Substrate-Gated Transformation of a Pre-Catalyst into an Iron-Hydride Intermediate [(NO)(CO)Fe(μ-H)Fe(CO)(NO)] for Catalytic Dehydrogenation of Dimethylamine Borane.

Continued efforts are made on the development of earth-abundant metal catalysts for dehydrogenation/hydrolysis of amine boranes. In this study, complex [K-18-crown-6-ether][(NO)Fe(μ-Pyr)(μ-CO)Fe(NO)] (, Pyr = 3-methylpyrazolate) was explored as a pre-catalyst for the dehydrogenation of dimethylamine borane (DMAB). Upon evolution of H from DMAB triggered by , parallel conversion of into [(NO)Fe(,'-PyrBHNMe)] () and an iron-hydride intermediate [(NO)(CO)Fe(μ-H)Fe(CO)(NO)] () was evidenced by X-ray diffraction/nuclear magnetic resonance/infrared/nuclear resonance vibrational spectroscopy experiments and supported by density functional theory calculations.

Fluoride-incorporated cobalt-based electrocatalyst towards enhanced hydrogen evolution reaction.

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.

Magnetic Responsive Release of Nitric Oxide from an MOF-Derived FeO@PLGA Microsphere for the Treatment of Bacteria-Infected Cutaneous Wound.

Nitric oxide (NO) is an essential endogenous signaling molecule regulating multifaceted physiological functions in the (cardio)vascular, neuronal, and immune systems. Due to the short half-life and location-/concentration-dependent physiological function of NO, translational application of NO as a novel therapeutic approach, however, awaits a strategy for spatiotemporal control on the delivery of NO. Inspired by the magnetic hyperthermia and magneto-triggered drug release featured by FeO conjugates, in this study, we aim to develop a magnetic responsive NO-release material (MagNORM) featuring dual NO-release phases, namely, burst and steady release, for the selective activation of NO-related physiology and treatment of bacteria-infected cutaneous wound.

Enhanced Oral NO Delivery through Bioinorganic Engineering of Acid-Sensitive Prodrug into a Transformer-like DNIC@MOF Microrod.

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-SCHCHCOOH)(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.

Endogenous Conjugation of Biomimetic Dinitrosyl Iron Complex with Protein Vehicles for Oral Delivery of Nitric Oxide to Brain and Activation of Hippocampal Neurogenesis.

Nitric oxide (NO), a pro-neurogenic and antineuroinflammatory gasotransmitter, features the potential to develop a translational medicine against neuropathological conditions. Despite the extensive efforts made on the controlled delivery of therapeutic NO, however, an orally active NO prodrug for a treatment of chronic neuropathy was not reported yet. Inspired by the natural dinitrosyl iron unit (DNIU) [Fe(NO)], in this study, a reversible and dynamic interaction between the biomimetic [(NO)Fe(μ-SCHCHOH)Fe(NO)] () and serum albumin (or gastrointestinal mucin) was explored to discover endogenous proteins as a vehicle for an oral delivery of NO to the brain after an oral administration of .

Theoretical Analysis of Fe K-Edge XANES on Iron Pentacarbonyl.

Iron pentacarbonyl (Fe(CO)) is a versatile material that is utilized as an inhibitor of flame, shows soot suppressibility, and is used as a precursor for focused electron-beam-induced deposition (FEBID). X-ray absorption near-edge structure (XANES) of the K edge, which is a powerful technique for monitoring the oxidation states and coordination environment of metal sites, can be used to gain insight into Fe(CO)-related reaction mechanisms in in situ experiments. We use a finite difference method (FDM) and molecular-orbital-based time-dependent density functional theory (TDDFT) calculations to clarify the Fe K-edge XANES features of Fe(CO).

Insight into chalcogenolate-bound {Fe(NO)} dinitrosyl iron complexes (DNICs): covalent character versus ionic character.

The synthesis, characterization and transformation of the thermally unstable {Fe(NO)2}9 dinitrosyl iron complex (DNIC) [(OMe)2Fe(NO)2]- (2) were investigated. The {Fe(NO)2}9 DNIC 2 characterized by single-crystal X-ray diffraction is exclusively stabilized by the weak intermolecular [Fe(OMe)2(K+)] interactions (O(3)K(1) and O(4)K(1) distances of 2.818(3) and 2.

Pressure effect on impurity local vibrational mode and phase transitions in n-type iron-doped indium phosphide.

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.

Effect of the Functional Groups of Racemic Rodlike Schiff Base Mesogens on the Stabilization of Blue Phase in Binary Mixture Systems.

Four series of rodlike racemic Schiff base mesogens possessing different alkyl chains and two types of linkages, ester and alkynyl linkages, were synthesized and applied to induce cubic blue phases (BPs) in simple binary mixture systems. The mesophases of these Schiff base mesogens were confirmed by variable-temperature X-ray diffraction and the characteristic texture from polarized optical microscopy (POM). In general, when chiral additive S-(+)-2-octyl 4-(4-hexyloxybenzoyloxy)benzoate (S811; 20-40 wt %) is added into the rodlike racemic salicylaldimine-based mesogens, the cubic BPs could be observed and its temperature range is larger than 20 K.

A Hydrogen-Bonded Cyanide-Bridged [Co Fe ] Square Complex Exhibiting a Three-Step Spin Transition.

Co-crystallization of a cyanide-bridged tetranuclear complex [Co Fe ] with 4-cyanophenol (CP) gave a hydrogen bonding donor-acceptor system, [Co Fe (bpy*) (CN) (tp*) ](PF ) ⋅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.

Broad temperature range of cubic blue phase present in simple binary mixture systems containing rodlike Schiff base mesogens with tolane moiety.

Four simple rodlike Schiff base mesogens with tolane moiety were synthesized and applied to stabilize cubic blue phases (BPs) in simple binary mixture systems for the first time. When the chiral additive or was added into a chiral salicylaldimine-based compound, the temperature range of the cubic BP could be extended by more than 20 °C. However, when the chiral Schiff base mesogen was blended with chiral dopant possessing opposite handedness, , BPs could not be observed.

Ligand free copper(I)-catalyzed synthesis of diaryl ether with Cs2CO3 via a free radical path.

Complexes [Cu(I)(2,4-dimethylphenoxy)2](-) (A) and [Cu(II)(2,4-dimethylphenoxy)2(p-tolyl)](-) (B) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the ligand free copper(I)-catalyzed C-O coupling reaction using Cs2CO3 under the catalytic reaction conditions indicating that they could be intermediates in the reaction. The radical scavenger cumene retarded the reaction. Catalytic cycles involving a free radical path are proposed based on these observations.

Insight into the reactivity and electronic structure of dinuclear dinitrosyl iron complexes.

A combination of N/S/Fe K-edge X-ray absorption spectroscopy (XAS), X-ray diffraction data, and density functional theory (DFT) calculations provides an efficient way to unambiguously delineate the electronic structures and bonding characters of Fe-S, N-O, and Fe-N bonds among the direduced-form Roussin's red ester (RRE) [Fe2(μ-SPh)2(NO)4](2-)(1) with {Fe(NO)2}(10)-{Fe(NO)2}(10) core, the reduced-form RRE [Fe2(μ-SPh)2(NO)4](-)(3) with {Fe(NO)2}(9)-{Fe(NO)2}(10) core, and RRE [Fe2(μ-SPh)2(NO)4] (4) with {Fe(NO)2}(9)-{Fe(NO)2}(9) core. The major contributions of highest occupied molecular orbital (HOMO) 113α/β in complex 1 is related to the antibonding character between Fe(d) and Fe(d), Fe(d), and S atoms, and bonding character between Fe(d) and NO(π*). The effective nuclear charge (Zeff) of Fe site can be increased by removing electrons from HOMO to shorten the distances of Fe···Fe and Fe-S from 1 to 3 to 4 or, in contrast, to increase the Fe-N bond lengths from 1 to 3 to 4.

Possible intermediates of Cu(phen)-catalyzed C-O cross-coupling of phenol with an aryl bromide by in situ ESI-MS and EPR studies.

The C-O coupling reaction between 2,4-dimethylphenol and 4-bromotoluene catalyzed by the CuI/K2CO3/phen system can be inhibited by the radical scavenger cumene. Complexes [Cu(i)(phen)(1-(2,4-dimethylphenoxy)-4-methylbenzene)](+) (denoted as A), {H[Cu(i)(phen)(2,4-dimethylphenoxy)]}(+) and [Cu(i)(2,4-dimethylphenoxy)2](-) (denoted as B) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the copper(i)-catalyzed C-O coupling reaction under the catalytic reaction conditions indicating that they could be intermediates in the reaction. The in situ EPR study of the reaction solution detected the Cu(ii) species with a fitted g value of 2.

Study of the nano-morphological versatility by self-assembly of a peptide mimetic molecule in response to physical and chemical stimuli.

A small peptide mimetic molecule can form diverse nanostructures such as nano-vesicles, nano-tubes and nano-ribbons/fibrils by self-assembly, in response to various physical and chemical stimulations.

Chemical bond characterization of a mixed-valence tri-cobalt complex, Co3(μ-admtrz)4(μ-OH)2(CN)6·2H2O.

Charge density study of a mixed-valence tri-cobalt compound, Co3(μ-admtrz)4(μ-OH)2(CN)6·2H2O (1) (admtrz = 3,5-dimethyl-4-amino-1,2,4-triazole), is investigated based on high resolution X-ray diffraction data and density functional theory (DFT) calculations. The molecular structure of this compound contains three cobalt atoms in a linear fashion, where two terminal ones are Co(III) at a low-spin (LS) state and a central one is Co(II) at a high-spin (HS) state with a total spin quantum number, S(total), of 3/2. It is centrosymmetric with the center of inversion located at the central Co atom (Co2).

Bond characterization of a unique thiathiophthene derivative: combined charge density study and X-ray absorption spectroscopy.

Thiathiophthene (TTP), a planar molecule with two fused heterocyclic five-membered rings and an essentially linear S-S-S bond, is a molecule of great interest due to its unique chemical bondings. To elucidate the remarkable bonding nature, a combined experimental and theoretical study on the electron density distribution of 2,5-dimethyl-3,4-trimethylene-6a-TTP (1) is investigated based on a multipole model through high-resolution X-ray diffraction data experimentally and on the density functional calculations (DFT) theoretically. In addition, S K-edge X-ray absorption spectroscopy (XAS) is measured to verify the chemical bonding concerning the sulfur atoms.

A fluorescent organic nanotube assembled from novel p-phenylene ethynylene-based dicationic amphiphiles.

Novel π-extended conjugated amphiphiles composed of a hydrophilic section of two quaternary ammonium groups and p-phenylene ethynylene with adjustable alkyl chain hydrophobic section were prepared by a multistep synthesis. These dicationic amphiphiles showed good water solubility and formed a tubular assembly in water. The evidence for the nanotubular comes from direct optical and TEM observations.

Insight into one-electron oxidation of the {Fe(NO)2}9 dinitrosyl iron complex (DNIC): aminyl radical stabilized by [Fe(NO)2] motif.

A reversible redox reaction ({Fe(NO)(2)}(9) DNIC [(NO)(2)Fe(N(Mes)(TMS))(2)](-) (4) ⇄ oxidized-form DNIC [(NO)(2)Fe(N(Mes)(TMS))(2)] (5) (Mes = mesityl, TMS = trimethylsilane)), characterized by IR, UV-vis, (1)H/(15)N NMR, SQUID, XAS, single-crystal X-ray structure, and DFT calculation, was demonstrated. The electronic structure of the oxidized-form DNIC 5 (S(total) = 0) may be best described as the delocalized aminyl radical [(N(Mes)(TMS))(2)](2)(-•) stabilized by the electron-deficient {Fe(III)(NO(-))(2)}(9) motif, that is, substantial spin is delocalized onto the [(N(Mes)(TMS))(2)](2)(-•) such that the highly covalent dinitrosyl iron core (DNIC) is preserved. In addition to IR, EPR (g ≈ 2.

Insight into the dinuclear {Fe(NO)2}10{Fe(NO)2}10 and mononuclear {Fe(NO)2}10 dinitrosyliron complexes.

The reversible redox transformations [(NO)(2)Fe(S(t)Bu)(2)](-) ⇌ [Fe(μ-S(t)Bu)(NO)(2)](2)(2-) ⇌ [Fe(μ-S(t)Bu)(NO)(2)](2)(-) ⇌ [Fe(μ-S(t)Bu)(NO)(2)](2) and [cation][(NO)(2)Fe(SEt)(2)] ⇌ [cation](2)[(NO)(2)Fe(SEt)(2)] (cation = K(+)-18-crown-6 ether) are demonstrated. The countercation of the {Fe(NO)(2)}(9) dinitrosyliron complexes (DNICs) functions to control the formation of the {Fe(NO)(2)}(10){Fe(NO)(2)}(10) dianionic reduced Roussin's red ester (RRE) [PPN](2)[Fe(μ-SR)(NO)(2)](2) or the {Fe(NO)(2)}(10) dianionic reduced monomeric DNIC [K(+)-18-crown-6 ether](2)[(NO)(2)Fe(SR)(2)] upon reduction of the {Fe(NO)(2)}(9) DNICs [cation][(NO)(2)Fe(SR)(2)] (cation = PPN(+), K(+)-18-crown-6 ether; R = alkyl). The binding preference of ligands [OPh](-)/[SR](-) toward the {Fe(NO)(2)}(10){Fe(NO)(2)}(10) motif of dianionic reduced RRE follows the ligand-displacement series [SR](-) > [OPh](-).

The metal core structures in the recombinant Escherichia coli transcriptional factor SoxR.

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.

Peptide-bound dinitrosyliron complexes (DNICs) and neutral/reduced-form Roussin's red esters (RREs/rRREs): understanding nitrosylation of [Fe-S] clusters leading to the formation of DNICs and RREs using a de novo design strategy.

This manuscript describes the interaction of low-molecular-weight DNICs with short peptides designed to explore the stability and structure of DNIC-peptide/RRE-peptide constructs. Although characterization of protein-bound and low-molecular-weight DNICs is possible via EPR, XAS, and NRVS, this study demonstrates that the combination of aqueous IR ν(NO) and UV-vis spectra can serve as an efficient tool to characterize and discriminate peptide-bound DNICs and RREs. The de novo chelate-cysteine-containing peptides KC(A)(n)CK-bound (n = 1-4) dinitrosyliron complexes KC(A)(n)CK-DNIC (CnA-DNIC) and monodentate-cysteine-containing peptides KCAAK-/KCAAHK-bound Roussin's red esters (RREs) KCAAK-RRE/KCAAHK-RRE were synthesized and characterized by aqueous IR, UV-vis, EPR, CD, XAS, and ESI-MS.

Discrimination of mononuclear and dinuclear dinitrosyl iron complexes (DNICs) by S K-edge X-ray absorption spectroscopy: insight into the electronic structure and reactivity of DNICs.

In addition to probing the formation of dinitrosyl iron complexes (DNICs) by the characteristic Fe K-edge pre-edge absorption energy ranging from 7113.4 to 7113.8 eV, the distinct S K-edge pre-edge absorption energy and pattern can serve as an efficient tool to unambiguously characterize and discriminate mononuclear DNICs and dinuclear DNICs containing bridged-thiolate and bridged-sulfide ligands.