Showing papers in "Inorganic Chemistry in 2014"
TL;DR: In this paper, a metal-organic framework (MOF) containing more than two kinds of metal ions mixed in one secondary building unit is described, where the synthesis often yields mixed MOF phases rather than a pure pha...
Abstract: Metal–organic frameworks (MOFs) containing more than two kinds of metal ions mixed in one secondary building unit are rare because the synthesis often yields mixed MOF phases rather than a pure pha...
373 citations
TL;DR: The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data and the extension of this analysis to more complex electroCatalytic schemes, such as H2 evolution and CO2 reduction, is discussed.
Abstract: The pursuit of solar fuels has motivated extensive research on molecular electrocatalysts capable of evolving hydrogen from protic solutions, reducing CO2, and oxidizing water. Determining accurate figures of merit for these catalysts requires the careful and appropriate application of electroanalytical techniques. This Viewpoint first briefly presents the fundamentals of cyclic voltammetry and highlights practical experimental considerations before focusing on the application of cyclic voltammetry for the characterization of electrocatalysts. Key metrics for comparing catalysts, including the overpotential (η), potential for catalysis (Ecat), observed rate constant (kobs), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsibl...
349 citations
TL;DR: New approaches to the measurement of thermodynamic hydride donor and acceptor abilities of transition-metal complexes were developed, and thermodynamic models that are powerful tools for predicting and understanding the relative free energies of intermediates in catalytic reactions were developed.
Abstract: Molecular electrocatalysts can play an important role in energy storage and utilization reactions needed for intermittent renewable energy sources. This manuscript describes three general themes that our laboratories have found useful in the development of molecular electrocatalysts for reduction of CO2 to CO and for H2 oxidation and production. The first theme involves a conceptual partitioning of catalysts into first, second, and outer coordination spheres. This is illustrated with the design of electrocatalysts for CO2 reduction to CO using first and second coordination spheres and for H2 production catalysts using all three coordination spheres. The second theme focuses on the development of thermodynamic models that can be used to design catalysts to avoid high- and low-energy intermediates. In this research, new approaches to the measurement of thermodynamic hydride donor and acceptor abilities of transition-metal complexes were developed. Combining this information with other thermodynamic informat...
344 citations
TL;DR: Although still in their infancy, it is believed that the compositional tunability and mild synthetic conditions of NMOF imaging agents should greatly facilitate their further development for clinical translation.
Abstract: Metal-organic frameworks (MOFs) are a class of hybrid materials self-assembled from organic bridging ligands and metal ion/cluster connecting points. The combination of a variety of organic linkers, metal ions/clusters, and structural motifs can lead to an infinite array of new materials with interesting properties for many applications. In this Forum Article, we discuss the design and applications of MOFs in chemical sensing and biological imaging. The first half of this article focuses on the development of MOFs as chemical sensors by highlighting how unique attributes of MOFs can be utilized to enhance sensitivity and selectivity. We also discuss some of the issues that need to be addressed in order to develop practically useful MOF sensors. The second half of this article focuses on the design and applications of nanoscale MOFs (NMOFs) as imaging contrast agents. NMOFs possess several interesting attributes, such as high cargo loading capacity, ease of postmodification, tunable size and shape, and intrinsic biodegradability, to make them excellent candidates as imaging contrast agents. We discuss the use of representative NMOFs in magnetic resonance imaging (MRI), X-ray computed tomography (CT), and optical imaging. Although still in their infancy, we believe that the compositional tunability and mild synthetic conditions of NMOF imaging agents should greatly facilitate their further development for clinical translation.
341 citations
TL;DR: A white LED device which is obtained by combining a 370 nm UV chip with commercial blue phosphor and the present yellow phosphor has been fabricated and exhibit good application properties.
Abstract: New compound discovery is of interest in the field of inorganic solid-state chemistry. In this work, a whitlockite-type structure Sr1.75Ca1.25(PO4)2 newly found by composition design in the Sr3(PO4)2–Ca3(PO4)2 join was reported. Crystal structure and luminescence properties of Sr1.75Ca1.25(PO4)2:Eu2+ were investigated, and the yellow-emitting phosphor was further employed in fabricating near-ultraviolet-pumped white light-emitting diodes (w-LEDs). The structure and crystallographic site occupancy of Eu2+ in the host were identified via X-ray powder diffraction refinement using Rietveld method. The Sr1.75Ca1.25(PO4)2:Eu2+ phosphors absorb in the UV–vis spectral region of 250–430 nm and exhibit an intense asymmetric broadband emission peaking at 518 nm under λex = 365 nm which is ascribed to the 5d–4f allowed transition of Eu2+. The luminescence properties and mechanism are also investigated as a function of Eu2+ concentration. A white LED device which is obtained by combining a 370 nm UV chip with commerci...
248 citations
TL;DR: This Award Article targets the evolving, yet surprisingly fruitful, chemistry of N-heterocyclic carbenes with low-oxidation-state main-group elements with a valuable historical perspective.
Abstract: This Award Article targets the evolving, yet surprisingly fruitful, chemistry of N-heterocyclic carbenes with low-oxidation-state main-group elements. Specifically, the chemistry of carbene-stabilized diatomic allotropes, diborenes, gallium octahedra, beryllium borohydride, and a host of related compounds will be presented. Providing a valuable historical perspective, the foundational work concerning the organometallic chemistry of gallium with sterically demanding m-terphenyl ligands from this laboratory will also be discussed.
217 citations
TL;DR: This work develops a new promising application approach for porous metal-organic frameworks by employing ZIF-67 as a promising formaldehyde gas sensor at a low operating temperature (150 °C) and could detect formaldehyde as low as 5 ppm.
Abstract: Traditional semiconducting metal oxide-based gas sensors are always limited on low surface areas and high operating temperatures. Considering the high surface area and high stability of zeolitic imidazolate framework (ZIF), ZIF-67 (surface area of 1832.2 m2 g–1) was first employed as a promising formaldehyde gas sensor at a low operating temperature (150 °C), and the gas sensor could detect formaldehyde as low as 5 ppm. This work develops a new promising application approach for porous metal–organic frameworks.
217 citations
TL;DR: Attributed to these additional functional groups (carbonyl and sulfone, respectively) in the ligands, BUT-10 and -11 show enhanced CO2 adsorption and separation selectivities over N2 and CH4, in spite of decreased pore sizes and surface areas compared with UiO-67.
Abstract: Introducing functional groups into pores of metal–organic frameworks (MOFs) through ligand modification provides an efficacious approach for tuning gas adsorption and separation performances of this type of novel porous material. In this work, two UiO-67 analogues, [Zr6O4(OH)4(FDCA)6] (BUT-10) and [Zr6O4(OH)4(DTDAO)6] (BUT-11), with functionalized pore surfaces and high stability were synthesized from two functional ligands, 9-fluorenone-2,7-dicarboxylic acid (H2FDCA) and dibenzo[b,d]thiophene-3,7-dicarboxylic acid 5,5-dioxide (H2DTDAO), respectively, and structurally determined by single-crystal X-ray diffraction. Notwithstanding skeleton bend of the two ligands relative to the linear 4,4′-biphenyldicarboxylic acid in UiO-67, the two MOFs have structures similar to that of UiO-67, with only lowered symmetry in their frameworks. Attributed to these additional functional groups (carbonyl and sulfone, respectively) in the ligands, BUT-10 and -11 show enhanced CO2 adsorption and separation selectivities over...
205 citations
TL;DR: It is shown that in this new phase the MO2 layers are maintained, but the phase exhibits a strong degree of disorder, and a much shorter interslab distance was found that may imply a gliding of theMO2 slab occurring at high voltage.
Abstract: The electrochemical properties of the P2-type NaxMn1/2Fe1/2O2 (x = 0.62) phase used as a positive electrode in Na batteries were tested in various voltage ranges at C/20. We show that, even if the highest capacity is obtained for the first cycles between 1.5 and 4.3 V, the best capacity after 50 cycles is obtained while cycling between 1.5 and 4.0 V (120 mAh g–1). The structural changes occurring in the material during the (de)intercalation were studied by operando in situ X-ray powder diffraction (XRPD) and ex situ synchrotron XRPD. We show that a phase with an orthorhombic P′2-type structure is formed for x ≈ 1, due to the cooperative Jahn–Teller effect of the Mn3+ ions. P2 structure type stacking is observed for 0.35 < x < 0.82, while above 4.0 V, a new phase appears. A full indexation of the XRPD pattern of this latter phase was not possible because of the broadening of the diffraction peaks. However, a much shorter interslab distance was found that may imply a gliding of the MO2 slab occurring at hig...
204 citations
TL;DR: Pseudooctahedral mononuclear cobat(II) complex, where abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole and tcm = tricyanomethanide anion, shows field-induced slow relaxation of magnetization, presenting a new example of a field- induced single-ion magnet with transversal magnetic anisotropy.
Abstract: Pseudooctahedral mononuclear cobat(II) complex [Co(abpt)2(tcm)2] (1), where abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole and tcm = tricyanomethanide anion, shows field-induced slow relaxation of magnetization with U = 86.2 K and large axial and rhombic single-ion zero-field-splitting parameters, D = +48(2) cm–1 and E/D = 0.27(2) (D = +53.7 cm–1 and E/D = 0.29 from ab initio CASSCF/NEVPT2 calculations), thus presenting a new example of a field-induced single-ion magnet with transversal magnetic anisotropy.
202 citations
TL;DR: It was found that the emission of 2 at ambient temperature represents a thermally activated delayed fluorescence (TADF) which renders the compound to be a good candidate for singlet harvesting in OLEDs and a reduction of nonradiative deactivation and thus an increase of emission quantum yield.
Abstract: The complexes [Cu(I)(POP)(dmbpy)][BF4] (1) and [Cu(I)(POP)(tmbpy)][BF4] (2) (dmbpy = 4,4′-dimethyl-2,2′-bipyridyl; tmbpy = 4,4′,6,6′-tetramethyl-2,2′-bipyridyl; POP = bis[2-(diphenylphosphino)-phenyl]ether) have been studied in a wide temperature range by steady-state and time-resolved emission spectroscopy in fluid solution, frozen solution, and as solid powders. Emission quantum yields of up to 74% were observed for 2 in a rigid matrix (powder), substantially higher than for 1 of around 9% under the same conditions. Importantly, it was found that the emission of 2 at ambient temperature represents a thermally activated delayed fluorescence (TADF) which renders the compound to be a good candidate for singlet harvesting in OLEDs. The role of steric constraints within the complexes, in particular their influences on the emission quantum yields, were investigated by hybrid-DFT calculations for the excited triplet state of 1 and 2 while manipulating the torsion angle between the bipyridyl and POP ligands. Bo...
TL;DR: Nonstoichiometric CaMnO(3-δ) is made a promising active, inexpensive bifunctional catalytic material for reversible ORR and OER because of the improved electrical conductivity.
Abstract: Perovskite oxides offer efficient and cheap electrocatalysts for both oxygen reduction reactions and oxygen evolution reactions (ORR/OER) in diverse oxygen-based electrochemical technologies. In this study, we report a facile strategy to enhance the electrocatalytic activity of CaMnO3 by introducing oxygen defects. The nonstoichiometric CaMnO(3-δ) (0 < δ ≤ 0.5) was prepared through thermal reduction of pristine perovskite microspheres and nanoparticles, which were synthesized from thermal-decomposition of carbonate precursors and the Pechini route, respectively. The as-prepared samples were analyzed by chemical titration, structural refinement, thermogravimetric analysis, and energy spectrometry. In 0.1 M KOH aqueous solution, the nonstoichiometric CaMnO(3-δ) with δ near 0.25 and an average Mn valence close to 3.5 exhibited the highest ORR activity (36.7 A g(-1) at 0.70 V vs RHE, with onset potential of 0.96 V), which is comparable to that of benchmark Pt/C. Density functional theory (DFT) studies and electrical conductivity measurement revealed that the enhanced ORR kinetics is due to facilitated oxygen activation and improved electrical properties. Besides high activity, the nonstoichiometric perovskite oxides showed respectable catalytic stability. Furthermore, the moderate oxygen-defective CaMnO(3-δ) (δ ≈ 0.25) favored the OER because of the improved electrical conductivity. This study makes nonstoichiometric CaMnO(3-δ) a promising active, inexpensive bifunctional catalytic material for reversible ORR and OER.
TL;DR: With careful adjustment of the relative concentration of the lanthanide ions, the color of the luminescence can be modulated, and white light-emission can indeed be achieved.
Abstract: Isostructural lanthanide metal–organic frameworks (MOFs) are synthesized through the spontaneous self-assembly of H3BTPCA (1,1′,1″-(benzene-1,3,5-triyl)tripiperidine-4-carboxylic acid) ligands and lanthanide ions (we term these MOFs Ln-BTPCA, Ln = La3+, Tb3+, Sm3+, etc.). Prompted by the observation that the different lanthanide ions have identical coordination environment in these MOFs, we explored and succeeded in the preparation of mixed-lanthanide analogues of the single-lanthanide MOFs by way of in situ doping using a mixture of lanthanide salts. With careful adjustment of the relative concentration of the lanthanide ions, the color of the luminescence can be modulated, and white light-emission can indeed be achieved. The mechanisms possibly responsible for the observed photophysical properties of these mixed-lanthanide MOFs are also discussed.
TL;DR: The results show that the novel octahedral microcrystals with a mean side length of 2 μm are obtained and could be favorable candidates in full-color phosphors for nUV-LEDs.
Abstract: Tm(3+), Dy(3+), and Eu(3+) codoped NaGd(WO4)2 phosphors were prepared by a facile hydrothermal process; they were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectrometer (EDS), photoluminescence spectra, and fluorescence lifetime. The results show that the novel octahedral microcrystals with a mean side length of 2 μm are obtained. Under the excitation of ultraviolet, individual RE(3+) ion (Tm(3+), Dy(3+), and Eu(3+)) activated NaGd(WO4)2 phosphors exhibit excellent emission properties in their respective regions. Moreover, when codoping Dy(3+) and Eu(3+)/Tm(3+) in the single component, the energy migration from Dy(3+) to Eu(3+) has been demonstrated to be a resonant type via a dipole-quadrupole mechanism as well as that from Tm(3+) to Dy(3+) ions, of which the critical distance (R(Dy-Eu)) is calculated to be 11.08 A. More significantly, in the Tm(3+), Dy(3+), and Eu(3+) tridoped NaGd(WO4)2 phosphors, the energy migration of Tm(3+)-Dy(3+)-Eu(3+), utilized for sensitizing Eu(3+) ions besides compensating the red component at low Eu(3+) doping concentration, has been discussed first. In addition, under 365 nm near-ultraviolet radiation (nUV), the color-tunable emissions in octahedral NaGd(WO4)2 microcrystals are realized by giving abundant blue, green, white, yellow, and red emissions, especially warm white emission, and could be favorable candidates in full-color phosphors for nUV-LEDs.
TL;DR: Electronic structure calculations performed using the experimentally determined centrosymmetric structure are similar to those performed with the inversion symmetry absent but with the important implication that Cd3As2 is a three-dimensional (3D)-Dirac semimetal with no spin splitting; all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi energy along Γ-Z in the Brillouin zone.
Abstract: The structure of Cd3As2, a high-mobility semimetal reported to host electrons that act as Dirac particles, is reinvestigated by single-crystal X-ray diffraction. It is found to be centrosymmetric rather than noncentrosymmetric as previously reported. It has a distorted superstructure of the antifluorite (M2X) structure type with a tetragonal unit cell of a = 12.633(3) and c = 25.427(7) A in the centrosymmetric I41/acd space group. The antifluorite superstructure can be envisioned as consisting of distorted Cd6□2 cubes (where □ = an empty cube vertex) in parallel columns, stacked with opposing chirality. Electronic structure calculations performed using the experimentally determined centrosymmetric structure are similar to those performed with the inversion symmetry absent but with the important implication that Cd3As2 is a three-dimensional (3D)-Dirac semimetal with no spin splitting; all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi energy along Γ–Z in the Brill...
TL;DR: This ligand possesses merits of both alkylamide and 2,9-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthroline (R-BTPhen) extractants for efficient actinide extraction and the selectivity toward minor actinides over lanthanides and hence renders huge potential opportunities in high-level liquid waste (HLLW) partitioning.
Abstract: In this work, we reported a phenanthroline-based tetradentate ligand with hard-soft donors combined in the same molecule, N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), for the group separation of actinides over lanthanides. The synthesis and solvent extraction as well as complexation behaviors of the ligand with actinides and lanthanides are studied experimentally and theoretically. The ligand exhibits excellent extraction ability and high selectivity toward hexavalent, tetravalent, and trivalent actinides over lanthanides in highly acidic solution. The chemical stoichiometry of Th(IV) and U(VI) complexes with Et-Tol-DAPhen is determined to be 1:1 using X-ray crystallography. The stability constants of some typical actinide and lanthanide complexes of Et-Tol-DAPhen are also determined in methanol by UV-vis spectrometry. Density functional theory (DFT) calculations reveal that the An-N bonds of the Et-Tol-DAPhen complexes have more covalent characters than the corresponding Eu-N bonds, which may in turn lead to the selectivity of Et-Tol-DAPhen toward actinides. This ligand possesses merits of both alkylamide and 219-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthroline (R-BTPhen) extractants for efficient actinide extraction and the selectivity toward minor actinides over lanthanides and hence renders huge potential opportunities in high-level liquid waste (HLLW) partitioning.
TL;DR: Examination of acid electroreduction in acetonitrile on glassy carbon electrodes by cyclic voltammetry provides a guide for selecting acids to use in electrocatalysis experiments such that direct electrode reduction is avoided.
Abstract: Molecular catalysts for electrochemically driven hydrogen evolution are often studied in acetonitrile with glassy carbon working electrodes and Bronsted acids. Surprisingly, little information is available regarding the potentials at which acids are directly reduced on glassy carbon. This work examines acid electroreduction in acetonitrile on glassy carbon electrodes by cyclic voltammetry. Reduction potentials, spanning a range exceeding 2 V, were found for 20 acids. The addition of 100 mM water was not found to shift the reduction potential of any acid studied, although current enhancement was observed for some acids. The data reported provides a guide for selecting acids to use in electrocatalysis experiments such that direct electrode reduction is avoided.
TL;DR: The crystal structures of the two new compounds 2 and 3 were determined and it was shown that at T1 (433 K) the infinite nickel oxide chains built of the repeating structural unit [Ni3(μ3-OH)2](4+) in 1 collapse and lead to infinite porous layers, forming compound 2.
Abstract: Dehydration of the hybrid compound [Ni3(OH)2(tp)2(H2O)4] (1) upon heating led to the sequential removal of coordinated water molecules to give [Ni3(OH)2(tp)2(H2O)2] (2) at T1 = 433 K and thereafter anhydrous [Ni2(OH)2(tp)] (3) at T2 = 483 K. These two successive structural transformations were thoroughly characterized by powder X-ray diffraction assisted by density functional theory calculations. The crystal structures of the two new compounds 2 and 3 were determined. It was shown that at T1 (433 K) the infinite nickel oxide chains built of the repeating structural unit [Ni3(μ3-OH)2](4+) in 1 collapse and lead to infinite porous layers, forming compound 2. The second transformation at T2 (483 K) gave the expected anhydrous compound 3, which is isostructural with Co2(OH)2(tp). These irreversible transitions directly affect the magnetic behavior of each phase. Hence, 1 was found to be antiferromagnetic at TN = 4.11 K, with metamagnetic behavior with a threshold field Hc of ca. 0.6 T. Compound 2 exhibits canted antiferromagnetism below TN = 3.19 K, and 3 is ferromagnetic below TC = 4.5 K.
TL;DR: Results indicate that complex 4 acts as an efficient and selective G-quadruplex ligand while being a modest PARP-1 inhibitor (i.e., poor DDR impairing agent) and thus provide preliminary insights into the molecular mechanism that underlies its antiproliferative behavior.
Abstract: Organometallic Au(I) NHC compounds bearing caffeine-type ligands have been synthesized and characterized as promising anticancer agents. The bis-carbene complex [Au(caffeine-2-yliene)2][BF4] appeared to be selective for human ovarian cancer cell lines in vitro and poorly toxic in healthy organs ex vivo. The compound shows high affinity and selectivity for G-quadruplex structures as demonstrated by FRET melting assay.
TL;DR: The results show that due to structural phase transition more significant distortion of the metal-formate framework occurs for the deuterated samples, and that magnetic properties of the studied compounds can be explained assuming that they are ordered ferrimagnetically with nearly compensated magnetic moments of Ni and Mn.
Abstract: We report the synthesis, crystal structure, thermal, dielectric, Raman, infrared, and magnetic properties of hydrogen and deuterated divalent metal formates, [(CH3)2NH2][M(HCOO)3] and [(CH3)2ND2][M(HCOO)3], where M = Ni, Mn. On the basis of Raman and IR data, assignment of the observed modes to respective vibrations of atoms is proposed. The thermal studies show that for the Ni compounds deuteration leads to a decrease of the phase transition temperature Tc by 5.6 K, whereas it has a negligible effect on Tc in the Mn analogues. This behavior excludes the possibility of proton (deuteron) movement along the N–H···O (N–D···O) bonds as the microscopic origin of the first-order phase transition observed in these crystals below 190 K. According to single-crystal X-ray diffraction, the dimethylammonium (DMA) cations are dynamically disordered at room temperature, because the hydrogen bonds between the NH2 (ND2) groups and the metal-formate framework are disordered. The highly dynamic nature of hydrogen bonds in ...
TL;DR: The results suggest that phosphors deriving from Ca14Al10Zn6O35:Mn(4+) have potential application for white LEDs and influence of cation substitution on the luminescence intensity of these phosphors is elucidated.
Abstract: A new, highly efficient deep red-emitting phosphor Ca14Al10Zn6O35:Mn4+ was developed as a component of solid-state white light-emitting diodes (LEDs). The structural and optical characterization of the phosphor is described. The phosphor exhibits strong emission in the range of 650–700 nm when excited by 460 nm excitation, with a quantum efficiency approaching 50%. Concentration dependence of Mn4+ luminescence in Ca14Al10Zn6O35:Mn4+ is investigated. Attempts to understand the thermal stability on the basis of the thermal quenching characteristics of Ca14Al10Zn6O35:Mn4+ is presented. The results suggest that phosphors deriving from Ca14Al10Zn6O35:Mn4+ have potential application for white LEDs. In addition, influence of cation substitution on the luminescence intensity of these phosphors is elucidated.
TL;DR: Six new zinc-1,3,5-benzenetricarboxylate-based metal-organic frameworks (MOFs) have been successfully synthesized using three different surfactants as reaction media, indicating that the surfactant-thermal method could offer exciting opportunities for preparing novel MOFs or other inorganic crystalline materials with diverse structures and interesting properties.
Abstract: Six new zinc-1,3,5-benzenetricarboxylate-based metal–organic frameworks (MOFs) have been successfully synthesized using three different surfactants (PEG 400, octanoic acid, and hexadecyltributylphosphonium bromide) as reaction media. These surfactants with different characteristics, such as being neutral, acidic, and cationic, have been demonstrated to show strong effects on directing the crystals’ growth and resulted in different secondary building units (SBUs) including an unusual SBU unit [Zn4(μ4-O)(CO2)7]. Our results clearly indicated that the surfactant–thermal method could offer exciting opportunities for preparing novel MOFs or other inorganic crystalline materials with diverse structures and interesting properties.
TL;DR: A novel on/off fluorescent rhodamine-based hexapodal Fe(3+) probe (L) containing a cyclotriphosphazene core was synthesized by an azide-alkyne "click-reaction" to test the reusability and stoichiometry of the sensor.
Abstract: A novel on/off fluorescent rhodamine-based hexapodal Fe3+ probe (L) containing a cyclotriphosphazene core was synthesized by an azide–alkyne “click-reaction”. The synthesized compounds (1–5 and L) were characterized by FT-IR; 1H, 13C, and 31P NMR; and MALDI MS spectrometry. The optical sensor features for the Fe3+ complex of L were investigated by UV–vis and fluorescence spectroscopy. The stoichiometry of L–Fe3+ complex was found to be 1:3 (ligand/metal ion), and the detection limit of L was determined as 4.8 μM (0.27 mg L–1) for Fe3+ ions. The reusability of the sensor was tested by the addition of ethylenediamine to L–Fe3+ complex solutions followed by the addition of Fe3+ solution.
TL;DR: A new benzoyl hydrazone based chemosensor R is synthesized by Schiff base condensation of 2,6-diformyl-4-methylphenol and phenyl carbohydrazide and acts as a highly selective fluorescence sensor for Cu (2+) and Zn(2+) ions in aqueous media.
Abstract: A new benzoyl hydrazone based chemosensor R is synthesized by Schiff base condensation of 2,6-diformyl-4-methylphenol and phenyl carbohydrazide and acts as a highly selective fluorescence sensor for Cu(2+) and Zn(2+) ions in aqueous media. The reaction of R with CuCl2 or ZnCl2 forms the corresponding dimeric dicopper(II) [Cu2(R)(CH3O)(NO3)]2(CH3O)2 (R-Cu(2+)) and dizinc(II) [Zn2(R)2](NO3)2 (R-Zn(2+)) complexes, which are characterized, as R, by conventional techniques including single-crystal X-ray analysis. Electronic absorption and fluorescence titration studies of R with different metal cations in a CH3CN/0.02 M HEPES buffer medium (pH = 7.3) show a highly selective binding affinity only toward Cu(2+)and Zn(2+) ions even in the presence of other commonly coexisting ions such as Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Fe(3+), Co(2+), Ni(2+), Cd(2+), and Hg(2+). Quantification of the fluorescence titration analysis shows that the chemosensor R can indicate the presence of Cu(2+)and Zn(2+) even at very low concentrations of 17.3 and 16.5 ppb, respectively. R-Zn(2+) acts as a selective metal-based fluorescent sensor for inorganic pyrophosphate ion (PPi) even in the presence of other common anions such as F(-), Cl(-), Br(-), I(-), CH3COO(-), CO3(2-), HCO3(-), N3(-), SO4(2-), PPi, AMP, ADP, and ATP in an aqueous medium. The propensity of R as a bioimaging fluorescent probe to detect Cu(2+) and Zn(2+) ions in human cervical HeLa cancer cell lines and their cytotoxicity against human cervical (HeLa), breast cancer (MCF7), and noncancer breast epithelial (MCF10a) cells have also been investigated. R-Cu(2+) shows better cytotoxicity and sensitivity toward cancer cells over noncancer cells than R and R-Zn(2+) under identical conditions, with the appearance of apoptotic bodies.
TL;DR: Complex [Co(PPh3)2Br2] possesses intermediate magnetic anisotropy, D/hc = -13 cm(-1), and displays superparamagnetic behavior either in the absence of the magnetic field or in fields of Bdc = 0.2 T.
Abstract: Complex [Co(PPh3)2Br2] possesses intermediate magnetic anisotropy, D/hc = −13 cm–1. It displays superparamagnetic behavior either in the absence of the magnetic field or in fields of Bdc = 0.05, 0.1, 0.15, and 0.2 T. At Bdc = 0.1 T, the barrier to spin reversal U/kB = 37 K and the extrapolated relaxation time τ0 = 9.4 × 10–11 s confirm its classification as a single-molecule magnet. At Bdc = 0.2 T, two relaxation processes are evidenced.
TL;DR: Calculations of rate constants for electron and proton transfer, as well as concerted PCET, have assisted in identifying the kinetically favorable mechanisms under specified conditions and in the design of more effective molecular electrocatalysts.
Abstract: Molecular electrocatalysts play an essential role in a wide range of energy conversion processes. The objective of electrocatalyst design is to maximize the turnover frequency and minimize the overpotential for the overall catalytic cycle. Typically, the catalytic cycle is dominated by key proton-coupled electron transfer (PCET) processes comprised of sequential or concerted electron and proton transfer steps. Theoretical methods have been developed to investigate the mechanisms, thermodynamics, and kinetics of PCET processes in electrocatalytic cycles. Electronic structure methods can be used to calculate the reduction potentials and pKa’s and to generate thermodynamic schemes, free energy reaction pathways, and Pourbaix diagrams, which indicate the most stable species under certain conditions. These types of calculations have assisted in identifying the thermodynamically favorable mechanisms under specified experimental conditions, such as acid strength and overpotential. Such calculations have also rev...
TL;DR: A coating of conductive polyanilime (PANI) on the CMK-3/sulfur composite is effective in enhancing the cycling performance and shed light on the basic study of rechargeable K-S batteries.
Abstract: We report room-temperature rechargeable potassium–sulfur (K-S) batteries using ordered mesoporous carbon (CMK-3)/sulfur and polyanilime (PANI) coated CMK-3/sulfur composites as the cathode and metallic potassium as the anode. The electrochemical reaction mechanism was investigated by electrochemical tests, TEM, XRD, and Raman spectra. It was found that K-S batteries delivered two reduction peaks located at about 2.1 and 1.8 V and one oxidation peak at about 2.2 V, respectively. Meanwhile, K2S3 was the major discharge product that could be charged to reversibly form S and K ion. Through optimization of sulfur content, the CMK-3/sulfur composite with 40.8 wt % S displayed an initial discharge capacity of 512.7 mAh g–1 and a capacity of 202.3 mAh g–1 after 50 cycles at a current density of 50 mA g–1. A coating of conductive polyanilime (PANI) on the CMK-3/sulfur composite is effective in enhancing the cycling performance. In comparison, PANI@CMK-3/sulfur composite showed a capacity of 329.3 mAh g–1 after 50 ...
TL;DR: The synthesis optimization and scale-up of the benchmarked microporous zirconium terephthalate UiO-66(Zr) were investigated by evaluating the impact of several parameters over the kinetics of crystallization by time-resolved in situ energy-dispersive X-ray diffraction, and the use of the less acidic ZrOCl2·8H2O as the precursor seemed to be a suitable alternative.
Abstract: The synthesis optimization and scale-up of the benchmarked microporous zirconium terephthalate UiO-66(Zr) were investigated by evaluating the impact of several parameters (zirconium precursors, acidic conditions, addition of water, and temperature) over the kinetics of crystallization by time-resolved in situ energy-dispersive X-ray diffraction. Both the addition of hydrochloric acid and water were found to speed up the reaction. The use of the less acidic ZrOCl2·8H2O as the precursor seemed to be a suitable alternative to ZrCl4·xH2O, avoiding possible reproducibility issues as a consequence of the high hygroscopic character of ZrCl4. ZrOCl2·8H2O allowed the formation of smaller good quality UiO-66(Zr) submicronic particles, paving the way for their use within the nanotechnology domain, in addition to higher reaction yields, which makes this synthesis route suitable for the preparation of UiO-66(Zr) at a larger scale. In a final step, UiO-66(Zr) was prepared using conventional reflux conditions at the 0.5...
TL;DR: This work demonstrates a novel calcium gallium germanium garnet (Ca3Ga2Ge3O12) host where lanthanide ions such as Tm(3+)/Yb(3+) and transition metal ions can be easily incorporated through substituting the Ca(2+) and Ga(3%) respectively.
Abstract: Currently, upconversion nanocrystals and long-lasting phosphorescent particles have attracted extensive research interest for their possible applications as bioimaging probes. However, there are few reports concerning the achievement of both upconversion luminescence of lanthanide ions and long-lasting phosphorescence of transition metal ions in a sole host so far. Herein, we demonstrate a novel calcium gallium germanium garnet (Ca3Ga2Ge3O12) host where lanthanide ions such as Tm3+/Yb3+ and transition metal ions such as Cr3+ can be easily incorporated through substituting the Ca2+ and Ga3+ respectively. This Cr/Yb/Tm:Ca3Ga2Ge3O12 phosphor exhibits both broadband near-infrared long-lasting phosphorescence of Cr3+ with an afterglow time of more than 7000 s and near-infrared to near-infrared upconversion luminescence of Tm3+. Impressively, it is evidenced that the addition of Yb3+/Tm3+ into Cr:Ca3Ga2Ge3O12 not only results in Tm3+ upconversion luminescence but also greatly increases Cr3+ afterglow time. Base...
TL;DR: The results suggest that this single-phased SCBPO_Cl:xEu(2+), yTb(3+), zMn(2+) phosphor may have a potential application as a near-UV convertible white-light emission phosphor for phosphor-converted white light-emitting diode.
Abstract: A series of single-phased (Sr3–x,Ca1–y–z,Ba)(PO4)3Cl (SCBPO_Cl):xEu2+, yTb3+, zMn2+ phosphors were synthesized by high-temperature solid-state reaction, and luminescent properties of these phosphors were investigated by means of photoluminescence and microcathode luminescence (μ-CL). Under UV excitation, white-light emission was obtained from triactivated SCBPO_Cl phosphors via combining three emission bands centered at 450, 543, and 570 nm contributed by Eu2+, Tb3+, and Mn2+, respectively. White-light emission with the three emission bands is further demonstrated in the fluorescence microscope images, CL spectrum, and μ-CL mappings, which strongly confirm that the luminescence distribution of as-prepared SCBPO_Cl:xEu2+, yTb3+, zMn2+ phosphors is very homogeneous. Both spectral overlapping and lifetime decay analyses suggest that dual energy transfers, that is, Eu2+→Tb3+ and Eu2+→Mn2+, play key roles in obtaining the white emission. The International Commission on Illumination value of white emission as w...