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Luminescence metal–organic materials (MOMs) are widely used as probes for detection. However, most of such probes are based on fluorescence and work in either turn‐off or turn‐on mode. In contrast, long‐lived (>10 ms) probes (LLPs) with recovery response to analyte are quite rare. Herein "solvation complex" strategy is used to prepare two new afterglow complexes with multiple coordinated solvents, trans‐complex 1 with both delayed fluorescence (DF) and room temperature phosphorescence (RTP), and cis‐complex 2 with RTP. Remarkably, they can serve as selective and recovery LLPs for l‐Arginine detection, with limit of detection down to 1.0 × 10−7 M. In addition, heating/fumigation can induce reversible arousal/silence of their afterglow, while H2O/DMSO vapor fumigation causes reversible crystalline‐to‐crystalline transformation between them. Detailed mechanism studies reveal that the change in coordinated solvent, including loss/acquisition, exchange, or replacement, plays a key role in such afterglow multi‐stimuli‐responsive properties. This work not only shows the potential of such long‐lived luminescence complex for recovery detection, but also reveals the unique advantages of solvation complex in the preparation of afterglow multi‐stimuli‐responsive materials [ABSTRACT FROM AUTHOR]

The first B-ring-naphthalene-substituted flavonol-based ratiometric fluorescent cysteine (Cys) probe NCA (2-(naphthalen-2-yl)-4-oxo-4H-chromen-3-yl acrylate) was developed, which also acts as a precursor of the photoCORM. NCA enables fast (20 s), highly selective and sensitive (limit of detection: 23 nM) detection and visualization of exogenous and endogenous Cys in live HeLa cells and zebrafish. The fluorophore HNC (3-hydroxy-2-(naphthalen-2-yl)-4H-chromen-4-one), driven and quantitatively produced by the Cys sensing reaction, was designed as a photoCORM. By controlling the light illumination intensity or duration or photoCORM dosage, HNC can supply accurate and quantitatively controlled linear CO gas in an aerobic environment. The location and CO releasing procedure of HNC can be monitored in real time by its own fluorescence. NCA and all its reaction products are biocompatible. Our study presents the first B-ring-naphthalene-substituted flavonol-based ratiometric fluorescent probe to efficiently detect and image exogenous and endogenous Cys both in vitro and in vivo, which also acts as a Cys-driven and visible-light triggerable photoCORM precursor, for linear CO delivery in an aerobic environment. This study not only has promising applications in Cys sensing, imaging and spatiotemporal control of CO liberation in live systems, but will also contribute to the development of handy molecular tools for CO gas therapy and clinical diagnosis. [ABSTRACT FROM AUTHOR]

The first water-soluble B-ring-indole-substituted flavonol-based cysteine (Cys) fluorescent probe, MICA (2-(1-methyl-1H-indol-3-yl)-4-oxo-4H-chromen-3-yl-acrylate), was developed, which simultaneously serves as a precursor of photoCORM. In PBS buffer (only 15% DMF), MICA can perform rapid (330 s), highly chemoselective (particularly for homocysteine and glutathione) and sensitive (limit of detection: 92 nM) sensing and visualization of exogenous and endogenous Cys in live HeLa cells and zebrafish over a wide linear concentration range (0–12 μM/2.4 equiv.). The fluorophore HMIC (3-hydroxy-2-(1-methyl-1H-indol-3-yl)-4H-chromen-4-one), actuated and quantitatively generated via the sensing reaction of the precursor MICA with Cys, was designed as a photoCORM. By modulating the light illumination intensity or illumination duration or photoCORM dosage, HMIC can provide precisely controlled quantitative and linear CO gas by visible light illumination in aerobic environments. For live HeLa cells, MICA and all reaction products showed low toxicity (over 85% cell viability versus 10 μM analyst) and efficient cellular uptake. In live HeLa cells and zebrafish, both exogenous and endogenous Cys can be visualized by MICA, and the location and CO liberation process of the generated HMIC can be tracked in real time through its fluorescence. Substitution of the B-ring of 3-hydroxy-flavone (3-FL) by indole results in a 52 nm absorption red-shift vs.3-FL. Our work is the first water-soluble B-ring-indole-substituted flavonol-based fluorescent probe that efficaciously detects and visualizes exogenous and endogenous Cys both in vitro and in vivo, simultaneously serving as a precursor of photoCORM, actuated by Cys and triggered by visible light, releasing linear CO in aerobic environments. This work not only provides promising applications for the detection and visualization of exogenous and endogenous Cys, and spatiotemporally controllable CO liberation in live systems, but will also facilitate the development of handy molecular tools for clinical diagnosis and CO gas therapy. [ABSTRACT FROM AUTHOR]

The first B-ring-extended (to biphenyl) flavonol-based Cys-ratiometric fluorescent probe B-bph-fla-acr (2-([1,1′-biphenyl]-4-yl)-4-oxo-4H-chromen-3-yl acrylate) is developed. B-bph-fla-acr can ratiometrically sense and non-ratiometrically image endogenous and exogenous cysteine (Cys) in living HeLa cells and zebrafish rapidly (45 s), selectively (vs. homocysteine and glutathione), sensitively (detection limit: 18.5 nM), and with a large Stokes shift (186 nm). Quantitatively released (from the reaction of B-bph-fla-acr with Cys) fluorophore B-bph-fla-OH (2-([1,1′-biphenyl]-4-yl)-3-hydroxy-4H-chromen-4-one) is designed as a photoCORM (photo-triggered CO releasing molecule). Under O2 and visible light irradiation, the amount of CO released by B-bph-fla-OH can be accurately controlled linearly by adjusting the light irradiation intensity, irradiation time, or photoCORM dose. This process is accompanied by fluorescence quenching; therefore, the location of the photoCORM and the CO release process can be monitored in real time. B-bph-fla-acr and all reaction products exhibit good membrane permeability and low toxicity for living HeLa cells. In living HeLa cells and zebrafish, B-bph-fla-acr can image endogenous and exogenous Cys, and the released B-bph-fla-OH can photo-release CO under O2 at room temperature. This study is the first to combine a B-ring-extended flavonol-based fluorescent probe (for the effective ratiometric sensing and non-ratiometric imaging of endogenous and exogenous Cys in vitro and in vivo) with a photoCORM (Cys-activated, visible light-triggered linear CO release under O2). Our study provides important insights into the biological roles of Cys and CO, as well as a reliable method for safely supplying accurately controlled amounts of CO to living systems, thereby facilitating the development of convenient clinical diagnostic molecular tools and therapeutic prodrugs. [ABSTRACT FROM AUTHOR]

To clarify structure‐function relationship among "typical" (2HisCOO) and "atypical" (3His, 3HisCOO, 4His) different active site dioxygenases, a set of model ligands 2NCOO, 3 N, 3NCOO, 4 N (L2NCOOH: 2‐((benzyl(pyridin‐2‐ylmethyl)amino)methyl)benzoic acid, L3N: N‐benzyl‐1‐(pyridin‐2‐yl)‐N‐(pyridin‐2‐ylmethyl)methanamine, L3NCOOH: 2‐{[bis(pyridin‐2‐ylmethyl)amino]methyl}benzoic acid, L4N: tris(pyridin‐2‐ylmethyl)amine) and their complexes [CoIILn(fla)] (n: 2NCOO (1), 3 N (2), 3NCOO (3), 4 N (4); fla: 3‐flavonolate) were designed as ES models of the Co(II)‐containing quercetin 2,4‐dioxygenase (Co‐2,4‐QD) from a structural and functional viewpoint. Their structure, properties, O2 reactivity, reaction mechanism, and structure‐reactivity relationship details were investigated. [CoLn(fla)] exhibit higher single turnover O2 reactivity to produce products similar to the enzymatic reaction, and model ligands dependent order 3 > 4 > 1 > 2. 3 (the same 3HisCOO structure as natural 2,4‐QD) shows higher reactivity, which highlight the role of active site Glu of 2,4‐QD. The reaction rate constant k shows linear correlation with E1/2(CoIII/II) and Epa(fla−/fla•), which highlights the structure‐property‐O2 reactivity relationship. This is the first biomimetic study of structure‐function correlation among 2HisCOO, 3His, 3HisCOO, 4His different active site dioxygenases, could shed light on understanding structure‐function relationship among them and reaction mechanism of Co‐2,4‐QD. [ABSTRACT FROM AUTHOR]

Abstract: Present here is a new dual ratiometric luminescent probe D which is a trichromatic and white‐light‐emitting metal‐organic framework (MOF) composite facilely obtained by incorporating red/green‐emitting complex modules into a blue‐emitting MOF. Probe D exhibits remarkable capabilities of sensing different volatile organic solvents (VOSs) via 2D code recognition of the two VOS‐dependent MOF ligand‐to‐module ratios of the emission‐peak intensities. For specific VOSs, the resultant luminescent color changes from the starting white color are sharp enough to be visible to the naked eye. Remarkably, D can differentiate solution‐phase nitroaromatics and metal ions by recording the evolution of the two ratios during titration processes, enabling an unusual 3D code recognition using the titrant amount as the third dimension for the first time. D also can be used to detect dinoseb, Fe3+ and Al3+ ions quantitatively by analysis of the ratios with detection limits as low as 0.050, 0.41, and 0.12 ppm, respectively. Clearly, such a self‐referencing trichromatic probe can maximize the output information and significantly enhance the detection selectivity and sensitivity via multi‐dimensional sensing, and has great potentials for practical applications. [ABSTRACT FROM AUTHOR]

A novel mononuclear copper(II)-flavonolate complex [Cu II L(fla)] (LH: 2-{[bis(pyridine-2-ylmethyl)-amino]methyl}-4-methoxy benzoic acid, flaH: flavonol) was prepared as a structural and functional model of the ES (enzyme-substrate) complex of Cu II -containing flavonol 2,4-dioxygenase. Its structure, properties and reactivity towards molecular dioxygen have been investigated in details. The complex shows the best reactivity in the copper(II)-flavonolate ES model system, may it could be contributed to the approximately monodentate coordination of the substrate flavonolate. [ABSTRACT FROM AUTHOR]

To obtain insights into the role of the carboxylate group of Glu73 in the active site of quercetin 2,4-dioxygenase (2,4-QD), the copper(II) complexes [CuIIL n(AcO)] [ 1 (L n = L1), 2 (L n = L2), 3 (L n = L3), and 4 (L n = L4)] supported by a series of carboxylate-containing ligands [ L1H = 2-{[bis(pyridin-2-ylmethyl)amino]methyl}benzoic acid; L2H = 3-{[bis(pyridin-2-ylmethyl)amino]methyl}benzoic acid,; L3H = 2-({bis[2-(pyridin-2-yl)ethyl]amino}methyl)benzoic acid; L4H = 3-({bis[2-(pyridin-2-yl)ethyl]amino}methyl)benzoic acid] as well as the ternary CuII flavonolate (fla-) complexes [CuIIL n(fla)] [ 5 (L n = L1), 6 (L n = L2), 7 (L n = L3), and 8 (L n = L4)] were synthesized and characterized as structural and functional models for the active site of 2,4-QD. The ternary complexes [CuIIL n(fla)] showed different reactivities in the dioxygenation of bound flavonolate to benzoic acid, salicylic acid, and N, N-dimethylbenzamide at 75-90 °C (single-turnover reaction) in the order 5 >> 7 > 8 ≈ 6. A similar reactivity tendency was found in the catalytic dioxygenation of the substrate flavonol (multiturnover reaction) by the binary complexes. The different reactivities of the copper complexes could be attributed to the different Lewis acidities of the copper(II) ions induced by the different coordination environments of the ligands. The results will provide important insights into the pivotal catalytic role of the carboxylate group of Glu73 in 2,4-QD. [ABSTRACT FROM AUTHOR]

The syntheses, structures, and magnetic properties of two series of Cr-Ln heterometallic clusters based on the 2,2'-bipyridine (bipy) ligand are reported; binuclear [LnCr(bipy)2-(µ2-OH)2(H2O)6](ClO4)4·2H2O {Ln = Gd (1Gd) or Dy (1Dy)} and trinuclear [LnCr2(bipy)4(µ2-OH)4(H2O)4](ClO4)5·H2O {Ln = Gd (2Gd), Dy (2Dy), or Tb (2Tb)}. Their syntheses could be controlled by the amount of lanthanide perchlorate used. The binuclear [CrLn] clusters could be formed with 24 equivalents of Ln(ClO4)3, whereas 12 equivalents of Ln(ClO4)3 gave the trinuclear [Cr2Ln] species with a CrLnCr core. The Cr3+ and Ln3+ ions are bridged by µ2-OH groups in the two systems, and the [Cr2Ln] cluster is further assembled into a 1D supramolecular architecture by weak intermolecular p-p interactions. Magnetic analyses reveal that the Cr···Gd interactions in 1Gd and 2Gd are both antiferromagnetic. [ABSTRACT FROM AUTHOR]

In order to get insights into the metal ion effects and the carboxylate effects on enzymatic activity, a series of the carboxylate ligand supported transition metal complexes [MIIL(OAc)] (M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5) and Zn (6); LH = 2-{[bis-(pyridin-2-ylmethyl)amino]methyl}-4-methoxy benzoic acid) were synthesized and characterized as structural and functional models for the active sites of various MII-substituted resting quercetin 2,3-dioxygenases (2,3-QD). Their structures, spectroscopic features, redox properties, as well as the catalytic reactivity toward the substrate flavonol and O2 have been investigated in detail. The model complexes show higher enzymatic reactivities in the catalytic dioxygenation (oxidative ring opening) of the substrate flavonol at lower temperatures (55–100 °C), presumably caused by the carboxylate group in the supporting model ligand, which could lower the redox potential of the bound substrate flavonolate by electron donation. The catalytic reactivity of [MIIL(OAc)] exhibits notable differences and it is in a metal ion dependent order of Co (3) ＞ Ni (4) ＞ Zn (6) ＞ Fe (2) ＞ Mn (1) ＞ Cu (5). The differences in the reactivities among them could be ascribed to the redox potential of the bound substrate flavonolate, which was drastically influenced by the metal ions via tuning the electron density of flavonolate, providing important insights into the metal ion effects and the carboxylate effects on the enzymatic activity of various MII-substituted 2,3-QD. Our model complexes [MIIL(OAc)] are the first examples of a series of structural and functional models of various MII-substituted resting 2,3-QD. [ABSTRACT FROM AUTHOR]

A new triflic acid (TfOH)-mediated cascade cyclization of ortho-anisole-substituted aryldiynes is described for the construction of indeno[1,2-c]chromenes. The cascade cyclization proceeds through an unusual TfOH-induced alkyne-alkyne cyclization followed by nucleophilic attack of the methoxy group on the benzylidene cation, which is completely different to the cyclization of ortho-aniline- or ortho-thioanisole-substituted aryldiynes. A new class of organic dyes with the indeno[1,2-c]chromene framework as both donor and p-linker were synthesized. These compounds exhibit high photovoltaic performances in dye-sensitized solar cells (DSCs). [ABSTRACT FROM AUTHOR]

Two inhibitor-containing ‘half-sandwich’ cobalt(II) complexes [(TpPh)Co(X)(CH3OH)m]·nCH3OH ((TpPh)=hydrotris(3-phenylpyrazolyl)borate; 1: X−=N3−, m=1, n=2; 2: X−=NCS−, m=0, n=0) have been synthesized and used as the catalysts in the bicarbonate dehydration reaction. The structures of 1 and 2 were determined by X-ray diffraction analysis, which shows that N3− and NCS− coordinate to the Co(II) ions of 1 and 2, respectively, with the Co&z.sbnd;N bond lengths of 1.992(6) A˚ and 1.901(3) A˚. The coordination geometries of the Co(II) complexes in solution are five-coordinated trigonal bipyramid as revealed by the spectroscopic measurements. The dehydration kinetic measurements of HCO3− are performed by the stopped-flow techniques at pH<7.9. The apparent dehydration rate constant kobs varies linearly with Co(II) complex and H+ concentrations, respectively, and the catalytic activity of 2 is lower than that of 1. The aqua Co(II) complex must be the reactive catalytic species in the catalyzed dehydration reaction and the rate-determining step is the substitution of the labile water molecule by HCO3−. The kobs values increase with increasing reaction temperature, and the large negative entropy of activation also indicates the associative activation mode. The inhibition ability of NCS− is stronger than that of N3−, which can be rationalized by the decreases in the Co&z.sbnd;N(N3−/NCS−) bond lengths and effective atomic charges of the Co(II) ions based on the X-ray crystallographic data and theoretical calculations in this work. [Copyright &y& Elsevier]

This communication reports the dehydration kinetic measurements of HCO3− catalyzed by three inhibitor-containing half-sandwich nickel(II) complexes [TpMe]NiX ([TpMe]=hydrotris(3,5-dimethylpyrazolyl)borate; X−=η2-NO2− (1), N3− (2), NCS− (3)) by employing the stopped-flow techniques at pH <7.9. The five- or six-coordinated aqua complexes must be the reactive catalytic species in the catalyzed bicarbonate dehydration reaction and the rate-determining step is the substitution of the labile water molecule by HCO3−. The dehydration rate constants k of the rate-determining step decrease in the order: 1 (186 M−1 s−1) > 2 (169 M−1 s−1) > 3 (120 M−1 s−1), which is correlated with an increase of the activation energy barrier heights, this being the origin of the variation in the inhibition abilities among the different inorganic anions. [Copyright &y& Elsevier]

This paper presents the syntheses, crystal structures and spectroscopic properties of a series of half-sandwich nickel(II) complexes with hydrotris(3,5-dimethylpyrazolyl)borate and azide or thiocyanate, [Tp*Ni(pz)*2(N3)] (1), [Tp*Ni(pz*)(SCN)(H2O)] (2) and [Tp*Ni(SCN)(CH3OH)2] (3) (Tp*: hydrotris(3,5-dimethylpyrazolyl)borate; pz*: 3,5-dimethylpyrazole). Compound 1 crystallizes in the triclinic system, P1¯ space group (No. 2), a=10.2957(11) A˚, b=11.5080(12) A˚, c=13.6748(15) A˚, α=81.993(2)°, β=72.999(2)°, γ=74.533(2)°, Z=2, R1=0.0454, wR2=0.1272. The nickel(II) ion in 1 is coordinated to six nitrogen atoms of Tp* and azide ion to form a distorted N6 octahedron. The structure of 2 is roughly determined by X-ray crystal diffraction and shown two structurally independent [Tp*Ni(pz)(SCN)(H2O)] units. The nickel(II) ion in 2 is six-coordinated to five nitrogen atoms of Tp*, pz*, thiocyanate and one oxygen atom of water molecule to form a N5O octahedral environment. Compound 3 crystallizes in the monoclinic system, P21/c space group, a=13.416(4) A˚, b=11.964(3) A˚, c=14.636(4) A˚, β=96.195(5)°, Z=4, R1=0.0379, wR2=0.1079 . The coordination environment of nickel(II) ion in 3 is better to be described as the N4O2 octahedron made up of three nitrogen atoms of Tp*, one nitrogen atom of thiocyanate and two oxygen atoms of coordinated methanol molecules. The half-sandwich compound [Tp*Ni(η2-O2N)(CH3OH)]4 (4), which has been previously reported in a short communication, has the nickel(II) center with N3O3 coordination environment. The influences of N3−, SCN− and NO2− in all these half-sandwich nickel(II) complexes were discussed in this paper. [Copyright &y& Elsevier]

The preparation and characterization of the half-sandwich zinc complexes [TpPh]ZnX ([TpPh] = hydrotris(3-phenylpyrazolyl)borate; X− = OH− (1), N3− (2), NCS− (3)) have been described. The bicarbonate dehydration kinetic measurements are performed by the stopped-flow techniques at pH < 7.9. The apparent dehydration rate constant kobsd varies linearly with the total Zn(II) concentration, and the catalytic activity of the model complexes decreases in the order 1>2>3. The catalytic activity decreases with increasing pH, which indicates that the aqua model complex must be the reactive catalytic species in the catalyzed dehydration reaction and the rate-determining step is the substitution of the labile water molecule by HCO3−. The kobsd values increase with increasing reaction temperature, and the apparent activation energies of the model complexes with small inorganic ions are remarkably higher, this being the origin of inhibition. The large negative entropy of activation also indicates an associative mode of activation in the rate-determining step. The inhibition ability of NCS− is strong than that of N3−, which can be rationalized by the decrease in effective atomic charges of the Zn(II) ions as revealed by the theoretical calculations. [Copyright &y& Elsevier]

Two nickel(II) complexes with thiocyanate and different substituted pyrazole ligands, [Ni(pzR)4(SCN)2] (R=ph for (1) and n-But for (2), pzR=3-substituted pyrazole), have been synthesized and their crystal structures have been determined. The compound 1 crystallizes in the monoclinic system, space group P21/n, a=8.591(5) A˚, b=17.936(10) A˚, c=12.861(7) A˚, β=106.490(10)°, Z=2, R1=0.0665, wR2=0.1375. The compound 2 crystallizes in the monoclinic system, space group P21/c, a=12.805(3) A˚, b=22.718(5) A˚, c=13.396(3) A˚, β=94.480(5)°, Z=4, R1=0.0729, wR2=0.1665. The nickel(II) ion in each complex is coordinated by four pyrazole nitrogen atoms and two nitrogen atoms of NCS− to form a distorted octahedron. The two nitrogen atoms of NCS− are located at axial positions and the four nitrogen atoms of pyrazoles are located at equatorial positions. The average Ni–N(pzR) and Ni–N(NCS) bond lengths are observed to be 2.111 and 2.068 A˚ for 1, 2.095 and 2.098 A˚ for 2, respectively. In 1, the intermolecular hydrogen bonds form quasi 1D structure. The intramolecular hydrogen bonds are found in 2. The spectroscopic and bond properties have also been discussed. [Copyright &y& Elsevier]

This paper presents the synthesis, crystal structure and spectroscopic properties of a novel half-sandwich mononuclear cobalt(III) complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand and thiocyanate [Tp*Co(Hpz*)(NCS)2]·H2O·CH3OH (Tp*: hydrotris(3,5-dimethyl- pyrazolyl)borate, Hpz*: 3,5-dimethylpyrazole). The structure was determined by X-ray diffraction. The complex crystallizes in the monoclinic system, space group Cc, a=18.591(6) A˚, b=10.536(3) A˚, c=17.568(5) A˚, β=11.284(5)°, Z=4, R1=0.0501, wR2=0.1179. The cobalt(III) ion in the complex is six-coordinated with nitrogen atoms, three from Tp*, two from pyrazole and two from two thiocyanates, to form octahedral environment. The hydrogen atoms of O(2) of water molecule are connected by hydrogen bonds with S atoms of two adjacent complex molecules to form 1-D chains. The hydrogen atom of N(8) of complex molecule is connected by hydrogen bond with methanol. The spectroscopic results are consistent with the crystallographic study. [Copyright &y& Elsevier]

Abstract: An unusual heterotrinuclear complex [LCo(μ-L1, 1-N3)2(μ-L1)Ni(μ-1, 1-N3)2(μ-L1)CoL] (1) was obtained by the reaction of the precursor of half-sandwich nickel(II) complex [LNi(HL1)2(N3)] (2) and CoCl2 ·6H2O (L=hydrotris(3,5-dimethylpyrazolyl)borate; L1 =3,5-dimethylpyrazolate), the complex 1 was characterized by X-ray single-crystal diffraction, elemental analysis, IR, UV–vis spectra and magnetic properties. [Copyright &y& Elsevier]

The cover picture shows dioxygen activation by CuII complexes supported by carboxylate‐containing ligands as structural and functional models of quercetin 2,4‐dioxygenase (2,4‐QD), highlighting the role of the carboxylate group in the structure and reactivity. The green fields, the blue sky, and the tree in the background symbolize molecular oxygen as a green and environmentally benign oxidant. Details are discussed in the article by Y.‐J. Sun, S. Itoh et al. on page 1845 ff (DOI: 10.1002/ejic.201601371). For more on the story behind the cover research, see the Cover Profile (DOI: 10.1002/ejic.201700245). [ABSTRACT FROM AUTHOR]

New ligand [KH2B(tz*)2] (tz*=3,5-dimethyl-1,2,4-triazolyl) has been synthesized and the reactions of two different metal salts (copper and zinc) with the new ligand in agar gave two similar crystalline polymorphic forms: [Cu{H2B(tz*)2}2(H2O)] (1) and [Zn{H2B(tz*)2}2(H2O)] (2). A single crystal X-ray study revealed that the compound 1 was the monoclinic system with space group C2/c and a=8.462(3) A˚, b=14.039(6) A˚, c=19.991(8) A˚, β=94.622(7)°, Z=4, R1=0.0451, wR2=0.1110. And the compound 2 was the monoclinic system with space group C2/c and a=8.4214(4) A˚, b=13.8765(7) A˚, c=20.2969(6) A˚, β=95.615(2)°, Z=4, R1=0.0667, wR2=0.1375. The metal(II) ion in the complex is five-coordinated with four nitrogen atoms which come from triazolyl and one oxygen atom which come from water molecular. In both compounds, the hydrogen atoms of water molecule are connected by hydrogen bonding with N atoms of two adjacent complex molecules to form 2-D planes. The spectroscopic results are consistent with the crystallographic study. [Copyright &y& Elsevier]

Present here is a new dual ratiometric luminescent probe D which is a trichromatic and white-light-emitting metal-organic framework (MOF) composite facilely obtained by incorporating red/green-emitting complex modules into a blue-emitting MOF. Probe D exhibits remarkable capabilities of sensing different volatile organic solvents (VOSs) via 2D code recognition of the two VOS-dependent MOF ligand-to-module ratios of the emission-peak intensities. For specific VOSs, the resultant luminescent color changes from the starting white color are sharp enough to be visible to the naked eye. Remarkably, D can differentiate solution-phase nitroaromatics and metal ions by recording the evolution of the two ratios during titration processes, enabling an unusual 3D code recognition using the titrant amount as the third dimension for the first time. D also can be used to detect dinoseb, Fe 3+ and Al 3+ ions quantitatively by analysis of the ratios with detection limits as low as 0.050, 0.41, and 0.12 ppm, respectively. Clearly, such a self-referencing trichromatic probe can maximize the output information and significantly enhance the detection selectivity and sensitivity via multi-dimensional sensing, and has great potentials for practical applications., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

With the aim of revealing the catalytic role of atypically coordinated (3His-1Glu) active site mononuclear non-heme Fe(II)-dependent quercetin 2,4-dioxygenase (Fe-2,4-QD) and the electronic effects of the model ligands on the reactivity toward dioxygen, a set of p/m-R-substituted carboxylate-containing ligand-supported Fe(II)-3-hydroxyflavonolate complexes, [Fe II L R (fla)] (L R H: 2-{[bis(pyridin-2-ylmethyl)amino]methyl}- p / m -R-benzoic acid; R: p -OMe ( 1 ), p -Me ( 2 ), m -Br ( 4 ), and m -NO 2 ( 5 ); fla: 3-hydroxyflavonolate), were synthesized and characterized as structural and functional models for the ES (enzyme-substrate) complexes of Fe-2,4-QD. [Fe II L R (fla)] show relatively high enzyme-type reactivity (dioxygenative ring opening of the coordinated substrate fla, single-turnover reaction) at low temperatures (30-65 °C). The reaction shows a linear Hammett plot (ρ = -1.21), and electron donating groups enhance the reaction rates. The notable difference on the reactivity can be rationalized from the electronic nature of the substituent in the ligands, which could tune the reactivity via tuning Lewis acidity of the Fe(II) ion, electron density, and the redox potential of fla. The properties and the reactivity show approximately linear correlations between λ max or E 1/2 of fla and the reaction rate constant k . This work sheds light not only on understanding of electronic effects of the ligands and the property-reactivity relationship but also on the role of the catalytic reaction by Fe-2,4-QD., Competing Interests: The authors declare no competing financial interest.

In order to get insights into the metal ion effects and the carboxylate effects on enzymatic activity, a series of the carboxylate ligand supported transition metal complexes [M(II)L(OAc)] (M = Mn (), Fe (), Co (), Ni (), Cu () and Zn (); LH = 2-{[bis-(pyridin-2-ylmethyl)amino]methyl}-4-methoxy benzoic acid) were synthesized and characterized as structural and functional models for the active sites of various M(II)-substituted resting quercetin 2,3-dioxygenases (2,3-QD). Their structures, spectroscopic features, redox properties, as well as the catalytic reactivity toward the substrate flavonol and O2 have been investigated in detail. The model complexes show higher enzymatic reactivities in the catalytic dioxygenation (oxidative ring opening) of the substrate flavonol at lower temperatures (55-100 °C), presumably caused by the carboxylate group in the supporting model ligand, which could lower the redox potential of the bound substrate flavonolate by electron donation. The catalytic reactivity of [M(II)L(OAc)] exhibits notable differences and it is in a metal ion dependent order of Co () > Ni () > Zn () > Fe () > Mn () > Cu (). The differences in the reactivities among them could be ascribed to the redox potential of the bound substrate flavonolate, which was drastically influenced by the metal ions via tuning the electron density of flavonolate, providing important insights into the metal ion effects and the carboxylate effects on the enzymatic activity of various M(II)-substituted 2,3-QD. Our model complexes [M(II)L(OAc)] are the first examples of a series of structural and functional models of various M(II)-substituted resting 2,3-QD.

A new triflic acid (TfOH)-mediated cascade cyclization of ortho-anisole-substituted aryldiynes is described for the construction of indeno[1,2-c]chromenes. The cascade cyclization proceeds through an unusual TfOH-induced alkyne-alkyne cyclization followed by nucleophilic attack of the methoxy group on the benzylidene cation, which is completely different to the cyclization of ortho-aniline- or ortho-thioanisole-substituted aryldiynes. A new class of organic dyes with the indeno[1,2-c]chromene framework as both donor and π-linker were synthesized. These compounds exhibit high photovoltaic performances in dye- sensitized solar cells (DSCs)., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ni(II)-flavonolate complexes [Ni(II)L(R)(fla)] (L(R)H: 2-{[bis(pyridin-2-ylmethyl)amino]methyl}-p/m-R-benzoic acid, R: p-OMe (1), p-Me (2), m-Br (4) and m-NO2 (5), fla: flavonolate) were synthesized and characterized with relevance to structural and functional models for the ES (enzyme-substrate) adduct of the Ni(II)-containing quercetin 2,3-dioxygenase (2,3-QD). Their structures, spectroscopic features, redox properties and the reactivity toward molecular oxygen have been investigated. The complexes show a similar distorted octahedral structure and higher enzyme-type dioxygenation reactivity than other reported metal-flavonolate complexes in the oxidative O-heterocyclic ring-opening of the bound substrate flavonolate at lower temperature owing to the introduced carboxylate group in the supporting model ligands. The reaction rate shows first-order dependence on both of the complex and O2 and the second-order rate constant k fits a Hammett linear free energy relationship (ρ = -0.71) for the substituent group in the supporting model ligand L(R). The complexes exhibit substituent group dependent structures, properties and reactivity and there are some relationship among them, which could be ascribed to the electronic nature of the substituent group via the benzoate, Ni(II) ion and O(4)=C(27)-C(21)=C(22) "electron conduit". In a word, the stronger electron donating group could induce a smaller torsion angle, larger λ(max) and lower redox potential of the bound flavonolate, making a higher reactivity finally. This study is the first example of a series of structural and functional ES models of the Ni(II)-containing 2,3-QD, providing important insights into the structure-property-reactivity relationship, the electronic substituent effects and carboxylate effects on the enzymatic reactivity and the catalytic role of the Ni(II)-containing 2,3-QD.

A series of mononuclear Co(II)-flavonolate complexes [Co(II)L(R)(fla)] (L(R)H = 2-{[bis(pyridin-2-ylmethyl)amino]methyl}-p/m-R-benzoic acid; R = p-OMe (1), p-Me (2), m-Br (4), and m-NO2 (5); fla = flavonolate) were designed and synthesized as structural and functional models for the ES (enzyme-substrate) complexes to mimic the active site of the Co(II)-containing quercetin 2,3-dioxygenase (Co-2,3-QD). The metal center Co(II) ion in each complex shows a similar distorted octahedral geometry. The model complexes display high enzyme-type dioxygenation reactivity (oxidative O-heterocyclic ring opening of the coordinated substrate flavonolate) at low temperature, presumably due to the attached carboxylate group in the ligands. The reactivity exhibits a substituent group dependent order of -OMe (1) > -Me (2) > -H (3)14b > -Br (4) > -NO2 (5), and the Hammett plot is linear (ρ = -0.78). This can be explained as the electronic nature of the substituent group in the ligands may influence the conformation and redox potential of the bound flavonolate and finally bring different reactivity. The structures, properties, and reactivity of the model complexes show some dependence on the substituent group in the supporting model ligands, and there is some relationship among them. This study is the first example of a series of structural and functional ES models of Co-2,3-QD, with focus on the effects of the electronic nature of substituted groups and the carboxylate group of the ligands to the dioxygenation reactivity, that will provide important insights into the structure-property-reactivity relationship and the catalytic role of Co-2,3-QD.

A series of flavonolate complexes [M(II)L(fla)] (M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5), and Zn (6), LH: 2-{[bis(pyridin-2-ylmethyl)amino]methyl}benzoic acid, fla: flavonolate) have been synthesized as structural and functional models for the ES (enzyme-substrate) complexes of the active site of various M(II)-containing quercetin 2,3-dioxygenase (2,3-QD) and their structures, spectroscopic features, and redox properties, as well as the reactivity toward molecular oxygen, have been investigated. The metal centers of [Fe(II)L(fla)]·H2O (2), [Co(II)L(fla)]·CH3OH (3), and [Ni(II)L(fla)] (4) exhibit a distorted octahedral geometry with two oxygen atoms of fla, one oxygen atom of the benzoate group of ligand L, and three nitrogen atoms of ligand L, in which oxygen atom of the carbonyl group of fla and one of the pyridine nitrogen atoms occupy the axial positions. The complexes [M(II)L(fla)] exhibit relatively high reactivity in the oxidative ring-opening of the bound flavonolate at lower temperature, presumably due to the existing carboxylate group in the supporting ligand. Thus, our complexes act as good functional ES models of various metal(II)-containing 2,3-QD. In addition, complexes [Fe(II)L(fla)]·H2O (2), [Co(II)L(fla)]·CH3OH (3), and [Ni(II)L(fla)] (4) are the first structurally characterized Fe(II)-, Co(II)-, and Ni(II)-flavonolate complexes, as an active site ES model of Fe(II)-, Co(II)-, and Ni(II)-containing 2,3-QD, respectively. The model complexes exhibit notably different reactivity in the order of Fe (2) > Cu (5) > Co (3) > Ni (4) > Zn (6) > Mn (1). The differences in the reactivity among them may be attributed to the redox potential of the coordinated flavonolate of the complexes, which are remarkably influenced by the Lewis acidity of the metal ion and its coordination environment. Our study is the first example of the metal ion effects on the enzyme-like dioxygenation reactivity, providing important insights into the metal ion effects on the enzymatic reactivity of various metal(II)-containing 2,3-QD.

We have shown previously that iodosylbenzene-iron(III) porphyrin intermediates (2) are generated in the reactions of oxoiron(IV) porphyrin pi-cation radicals (1) and iodobenzene (PhI), that 1 and 2 are at equilibrium in the presence of PhI, and that the epoxidation of olefins by 2 affords high yields of epoxide products. In the present work, we report detailed mechanistic studies on the nature of the equilibrium between 1 and 2 in the presence of iodoarenes (ArI), the determination of reactive species responsible for olefin epoxidation when two intermediates (i.e., 1 and 2) are present in a reaction solution, and the fast oxygen exchange between 1 and H(2)18O in the presence of ArI. In the first part, we have provided strong evidence that 1 and 2 are indeed at equilibrium and that the equilibrium is controlled by factors such as the electronic nature of iron porphyrins, the electron richness of ArI, and the concentration of ArI. Secondly, we have demonstrated that 1 is the sole active oxidant in olefin epoxidation when 1 and 2 are present concurrently in a reaction solution. Finally, we have shown that the presence of ArI in a reaction solution containing 1 and H(2)18O facilitates the oxygen exchange between the oxo group of 1 and H(2)18O and that the oxygen exchange is markedly influenced by factors such as ArI incubation time, the amounts of ArI and H(2)18O used, and the electronic nature of ArI. The latter results are rationalized by the formation of an undetectable amount of 2 from the reaction of 1 and ArI through equilibrium that leads to a fast oxygen exchange between 2 and H(2)18O.

The catalytic epoxidation of cyclohexene by iron(III) porphyrin complexes and H2O2 has been investigated in alcohol solvents to understand factors affecting the catalyst activity in protic solvents. The yields of cyclohexene oxide and the Fe(III/II) reduction potentials of iron porphyrin complexes were significantly affected by the protic solvents, and there was a close correlation between the product yields and the reduction potentials of the iron porphyrin catalysts. The role of alcohol solvents was proposed to control the electronic nature of iron porphyrin complexes that determines the catalyst activity in the epoxidation of olefins by H2O2. We have also demonstrated that an electron-deficient iron porphyrin complex can catalyze the epoxidation of olefins by H2O2 under conditions of limiting substrate with high conversion efficiency in a solvent mixture of CH3OH and CH2Cl2.

A series of half-sandwich copper(II) complexes [TpPh]CuX ([TpPh] = hydrotris(3-phenyl-pyrazolyl)borate; X- = OH- (1), N3- (2), NCS- (3)) have been synthesized as models for carbonic anhydrase. The structure of 3 was determined by X-ray diffraction analysis. Crystals of 3 (C37H30BCuN9S) are triclinic, space group P1 with a = 11.997(3) A, b = 12.116(3) A, c = 13.384(4) A, alpha = 81.088(5) degrees, beta = 79.289(6) degrees, gamma = 68.668(5) degrees, V = 1772.4(8) A3, and Z = 2. The dehydration kinetic measurements of HCO3- are performed by the stopped-flow techniques at pH < 7.9. The apparent dehydration rate constant kdobs varies linearly with total Cu(II) concentration, and the catalytic activity of the model complexes decreases in the order 1 > 2 > 3. The catalytic activity decreases with increasing pH indicating that the aqua model complex must be the reactive catalytic species in the catalyzed dehydration reaction and the rate-determining step is the substitution of the labile water molecule by HCO3-. The kdobs values increase with increasing reaction temperature, and the apparent activation energies of the model complexes with inhibitors are remarkably higher than that of the complex with no inhibitors, this being the origin of inhibition. The large negative entropy of activation also indicates an associative mode of activation in the rate-determining step. The inhibition ability of the inhibitor NCS- is stronger than that of the inhibitor N3-, which can be rationalized by the decrease in effective atomic charges of the Cu(II) ions as revealed by the theoretical calculations.