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Showing papers in "European Journal of Inorganic Chemistry in 2014"


Journal ArticleDOI
TL;DR: In this paper, a microreview of the recent results of vapochromic coordination complexes centered on one-dimensionally stacked PtII systems from the viewpoint of the origin of their behaviour is presented.
Abstract: Vapochromic materials that show reversible color change driven by vapor adsorption/desorption have drawn significant attention because of their potential applications in chemical sensors and chemical-switching modules. Among the vapochromic coordination complexes reported so far, a series of square-planar PtII complexes has been studied and represents one of the most promising systems for practical chemical sensors. For such systems, the color of the complexes strongly depends not only on the ligand-field splitting, but also on the intermolecular distance between the PtII ions. This microreview presents recent results of vapochromic complexes centered on one-dimensionally stacked PtII systems from the viewpoint of the origin of their vapochromic behavior. The design of vapochromic materials has been facilitated because several useful chromophores, including metallophilic interaction between PtII ions, have been developed. However, it is still challenging to realize a specifically sensitive and selective response to targeted vapors. This review focuses on strategies to achieve assembled PtII complexes with selective vapochromic responses.

127 citations


Journal ArticleDOI
TL;DR: In this article, a microreview focuses on factors to determine if the actual catalysts for water oxidation are homogeneous or heterogeneous depending on the conditions under which the catalysts are used.
Abstract: Recent developments in thermal and photochemical water oxidation by using homogeneous and heterogeneous catalysts is described together with the conversion of the homogeneous catalysts into heterogeneous catalysts during the course of water oxidation. The use of homogeneous catalysts is advantageous in the elucidation of detailed catalytic mechanisms including the detection of active intermediates for water oxidation. In contrast, heterogeneous catalysts are advantageous for practical applications, because of their high catalytic activity and the ease with which they can be separated by filtration. However, it is quite difficult to identify the active intermediates on the surfaces of heterogeneous catalysts, and therefore, the heterogeneous catalytic mechanism of water oxidation has not been clarified. Although investigations on homogeneous and heterogeneous catalysts for water oxidation have been performed rather independently, the link between homogeneous and heterogeneous catalysts is becoming more important for the development of efficient WOCs. This microreview focuses on factors to determine if the actual catalysts for water oxidation are homogeneous or heterogeneous depending on the conditions under which the catalysts are used. Ligand oxidation of homogeneous catalysts sometimes results in dissociation of the ligands to form nanoparticles, which act as much more efficient catalysts for water oxidation.

114 citations


Journal ArticleDOI
TL;DR: In this article, the cover image shows one aspect of the photocatalytic use of heteropolyacids: dye bleaching by irradiation with sunlight, and the group of Giuseppe Marci and Leonardo Palmisano at the Universita degli Studi di Palermo.
Abstract: Invited for the cover of this issue is the group of Giuseppe Marci and Leonardo Palmisano at the Universita degli Studi di Palermo, Italy. The cover image shows one aspect of the photocatalytic use of heteropolyacids: dye bleaching by irradiation with sunlight.

102 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyzed the five-coordinate geometry of VO4X coordination spheres with regard to their structure from the point of view of square pyramidal or trigonal bipyramidal geometries.
Abstract: The five-coordinate geometry is an important factor in phosphoryl group transfer, particularly for phosphate ester hydrolysis. In the following review we analyze the five-coordinate geometries for a range of VO4X coordination spheres with regard to their structure from the point of view of square pyramidal or trigonal bipyramidal geometries. The actual differences for the coordination environment of the reported small molecule structures are compared to the coordination environment of vanadate complexed to a protein tyrosine phosphatase (PTP) with four coordinating O atoms and one S atom. These considerations demonstrate that actual differences between the coordination environments are very small and presumably less critical than generally anticipated. This analysis suggests that it is a combination of structural and electronic properties leading to the perfect combination of reactivity and stability for the potent protein phosphatase inhibitor complex, thus confirming the fact that some other geometries have been reported.

91 citations


Journal ArticleDOI
TL;DR: The role of noncovalent interactions in the context of stimuli-responsive behavior of gold(I) and gold-heterometal======complexes is reviewed in this article, where representative examples of gold (I) complexes are summarized.
Abstract: The role of noncovalent interactions is reviewed in the context of stimuli-responsive behaviour of gold(I) and gold-heterometal complexes. These noncovalent interactions are often highly sensitive to physical (thermal, optical, electrical, mechanical, etc.) or chemical (solvents, guests, etc.) stimuli so as to trigger alterations in molecular and crystal structures leading to dynamic changes in macroscopic properties of gold compounds. In this microreview, we summarized some representative examples of gold(I) complexes that exhibit intriguing stimuli-responsive properties such as thermochromic, mechanochromic, vapochromic and solvatochromic luminescence, as well as vapochromism and gas sorption. Stimuli-responsive functional materials with specific properties have potential for various applications including chemical sensors, memories, data storage, security inks and separation technologies.

88 citations


Journal ArticleDOI
TL;DR: A trinuclear zinc(II)-Schiff base complex with distorted-octahedral coordination geometry has been synthesized and crystallographically characterized in this paper, which has shown significant catecholase activity in methanolic medium through a ligand-centered radical pathway.
Abstract: A novel trinuclear zinc(II) complex [Zn3L2(μ-O2CCH3)2(CH3OH)4] (1) that contains an N,O-donor Schiff base ligand {H2L = 2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol} has been synthesized and crystallographically characterized The X-ray crystal structure of 1 contains three zinc(II) centers, which have distorted-octahedral coordination geometry, and the molecule crystallizes in the Pbcn space group The zinc(II) complex displays significant catecholase oxidation activity in methanolic medium through a ligand-centered radical pathway This is the first example of catecholase oxidation through a trinuclear zinc(II)–Schiff base complex by means of the formation of a mononuclear intermediate as [ZnL(dtbc)] (dtbc = 3,5-di-tert-butylcatechol) The fluorescence property of 1 indicates that it can serve as a potential photoactive material It effectively cleaves the double strand of pBR 322 plasmid DNA at a given concentration (25 μM) The complex shows remarkable cytotoxicity against a human hepatocarcinoma cell line (HepG2)

85 citations


Journal ArticleDOI
TL;DR: Polyoxometalates (POMs) constitute a huge class of complexes with extensively tunable properties that are oxidatively, thermally, and (over wide and adjustable pH ranges) hydrolytically stable as mentioned in this paper.
Abstract: The viable production of solar fuels requires a visible-light-absorbing unit, a H2O (or CO2) reduction catalyst (WRC), and a water oxidation catalyst (WOC) that work in tandem to split water or reduce CO2 with H2O rapidly, selectively, and for long periods of time. Most catalysts and photosensitizers developed to date for these triadic systems are oxidatively, thermally, and/or hydrolytically unstable. Polyoxometalates (POMs) constitute a huge class of complexes with extensively tunable properties that are oxidatively, thermally, and (over wide and adjustable pH ranges) hydrolytically stable. POMs are some of the fastest and most stable WOCs to date under optimal conditions. This Microreview updates the very active POM WOC field; it reports the application of POMs as WRCs and initial self-assembling metal oxide semiconductor–photosensitizer–POM catalyst triad photoanodes. The complexities of investigating these POM systems, including but not limited to the study of POM-hydrated metal-ion–metal-oxide speciation processes, are outlined. The achievements and challenges in POM WOC, WRC, and triad research are outlined.

80 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that polyoxoniobates are exceptional amongst polyoxometalates in that they can potentially perform base catalysis in water, a process in which a proton is bonded to an oxo ligand, and a hydroxyl is released.
Abstract: Polyoxoniobates are exceptional amongst polyoxometalates in that they can potentially perform base catalysis in water, a process in which a proton is bonded to an oxo ligand, and a hydroxyl is released. Catalytic decomposition of chemical warfare agents such as organofluorophosphates that were used recently in the infamous civilian attacks in Syria is one opportunity to employ this process. Upon evaluation of the polyoxoniobate Lindqvist ion, [Nb6O19]8–, fast neutralization kinetics was discovered for the breakdown of the nerve agent simulant diisopropyl fluorophosphate (DFP). The polyoxoniobates were also tested against the nerve agents Sarin (GB) and Soman (GD). It was determined that different Lindqvist countercations (Li, K, or Cs) affect the rate of decomposition of the organophosphate compounds in both aqueous media (homogeneous reaction), and in the solid state (heterogeneous reaction). Small-angle X-ray scattering analysis of solutions of the Li, K, and Cs salts of [Nb6O19]8– for concentrations at which the experiments were performed revealed distinct differences that could be linked to their relative reaction rates. This study represents the first demonstration of exploiting the unique alkaline reactivity of polyoxoniobates for nerve agent decontamination.

77 citations


Journal ArticleDOI
TL;DR: Mechanistic information on the system derived from biotin-conjugated iodoacetamide assays showed selective metal binding to selenocysteine residues, and preliminary confocal fluorescence microscopy experiments proved that 3 enters tumor cells, where it reaches the nuclear compartment.
Abstract: N-Heterocyclic carbene gold(I) complexes bearing a fluorescent coumarin ligand were synthesized and characterized by various techniques. The compounds were examined for their antiproliferative effects in normal and tumor cells in vitro; they demonstrated moderate activity and a certain degree of selectivity. The compounds were also shown to efficiently inhibit the selenoenzyme thioredoxin reductase (TrxR), whereas they were poorly effective towards the glutathione reductase (GR) and glutathione peroxidase enzymes. Notably, {3-[(7-methoxy-2-oxo-2H-chromen-4-yl)methyl]-1-methylimidazol-2-ylidene}(tetra-O-acetyl-1-thio-β-D-glucopyranosido)gold(I) (3) showed a pronounced inhibition of TrxR also in cell extracts, and it appeared to activate GR. Mechanistic information on the system derived from biotin-conjugated iodoacetamide assays showed selective metal binding to selenocysteine residues. Preliminary confocal fluorescence microscopy experiments proved that 3 enters tumor cells, where it reaches the nuclear compartment.

71 citations


Journal ArticleDOI
TL;DR: In this article, the authors reported that broadly tunable bismuth emission indeed occurs even within the same host (CaMoO4) when the local microenvironment around Bi3+ is modified by intentional introduction of alkali ions.
Abstract: The trivalent green element of bismuth, when doped into different compounds, can produce multiple emissions in ultraviolet, blue, green or even yellow spectral regimes. The emission adjustability comes from the susceptibility of bismuth naked 6s electrons to the crystal field particularly surrounding Bi3+. However, this has never been observed in a single compound. In this work, we report that broadly tunable bismuth emission indeed occurs even within the same host (CaMoO4) when the local microenvironment around Bi3+ is modified by intentional introduction of alkali ions. As the radius of the selected alkali ion decreases, the emission regularly blue-shifts from 586 to 554 nm, and its intensity is enhanced greatly. For instance, the integrated intensity for the Li+ and Bi3+ codoped sample is 4.46 times stronger than the Bi3+ single-doped sample upon excitation at 300 nm. Low-temperature photoluminescence spectra surprisingly reveal that energy transfer can partially take place from the MoO42– group to Bi3+ at lower temperature when excited into the charge transfer state of the MoO42– group, however, this does not occur at higher temperature. The mechanism needs further study. Dynamic luminescence analysis between 10 and 300 K implies a population dependence of the excited states 3P0 and 3P1 on temperature that is responsible for the evolution of the Bi3+ emission lifetime with temperature.

69 citations


Journal ArticleDOI
TL;DR: This class of rhenium(I) pyridocarbazole complexes point into the direction of dual function antiproliferative therapy with a single drug in which photodynamic therapy is combined with the inhibition of cancer related protein kinases.
Abstract: Rhenium(I) pyridocarbazole complexes with photoinduced antiproliferative activity are reported. The substitutionally inert complexes induce cell death by singlet oxygen generation upon irradiation with red light (λ ≥ 620 nm), while only weak background cytotoxicity is observed in the dark. Due to their ability to inhibit protein kinases (nanomolar IC50 values against Pim1 at 10 μM ATP), this class of rhenium complexes point into the direction of dual function antiproliferative therapy with a single drug in which photodynamic therapy is combined with the inhibition of cancer related protein kinases.

Journal ArticleDOI
TL;DR: The characteristics of field effect transistors (FETs) fabricated from thin films and single crystals of phenacene molecules are fully reported in this article together with the electronic and crystal structures of the phenacenes.
Abstract: The characteristics of field-effect transistors (FETs) fabricated from thin films and single crystals of phenacene molecules are fully reported in this review together with the electronic and crystal structures of phenacenes. Phenacene molecules possess a low HOMO level and a wide band gap. The highest mobility observed in the phenacene thin-film FETs is 7.4 cm2 V–1 s–1 for [6]phenacene, and in single-crystal FETs the highest value is 6.3 cm2 V–1 s–1 for [7]phenacene. The phenacene thin-film FETs show O2-sensing properties unlike their single-crystal FETs. The bias-stress effect is fully investigated for phenacene single-crystal FETs. Furthermore, the low-voltage operation of phenacene single-crystal FETs with electric-double-layer (EDL) capacitors is reported. The temperature dependence of phenacene single-crystal FETs is reported to clarify the transport mechanism, which is suggestive of band-like transport.

Journal ArticleDOI
TL;DR: A series of homoleptic copper(I), silver(I, and gold(I) complexes of two bisphosphine ligands {1,2-bis(diphenylphosphino)benzene, dppb; bis[2]-phenyl]ether, POP} have been prepared and the emission properties of these compounds in solution, in frozen rigid matrices at 77 K, and in the solid state at room temperature have been systematically investigated as discussed by the authors.
Abstract: A series of homoleptic copper(I), silver(I), and gold(I) complexes of two bisphosphine ligands {1,2-bis(diphenylphosphino)benzene, dppb; bis[2-(diphenylphosphino)phenyl]ether, POP} have been prepared. Whilst all three [M(dppb)2]BF4 complexes are tetracoordinate, this geometry is found only for the silver(I) complex with POP. Instead, [Cu(POP)2]+ and [Au(POP)2]+ adopt a trigonal coordination geometry with an uncoordinated phosphorus atom. A close inspection of the P–M bond lengths reveals an interesting trend. From the copper to silver and gold complexes, a substantial elongation is found. On the other hand, from the silver to gold compounds, a decrease in the M–P bond length is found. Indeed, gold(I) has a smaller van der Waals radius than silver(I) as a result of its peculiar relativistic effects. Electrochemical investigations revealed two oxidation processes for all of the [M(dppb)2]BF4 and [M(POP)2]BF4 complexes. The first oxidation is likely metal-centered, whereas the second one corresponds to ligand-centered processes in all cases. The emission properties of these compounds in solution, in frozen rigid matrices at 77 K, and in the solid state at room temperature have been systematically investigated. Although all of them are weak emitters in solution, remarkably high emission quantum yields were found in the solid state, in particular for [Cu(dppb)2]BF4 and [Ag(dppb)2]BF4. Finally, these two compounds were used for the fabrication of light-emitting devices. Interestingly, both the copper(I) and the silver(I) complex afford quite broad electroluminescence spectra with white light emission.

Journal ArticleDOI
TL;DR: In this article, the nanorods have been used for the adsorption of various cationic dyes (rhodamine B, methylene blue, and malachite green) from aqueous solution.
Abstract: α-Ag2WO4 nanorods with an average diameter of 15 to 25 nm and a surface area of ca. 115.0 ± 0.2 m2/g have been synthesized by a facile sonochemical technique. These nanorods have been used for the adsorption of various cationic dyes (rhodamine B, methylene blue, and malachite green) from aqueous solution. The adsorption process is fast, and ca. 100 % adsorption of a 20 ppm mixture of all three dyes occurs within 10 min. The adsorption process was studied by varying different regulating parameters such as the solution pH and the initial dye and Ag2WO4 concentrations, and the results were analyzed with various isotherm and kinetic models. The mechanistic pathway for the selective adsorption of cationic dyes has been explained through zeta potential studies. Moreover, the thermal regeneration of the sorbent was possible by furnace heating at 250 °C, and the nanorods were efficient for multicyclic use. X-ray photoelectron spectroscopy (XPS) has been performed on the thermally regenerated samples to ascertain their surface purity. The Ag2WO4 nanorods have a bactericidal effect and are active against both Gram-negative and -positive bacterial strains of Escherichia coli and Bacillus subtilis, respectively. However, the efficiency is more pronounced for Gram-positive bacteria. Thus, these sonochemically synthesized Ag2WO4 nanorods have great potential for the treatment of dye industry effluents as a promising adsorbent for cationic dyes from aqueous solution and are also useful as an antibacterial agent.

Journal ArticleDOI
TL;DR: In this paper, the cover image shows the bis(terpyridine)ruthenium(II) amino acid [Ru(4′-tpy-COOH), 4′- tpy-NH2]2+ (tpy = 2,2′;6′,2″-terpyrus), illustrating some of its multifaceted optical and redox chemical properties as well as highlighting its potential applications in light-to-energy conversion and energy-tolight conversion schemes.
Abstract: Invited for the cover of this issue is the group of Katja Heinze at the Johannes Gutenberg University of Mainz, Germany. The cover image shows the bis(terpyridine)ruthenium(II) amino acid [Ru(4′-tpy-COOH)(4′-tpy-NH2)]2+ (tpy = 2,2′;6′,2″-terpyridine), illustrating some of its multifaceted optical and redox chemical properties as well as highlighting its potential applications in light-to-energy conversion and energy-to-light conversion schemes.

Journal ArticleDOI
TL;DR: In this article, the bidentate bipyridine ligand (N,N) was modified with alkoxy or hydroxy substituents on the 2,2′-bipyridyl (bipy) ring cis to X = Cl and formed [(terpy)RuII(N, N)X] (X = Cl, H2O; terpy = 2, 2′; 6′, 2"-terpyridine).
Abstract: Water-oxidation catalysts (WOCs) can potentially be improved by installing pendant electron-donor groups that may also be proton donors or acceptors. We have modified one of the most well-studied WOCs with alkoxy or hydroxy substituents on the bidentate bipyridine ligand (N,N), thereby forming [(terpy)RuII(N,N)X] (X = Cl, H2O; terpy = 2,2′;6′,2"-terpyridine). A combination of NMR spectroscopy (particularly 15N chemical-shift data), UV/Vis spectroscopy, X-ray diffraction, and oxygen evolution data point to interesting and beneficial effects of an oxygenated group proximal to X. A methoxy group on the 2,2′-bipyridyl (bipy) ring cis to X = Cl is shown to facilitate ionization of the chloride ligand in aqueous acetone, perhaps by acceptance of a hydrogen bond from the aquo ligand. Hydrogen-bond donation of a proximal hydroxy group to a bound aquo ligand is shown by X-ray diffraction. Distinct differences in pKa values for the 4,4′- and 6,6′-dihydroxy bipy complexes are seen. In water oxidation driven by ceric ammonium nitrate, the 6,6′-dimethoxy species is somewhat faster and longer-lived than the analogue that lacks the oxygenated groups [a turnover number (TON) of 215 instead of 138 in 10 h, and a turnover frequency (TOF) of 0.36 min–1 instead of 0.23 over the same time period]. Taken together, oxygenated groups near the WOC active site are promising electron or proton donors and/or hydrogen-bond acceptors, and are the subject of further scrutiny.

Journal ArticleDOI
TL;DR: In this article, a core-shell magnetic Fe3O4@C nanoparticles functionalized with sulfonic and carboxylic acid groups were synthesized and employed to capture heavy metal ions in aqueous media.
Abstract: Core–shell magnetic Fe3O4@C nanoparticles functionalized with sulfonic and carboxylic acid groups were synthesized and employed to capture heavy metal ions in aqueous media. The Fe3O4 cores possess unique magnetic properties for adsorbent separation, and the –SO3H and –COOH groups attached to the surface of the carbon shells determine the efficiency of heavy metal ion removal. Batch adsorption experiments showed that Pb2+, Hg2+, and Cd2+ ions can be completely and quickly removed by the Fe3O4@C nanoparticles. The equilibrium was established within 5 min, and the maximum adsorption capacities of the Fe3O4@C nanoparticles toward Pb2+, Hg2+, and Cd2+ ions were 90.7, 83.1, and 39.7 mg/g, respectively. The removal efficiencies were 96.3, 98.1, and 93.8 % for Pb2+, Hg2+, and Cd2+ ions, respectively. This work provides a facile and general approach to synthesize magnetic functional nanocomposites for wastewater treatment.

Journal ArticleDOI
TL;DR: In this paper, density functional calculations are used to elucidate the reaction mechanism of water oxidation catalyzed by TAML-Fe5+=O, which can undergo nucleophilic attack by either a water molecule or a nitrate ion.
Abstract: Density functional calculations are used to elucidate the reaction mechanism of water oxidation catalyzed by iron tetra-amido macrocyclic ligand (TAML) complexes. The oxidation of the starting TAML-Fe3+-OH2 complex by removing three electrons and two protons leads to the formation of a key intermediate, TAML-Fe5+=O, which can undergo nucleophilic attack by either a water molecule or a nitrate ion. Both pathways involve attack on the oxo group and lead to the production of O-2. The water attack is more favoured and has a total barrier of 15.4 kcal/mol. The alternative nitrate attack pathway has a barrier of 19.5 kcal/mol. Nitrate functions as a cocatalyst by first donating an oxygen atom to the oxo group to form O-2 and a nitrite ion, which can then be reoxidized to regenerate a nitrate ion. Three possible competing pathways result in ligand modification, namely, water and nitrate attack on the ligand, as well as ligand amide oxidation. The water attack on the ligand has a low barrier of only 10.9 kcal/mol and leads to the opening of the benzene ring, which explains the observation of fast catalyst degradation. The lack of activity or lower activity of other catalysts with different substituents is also rationalized.

Journal ArticleDOI
TL;DR: In this paper, a solution to the crystal structure of 1,4-benzenedicarboxylate (BDC) was determined by using ab initio quantum molecular calculations and refinement with synchrotron X-ray powder diffraction data.
Abstract: In the synthesis of the microporous metal–organic framework copper 1,4-benzenedicarboxylate [Cu(BDC)], solvent exchange with methanol prior to recrystallization lowers the desolvation temperature to 160 °C and produces more crystalline Cu(BDC). The solution to the crystal structure of Cu(BDC) has been determined by using ab initio quantum molecular calculations and refinement with synchrotron X-ray powder diffraction data. This solution is in the P space group with a = 5.25 A, b = 9.67 A, c = 10.77 A, α = 90.29°, β = 91.06°, γ = 92.413°, and V = 546.04 A3. The Brunauer–Emmett–Teller (BET) surface area was 903 m2 g–1 with 777 m2 g–1 of micropore surface area. The uptake of CO2 and CH4 up to 20 bar were 5.2 and 2.7 mmol g–1, respectively. These values are compared to those of 1,3,5-benzenetricarboxylate [Cu3(BTC)2, HKUST-1] and used to show that the elevated metal-site density per unit volume is responsible for a proportionally higher uptake on the basis of relative surface areas. The platelike particles with perpendicular pores are promising candidates for mixed-matrix membranes.

Journal ArticleDOI
TL;DR: In this paper, the ferrocenylphosphine-borane adducts were used for selective dehydrocoupling to yield an ionic polymer, which was characterized by multinuclear NMR and IR spectroscopy, gel permeation chromatography (GPC), and thermal analysis.
Abstract: Dehydrocoupling of the ferrocenylphosphine–borane adducts [FcPH2(BH3)] (1) [Fc = Fe(C5H5)(C5H4)] and [FcCH2PH2(BH3)] (2) with [{Rh(μ-Cl)(cod)}2] (cod = 1,5-cyclooctadiene) as catalyst gave the corresponding phosphorus–boron-based polymers [FcPH(BH2)]n (3) and [FcCH2PH(BH2)]n (4) as low- (heating in toluene, 3low and 4low) or high-molecular-weight (heating without solvent, 3high or 4high) poly(ferrocenylphosphinoborane)s depending on the reaction conditions. Dehydrocoupling of a racemic mixture of [2-N,N-dimethyl(N-borane)aminomethyl-1-ferrocenyl]phosphine–borane (6) resulted in several products, as both BH3 moieties are apparently involved in polymer formation. Quaternization of the amino group in planar-chiral [Fe(C5H5){C5H3(CH2NMe2)PH2}] (5) with MeI and treatment of the corresponding ammonium salt [Fe(C5H5){C5H3(CH2NMe3)PH2}]I (8) with BH3(THF) gave [Fe(C5H5){C5H3(CH2NMe3)PH2(BH3)}]I (9), which proved to be a suitable precursor for selective dehydrocoupling to yield an ionic polymer, namely, {[Fe(C5H5){C5H3(CH2NMe3)PH(BH2)}]I}n. The ferrocenylphosphine–borane adducts 1, 2, and 6 were characterized by 31P, 11B, 1H, and 13C NMR spectroscopy, and the polymers were characterized by multinuclear NMR and IR spectroscopy, gel permeation chromatography (GPC), and thermal analysis [differential thermal analysis (DTA)/thermogravimetry (TG)]. The ionic precursor 9 and the resulting polymer are highly insoluble and were characterized by solid-state 31P NMR spectroscopy, IR spectroscopy, and thermal analysis. Molecular structures of 1, 6, 8, and 9 were determined by X-ray crystallography.

Journal ArticleDOI
TL;DR: In this paper, a terpyridine bearing a protonable pyridyl substituent (pytpy) and a carbene ligand (carb) has been characterized by UV/Vis spectroscopy and TD-DFT computations.
Abstract: New heteroleptic iron complexes mixing a terpyridine bearing a protonable pyridyl substituent (pytpy) and a pyridyl carbene ligand (carb) have been prepared and characterised by UV/Vis spectroscopy, cyclic voltammetry and TD-DFT computations. The absorption spectrum of [Fe(carb)(pytpy)](2+) showed a notable redshift compared with the homoleptic [Fe(carb)(2)](2+) complex. The MLCT transition occurred at even lower energy when the pendant pyridine was protonated, leading to a wide absorption domain in the 450-650 nm range. Calculations revealed the strong propensity of excited electrons to move from the metal to the pytpy ligand in the complex. This new family of complexes is a promising addition to the arsenal of iron-based chromophores with tuneable electronic properties.

Journal ArticleDOI
TL;DR: In this paper, a series of organic-metal chelate complexes of symmetric tetradentate Schiff base ligands derived from salicylaldehyde and 2-hydroxy-1-naphthaldehyde were designed and investigated.
Abstract: A series of organic–metal chelate complexes of symmetric tetradentate Schiff base ligands derived from salicylaldehyde and 2-hydroxy-1-naphthaldehyde were designed and investigated. The combination of five nonconjugated flexible spacers and five conjugated rigid spacers with four salicylaldehyde derivatives provided a series of forty complexes. The series of blue to red photoluminescent complexes was investigated by UV/Vis absorption and luminescence spectroscopy in solution and in the solid state as well as cyclic voltammetry. The nature of the bridge in the ligand scaffold was determined to be the main parameter that influences the absorption and the emission color of the investigated zinc(II) complexes.

Journal ArticleDOI
TL;DR: In this paper, the authors present half-sandwich complexes of RuII, OsII, and IrIII with click-derived 1,2,3-triazole (L1) and 1 2,3,triazol-5-ylidene (L2) ligands containing a potentially hemilabile thioether donor.
Abstract: Hemilabile ligands are known to impart remarkable properties to their metal complexes. Herein, we present arene half-sandwich complexes of RuII, OsII, and IrIII with “click”-derived 1,2,3-triazole (L1) and 1,2,3-triazol-5-ylidene (L2) ligands containing a potentially hemilabile thioether donor. Structural elucidation of the complexes revealed localization of double bonds within the triazole in L1 and a delocalized situation within the triazolylidene ring of L2. For complexes with L1, unusual coordination occurs through the less basic nitrogen “N2” of the 1,2,3-triazole. All complexes were applied for the catalytic oxidation of benzyl alcohol to benzaldehyde using N-methylmorpholine N-oxide as sacrificial oxidant. Furthermore, oxidation of diphenylmethanol to benzophenone was also achieved by using low catalyst loadings in very good yields. These are rare examples of OsII–triazole, as well as of OsII–triazolylidene complexes with “click”-derived ligands.

Journal ArticleDOI
TL;DR: In this article, the reactions of three iridium water-oxidation catalysts {Cp*IrL1L2L3]Xn with cerium ammonium nitrate (CAN) and NaIO4 (sacrificial oxidants, SOs) have been studied by Clark electrode measurements (both in solution and in the gas phase), on-line mass spectrometry, manometry and UV/Vis spectroscopy.
Abstract: The reactions of three iridium water‐oxidation catalysts {[Cp*IrL1L2L3]Xn; 1: L1, L2 = 2,2‐bipyridine (bpy), L3 = Cl, n = 1, X = Cl; 2: L1, L2 = 2‐benzoylpyridine (bzpy), L3 = NO3; 3: L1 = L2 = L3 = H2O, n = 2, X = NO3; Cp* = pentamethylcyclopentadienyl} with cerium ammonium nitrate (CAN) and NaIO4 (sacrificial oxidants, SOs) have been studied by Clark electrode measurements (both in solution and in the gas phase), on‐line mass spectrometry, manometry and UV/Vis spectroscopy. Furthermore, cyclic voltammetry has been applied to evaluate the relative tendency of 1 and 2 to be oxidized. The turnover frequency (TOF) increases as the ratio (R) between the concentration of the SO and that of the catalyst increases. O2 production with CAN is observed in experiments with R = 20 for 1 and 3, whereas O2 becomes detectable with 2 only when R = 40. Catalyst 2 has the highest tendency to be oxidized to IrIV and forms a blue intermediate I characterized by a UV/Vis band at 574 nm. The formation of I occurs with the same velocity as that of the production of O2, which indicates that I is a species directly involved in the catalytic cycle. The disappearance of I, when O2 evolution is finished, is a second‐order process more than one order of magnitude slower than O2 production and is strongly accelerated by the presence of benzyl alcohol. This suggests that I is a molecular species that slowly undergoes disproportion when catalysis is over. Experiments in which multiple aliquots of SO (CAN) were added (R = 20 and 40) indicate that catalysts 1–3 can reinitiate the catalytic cycle once they have been kept in a dormant state for 0–9 min; the TOFs of the second and third additions are approximately equal and higher than that of the first addition. By combining manometry and on‐line mass spectrometry measurements, it was found that O2 evolution is parallel to the production of a small amount of CO2 owing to catalyst degradation. The TOFs of the experiments performed with NaIO4 as the SO are about 2–3 times lower than those with CAN, but the same reactivity order is found 3 > 2 > 1. The activation parameters were evaluated with NaIO4 for all catalysts and with CAN for 2 at 10–45 °C. ΔG# is practically the same in all situations (25–26 kcal mol–1), whereas ΔH# is appreciably lower for 2 (13.1 kcal mol–1 with CAN and 13.3 kcal mol–1 with NaIO4) than for 1 (16 kcal mol–1) and 3 (16.9 kcal mol–1). The lowest enthalpic cost with 2 is balanced by the highest entropic cost (–41 cal mol–1 K–1) that approaches that typical for an associative bimolecular process.

Journal ArticleDOI
TL;DR: In this article, the authors used cyclometalated ir or Rucomplexes or metalloporphyrinoids for the fabrication of a wide range of photoactive ma-terials.
Abstract: Phosphorescent dyes, such as cyclometalated Ir or Rucomplexes or metalloporphyrinoids, possess suitable prop-erties for the fabrication of a wide range of photoactive ma-terials. Their excited singlet states are converted to tripletstates via efficient intersystem crossing promoted by thepresence of heavy atoms. The relaxation of the formedtriplet states by phosphorescence or energy transfer to oxy-gen predetermines the use of these dyes in various applica-tions such as PHOLED,

Journal ArticleDOI
TL;DR: In this article, the zinc-imidazolate-based framework ZIF-8 was loaded with preformed surfactant-stabilized bimetallic Pd/Au nanoparticles and its corresponding monometallic counterparts Au and Pd by a controlled encapsulation process during the crystal growth.
Abstract: The zinc-imidazolate-based framework ZIF-8 was loaded with preformed surfactant-stabilized bimetallic Pd/Au nanoparticles and its corresponding monometallic counterparts Au and Pd by a controlled encapsulation process during the ZIF-8 crystal growth. The nanoparticle-loaded materials were characterized by powder X-ray diffraction (PXRD), FTIR spectroscopy, N2-sorption measurements, as well as by transmission electron microscopy (TEM). The ZIF-8 matrix material remained intact and the NP@ZIF-8 materials revealed the permanent porosity of Brunauer–Emmett–Teller (BET) surface areas above 1100 m2 g–1. The nanoparticles are exclusively found inside the volume of the nanocrystals and exhibit unchanged composition and size distribution as revealed by TEM investigations. Additionally, scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) confirmed the solid solution-type alloying of Pd and Au in the embedded Pd/Au nanoparticles. The materials were briefly evaluated in aqueous-phase aerobic alcohol oxidation to investigate the synergetic effects of alloyed Pd/Au nanoparticles and the microporous, hydrophobic matrix ZIF-8.

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TL;DR: In this paper, a modular synthesis of four unsymmetrical diborane(4) derivatives was proposed for the selective preparation of diaminoboryl PtII complexes as well as sterically little encumbered diboryl CuI complexes.
Abstract: Diaminoboryl ligands are currently intensively investigated because of their unique coordination chemical properties, for example, as part of pincer ligands. Owing to synthetic restrictions, however, access to diaminoboryl complexes is limited. Unsymmetrical diborane(4) derivatives comprising a dialkoxy- and a diaminoboron moiety provide efficient access to diaminoboryl complexes either by oxidative addition or by σ-bond metathesis reactions. Especially, the latter is complementary to existing methods and overcomes the existing limitations. This is illustrated by the modular synthesis of four unsymmetrical diborane(4) derivatives and their application in the selective preparation of unprecedented unsymmetrical diboryl PtII complexes as well as sterically little encumbered diaminoboryl CuI complexes.

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TL;DR: The cover image shows metal complexes capable of cleaving DNA, so-called artificial metallonucleases based on copper as the central atom and comprising N-donor ligands.
Abstract: Invited for the cover of this issue is the group of Nora Kulak at Freie Universitat Berlin. The cover image shows metal complexes capable of cleaving DNA, so-called artificial metallonucleases based on copper as the central atom and comprising N-donor ligands. Heteroaromatic, macrocyclic, and peptidic ligand systems are adumbrated in the background.

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Yi Luan1, Nannan Zheng1, Yue Qi1, Jie Yu1, Ge Wang1 
TL;DR: In this article, a novel metal-organic framework UiO-66-NH2-derived Bronsted acid catalyst was synthesized on a gram scale by employing a postsynthetic modification strategy under mild conditions.
Abstract: A novel metal–organic framework UiO-66-NH2-derived Bronsted acid catalyst was synthesized on a gram scale by employing a postsynthetic modification strategy under mild conditions. The nanomorphology of the catalyst was designed and developed to enhance its catalytic performance. Acetalization and benzimidazole formation were evaluated to demonstrate the high reactivity and selectivity of the nanoscaled UiO-66-NH-RSO3H catalyst, which were found to be comparable to the reactivity and selectivity of the strong homogeneous Bronsted acid catalyst. Furthermore, the UiO-66-NH-RSO3H catalyst was recycled several times without compromising the yield and selectivity.

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TL;DR: In this article, three uranyl isophthalates (1,3-bdc) and two uranyl pyromellitates (btec) of coordination-polymer type were hydrothermally synthesized (200 °C for 24 h) in the presence of different amine-based molecules.
Abstract: Three uranyl isophthalates (1,3-bdc) and two uranyl pyromellitates (btec) of coordination-polymer type were hydrothermally synthesized (200 °C for 24 h) in the presence of different amine-based molecules [1,3-diaminopropane (dap) or dimethylamine (dma) originating from the in situ decomposition of N,N-dimethylformamide]. (UO2)2(OH)2(H2O)(1,3-bdc)·H2O (1) is composed of inorganic tetranuclear cores, which are linked to each other through the isophthalato ligand to generate infinite neutral ribbons, which are intercalated by free H2O molecules. The compounds (UO2)1.5(H2O)(1,3-bdc)2·0.5H2dap·1.5H2O (2) and UO2(1,3-bdc)1.5·0.5H2dap·2H2O (3) consist of discrete uranyl-centered hexagonal bipyramids connected to each other by a ditopic linker to form a single-layer network for 2 or a double-layer network for 3. The protonated diamine molecules are located between the uranyl–organic sheets and balance the negative charge of the layered sub-networks. The phase (UO2)2O(btec)·2Hdma·H2O (4) presents a 2D structure built up from tetranuclear units, which consist of two central sevenfold coordinated uranium centers and two peripheral eightfold coordinated uranium centers. The connection of the resulting tetramers through the pyromellitate molecules generates an anionic layerlike structure, in which the protonated dimethylammonium species are inserted. The compound UO2(btec)·2Hdma (5) is also a lamellar coordination polymer, which contains isolated eightfold coordinated uranium cations linked through pyromellitate molecules and intercalated by protonated dimethylammonium species. In both phases 4 and 5, the btec linker has non-bonded carboxyl oxygen atoms, which preferentially interact with the protonated amine molecules through a hydrogen-bond network. The different illustrations show the structural diversity of uranyl–organic coordination polymers with organic amine molecules as countercations.