term treatment of chronic cardiovascular diseases. Herein, immobilization of NO-delivery Fe
(μ-SCH
CH
COOH)
(NO)
(
) onto MIL-88B, a metal-organic framework (MOF) consisting of biocompatible Fe
and 1,4-benzenedicarboxylate (BDC), was performed to prepare a DNIC@MOF microrod for enhanced oral delivery of NO. In simulated gastric fluid, protonation of the BDC linker in DNIC@MOF initiates its transformation into a DNIC@tMOF microrod, which consisted of
well dispersed and confined within the BDC-based framework. Moreover, subsequent deprotonation of the BDC-based framework in DNIC@tMOF under simulated intestinal conditions promotes the release of
and NO. Of importance, this discovery of transformer-like DNIC@MOF provides a parallel insight into its stepwise transformation into DNIC@tMOF in the stomach followed by subsequent conversion into molecular
in the small intestine and release of NO in the bloodstream of mice. In comparison with acid-sensitive
, oral administration of DNIC@MOF results in a 2.2-fold increase in the oral bioavailability of NO to 65.7% in mice and an effective reduction of systolic blood pressure (SBP) to a ΔSBP of 60.9 ± 4.7 mmHg in spontaneously hypertensive rats for 12 h.
Two types of racemic rodlike Schiff base mesogens with –CN– (type I ) and –NC– (type III ) linkages were prepared. These mesogens possessed either difluoro substitutions at the inner-core position ...of the phenyl ring or hydroxy group to form intramolecular hydrogen bonding with an ester or/and imine linkage. When the appropriate concentration of chiral additive is doped into them, the incorporation of two fluoro substituents is more useful for blue phase (BP) stabilization than that of a hydroxy group near the ester linkage in Schiff base mesogens. BPI and BPII can be identified by reflectance spectra and polarized optical microscope images. BPII emerges easily on cooling when the appropriate chiral dopant ISO(6OBA)2 or chiral dopant S811 is doped into the Schiff base mesogen having only a hydroxy group near the ester linkage. Interestingly, BPI can be observed when 10–15 wt% ISO(6OBA)2 was doped into the difluoro substituted Schiff base mesogen III during a heating process. The experimental and molecular modeling results indicate that most of the difluorinated Schiff base mesogens with larger dipole moments exhibit wider BP ranges than their corresponding non-fluorinated homologues under the same chirality condition. In addition, wide BPs can be induced for racemic rodlike Schiff base mesogens I in the chiral system and this is easier than that for racemic rodlike Schiff base mesogens III . In Schiff base mesogens I , the dipole moment is dominant for BP stabilization. However, the fluorine substituent effect is the main factor in Schiff base mesogens III .
X‐ray absorption, circular dichroism, and EPR spectroscopy were employed to investigate the metal‐core structures in the Escherichia coli transcriptional factor SoxR under reduced, oxidized, and ...nitrosylated conditions. The spectroscopic data revealed that the coordination environments of the metal active centers varied only very slightly between the reduced and oxidized states, similar to most other proteins containing iron–sulfur clusters. Upon nitrosylation of oxidized SoxR, however, we observed a low‐temperature EPR spectrum characteristic of a protein dinitrosyl iron complex (DNIC), with an intensity corresponding to about two DNICs per iron sulfur cluster in the protein, according to spin quantification relative to a low‐molecular‐weight DNIC standard. In addition, there was no evidence for dichroic spectral features in the responsive region of the nitrosyl iron complexes, as well as for FeFe back‐scattering in the fitting of the Fe extended X‐ray absorption fine structure (EXAFS) spectrum. Instead the Fe EXAFS spectrum of the nitrosylated SoxR core exhibited the same first‐ and second‐shell coordination environments characteristic of modeled small molecular DNICs, indicating that each of the 2 Fe2 S cores in the homodimeric SoxR was dissociated into two individual DNICs. Similar nitrosylation of the reduced mixed‐valence SoxR for 1 min led to degradation of the iron–sulfur clusters to give several iron species, including one with EPR signals characteristic of a reduced Roussin’s red ester (rRRE), a diamagnetic species, presumably Roussin’s red ester (RRE), and a small amount of DNIC. We also undertook in vivo time‐course studies of E. coli cells containing recombinant SoxR after rapid purging of the cells with exogenous NO gas. Rapid freeze‐quenched EPR experiments demonstrated rapid formation of the SoxR rRRE species, followed by fast breakup of this precursor intermediate to form the stable protein‐bound DNIC species. Accordingly, under nitrosative stress, we believe that the response of SoxR to NO could depend on the intracellular redox state of E. coli, the central modulator of which could be exploited to deduce the appropriate mechanism to sense the presence of NO for physiological regulation.
NO sense! Spectroscopic studies of the reduced and oxidized forms of the E. coli transcriptional factor SoxR, followed by mechanistic analyses of the nitrosylation process of these species, allowed the elucidation of the redox chemistry associated with NO sensing that triggers transcriptional activation for the sensing of small molecules in a prokaryote (see figure).
The evolution of iron local vibrational mode (Fe LVM) and phase transitions in n-type iron-doped indium phosphide (InP:Fe) were investigated at ambient temperature. In-situ angle-dispersive X-ray ...diffraction measurements revealed that InP:Fe starts to transform from zinc-blende (ZB) to rock-salt (RS) structure around 8.2(2) GPa and completes around 16.0(2) GPa. The Raman shift of both transverse and longitudinal optical modes increases monotonically with increasing pressure, while their intensities become indiscernible at 11.6(2) GPa, suggesting that the pressure-induced phase transition is accompanied by significant metallization. In contrast, originally absent at ambient pressure, the Raman shift of Fe LVM appears at ∼420 cm
near 1.2 GPa and exhibits a dome shape behavior with increasing pressure, reaching a maximum value of ∼440 cm
around 5 GPa, with an apparent kink occurring around the ZB-RS transition pressure of ∼8.5(2) GPa. The Fe K-edge X-ray absorption near edge structure (XANES) confirmed the tetrahedral site occupation of Fe
with a crystal field splitting parameter Δ
= 38 kJ·mole
. Our calculations indicate that the energy parameters governing the phase transition are Δ
0.49 and Δ
= 1.10 kJ·mole
, respectively, both are much smaller than Δ
= 38 kJ·mole
at ambient.
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