A photoswitchable [2]catenane receptor.

A [2]catenane-based receptor functionalized with stiff-stilbene can be reversibly switched with 340/385 nm light between its - and -isomers, which leads to a considerable change in chloride binding affinity. Photoisomerization in the presence of chloride allows for on demand guest uptake and release.

Mimicking the Reactivity of LPMOs with a Mononuclear Cu Complex.

Lytic polysaccharide monooxygenases (LPMOs) are Cu-dependent metalloenzymes that catalyze the hydroxylation of strong C-H bonds in polysaccharides using O or HO as oxidants (monooxygenase/peroxygenase). In the absence of C-H substrate, LPMOs reduce O to HO (oxidase) and HO to HO (peroxidase) using proton/electron donors. This rich oxidative reactivity is promoted by a mononuclear Cu center in which some of the amino acid residues surrounding the metal might can accept and donate protons and/or electrons during O and HO reduction.

Nonheme Mononuclear and Dinuclear Iron(II) and Iron(III) Fluoride Complexes and Their Fluorine Radical Transfer Reactivity.

The nonheme iron(II) complexes containing a fluoride anion, Fe(BNPAO)(F) () and [Fe(BNPAOH)(F)(THF)](BF) (), were synthesized and structurally characterized. Addition of dioxygen to either or led to the formation of a fluoride-bridged, dinuclear iron(III) complex [Fe(BNPAO)(F)(μ-F)] (), which was characterized by single-crystal X-ray diffraction, H NMR, and elemental analysis. An iron(II)(iodide) complex, Fe(BNPAO)(I) (), was prepared and reacted with O to give the mononuclear complex -Fe(BNPAO)(OH)(I) ().

FON: An Innovative Fluorinated Group via Hydroetherification-Type Reactivity.

An efficient strategy for preparing the novel -difluoroalkylhydroxylamine fluorinated functional group, coined FON, is reported. This analogue of medicinally important β-phenethyl ether scaffolds in uniting -difluoro and N-O moieties is synthesized in one step via chemo- and regioselectivity metal-free hydroetherification-type additions. As shown, this unique mode of reactivity is realized for a diverse substrate scope and applied to gram-scale synthesis and site-selective deuterium incorporation.

Enhanced Proton-Coupled Electron-Transfer Reactivity by a Mononuclear Nickel(II) Hydroxide Radical Complex.

The synthesis, characterization, and reactivity of a NiOH core bearing a tridentate redox-active ligand capable of reaching three molecular oxidation states is presented in this paper. The reduced complex [LNiOH] was characterized by single-crystal X-ray diffraction analysis, depicting a square-planar NiOH core stabilized by intramolecular H-bonding interactions. Cyclic voltammetry measurements indicated that [LNiOH] can be reversibly oxidized to [LNiOH] and [LNiOH] at very negative reduction potentials (-1.

Control of Bilayer Transport through a Photoswitchable Membrane-Stiffening Agent.

The mobility of proteins in the bilayer membrane is affected by (local) changes in lipid environment, which is important to their biological functioning. Artificial molecular systems that-to some extent-imitate tasks of membrane-embedded proteins are increasingly developed, however, they are usually controlled through responsive units in their core structure. Here we present an alternative approach based on an amphiphilic stiff-stilbene derivative that enables control of membrane fluidity by light.

Influence of the second coordination sphere on O activation by a nonheme iron(II) thiolate complex.

The synthesis and characterization of a new ligand, 1-(bis(pyridin-2-ylmethyl) amino)-2-methylpropane-2-thiolate (BPAS) and its nonheme iron complex, Fe(BPAS)Br (1), is reported. Reaction of 1 with O at -20 °C generates a high-spin iron(III)-hydroxide complex, [Fe(OH)(BPAS)(Br)] (2), that was characterized by UV-vis, Fe Mössbauer, and electron paramagnetic resonance (EPR) spectroscopies, and electrospray ionization mass spectrometry (ESI-MS). Density functional theory (DFT) calculations were employed to support the spectroscopic assignments.

Activity Control of a Synthetic Transporter by Photodynamic Modulation of Membrane Mobility and Incorporation.

Artificial transmembrane transport systems are receiving a great deal of attention for their potential therapeutic application. A major challenge is to switch their activity in response to environmental stimuli, which has been achieved mostly by modulating the binding affinity. We demonstrate here that the activity of a synthetic anion transporter can be controlled through changes in the membrane mobility and incorporation.

Tolerance Factor Approach for the Design of Quaternary Materials as Applied to the ALnCuQ Homologous Series.

The design of novel quaternary materials can be a chemically challenging endeavor. Here, we show that a new tolerance factor, we herein call the quaternary tolerance factor (QTF), akin to the Goldschmidt ratio, can be applied to a homologous series of quaternary materials to aid in the prediction of structural stability in new phases. Single crystals of nine new members of the CuQ homologous series were synthesized ( = K, Rb, Cs, = Sm, Gd, Tb, Dy, Er, Yb, Lu, = S, Se) for = 1, 2, and 3 using a reactive KCl flux method as the sole potassium source.

Dioxygenase Chemistry in Nucleophilic Aldehyde Deformylations Utilizing Dicopper O-Derived Peroxide Complexes.

The chemistry of copper-dioxygen complexes is relevant to copper enzymes in biology as well as in (ligand)Cu-O (or Cu-O) species utilized in oxidative transformations. For overall energy considerations, as applicable in chemical synthesis, it is beneficial to have an appropriate atom economy; both O-atoms of O are transferred to the product(s). However, examples of such dioxygenase-type chemistry are extremely rare or not well documented.

Can the -CF Group Act as a Tight, Well-Defined Hydrogen Bond Acceptor? A Clear Crystallographic CF-F···H-N Interaction Says Yes.

The CF group is well noted for being noninteractive with other functional groups. In this Note, we present a highly rigid model system containing a significant hydrogen bonding interaction between a charged N-H donor and a CF acceptor that challenges this accepted wisdom. Spectroscopic and single crystal X-ray crystallography data characterize this interaction, consistent with a weak to moderate hydrogen bond that would be difficult to observe in an intermolecular system.

Oxygen-Dependent Interactions between the Ruthenium Cage and the Photoreleased Inhibitor in NAMPT-Targeted Photoactivated Chemotherapy.

Photoactivated chemotherapy agents form a new branch of physically targeted anticancer agents with potentially lower systemic side effects for patients. On the other hand, limited information exists on the intracellular interactions between the photoreleased metal cage and the photoreleased anticancer inhibitor. In this work, we report a new biological study of the known photoactivated compound in the glioblastoma cancer cell line, U87MG.

Comprehensive Analyses of the Effects of the Small-Molecule Inhibitor of the UHM Domain in the Splicing Factor in Leukemia Cells.

Mutations in RNA splicing factor genes including , , and have been reported to contribute to development of myeloid neoplasms including myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (sAML). Chemical tools targeting cells carrying these mutant genes remain limited and underdeveloped. Among the four proteins, mutant U2AF1 (U2AF1) acquires an altered 3' splice site selection preference and co-operates with the wild-type U2AF1 (U2AF1) to change various gene isoform patterns to support MDS cells survival and proliferation.

Chemoselective Proteomics, Zinc Fingers, and a Zinc(II) Model for HS Mediated Persulfidation.

The gasotransmitter hydrogen sulfide (HS) is thought to be involved in the post-translational modification of cysteine residues to produce reactive persulfides. A persulfide-specific chemoselective proteomics approach with mammalian cells has identified a broad range of zinc finger (ZF) proteins as targets of persulfidation. Parallel studies with isolated ZFs show that persulfidation is mediated by Zn, O, and HS, with intermediates involving oxygen- and sulfur-based radicals detected by mass spectrometry and optical spectroscopies.

Intramolecular Phenolic H-Atom Abstraction by a NArOH Ligand-Supported (μ-η:η-Peroxo)dicopper(II) Species Relevant to the Active Site Function of oxy-Tyrosinase.

Synthetic side-on peroxide-bound dicopper(II) () complexes are important for understanding the active site structure/function of many copper-containing enzymes. This work highlights the formation of new {Cu(μ-η:η-O)Cu} complexes (with electronic absorption and resonance Raman (rR) spectroscopic characterization) using tripodal NArOH ligands at -135 °C, which spontaneously participate in intramolecular phenolic H-atom abstraction (HAA). This results in the generation of bis(phenoxyl radical)bis(μ-OH)dicopper(II) intermediates, substantiated by their EPR/UV-vis/rR spectroscopic signatures and crystal structural determination of a diphenoquinone dicopper(I) complex derived from ligand -C═C coupling.

Tuning the Thermochemistry and Reactivity of a Series of Cu-Based 4H/4e Electron-Coupled-Proton Buffers.

Electron-coupled-proton buffers (ECPBs) store and deliver protons and electrons in a reversible fashion. We have recently reported an ECPB based on Cu and a redox-active ligand that promoted 4H/4e reversible transformations ( , 144, 16905). Herein, we report a series of Cu-based ECPBs in which the ability of these to accept and/or donate H equivalents can be tuned via ligand modification.

Angle-strained sila-cycloalkynes.

Second row elements in small- and medium-rings modulate strain. Herein we report the synthesis of two novel oligosilyl-containing cycloalkynes that exhibit angle-strain, as observed by X-ray crystallography. However, the angle-strained sila-cyclooctynes are sluggish participants in cycloadditions with benzyl azide.

A Nonheme Iron(III) Superoxide Complex Leads to Sulfur Oxygenation.

A new alkylthiolate-ligated nonheme iron complex, Fe(BNPAS)Br (), is reported. Reaction of with O at -40 °C, or reaction of the ferric form with O at -80 °C, gives a rare iron(III)-superoxide intermediate, [Fe(O)(BNPAS)] (), characterized by UV-vis, Fe Mössbauer, ATR-FTIR, EPR, and CSIMS. Metastable then converts to an S-oxygenated Fe(sulfinate) product via a sequential O atom transfer mechanism involving an iron-sulfenate intermediate.

PhenTAA: A Redox-Active N-Macrocyclic Ligand Featuring Donor and Acceptor Moieties.

Here, we present the development and characterization of the novel PhenTAA macrocycle as well as a series of [Ni(RPhenTAA)] complexes featuring two sites for ligand-centered redox-activity. These differ in the substituent R (R = H, Me, or Ph) and overall charge of the complex n (n = -2, -1, 0, +1, or +2). Electrochemical and spectroscopic techniques (CV, UV/vis-SEC, X-band EPR) reveal that all redox events of the [Ni(RPhenTAA)] complexes are ligand-based, with accessible ligand charges of -2, -1, 0, +1, and +2.

A Photoswitchable Macrocycle Controls Anion-Templated Pseudorotaxane Formation and Axle Relocalization.

Important biological processes, such as signaling and transport, are regulated by dynamic binding events. The development of artificial supramolecular systems in which binding between different components is controlled could help emulate such processes. Herein, we describe stiff-stilbene-containing macrocycles that can be switched between (Z)- and (E)-isomers by light, as demonstrated by UV/Vis and H NMR spectroscopy.

Scaling Relation between the Reduction Potential of Copper Catalysts and the Turnover Frequency for the Oxygen and Hydrogen Peroxide Reduction Reactions.

Changes in the electronic structure of copper complexes can have a remarkable impact on the catalytic rates, selectivity, and overpotential of electrocatalytic reactions. We have investigated the effect of the half-wave potential () of the Cu/Cu redox couples of four copper complexes with different pyridylalkylamine ligands. A linear relationship was found between of the catalysts and the logarithm of the maximum rate constant of the reduction of O and HO.

Selective Radical Transfer in a Series of Nonheme Iron(III) Complexes.

A series of nonheme iron complexes, Fe(BNPAO)(L)(L) (L = N, NCS, NCO, and Cl) have been synthesized using the previously reported BNPAO ligand. The ferrous analogs Fe(BNPAO)(L) (L = N, NCS, and NCO) were also prepared. The complexes were structurally characterized using single crystal X-ray diffraction, which shows that all the Fe complexes are six-coordinate, with one anionic ligand (L) in the H-bonding axial site and the other anionic ligand (L) in the equatorial plane, cis to the L ligand.