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Nitric oxide (NO) holds great promise as a treatment for cancer hypoxia, if its concentration and localization can be precisely controlled. Here, we report a "Trojan Horse" strategy to provide the necessary spatial, temporal, and dosage control of such drug-delivery therapies at targeted tissues. Described is a unique package consisting of (1) a manganese-nitrosyl complex, which is a photoactivated NO-releasing moiety (photoNORM), plus Nd3+-doped upconverting nanoparticles (Nd-UCNPs) incorporated into (2) biodegradable polymer microparticles that are taken up by (3) bone-marrow derived murine macrophages. Both the photoNORM [Mn(NO)dpaqNO2 ]BPh4(dpaqNO2 = 2-[N,N-bis(pyridin-2-yl-methyl)]-amino-N'-5-nitro-quinolin-8-yl-acetamido) and the Nd-UCNPs are activated by tissue-penetrating near-infrared (NIR) light at ∼800 nm. Thus, simultaneous therapeutic NO delivery and photoluminescence (PL) imaging can be achieved with a NIR diode laser source. The loaded microparticles are non-toxic to their macrophage hosts in the absence of light. The microparticle-carrying macrophages deeply penetrate into NIH-3T3/4T1 tumor spheroid models, and when the infiltrated spheroids are irradiated with NIR light, NO is released in quantifiable amounts while emission from the Nd-UCNPs provides images of microparticle location. Furthermore, varying the intensity of the NIR excitation allows photochemical control over NO release. Low doses reduce levels of hypoxia inducible factor 1 alpha (HIF-1α) in the tumor cells, while high doses are cytotoxic. The use of macrophages to carry microparticles with a NIR photo-activated theranostic payload into a tumor overcomes challenges often faced with therapeutic administration of NO and offers the potential of multiple treatment strategies with a single system.

Under anaerobic conditions, thioanisole derivatives bearing a thiomethyl group participated in dual carbon‐carbon bond‐forming reactions with maleimide derivatives in the presence of titanium dioxide. Blue light irradiation facilitated these reactions, producing thiochromenopyrroledione derivatives and nearly equimolar quantities of succinimide derivatives. Specifically, a thiochromenopyrroledione derivative formed from thioanisole and N‐benzylmaleimide was achieved with a 43% yield after 12 hours of blue light exposure (>420 nm), approaching its theoretical maximum yield of 50%. Without titanium dioxide, the reaction remained dormant. Our investigations with five varieties of 4‐substituted thioanisoles and four N‐substituted maleimides as precursors resulted in the synthesis of 20 distinct thiochromenopyrroledione derivatives with moderate to high yields. From observed substituent effects, we postulate that this reaction proceeds through a charge transfer from thioanisole to the conduction band of titanium dioxide during blue light irradiation, initiating the one‐electron oxidation of thioanisole and subsequent generation of α‐thioalkyl radicals via deprotonation. [ABSTRACT FROM AUTHOR]

This study documents the formation of an electron donor‐acceptor complex between thioanisole and benzylidenemalononitrile. Upon irradiation, the electron donor‐acceptor complex generates α‐thioalkyl radicals, facilitating carbon‐carbon bond formation. Mechanistic investigations underscore the crucial roles of both one‐electron oxidation and deprotonation processes in achieving a reaction yield up to 43 %. [ABSTRACT FROM AUTHOR]

Nanoparticles exhibiting enzymatic functions have garnered considerable attention due to their structural robustness and the profusion of active sites that can be introduced to a single nanosized particle. Here we report that nanosized mixed‐metal zeolitic imidazolate frameworks (ZIFs) show a superoxide dismutase (SOD)‐like catalytic activity. We chose a ZIF composed of copper and zinc ions and 2‐methylimidazole, CuZn‐ZIF‐8, in which the Cu and Zn ions are bridged by an imidazolato ligand. This coordination geometry closely mimics the active site of CuZn superoxide dismutase (CuZnSOD). The CuZn‐ZIF‐8 nanoparticles exhibit potent SOD‐like activity, attributed to their porous nature and numerous copper active sites, and also possess exceptional recyclability. [ABSTRACT FROM AUTHOR]

Epoxides are essential precursors for epoxy resins and other chemical products. In this study, we investigated whether electrochemically oxidizing carbonate ions could produce percarbonate to promote an epoxidation reaction in the presence of appropriate metal catalysts, although Tanaka and co-workers had already completed a separate study in which the electrochemical oxidation of chloride ions was used to produce hypochlorite ions for electrochemical epoxidation. We found that epoxides could be obtained from styrene derivatives in the presence of metal complexes, including manganese(III) and oxidovanadium(IV) porphyrin complexes and manganese salen complexes, using a boron-doped diamond as the anode. After considering various complexes as potential catalysts, we found that manganese salen complexes showed better performance in terms of epoxide yield. Furthermore, the substituent effect of the manganese salen complex was also investigated, and it was found that the highest epoxide yields were obtained when Jacobsen's catalyst was used. Although there is still room for improving the yields, this study has shown that the in situ electrochemical generation of percarbonate ions is a promising method for the electrochemical epoxidation of alkenes. [ABSTRACT FROM AUTHOR]

Introducing HAT mediator boosted the oxidation activity of toluene to benzaldehyde on the Pd loaded BiVO 4 photocatalyst under blue-to-green light irradiation, along with good selectivity. [Display omitted] • N -hydroxy compounds were applied to toluene oxidation using Pd-loaded BiVO 4 photocatalyst. • Introduction of N -hydroxyphthalimide boosted the activity up to ca. 28 times. • Excellent efficiency (apparent quantum yield = 10.8% at 420 nm and 5.4% at 520 nm) was realized. • The use of nanoparticulate Pd-loaded BiVO 4 was also effective to improve the photocatalytic activity. • Addition of N -hydroxyphthalimide also resulted in good selectivity (>99 %) of benzaldehyde production. Selective organic conversion using semiconductor photocatalysts has been focused on the viewpoint of sustainable synthesis processes. Especially, C-H activation is one of the most attractive reactions. We recently reported photo-oxidation of toluene to benzaldehyde over visible-light responsible Pd-loaded BiVO 4 (Pd/BiVO 4) photocatalyst. However, it remains challenging due to its low efficiency. Herein, we introduce a novel strategy to apply a cyclic nitroxide compound as an efficient redox mediator along with Pd/BiVO 4 for toluene oxidation. Including N -hydroxyphthalimide (NHPI) could significantly expedite the activity of benzaldehyde production up to ca. 28 times compared to without NHPI under blue-to-green light irradiation. The sustainable conditions realized a conversion in high efficiency (apparent quantum yield = 10.8 and 5.4 %@420 and 520 nm, respectively) and with excellent selectivity (>99 %). The excellent efficiency was realized by the synergistic effect between the presence of NHPI and the use of nanoparticulate Pd/BiVO 4 with a relatively large surface area. [ABSTRACT FROM AUTHOR]

The relationship between the spin state and the reactivity with O2 of a series of the chlorocatecholatoiron(III) complexes is investigated. The study revealed that the low-spin complex has a lower reactivity with O2 than high-spin analogue, despite higher semiquinonate character in the low-spin state than in the high-spin state.

The bis(mu-oxo)dimanganese(III,III) complex [Mn(super II)(sub 2)(mu-oxo)2(TPA)2](super 2+) exhibits a high catechol oxidase activity. The reaction is very unique because the aerobic oxidation of catechols are catalyzed by a manganese complex through mononuclear Mn(II)-SQ and bis(mu-oxo-dimanganese(III,III) complexes.

Dicopper complexes [Cu2(μ-OH)(Ln)](ClO4)2 [n = 1 (1) and 2 (2)] with a novel phenanthrene amide-tether ligand conjugate (HL1) and the original p-cresol-2,6-bis(amidecyclen) (HL2) were synthesized. A phenanthrene unit of 1 enhances the DNA-binding by 9-fold, enabling 1 to convert supercoiled plasmid DNA with H2O2 to a linear one in a 9.3-fold higher yield than 2. 1 reacts with H2O2 to form the μ-1,1-hydroperoxodicopper(II) complex 3 as the active species. The IC50 values of 1 against cancer cells of the lung and pancreas are 23.8 and 18.4 μM, respectively, 12-fold more toxic than the 284 and 241 μM of 2. Confocal microscopy, fluorescence-activated cell sorting, and caspase activity assays using HeLa cells revealed that 1 induces mitochondrial apoptosis. A DNA-targeting phenanthrene unit of 1 enhances the cancer-cell-selective toxicity via mitochondrial apoptosis. [ABSTRACT FROM AUTHOR]

A study illustrates how the modification of heme-propionates improves the peroxidase activity of reconstituted myoglobin for small molecule substrates, which led to the engineering of a new binding domain on the myoglobin surface. The existing chemical mutation of the prosthetic group will function as a new strategy for synthesizing novel catalysts with tailored properties. Experimental methods and findings are presented.

Research was conducted to evaluate artificial protein-protein complexation between the cytochrome c and a reconstituted myoglobin. In this study, novel myoglobins were developed by inserting artificial prosthetic porphyrins into apomyglobin. Results show that an effective recognition domain can be formed from the artificial functional groups bound to the terminal of porphyrin in the reconstituted myoglobin.

The synthesis and characterization of several new Cu(II)-ACC (1-aminocyclopropane carboxylic acid) complexes, [Cu(ACC)(1,10-phenanthroline)](Cl[O.sub.4]) and [Cu(ACC)(2-picolylamine)](Cl[O.sub.4]) is presented. The results from density functional theory calculations provide insight into the Cu(I)-OOH as a possible active species for the conversion of ACC into ethylene.

A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane (6-hpa), [Cu2(μ-OH)(6-hpa)]3+, was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H2O2, thus attaining large turnover numbers (TONs) and high H2O2 efficiency. The TON after 40 hours for the phenol production exceeded 12000 in MeCN at 50 °C under N2, the highest value reported for benzene hydroxylation with H2O2 catalyzed by homogeneous complexes. At 22 % benzene conversion, phenol (95.2 %) and p-benzoquinone (4.8 %) were produced. The mechanism of H2O2 activation and benzene hydroxylation is proposed. [ABSTRACT FROM AUTHOR]

A method to determine the zinc-binding thermodynamics of the intracellular zinc metalloregulatory protein ZntR is presented.

Recently, it was shown that μ-oxo-μ-peroxodiiron(III) is converted to high-spin μ-oxodioxodiiron(IV) through O−O bond scission. Herein, the formation and high reactivity of the anti-dioxo form of high-spin μ-oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic-absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ-oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluene8]toluene is 95 at −30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2O2. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new synthesis method to prepare fine particles of BiVO4 with a scheelite-monoclinic (s-m) phase, which is known as the most favorable crystal phase for photocatalytic water oxidation (O2 evolution) under visible light irradiation, based on a coordination chemistry approach in water. Stable aqueous solutions that contain both Bi3+ and V5+ complexes were prepared by simply mixing two aqueous solutions in which each cation was stabilized with an appropriate chelating agent. The use of chelating agents (glycolic acid (gly), l(+)-tartaric acid (tart), citric acid (cit), or ethylenediamine tetraacetic acid (edta)) was effective to form stable V5+ complexes from NH4VO3. On the other hand, only the use of two equivalents of edta with Bi(NO3)3·5H2O was effective to stabilize the Bi3+ complex in water, while the use of other ligands resulted in precipitations. Evaporation of the aqueous solution containing the stable Bi3+ and V5+ complexes and subsequent calcination in air at 500 °C yielded s-m BiVO4 particles smaller than 300 nm, which were much smaller than BiVO4 particles prepared via conventional solid-state reactions (1–10 μm). In particular, the BiVO4 particles that were prepared with the tart ligand for V5+ stabilization possessed the smallest size (∼80 nm) and exhibited the highest photocatalytic activity for O2 evolution from an aqueous solution containing an electron acceptor (Ag+ or Fe3+) under visible-light irradiation. These results strongly suggested that the tart ligand effectively suppresses particle growth during the crystallization process and thereby affords small BiVO4 particles with high crystallinity, both of which are necessary to achieve highly efficient photocatalysis. [ABSTRACT FROM AUTHOR]

The photo-initiated cytotoxicity of a newly developed manganese nitrosyl {MnNO}6 complex (UG1NO) to HeLa cells is described. The complex was found to be strongly cytotoxic after being exposed to light with a wavelength of 650 nm. Cell death was caused by a manganese(ii) complex, UG1, generated from UG1NO through the photo-dissociation of NO, rather than by NO directly. Mechanistic studies revealed that UG1 consumes O2 only in the presence of a reducing agent to catalytically produce H2O2. [ABSTRACT FROM AUTHOR]

Highly stable aqueous titania sols were prepared via a facile process using titanium tetraisopropoxide in the co-existence of acetylacetone and acetic acid. Their co-existence efficiently suppressed the hydrolysis and condensation reaction of titanium tetraisopropoxide even in water, retaining the diameter of titania colloidal particles lower than 10 nm (average diameter d = ca. 4 nm). The titania sols possessed significantly high stability for more than 1 year and could be easily coated on various substrates such as quartz glass via a simple spin-coating method, forming highly homogeneous and transparent films. The calcinations of the coated films in the air at 600 °C produced densely packed anatase TiO2 particles; the diameter was retained below 50 nm even after the calcinations at 900 °C without phase transition to rutile, maintaining the fairly good transparency of the films. On the other hand, the TiO2 particles prepared on a quartz substrate from other precursors, such as titanium–peroxo-citrate complexes, were found to transform from anatase into the rutile phase at above 700 °C with a significant increase in the particle size up to ca. 200 nm. The TiO2 films prepared from the present aqueous titania sols exhibited higher activity for photo-induced surface superhydrophilicity under UV light irradiation than those prepared from other precursors. [ABSTRACT FROM AUTHOR]

We have reported previously that an iron(III) complex supported by an anionic pentadentate monoamido ligand, dpaqH (dpaqH=2-[bis(pyridin-2-ylmethyl)]amino- N-quinolin-8-yl-acetamido), promotes selective CH hydroxylation with H2O2 with high regioselectivity. Herein, we report on the preparation of FeIII-dpaq derivatives that have a series of substituent groups at the 5-position of a quinoline moiety in the parent ligand dpaqH (dpaqR, R: OMe, H, Cl, and NO2), and examine them with respect to their catalytic activity in CH hydroxylation with H2O2. As the substituent group becomes more electron-withdrawing, both the selectivity and the turnover number increase, but the selectivity of epoxidation shows the opposite trend. [ABSTRACT FROM AUTHOR]

A mononuclear iron(iii) complex of a noncyclic tetradentate monoamido ligand, Fe(iii)mpaq, catalyses the oxidation of Orange II, guaiacol, ABTS and Amplex Red with H2O2 in aqueous solutions at neutral pH. Under identical conditions, other structurally related nonheme iron complexes showed only negligible activities. [ABSTRACT FROM AUTHOR]

We developed a metal-based fluorescent probe for H2O2 called MBFh1, which has an iron complex as a reaction site for H2O2 and a 3,7-dihydroxyphenoxazine derivative as the fluorescent reporter unit. The iron complex reacts quickly with H2O2 to form oxidants, and then the oxidants convert the closely appended nonfluorescent 3,7-dihydroxyphenoxazine moiety to resorufin in an intramolecular fashion. The quick response to H2O2 allows us to plot the enzymatic evolution of H2O2. A combination of N-acetyl-3,7-dihydroxyphenoxazine and horseradish peroxidase has been frequently used to detect enzymatically generated H2O2, but this method has interference with phenol derivatives. The use of MBFh1 overcomes this drawback. [ABSTRACT FROM AUTHOR]

The electronic and geometric structures of a series of iron(II) complexes supported by tetradentate tris(pyrid-2-ylmethyl)amine-type ligands with different numbers of 4-nitropyridine groups, [(PyCH2)3-n(4-NO2PyCH2)nN] (n = 0-3), were examined by X-ray absorption fine-structure and variable-temperature ¹H NMR spectroscopies and theoretical calculations to reveal how the low-spin state is stabilized through π back-bonding interactions between iron(II) and 4-nitropyridine donor group(s). [ABSTRACT FROM AUTHOR]

We previously reported that a porphyrin-cored tetradentate passivant, which has two disulfide straps over one face of the porphyrin plane, can produce monolayer-protected gold nanoparticles, 2–4 nm in size, by the one-pot reduction of HAuCl4in DMF. The resulting nanoparticles are smaller than those prepared using the same S/Au molar ratio of a monodentate passivant. To examine the formation mechanism of small gold nanoparticles, the formation of gold nanoparticles in the presence of porphyrin-cored tetradentate passivants or a structurally related monodentate passivant was studied by time-resolved quick X-ray absorption fine structure spectroscopy. The results demonstrated that all of Au ions in solution are reduced to compose small Au clusters, i.e.nuclei, just after the NaBH4reduction of HAuCl4in both cases, but their size varied with the initial S/Au molar ratios and structure of the passivants. Thus, the size of Au nuclei was kinetically controlled by the passivants. Interestingly, the porphyrin-cored tetradentate passivant could stabilize smaller gold nanoparticles, 2–4 nm in size, but it was less efficient in trapping the Au nuclei formed at a very early stage, in comparison to the monodentate passivant. [ABSTRACT FROM AUTHOR]