Showing papers in "Inorganic Chemistry in 2011"
TL;DR: Several crystal chemical properties appear to promote the high Li-ion conductivity in cubic Al-containing Li(7)La(3)Zr(2)O(12) garnet, which is the best conducting Li-oxide garnet discovered to date.
Abstract: Recent research has shown that certain Li-oxide garnets with high mechanical, thermal, chemical, and electrochemical stability are excellent fast Li-ion conductors. However, the detailed crystal chemistry of Li-oxide garnets is not well understood, nor is the relationship between crystal chemistry and conduction behavior. An investigation was undertaken to understand the crystal chemical and structural properties, as well as the stability relations, of Li7La3Zr2O12 garnet, which is the best conducting Li-oxide garnet discovered to date. Two different sintering methods produced Li-oxide garnet but with slightly different compositions and different grain sizes. The first sintering method, involving ceramic crucibles in initial synthesis steps and later sealed Pt capsules, produced single crystals up to roughly 100 μm in size. Electron microprobe and laser ablation inductively coupled plasma mass spectrometry (ICP-MS) measurements show small amounts of Al in the garnet, probably originating from the crucible...
561 citations
TL;DR: The relationships of noninnocent ligand behavior with excited-state descriptions and perspectives regarding material properties and single-electron or multielectron reactivity are illustrated briefly.
Abstract: The potential of redox-active ligands to behave “noninnocently” in transition-metal coordination compounds is reflected with respect to various aspects and situations. These include the question of establishing “correct” oxidation states, the identification and characterization of differently charged radical ligands, the listing of structural and other consequences of ligand redox reactions, and the distinction between barrierless delocalized “resonance” cases Mn/Ln ↔ Mn+1Ln–1 versus separated valence tautomer equilibrium situations Mn/Ln ⇌ Mn+1Ln–1. Further ambivalence arises for dinuclear systems with radical bridge Mn(μ-L•)Mn versus mixed-valent alternatives Mn+1(μ-L–)Mn, for noninnocent ligand-bridged coordination compounds of higher nuclearity such as (μ3-L)M3, (μ4-L)M4, (μ-L)4M4, or coordination polymers. Conversely, the presence of more than one noninnocently behaving ligand at a single transition-metal site in situations such as Ln–M–Ln–1 or L•–M–L• may give rise to corresponding ligand-to-ligand ...
433 citations
TL;DR: This type of thermally activated delayed fluorescence (TADF) creates a new mechanism that allows to harvest both singlet and triplet excitons (excitations) in the lowest singlet state and leads to drastically higher radiative rates than obtainable for emissions from triplet states of Cu(I) complexes.
Abstract: Strongly luminescent neutral copper(I) complexes of the type Cu(pop)(NN), with pop = bis(2-(diphenylphosphanyl)phenyl)ether and NN = bis(pyrazol-1-yl)borohydrate (pz(2)BH(2)), tetrakis(pyrazol-1-yl)borate (pz(4)B), or bis(pyrazol-1-yl)-biphenyl-borate (pz(2)Bph(2)), are readily accessible in reactions of Cu(acetonitrile)(4)(+) with equimolar amounts of the pop and NN ligands at ambient temperature. All products were characterized by means of single crystal X-ray diffractometry. The compounds exhibit very strong blue/white luminescence with emission quantum yields of up to 90%. Investigations of spectroscopic properties and the emission decay behavior in the temperature range between 1.6 K and ambient temperature allow us to assign the emitting electronic states. Below 100 K, the emission decay times are in the order of many hundreds of microseconds. Therefore, it is concluded that the emission stems from the lowest triplet state. This state is assigned to a metal-to-ligand charge-transfer state (3MLCT) involving Cu-3dand pop-π* orbitals. With temperature increase, the emission decay time is drastically reduced, e.g. to 13 μs [corrected] (Cu(pop)-(pz(2)Bph(2))), at ambient temperature. At this temperature, the complexes exhibit high emission quantum yields, as neat material or doped into poly(methyl methacrylate) (PMMA). This behavior is assigned to an efficient thermal population of a singlet state (being classified as (1)MLCT), which lies only 800 to 1300 cm(-1) above the triplet state, depending on the individual complex. Thus, the resulting emission at ambient temperature largely represents a fluorescence. For applications in OLEDs and LEECs, for example, this type of thermally activated delayed fluorescence (TADF) creates a new mechanism that allows to harvest both singlet and triplet excitons (excitations) in the lowest singlet state. This effect of singlet harvesting leads to drastically higher radiative rates than obtainable for emissions from triplet states of Cu(I) complexes.
393 citations
354 citations
TL;DR: The synthesis of Co(3)O(4)@graphene composites (CGC) and their applications as anode materials in lithium ion batteries (LIBs) through a chemical deposition method may find its application in the design and synthesis of novel electrode materials used in LIBs.
Abstract: This paper reports on the synthesis of Co3O4@graphene composites (CGC) and their applications as anode materials in lithium ion batteries (LIBs). Through a chemical deposition method, Co3O4 nanoparticles (NPs) with sizes in the range of 10−30 nm were homogeneously dispersed onto graphene sheets. Due to their high electrical conductivity, the graphene sheets in the CGC improved the electrical conductivity and the structure stability of CGC. CGC displayed a superior performance in LIBs with a large reversible capacity value of 941 mA hg−1 in the initial cycle with a large current density and an excellent cyclic performance of 740 mA hg−1 after 60 cycles, corresponding to 88.3% of the theoretical value of CGC, owing to the interactions between graphene sheets and Co3O4 NPs anchored on the graphene sheets. This synthesis approach may find its application in the design and synthesis of novel electrode materials used in LIBs.
345 citations
TL;DR: This work proposes a probabilistic model assessing the likelihood for ionic species to substitute for each other while retaining the crystal structure, and can be used to quantitatively suggest novel compounds and their structures.
Abstract: The existence of new compounds is often postulated by solid state chemists by replacing an ion in the crystal structure of a known compound by a chemically similar ion. In this work, we present how this new compound discovery process through ionic substitutions can be formulated in a mathematical framework. We propose a probabilistic model assessing the likelihood for ionic species to substitute for each other while retaining the crystal structure. This model is trained on an experimental database of crystal structures, and can be used to quantitatively suggest novel compounds and their structures. The predictive power of the model is demonstrated using cross-validation on quaternary ionic compounds. The different substitution rules embedded in the model are analyzed and compared to some of the traditional rules used by solid state chemists to propose new compounds (e.g., ionic size).
326 citations
TL;DR: Three new MOFs that are isoreticular expansions of known materials with the tbo and pto topologies are described, including one that has the highest porosity and lowest density of any MOFs reported to date.
Abstract: The concept and occurrence of isoreticular (same topology) series of metal–organic frameworks (MOFs) is reviewed. We describe the preparation, characterization, and crystal structures of three new MOFs that are isoreticular expansions of known materials with the tbo (Cu3(4,4′,4″-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate)2, MOF-399) and pto topologies (Cu3(4,4′,4″-(benzene-1,3,5-triyl-tribenzoate)2, MOF-143; Cu3(4,4′,4″-(triazine-2,4,6-triyl-tris(benzene-4,1-diyl))tribenzoate)2, MOF-388). One of these materials (MOF-399) has a unit cell volume 17 times larger than that of the first reported material isoreticular to it, and has the highest porosity (94%) and lowest density (0.126 g cm–3) of any MOFs reported to date.
321 citations
TL;DR: This article highlights recent efforts of this laboratory in the stabilization of highly reactive, low-oxidation-state, main-group molecules using bulky N-heterocyclic carbene ligands.
Abstract: This article highlights recent efforts of this laboratory in the stabilization of highly reactive, low-oxidation-state, main-group molecules using bulky N-heterocyclic carbene ligands [L: = :C{N(2,6-Pri2C6H3)CH}2; L′: = :C{N(2,4,6-Me3C6H2)CH}2; L′′: = :C{(i-Pr)NC(Me)}2]. The syntheses, structures, and computational studies of carbene-stabilized neutral diborenes [L:(H)B═B(H):L and L′:(H)B═B(H):L′], a neutral Ga6 octahedron (L′′:Ga[Ga4Mes4]Ga:L′′), disilicon (L:Si═Si:L), bis-silylene [L:(Cl)Si–Si(Cl):L], dipnictogens (L:E–E:L, E = P, As; L′:P–P:L′), and parent phosphinidene (L:PH) are discussed. Some of the unique challenges associated with this “carbene-stabilization” strategy are also presented.
318 citations
TL;DR: Electronic structural calculations employing extended Hückel and other semiempirical computational methods revealed extensive ligand-metal mixing in the frontier orbitals of these systems, including the observation of structures in which filled metal-based orbitals were more stable than ligand of the same type, suggesting that the one-electron changes upon oxidation or reduction were occurring on the ligand rather than on the metal center.
Abstract: Noninnocence in inorganic chemistry traces its roots back half a century to work that was done on metal complexes containing unsaturated dithiolate ligands. In a flurry of activity in the early 1960s by three different research groups, homoleptic bis and tris complexes of these ligands, which came to be known as dithiolenes, were synthesized, and their structural, electrochemical, spectroscopic, and magnetic properties were investigated. The complexes were notable for facile one-electron transfers and intense colors in solution, and conventional oxidation-state descriptions could not account for their electronic structures. The bis complexes were, in general, found to be square-planar, including the first examples of this geometry for paramagnetic complexes and different formal dn configurations. Several of the neutral and monoanionic tris complexes were found to have trigonal-prismatic coordination, the first time that this geometry had been observed in molecular metal complexes. Electronic structural calculations employing extended Huckel and other semiempirical computational methods revealed extensive ligand–metal mixing in the frontier orbitals of these systems, including the observation of structures in which filled metal-based orbitals were more stable than ligand-based orbitals of the same type, suggesting that the one-electron changes upon oxidation or reduction were occurring on the ligand rather than on the metal center. A summary of this early work is followed with a brief section on the current interpretations of these systems based on more advanced spectroscopic and computational methods. The take home message is that the early work did indeed provide a solid foundation for what was to follow in investigations of metal complexes containing redox-active ligands.
288 citations
TL;DR: A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction and display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping.
Abstract: A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba2Ln(BO3)2Cl:Eu2+ (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln3+ sites in Ba2Ln(BO3)2Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba2Ln(BO3)2Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P21/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu2+-doping. Ba2Ln(BO3)2Cl:Eu2+ phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba2Y(BO3)2Cl:Eu2+, Ba2Gd(BO3)2Cl:Eu2+, and Ba2...
278 citations
TL;DR: Electrochemical experiments reveal that the layered parallel folding structure of mesoporous Co(3)O(4) nanostructures are promising electrode materials for supercapacitors and the specific capacitance decay after 1000 continuous charge-discharge cycles was negligible, revealing the excellent stability of the electrode.
Abstract: In this work, one-dimensional and layered parallel folding of cobalt oxalate nanostructures have been selectively prepared by a one-step, template-free, water-controlled precipitation approach by simply altering the solvents used at ambient temperature and pressure. Encouragingly, the feeding order of solutions played an extraordinary role in the synthesis of nanorods and nanowires. After calcination in air, the as-prepared cobalt oxalate nanostructures were converted to mesoporous Co(3)O(4) nanostructures while their original frame structures were well maintained. The phase composition, morphology, and structure of the as-obtained products were studied in detail. Electrochemical properties of the Co(3)O(4) electrodes were carried out using cyclic voltammetry (CV) and galvanostatic charge-discharge measurements by a three-electrode system. The electrochemical experiments revealed that the layered parallel folding structure of mesoporous Co(3)O(4) exhibited higher capacitance compared to that of the nanorods and nanowires. A maximum specific capacitance of 202.5 F g (-1) has been obtained in 2 M KOH aqueous electrolyte at a current density of 1 A g(-1) with a voltage window from 0 to 0.40 V. Furthermore, the specific capacitance decay after 1000 continuous charge-discharge cycles was negligible, revealing the excellent stability of the electrode. These characteristics indicate that the mesoporous Co(3)O(4) nanostructures are promising electrode materials for supercapacitors.
TL;DR: The development and applications of "frustrated Lewis pair" (FLP) catalysts for hydrogenation are reviewed, and some previously unpublished data are reported.
Abstract: In 2006, our group reported the first metal-free systems that reversibly activate hydrogen. This finding was extended to the discovery of “frustrated Lewis pair” (FLP) catalysts for hydrogenation. It is this catalysis that is the focal point of this article. The development and applications of such FLP hydrogenation catalysts are reviewed, and some previously unpublished data are reported. The scope of the substrates is expanded. Optimal conditions and functional group tolerance are considered and applied to targets of potential commercial significance. Recent developments in asymmetric FLP hydrogenations are also reviewed. The future of FLP hydrogenation catalysts is considered.
TL;DR: The early hydrosilylation chemistry and its subsequent applications to a variety of transformations of importance to organic and inorganic chemists are described, drawing parallels with the more recent hydrogen activation chemistry.
Abstract: In the mid-1990s, it was discovered that tris(pentafluorophenyl)borane, B(C6F5)3, was an effective catalyst for hydrosilylation of a variety of carbonyl and imine functions. Mechanistic studies revealed a counterintuitive path in which the function of the borane was to activate the silane rather than the organic substrate. This was the first example of what has come to be known as “frustrated Lewis pair” chemistry utilizing this remarkable class of electrophilic boranes. Subsequent discoveries by the groups of Stephan and Erker showed that this could be extended to the activation of dihydrogen, initiating an intense period of activity in this area in the past 5 years. This article describes the early hydrosilylation chemistry and its subsequent applications to a variety of transformations of importance to organic and inorganic chemists, drawing parallels with the more recent hydrogen activation chemistry. Here, we emphasize the current understanding of the mechanism of this process rather than focusing on...
TL;DR: The present study provides a new strategy to enhancing the photocatalytic activity of visible-light-responsive Bi-based photocatalyst by p-n heterojunction by synthesizing hollow olive-shaped and n-p core-shell BiVO(4) microspheres.
Abstract: In this study, hollow olive-shaped BiVO(4) and n-p core-shell BiVO(4)@Bi(2)O(3) microspheres were synthesized by a novel sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-assisted mixed solvothermal route and a thermal solution of NaOH etching process under hydrothermal conditions for the first time, respectively. The as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, Brunauer-Emmett-Teller surface area, and UV-vis diffuse-reflectance spectroscopy in detail. The influence of AOT and solvent ratios on the final products was studied. On the basis of SEM observations and XRD analyses of the samples synthesized at different reaction stages, the formation mechanism of hollow olive-shaped BiVO(4) microspheres was proposed. The photocatalytic activities of hollow olive-shaped BiVO(4) and core-shell BiVO(4)@Bi(2)O(3) microspheres were evaluated on the degradation of rhodamine B under visible-light irradiation (λ > 400 nm). The results indicated that core-shell BiVO(4)@Bi(2)O(3) exhibited much higher photocatalytic activities than pure olive-shaped BiVO(4). The mechanism of enhanced photocatalytic activity of core-shell BiVO(4)@Bi(2)O(3) microspheres was discussed on the basis of the calculated energy band positions as well. The present study provides a new strategy to enhancing the photocatalytic activity of visible-light-responsive Bi-based photocatalysts by p-n heterojunction.
TL;DR: The obtained ZCIS/ZnS NCs show promising photocatalytic activity in the degradation of rhodamine B and the PL emission wavelength can be tuned conveniently via variation of the stoichiometric ratio of their components.
Abstract: High-quality ZnS−CuInS2 (ZCIS) alloy nanocrystals have been synthesized via reaction between the acetate salts of the corresponding metals and elemental sulfur in the presence of dodecanethiol in octadecene media at 230 °C. The PL emission wavelength can be tuned conveniently via variation of the stoichiometric ratio of their components. The influence of various experimental variables, including Zn/CuIn ratio, amount of sulfur and dodecanethiol, and reaction temperature, on the optical properties and composition of the obtained ZCIS NCs have been systematically investigated. The plain ZCIS NCs did show PL emission but with quite low PL quantum yield (typically below 3%). In order to improve the PL emission efficiency, the ZnS shell was subsequently overcoated around the ZCIS core NCs. With ZnS shell growth, the PL emission wavelength of the resulting ZCIS/ZnS NCs can cover from 518 to 810 nm with the maximum PL quantum efficiency up to 56%. Furthermore, the obtained ZCIS/ZnS NCs show promising photocataly...
TL;DR: Five new flexible functionalized aluminum hydroxo terephthalates [Al(OH)(BDC-X)]·n(guests) (Al-MIL-53-X-AS) retain their structural flexibility depending on the nature of guest molecules and temperature, as verified by cell parameter determination from XRPD data.
Abstract: Five new flexible functionalized aluminum hydroxo terephthalates [Al(OH)(BDC-X)]·n(guests) (BDC = 1,4-benzene-dicarboxylate; X = -Cl, 1-Cl; -Br, 2-Br; -CH3, 3-CH3; -NO2, 4-NO2; -(OH)2, 5-OH2) were synthesized under solvothermal conditions. The as synthesized (Al-MIL-53-X-AS) as well as the activated compounds were characterized by X-ray powder diffraction (XRPD), IR spectroscopy, thermogravimetric (TG), and elemental analysis. Activation, that is, removal of unreacted H2BDC-X molecules and/or occluded solvent molecules, followed by hydration in air at room temperature, led to the narrow pore (NP) form of the title compounds [Al(OH)(BDC-X)]·n(H2O) (Al-MIL-53-X). Thermogravimetric analysis (TGA) and temperature-dependent XRPD (TDXRPD) experiments performed on the NP-form of the compounds indicate high thermal stability in the range 325–500 °C. As verified by N2, CO2, or H2O sorption measurements, most of the thermally activated compounds exhibit significant microporosity. Similar to pristine Al-MIL-53, the ...
TL;DR: The interaction of complexes with calf-thymus DNA (CT DNA) has been explored by using absorption, emission, thermal denaturation, and viscosity studies, and the intercalating mode of DNA binding has been proposed.
Abstract: Two mononuclear fluorophore-labeled copper(II) complexes [Cu(nip)(acac)]+(2) and [Cu(nip)2]2+ (3), where fluorophore is 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (nip) (1) and acac is acetylacetone, have been synthesized and characterized by various techniques. The ligand 1 and complex 2 are structurally characterized by single-crystal X-ray diffraction. The coordination geometries around the copper are square planar in solid as well as solution state as evidenced by electron paramagnetic resonance (EPR) spectroscopy. The density functional calculations carried out on 1−3 have shown that electron-rich regions in the highest occupied orbital are localized on the naphthalene and partly on the phenanthroline moiety. Both complexes 2 and 3 in dimethyl sulfoxide (DMSO) exhibit near square planar structure around the metal ion in their ground state. Time-dependent density functional theory (TD-DFT) calculations reveal that Cu(II) ion in complex 2 shows tetrahedral coordination around the metal w...
TL;DR: Three copper(I) iodide clusters coordinated by different phosphine ligands formulated have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis and appear particularly interesting for the synthesis of original emissive materials.
Abstract: Three copper(I) iodide clusters coordinated by different phosphine ligands formulated [Cu(4)I(4)(PPh(3))(4)] (1), [Cu(4)I(4)(Pcpent(3))(4)] (2), and [Cu(4)I(4)(PPh(2)Pr)(4)] (3) (PPh(3) = triphenylphosphine, Pcpent(3) = tricyclopentylphosphine, and PPh(2)Pr = diphenylpropylphosphine) have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa 3, and tetragonal I 42m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu-Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu-Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials.
TL;DR: These phosphors meet the application requirements for near-UV LED chips and exhibit strong yellow emissions centered at 518, 610, and 611 nm with better thermal stability than (Ba,Sr)(2)SiO(4) (570 nm) commodity phosphors.
Abstract: Eu2+-activated Sr8MgY(PO4)7 and Sr8MgLa(PO4)7 yellow-emitting phosphors were successfully synthesized by solid-state reactions for applications in excellent color rendering index white light-emitting diodes (LEDs). The excitation and reflectance spectra of these phosphors show broad band excitation and absorption in the 250–450 nm near-ultraviolet region, which is ascribed to the 4f7 → 4f65d1 transitions of Eu2+. Therefore, these phosphors meet the application requirements for near-UV LED chips. Upon excitation at 400 nm, the Sr8MgY(PO4)7:Eu2+ and Sr8MgLa(PO4)7:Eu2+ phosphors exhibit strong yellow emissions centered at 518, 610, and 611 nm with better thermal stability than (Ba,Sr)2SiO4 (570 nm) commodity phosphors. The composition-optimized concentrations of Eu2+ in Sr8MgLa(PO4)7:Eu2+ and Sr8MgY(PO4)7:Eu2+ phosphors were determined to be 0.01 and 0.03 mol, respectively. A warm white-light near-UV LED was fabricated using a near-UV 400 nm chip pumped by a phosphor blend of blue-emitting BaMgAl10O17:Eu2+ a...
TL;DR: This article provides an update-to-date account on the application aspects of this important class of compounds in materials science with the emphasis on OLED applications and photochromic switching.
Abstract: Four-coordinate organoboron compounds with a π-conjugated chelate backbone have emerged recently as highly attractive materials for a number of applications including use as emitters and electron-transport materials for organic light-emitting diodes (OLEDs) or organic field transistors, photoresponsive materials, and sensory and imaging materials. Many applications of this class of boron compounds stem from the electronic properties of the π-conjugated chelate backbone. Charge-transfer transitions from an aromatic substituent attached to the boron center of the π-conjugated chelate backbone and steric congestion have also been found to play important roles in the luminescent and photochromic properties of the four-coordinate boron compounds. This article provides an update-to-date account on the application aspects of this important class of compounds in materials science with the emphasis on OLED applications and photochromic switching.
TL;DR: A new set of ionic radii in aqueous solution has been derived for lanthanoid(III) cations starting from a very accurate experimental determination of the ion-water distances obtained from extended X-ray absorption fine structure (EXAFS) data.
Abstract: A new set of ionic radii in aqueous solution has been derived for lanthanoid(III) cations starting from a very accurate experimental determination of the ion-water distances obtained from extended X-ray absorption fine structure (EXAFS) data. At variance with previous results, a very regular trend has been obtained, as expected for this series of elements. A general procedure to compute ionic radii in solution by combining the EXAFS technique and molecular dynamics (MD) structural data has been developed. This method can be applied to other ions allowing one to determine ionic radii in solution with an accuracy comparable to that of the Shannon crystal ionic radii.
TL;DR: Thermal quenching properties reveal that BaMg(2)Al(6)Si(9)O(30): Eu(2+), Tb(3+), Mn(2+) exhibits excellent characteristics even better than that of YAG:Ce, which can serve as a key material for phosphor-converted light-emitting diode and fluorescent lamps.
Abstract: A series of single-phase full-color emitting BaMg2Al6Si9O30:Eu2+, Tb3+, Mn2+ phosphors has been synthesized by solid-state reaction. Energy transfer from Eu2+ to Tb3+ and Eu2+ to Mn2+ in BaMg2Al6Si9O30 host matrix is studied by luminescence spectra and energy-transfer efficiency and lifetimes. The wavelength-tunable white light can be realized by coupling the emission bands centered at 450, 542, and 610 nm ascribed to the contribution from Eu2+ and Tb3+ and Mn2+, respectively. By properly tuning the relative composition of Tb3+/Mn2+, chromaticity coordinates of (0.31, 0.30), high color rendering index Ra = 90, and correlated color temperature (CCT) = 5374 K can be achieved upon excitation of UV light. Thermal quenching properties reveal that BaMg2Al6Si9O30: Eu2+, Tb3+, Mn2+ exhibits excellent characteristics even better than that of YAG:Ce. Our results indicate our white BaMg2Al6Si9O30:Eu2+, Tb3+, Mn2+ can serve as a key material for phosphor-converted light-emitting diode and fluorescent lamps.
TL;DR: It is shown by solid-state (15)N NMR measurements that an important zirconium metal-organic framework (UiO-66) with amino-functionalized links is composed of a mixture of amino and -NH(3)(+)Cl(-) salt functionalities rather than all amino functionality to give a composition of Zr(6)O(4)(OH)(4)(BDC-NH(2))(4).
Abstract: In our study, we show by solid-state 15N NMR measurements that an important zirconium metal–organic framework (UiO-66) with amino-functionalized links is composed of a mixture of amino and −NH3+Cl– salt functionalities rather than all amino functionality to give a composition of Zr6O4(OH)4(BDC-NH2)4(BDC-NH3+Cl–)2 (UiO-66-A). UiO-66-A was postsynthetically modified to form a mixture of three functionalities, where the hemiaminal functionality is the majority species in UiO-66-B and aziridine is the majority functionality in UiO-66-C. UiO-66-A–C are all porous with surface areas ranging from 780 to 820 m2/g and have chemical stability, as evidenced by reversible ammonia uptake and release showing capacities ranging from 134 to 193 cm3/g.
TL;DR: In the search of Ni based metal-organic frameworks (MOFs) containing paddle-wheel type building units, three chemical systems Ni(2+)/H(n)L/base/solvent with H(2)BDC (terephthalic acid) were investigated using high-throughput (HT) methods, and six new compounds were discovered, and their fields of formation were established.
Abstract: In the search of Ni based metal–organic frameworks (MOFs) containing paddle-wheel type building units, three chemical systems Ni2+/HnL/base/solvent with HnL = H3BTC (1,3,5-benzenetricarboxylic acid), H3BTB (4,4′,4′′,-benzene-1,3,5-triyl-tris(benzoic acid)), and H2BDC (terephthalic acid) were investigated using high-throughput (HT) methods. In addition to the conventional heating, for the first time HT microwave assisted synthesis of MOFs was carried out. Six new compounds were discovered, and their fields of formation were established. In the first system, H3BTC was employed and a comprehensive HT-screening of compositional and process parameters was conducted. The synthesis condition for the Ni paddle-wheel unit was determined and two compounds [Ni3(BTC)2(Me2NH)3]·(DMF)4(H2O)4 (1a) and [Ni6(BTC)2(DMF)6(HCOO)6] (1b) were discovered (Me2NH = dimethylamine, DMF = dimethylformamide). In the second system, the use of the extended tritopic linker H3BTB and the synthesis conditions for the paddle-wheel units le...
TL;DR: The mechanistic pathways for hydrogen evolution catalyzed by cobalt complexes with supporting diglyoxime ligands are analyzed with computational methods and the preferred bimetallic pathway involves the reaction of two Co(III)H complexes to produce H(2), important for designing more effective catalysts for solar energy conversion.
Abstract: The mechanistic pathways for hydrogen evolution catalyzed by cobalt complexes with supporting diglyoxime ligands are analyzed with computational methods. The cobaloximes studied are Co(dmgBF2)2 (dmg = dimethylglyoxime) and Co(dpgBF2)2 (dpg = diphenylglyoxime) in acetonitrile. The reduction potentials and pKa values are calculated with density functional theory in conjunction with isodesmic reactions, incorporating the possibility of axial solvent ligand loss during the reduction process. The solvent reorganization energies for electron transfer between the cobalt complex and a metal electrode and the inner-sphere reorganization energies accounting for intramolecular rearrangements and the possibility of ligand loss are also calculated. The relative reduction potentials agree quantitatively with the available experimental values. The pKas and reorganization energies agree qualitatively with estimates based on experimental data. The calculations suggest that a peak measured at ca. −1.0 V vs SCE in cyclic vo...
TL;DR: The reaction of 1-aminotetrazole with acidic sodium dichloroisocyanurate allowed isolation of 1,1'-azobis(tetrazoles), and the rare chain of 10 nitrogen atoms in this compound was confirmed by X-ray crystallography and the physical and explosive properties of the azo compound were characterized.
Abstract: The reaction of 1-aminotetrazole with acidic sodium dichloroisocyanurate allowed isolation of 1,1'-azobis(tetrazole). The rare chain of 10 nitrogen atoms in this compound was confirmed by X-ray crystallography, and the physical and explosive properties of the azo compound were characterized. The title compound possesses both exceedingly high explosive performance and sensitivity.
TL;DR: Two newly prepared oligothienylpyridines bind to platinum(II) and iridium(III) as N∧C-coordinating ligands, cyclometallating at position C(4) in the thiophene ring adjacent to the pyridine, leaving a chain of either one or two pendent thiophenes.
Abstract: Two newly prepared oligothienylpyridines, 5-(2-pyridyl)-5'-dodecyl-2,2'-bithiophene, HL(2), and 5-(2-pyridyl)-5''-dodecyl-2,2':5',2''-ter-thiophene, HL(3), bind to platinum(II) and iridium(III) as N∧C-coordinating ligands, cyclometallating at position C(4) in the thiophene ring adjacent to the pyridine, leaving a chain of either one or two pendent thiophenes. The synthesis of complexes of the form [PtL(n)(acac)] and [Ir(L(n))(2)(acac)] (n = 2 or 3) is described. The absorption and luminescence properties of these four new complexes are compared with the behavior of the known complexes [PtL(1)(acac)] and [Ir(L(1))(2)(acac)] {HL(1) = 2-(2-thienyl)pyridine}, and the profound differences in behavior are interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations. Whereas [PtL(1)(acac)] displays solely intense phosphorescence from a triplet state of mixed ππ*/MLCT character, the phosphorescence of [PtL(2)(acac)] and [PtL(3)(acac)] is weak, strongly red shifted, and accompanied by higher-energy fluorescence. TD-DFT reveals that this difference is probably due to the metal character in the lowest-energy excited states being strongly attenuated upon introduction of the additional thienyl rings, such that the spin-orbit coupling effect of the metal in promoting intersystem crossing is reduced. A similar pattern of behavior is observed for the iridium complexes, except that the changeover to dual emission is delayed to the terthiophene complex [Ir(L(3))(2)(acac)], reflecting the higher degree of metal character in the frontier orbitals of the iridium complexes than their platinum counterparts.
TL;DR: The first two decomposition steps are confirmed and a third process initiating at 1170 °C which leads to a semicrystalline hexagonal phase boron nitride is identified which can be released in appreciable quantities with the other major impurity, borazine.
Abstract: The thermal decomposition of ammonia borane was studied using a variety of methods to qualitatively identify gas and remnant solid phase species after thermal treatments up to 1500 °C. At about 110 °C, ammonia borane begins to decompose yielding H2 as the major gas phase product. A two step decomposition process leading to a polymeric -[NH═BH]n- species above 130 °C is generally accepted. In this comprehensive study of decomposition pathways, we confirm the first two decomposition steps and identify a third process initiating at 1170 °C which leads to a semicrystalline hexagonal phase boron nitride. Thermogravimetric analysis (TGA) was used to identify the onset of the third step. Temperature programmed desorption-mass spectroscopy (TPD-MS) and vacuum line methods identify molecular aminoborane (H2N═BH2) as a species that can be released in appreciable quantities with the other major impurity, borazine. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify th...
TL;DR: The synthesis of 4-aryl-1-benzyl-1H-1,2,3-triazoles (atl) is made via "Click chemistry" and their incorporation as cyclometallating ligands into new heteroleptic iridium(III) complexes containing diimine (N(^)N) ancillary ligands 2,2'-bipyridine (bpy) and 4,4'-di-tert-butyl-2,
Abstract: Herein we report the synthesis of 4-aryl-1-benzyl-1H-1,2,3-triazoles (atl), made via “Click chemistry” and their incorporation as cyclometallating ligands into new heteroleptic iridium(III) complexes containing diimine (N∧N) ancillary ligands 2,2′-bipyridine (bpy) and 4,4′-di-tert-butyl-2,2′-bipyridine (dtBubpy). Depending on decoration, these complexes emit from the yellow to sky blue in acetonitrile (ACN) solution at room temperature (RT). Their emission energies are slightly blue-shifted and their photoluminescent quantum efficiencies are markedly higher (between 25 and 80%) than analogous (C∧N)2Ir(N∧N)+ type complexes, where C∧N is a decorated 2-phenylpyridinato ligand. This increased brilliance is in part due to the presence of the benzyl groups, which act to sterically shield the iridium metal center. X-ray crystallographic analyses of two of the atl complexes corroborate this assertion. Their electrochemistry is reversible, thus making these complexes amenable for inclusion in light-emitting electr...
TL;DR: Investigations of antioxidative properties showed that all of the compounds have strong radical scavenging potencies against hydroxyl radicals, 2,2-diphenyl-1-picrylhydrazol radicals, nitric oxide, and superoxide anion radicals, and all three complexes exhibited substantial cytotoxic activity.
Abstract: A new ligand, 2-oxo-1,2-dihydroquinoline-3-carbaldehyde semicarbazone (OQsc-H) (1);, its N(4)-phenyl derivative (OQsc-Ph) (2); and their corresponding copper(II) complexes [CuCl(2)(OQsc-H)]·H(2)O·CH(3)OH (3), [CuCl(2)(OQsc-Ph)(H(2)O)]·CH(3)OH (4), and [CuNO(3)(OQsc-Ph)(H(2)O)]NO(3)·H(2)O·C(2)H(5)OH (5) have been synthesized and characterized by structural, analytical, and spectral methods, in order to investigate the influence of N(4)-phenyl substitution on structure and pharmacological properties. In all of the complexes, the ligands coordinated to the Cu(II) ion in a neutral fashion via ONO donor atoms. The single-crystal X-ray structures of neutral complex (3) and cationic complex (5) exhibit a slightly distorted square-pyramidal structure, while neutral complex (4) revealed an octahedral structure. The interaction of the compounds with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that compounds 1-5 could interact with CT-DNA through intercalation. A gel electrophoresis pictogram demonstrated the ability of the complexes (3-5) to cleave the pBR322 plasmid DNA through a hydrolytic process. The interactions of the compounds with bovine serum albumin (BSA) were also investigated using UV-visible, fluorescence, and synchronous fluorescence spectroscopic methods. The results indicated that all of the compounds could quench the intrinsic fluorescence of BSA in a static quenching process. Investigations of antioxidative properties showed that all of the compounds have strong radical scavenging potencies against hydroxyl radicals, 2,2-diphenyl-1-picrylhydrazyl radicals, nitric oxide, and superoxide anion radicals. Further, the cytotoxic effect of the compounds examined on cancerous cell lines such as human cervical cancer cells (HeLa), human laryngeal epithelial carcinoma cells (HEp-2), human liver carcinoma cells (Hep G2), human skin cancer cells (A431), and noncancerous NIH 3T3 mouse embryonic fibroblasts cell lines showed that all three complexes exhibited substantial cytotoxic activity. Further, all of the pharmacological investigations support the fact that there exists a strong influence of N(4)-phenyl substitution in semicarbazone.