Two new dinuclear complexes with flexible bipyrazole ligand bridged via μ-Cl or μ1,1-N3

Two dinuclear complexes, {[Cd(bdpp)Cl₂](CH₃OH)}₂ (1) and [Cd(bdpp)(N₃)(NO₃)]₂ (2), have been synthesized by reactions of bdpp with cadmium salts (bdpp?=?1,3-bis(3′,5′-dimethylpyrazol-1′-yl)propane), and characterized by IR, element analysis, fluorescence properties and single crystal structural analysis. Cd in 1 has a trigonal bipyramidal coordination geometry and two such units form a dimer through two μ-Cl bridges. Each Cd in 2 has a distorted octahedral coordination geometry and two Cd units form a dimer through μ_1,1-N₃ bridges. The emission spectra show λ_em?=?413?nm for 1 and λ_em?=?338?nm for 2.     

Oxidation and coupling of β-diketiminate ligand in lanthanide complexes: novel eight-nuclear lanthanide clusters with μ-, μ3-Cl, and μ4-O bridge

Two novel eight-nuclear lanthanide oxide and chloride clusters Ln(8)(μ-η(2)-L(4))(2)(μ(3)-Cl)(4)(μ-Cl)(10)(μ(4)-O)(3)(THF)(8) (Ln = Er(3), Dy(4); L(4) = [OC{(Me)CN-2,6-(i)PrC(6)H(3)}(2)](2-)) have been synthesized by the reaction of β-diketiminate rare-earth metal chlorides with oxygen, providing a new oxidation and coupling reaction of the β-diketiminate ligand.     

Hydrothermal Tm3+-Lu2O3 nanorods with highly efficient 2 μm emission

Cubic Ia3Tm-Lu(2)O(3) porous nanorods of ～45 μm length and 90 nm diameter have been prepared with precise compositions through a soft hydrothermal route (i.e., autogenic pressure, neutral pH, and 185 °C for 24 h) by using chloride reagents. For these nanorods, room temperature excitation and photoluminescence spectra of Tm(3+) multiplets related to the eye-safe (3)F(4)→(3)H(6) laser transition at ～1.85-2.05 μm are similar to those of bulk crystals. Room-temperature luminescence decays of (3)H(4) and (3)F(4) exhibit nonexponential dynamics analytically reproduced by the sum of two exponential regimes, which are ascribed to the different rates of nonradiative relaxations in defects at the surface and in the body of the nanocrystals, respectively. Measured fluorescence lifetimes τ ～ 200-260 μs and τ ～ 2.3-2.9 ms for (3)H(4) and (3)F(4), respectively, in 0.2% mol Tm-Lu(2)O(3) nanorods, are considerably larger than in previous nanocrystalline Tm-doped sesquioxides, and they are close to values of bulk sesquioxide crystals with equivalent Tm(3+) content.     

Syntheses,Structures and Vitro Anticancer Activities of μ_2-O-and μ_2-Dimethylglyoximato-bridged μ_3-O-Tris[di(m-fluorobenzyl)tin] Bis(dimethylglyoximate)

μ_2-O-and μ_2-dimethylglyoximato-bridged μ_3-O-tris[di(m-fluorobenzyl)tin] bis(dimethylglyoximate)(1) has been synthesized by the reaction of di(m-fluorobenzyl)tin dichloride with dimethylglyoxime. Complex 1 was characterized by means of IR,~1H NMR,elemental analysis and X-ray diffraction. It crystallizes in orthorhombic system,space group Pna21 with a = 2.22172(12),b = 1.05566(6),c = 2.15577(12) nm,V = 5.0561(5) nm~3,Z = 4,C_(50)H_(50)F_6N_4O_6Sn_3,Mr = 1273.01,Dc = 1. 6721 g/cm3,μ_(MoΚα) = 15.44 cm~(-1),F(000) = 2520,R = 0.0281 and wR = 0.0683. The stabilities,orbital energies and composition characteristics of some frontier molecular orbitals of 1 have been investigated with the quantum chemistry calculation. The properties of thermogravimetric and vitro anticancer activities of the compound have been discussed.     

Theoretical Investigation of Transparent (3–5 μm) and High Reflective (1.3 μm) Filter by Sol-Gel Process

When designing a cut-off interference filter, extra layers are needed to add on each side of periodic symmetrical multilayer to match the incident medium and the substrate. In this paper, we use sol-gel film with adjustable refractive index as the match layer. The influence of the refractive index and thickness of the match layer on the film system is discussed in detail. As an example, a special filter which is transparent (>80%) at the wavelength 3–5 m and high reflective (>90%) at the wavelength 1.3 m is designed. Finally a series of optimized film parameters are presented. The whole design process is a good reference to the other multilayer special filter made by sol-gel process.     

Ammonia activation by μ3-alkylidyne fragments supported on a titanium molecular oxide model

Ammonolysis of the μ(3)-alkylidyne derivatives [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CR)] [R = H (1), Me (2)] produces a trinuclear oxonitride species, [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-N)] (3), via methane or ethane elimination, respectively. During the course of the reaction, the intermediates amido μ-alkylidene [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ-CHR)(NH(2))] [(R = H (4), Me (5)] and μ-imido ethyl species [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ-NH)Et] (6) were characterized and/or isolated. This achievement constitutes an example of characterization of the three steps of successive activation of N-H bonds in ammonia within the same transition-metal molecular system. The N-H σ-bond activation of ammonia by the μ(3)-alkylidyne titanium species has been theoretically investigated by DFT method on [{Ti(η(5)-C(5)H(5))(μ-O)}(3)(μ(3)-CH)] model complex. The calculations complement the characterization of the intermediates, showing the multiple bond character of the terminal amido and the bridging nature of imido ligand. They also indicate that the sequential ammonia N-H bonds activation process goes successively downhill in energy and occurs via direct hydron transfer to the alkylidyne group on organometallic oxides 1 and 2. The mechanism can be divided into three stages: (i) coordination of ammonia to a titanium center, in a trans disposition with respect to the alkylidyne group, and then the isomerization to adopt the cis arrangement, allowing the direct hydron migration to the μ(3)-alkylidyne group to yield the amido μ-alkylidene complexes 4 and 5, (ii) hydron migration from the amido moiety to the alkylidene group, and finally (iii) hydron migration from the μ-imido complex to the alkyl group to afford the oxo μ(3)-nitrido titanium complex 3 with alkane elimination.     

Some practical comparisons of the efficiency and overloading behaviour of sub-2 μm porous and sub-3 μm shell particles in reversed-phase liquid chromatography

At their optimum flow, sub-3 μm superficially porous or "shell" particles demonstrate similar efficiency to sub-2 μm totally porous particles. The performance of 0.21 cm i.d shell columns is however inferior to those of 0.46 cm i.d., presumably due to packing difficulties. At high flow, shell columns can give flatter Knox curves due to lower operating pressure (half or less of that of the totally porous particles) producing less frictional heating, which combined with the increased thermal conductivity of their non-porous core, gives more efficient heat dissipation. However, the effects of frictional heating for sub-2 μm columns are considerably exaggerated when using pure ACN as mobile phase, as it has a thermal conductivity 3 times less than that of pure water, leading to poorer heat dissipation. Overloading is already problematic for ionised solutes, a group which contains many pharmaceuticals and compounds of clinical relevance, on conventional columns (5 μm porous particles). However, it becomes a more serious issue for both new column types, partially as a result of their very high efficiency, which concentrates the sample as a very narrow band. The sample capacity of one type of shell particle was estimated to be 60% of that of the small totally porous particles, in line with the fraction of the particle volume that is porous. Due to overloading, it is barely possible to achieve perfect peak symmetry for ionised acids or bases with either of these new column types, even by injecting the lowest amounts of sample detectable by UV. While ammonium formate and potassium phosphate buffers gave similar results in overloading studies, use of formic acid as sole mobile phase additive is not recommended for these solutes, as its ionic strength is too low, leading to a catastrophic deterioration in efficiency when sample concentrations of even a few mg/L are injected.     

Jahn-Teller effect in trigonal μ-oxoclusters

A theory of the Jahn-Teller effect in trinuclear Cr^III and Fe^III -oxocomplexes based on the generalized angular overlap model is developed. The central bridging O atom is not localized at the center of the triangle formed by the metal atoms. Rather, it executes a free or hindered motion along a circular groove of radius 0.05–0.1 . The theory provides a qualitative explanation for apparent discrepancy between the X-ray structural data and the results of the heat capacity, magnetic susceptibility, and inelastic neutron scattering measurements. Namely, X-ray structural data correspond to a regular triangle symmetry while other data correspond to an equilateral or even irregular triangle symmetry.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2375–2380, November, 2004.     

The μ3 model of acids and bases: extending the Lewis theory to intermetallics

A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of μ(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system.     

An unexpected tetranuclear Li2Cr2 trimethylsilylacetylide complex bridged by two μ3-pyrazolates

A tetranuclear Li 2 Cr 2 acetylide precursor complex, [Li(Tp)CrⅢ (C≡CSiMe 3 ) 2 (μ3 -pz)] 2 ·(n-pentane) 2 (Tp = hydridotris(pyrazolyl)borate, pz = pyrazolate) (1) has been synthesized and characterized. The X-ray structure analysis shows that the complex contains a Li2Cr2 core bridged by two μ3 -pyrazolates. The magnetic data exhibit the existence of weak antiferromagnetic interaction in the cluster.     

Effect of fluorine ions on 2.7 μm emission in Er3+/Nd(3+)-codoped fluorotellurite glass

The 2.7 μm emission properties of Er(3+)/Nd(3+)-codoped fluorotellurite glasses were investigated in the present work. The thermal stability, refractive index, absorption and transmission spectra, and emission spectra were measured and investigated. The 2.7 μm emission in Er(3+)/Nd(3+)-codoped fluorotellurite glasses was enhanced with the increase of fluorine ions. The Judd-Ofelt analysis based on absorption spectra was performed in order to determine the Judd-Ofelt intensity parameters Ωt (t = 2, 4, 6), spontaneous emission probability, radiative lifetime and branching ratios of Er(3+):(4)I(11/2) → (4)I(13/2) transition. It is found that the Er(3+)/Nd(3+)-codoped fluorotellurite glass possesses a lower spontaneous transition probability A (58.95 s(-1)) but a higher branching ratio β (15.72%) corresponding to the stimulated emission of Er(3+):(4)I(11/2) → (4)I(13/2) transition. Additionally, the transmittance was also tested and reached a maximum when the molar concentration of ZnF(2) is 15%. The presence of fluorine ions greatly decreases the population of OH(-) groups, which affects the 2.7 μm emission effectively by means of decreasing the rate of energy transfer to impurities (e.g., OH(-) groups).     

Tm3+掺杂锗镓酸盐玻璃的2 μm中红外光谱特性

用高温熔融法制备了Tm2O2掺杂浓度分别为1.526%,3.006%,5.836%,11.028%,15.678%(质量分数,以下同)的65GeO2-12Ga2O3-10BaO-8Li2O-5La2O3(摩尔比)玻璃.从其吸收光谱特性出发,应用Judd-Ofelt理论,计算了Tm3+离子的J-O强度参数(Ω2,Ω4,Ω6)及Tm3+离子各激发态能级的自发跃迁几率、荧光分支比以及辐射寿命等光谱参量.在808 nm波长光的激发下,研究了不同Tm3+掺杂浓度玻璃在～1.47 μm与～1.8 μm的荧光特性,发现当Tm2O3掺杂浓度约达到～3.006%时,在1.8 μm处的荧光强度达最大;然后随着掺杂浓度的增大,其荧光强度反而降低.本文从Tm3+离子间的能量交叉弛豫效应与浓度猝灭效应解释了这一荧光强度变化的现象.同时,根据Mc-Cumber理论,计算了Tm3+离子能级3F4→3H6(1.8 μm)跃迁的吸收截面和受激发射截面,该荧光的受激发射截面峰值比氟锆铝酸盐玻璃大.由于该玻璃材料表现出较好的光谱性能,因此该材料可望成为～2.0 μm波段中红外光纤激光器的候选基质材料.     

Small Diameter (3 μm), Large Pore (1500 Å) Octadecylsilica for Capillary Electrochromatography

An ODS packing material was specially designed for CEC to achieve high efficiency. The size of the particles was approximately 3.2 m based on scanning electron microscopy, and the average pore size of the particles was 1500 Å by mercury intrusion porosimetry measurement. The packing materials were used in sol-gel bonded continuous-bed columns. The performance of columns containing these 3 m, 1500 Å ODS particles was evaluated for CEC and compared to 3 m, 80 Å ODS particles. The electroosmotic velocity (EOF) for the 1500 Å ODS material was slightly greater than that for the 80 Å ODS material. An efficiency of 410,000 plates m^–1 was obtained for unretained thiourea with a 30 cm × 75 m i.d. 1500 Å ODS column, which was more than 2 times higher than the efficiency obtained from the 80 Å ODS column.Dedicated to Professor K. Jinno on the occasion of his 60th, birthday.     

Expansion Reaction of μ-FcCCHCo_2(CO)_6 with Benzylideneacetonetricarbonyliron, and Molecular Structure of μ_3-FcCHCFeCo_2(CO)_9

Alkyne-andvinylidene-bridgedclusters0fgeneraltype(p3-L)FeCo2(C0)9havebeensh0wntobeimPortantprecursorsforthesynthesisofchiralskelet0nclusters.Thesecompoundscanbepreparedfromalkyne-bridgeddicobaltcomPlexesandmetalcarbonylssuchasFe2(CO)9orFe,(C0),,,"'buttheyieldswerepoorduetoeasydec0mP0siti0nofthestartingmaterialinreactionconditions.Moreover,inordertostudythecooperativeinteractionsaswellasinductive/mesomericeffectSbetweentheferr0ceneunitandtransitionmetalclusterframework,thep3-FcCHCFeCo2(…     

Characterization of a 2.6 μm Kinetex porous shell hydrophilic interaction liquid chromatography column in supercritical fluid chromatography with a comparison to 3 μm totally porous silica

The first systematic study of the performance of a porous shell, hydrophylic interaction liquid chromatography (HILIC) column in supercritical fluid chromatography (SFC) is presented. Observed efficiency on 2.6-μm porous shell particles exceeded all reports using UHPLC on 100-mm long columns packed with <2-μm totally porous particles. A Kinetex 4.6 × 150 mm, 2.6 μm HILIC column significantly outperformed a 3 μm Luna totally porous silica of the same length and diameter. A 17 component, low molecular weight test mix, consisting of a range of small drug-like molecules was separated isocratically on each column, with similar selectivity, but the porous shell column required ½ the time (≈2 min vs. 4 min), with almost 50% higher efficiency. Even little retained compounds (k < 0.5) exhibited more than 30,000 plates under some conditions. Reduced plate heights were higher than previously reported on porous shell particles in both HILIC and rHPLC, with the lowest value of 1.62. Significant fronting was sometimes observed. The cause of the fronting was not determined. The least symmetrical peaks showed the highest apparent efficiency. Pressure drop at optimum velocity (2.5 ml/min) and low modifier concentrations was <60 bar, and only exceeded 250 bar at near double optimum flow and 65% modifier. Peak widths were mostly just over 0.01 min (20 Hz) wide. There was a loss of efficiency when the injection volume was increased. The chromatograph was shown to have extremely low extra-column dispersion, on the order of 5–10 μL², which is also the lowest reported in an SFC, in spite of using standard components. This is likely due to turbulent flow in the tubing and fittings.     

Heterobinuclear and heterotrinuclear transition-metal μ-allenyl complexes

Binuclear and trinuclear transition-metal -allenyl complexes—especially mixedmetal complexes—are reviewed. In recent years, a number of such compounds have been prepared by use of several synthetic methods. The most general of these methods, viz. reactions of metal propargyls and of the lower nuclearity metal allenyls with low-valent metal complexes such as metal carbonyls and platinum(0) compounds, are considered in some detail. The structures of the binuclear metal -¹,²- and -³,²-allenyl complexes and of the trinuclear metal ₃-¹,²,²-allenyl complexes—both triangular and open—are presented and compared. Trends in the¹H and¹³C NMR spectroscopic properties of these compounds are examined. Some aspects of reaction chemistry of the heteronuclear platinum-ruthenium -¹,²-allenyl complexes are presented.