Photoelectron spectroscopy of silicon and germanium-fluorine binary cluster anions (SinF m − , GenF m − )

Electronic properties of silicon-fluorine and germanium-fluorine cluster anions (Si_nF _m ^? n = 1–9, m = 1–3, Ge_nF _m ^? ; n =1–9, m = 1–3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon/germanium rod in an He carrier gas mixed with a small amount of SiF₄ or F₂ gas. Comparison between photoelectron spectra of Si_nF^?/Ge_nF^? and Sin /Gen (n = 4–9) gives the insight that the doped F atom can remove one electron from the corresponding Sin _n ^? /Ge _n ^? cluster without any serious rearrangement of Sin/Gen framework, because only the first peak of Si _n ^? /Ge _n ^? , corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping     

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.     

Zur Kenntnis des m,m′-Divinylazobenzols und des m,m′-Divinylazoxybenzols

Ohne Zusammenfassung     

Synthesis and Characterizaiton of Poly（ether imide）s Containing m—Methyl and Phthalazinone Moieties

Three novel poly(ether imide)s were synthesized by one-step solution polymerization from 2-(3,4-dicarboxyl-N-phenyl)-4-(3‘‘‘‘‘‘‘‘,4‘‘‘‘‘‘‘‘-dicarboxly-phenoxyl-4-(2-methyl)-phenyl)-2,3-phthalazin-l-one dianhydride and three amines,and characterized.The polymers show good solubility and thermal properties.     

Theoretical Studies of the Electronic Structures and Spectrum Properties of Pt n Ni m (n + m = 7, n, m ≠ 0) Clusters

We studied Pt _n Ni _m (n + m = 7, n, m ≠ 0) clusters within the framework of the density functional theory (B3LYP) at the LANL2DZ level. The calculated results show that the Fermi levels are determined by the number of Pt atoms, which gain electrons from Ni atoms. Meanwhile, multifarious orbital hybridization is found in the frontier molecular orbital, and the more platinum or nickel atoms, the smaller energy gap it has. Moreover, the calculated IR and Raman spectrum indicates the aromatic character, which is vital for transitional metal clusters.     

Graphene oxide-octadecylsilane incorporated monolithic nano-columns with 50 μm id and 100 μm id for small molecule and protein separation by nano-liquid chromatography

In this study, graphene oxide-octadecylsilane incorporated monolithic nano-columns were developed for protein analysis by nano liquid chromatography (nano LC). The monolithic column with 100 μm id was first prepared by an in situ polymerization using ethylene dimethacrylate (EDMA), 3-chloro-2-hydroxypropylmethacrylate (HPMA-Cl), and methacryloyl graphene oxide nanoparticles (MGONPs). MGONPs were synthesized by the treatment of 3-(trimethoxysilyl)propylmethacrylate (TMSPM) and GO. Tetrahydrofuran (THF) and dodecanol were used as the porogenic solvent. The resulting column was functionalized by dimethyloctadecylch lorosilane (DODCS) for the enhancement of hydrophobicity. The functionalization greatly improved the baseline separation of hydrophobic compounds such as polyaromatic hydrocarbons (PAHs). The optimized monolith with respect to total polymerization mixture was characterized by using Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) X-ray diffraction (XRD) and chromatographic analyses. The blank monoliths without functionalization exhibited poor separation while a good separation performance of MGONPs functionalized monoliths was achieved. The monolith with 100 μm id was evaluated in protein separation in nano LC using RNase A, Cytochrome C, Lysozyme, Trypsin, and Ca isozyme II as the test proteins. It was shown that protein separation mechanism was based on large π-system of GO and hydrophobicity of the monolithic structure. Theoretical plates number up to 57 600 plates were achieved. The nano-column with 50 μm id was also prepared using the same polymerization mixture under the same chemical conditions. These nano-columns were employed for protein separation by nano LC, and the dependence of both nano-column performance on the internal diameter was also discussed.     

Structure of carbon fluorochlorides CF n Cl m (n,m ≤ 3) and their singly charged negative ions

The electronic and geometrical structures of carbon fluorochlorides with low coordination numbers (n 3) and their singly charged anions are calculated using the functional density method. The results of the calculations are used to evaluate the electron affinities (EA) of the neutral compounds and the first ionization potentials of the anions as well as the energies of fragmentation through different decay channels of both series. The adiabatic EA of carbon fluorochloride CF _k Cl _3–k is shown to be determined mainly by the presence of a CX₂ unit in these compounds. There are no monotonic changes in stability of either the neutral compounds withn = 3 or the anions withn = 2 or 3 upon successive substitution of one halogen by another.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1044–1049, June, 1993.     

Synthesis and 1.1 μm near-infrared electrophosphorescence properties of a phenoxy-substituents copper phthalocyanine

A novel copper phthalocyanine bearing phenoxy-substituents was prepared and characterized by MS and Elemental analysis. Its UV/Vis absorption and photoluminescence (PL) spectra were investigated. Organic light-emitting devices (OLEDs) were demonstrated by employing this copper phthalocyanine doped into 4, 4′-N,N′-dicarbazole-biphenyl (CBP). Room-temperature electrophosphorescence was observed at about 1.1 μm due to transitions from the first excited triplet state to the singlet ground state (T ₁–S₀) of this CuPc. The intensity of NIR emission at lower doping concentrations (about 10 wt %) was extremely high compared with devices doped with fluorescent dyes. The results indicated that direct charge trapping appears to be the dominant mechanism. The article is published in the original.     

Comparison of LC Columns Packed with 2.6?��m Core-Shell and Sub-2?��m Porous Particles for Gradient Separation of Antibiotics

The recently introduced Kinetex C18 column packed with core-shell 2.6 ??m particles is declared to provide similar efficiency and short analysis as Acquity BEH C18 column with 1.7 ??m porous particles. Unlike Acquity BEH C18 column, Kinetex C18 column exhibited lower column backpressure making this column compatible to conventional LC systems. The performance of Kinetex C18 column (2.1 × 50 mm) and Acquity BEH C18 column (2.1 × 50 mm) for gradient separation of tetracyclines under acidic conditions (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) and macrolides under alkaline conditions (tylosin, clarithromycin, roxithromycin, and carbomycin) was studied. The columns were compared by evaluation of their experimental peak capacity and its dependence on linear velocity and gradient slope. The maximal experimental peak capacities for analysis of tetracyclines were 51.8 (Acquity BEH C18 column) and 48.4 (Kinetex C18 column). This indicated that Kinetex C18 was a suitable alternative to Acquity BEH C18 column for the analysis of tetracyclines under acidic conditions. On the contrary, the maximal experimental peak capacities for analysis of macrolides on Acquity BEH C18 column was higher (46.7) than that on Kinetex C18 column (36.9). Moreover, application of Kinetex C18 column for the analysis of macrolides under alkaline conditions was limited with respect to its decreasing performance with growing number of injections on the column.     

Identification of acyl protein thioesterases 1 and 2 as the cellular targets of the ras-signaling modulators palmostatin b and m

Finding the target: Activity-based proteomic profiling probes based on the depalmitoylation inhibitors palmostatin?B and M have been synthesized and were found to target acyl protein thioesterase?1 (APT1) and 2 (APT2) in cells.     

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.     

Solvothermal syntheses,structures, and luminescence of two heterometallic metal-organic frameworks constructed from m -BDC ( m -BDC = 1,3-benzene-dicarboxylate)

The reactions of m-H₂BDC, NaOH with Cd(NO₃)₂?·?4H₂O and Co(NO₃)₂?·?4H₂O (m-BDC?=?1,3-benzene-dicarboxylate) in DMF gave two isostructural three-dimensional (3D) heterometallic coordination polymers: [CdNa(m-BDC)₂]?·?[NH₂(CH₃)₂] (1) and [CoNa(m-BDC)₂]?·?[NH₂(CH₃)₂] (2), respectively. The compounds were characterized by single-crystal X-ray diffraction, X-ray powder diffraction, ICP, TGA, IR, and photoluminescence spectroscopy. The crystal structures were determined by X-ray diffraction and refined by full-matrix least-squares methods to R?=?0.0221 and wR?=?0.0579 using 1925 reflections with I?>?2σ(I) for 1; and R?=?0.0654 and wR?=?0.1591 using 1881 reflections with I?>?2σ(I) for 2. Their frameworks are constructed from M–O–C (M?=?Na, Cd and Co) chains composed of alternating six-coordinate Na(I) centers and four-coordinate Cd(II) or Co(II) centers. These chains are further linked by m-BDC to form unusual 3D open-framework structures.     

Theoretical Study of Electronic Structure and Stability of Mixed AlmBn−mH n 2− and CmBn−mH n 2−m (n = 6, 10, 12 and m = 1, 2) Clusters

Density functional theory (DFT) method with B3LYP functional and 6-311++G(d,p) basis set has been used to predict the geometries, relative stabilities, electronic structures and bonding analysis of Mixed Al_mB_n?mH _n ^2? and C_mB_n?mH _n ^2?m (n = 6, 10, 12 and m = 1, 2) clusters; being compared to the B_nH _n ^2? ones. Therefore, the DFT results suggest that the replacing of boron by aluminium or carbon is governed by Natural net charges following Gimar’s and Williams’s rules. The Al_mB_n?mH _n ^2? structures are relatively distorted compared to those of B_nH _n ^2? and C_mB_n?mH _n ^2?m . In Al_mB_n?mH _n ^2? structures Al atoms prefer the adjacent sites, however for the C₂B_n?2H_n cluster cages, the carbon atoms are positioned at diametrically opposed sites. The large HOMO–LUMO gaps show that the predicted clusters have chemical stabilities, principally, those of Al_mB_n?mH _n ^2? ones, which are not experimentally isolated. The optimized geometries obtained through boron substitution by Al and C lead to compactness and to contracted structures, respectively, where B–B bonds are the shortest in mono- and di-carbaboranes.     

Structural,Energetic, and Magnetic Properties of Ag$$_{}$$Rh$$_{m}$$m and Ag$$_{m}$$mRh$$_{}$$ Clusters with $$n \le 20$$n≤20 and $$m=0,1$$m=0,1

At first, a genetic algorithm in combination with either the parametrized density-functional tight-binding method or a Gupta-potential is used to determine the putative global minimum energy structures of mixed Ag\(_{n-m}\)Rh\(_{m}\) and Ag\(_{m}\)Rh\(_{n-m}\) clusters with \(n\le 20\) and \(m=0,1\). Subsequently, the resulting structures are re-optimized with a first-principles method. The results demonstrate that the exchange of a single silver atom by rhodium leads to compact core-shell-like structures with structural motifs well known from the Lennard-Jones system. For the systems of the present study, AgRh\(_{n-1}\) clusters retain their cube-based structural motif and the silver atoms typically avoid the corner positions within a cube if possible. Population analysis of both cluster systems shows that the total magnetic moment is mainly due to unpaired electrons on the rhodium atoms with a small ferro-magnetic contribution of the silver host in Ag\(_{n-1}\)Rh and virtually no contribution to the total magnetic moment from the single silver atom in AgRh\(_{n-1}\) clusters.     

Simultaneous production of89Zr and90,91m92mNb in α-particle activated yttrium and their subsequent separation by TOA

A study on the separation of lithium isotopes was carried out with an ion exchange resin having 1,7,13-trioxa-4,10,16-triazacyclooctadecane (N₃O₃) as an anchor group. The lighter isotope,⁶Li concentrated in the resin phase, while the heavier isotope,⁷Li is enriched in the fluid phase. Upon column chromatography [0.6 cm (I. D.)×20 cm (height)] using 1.0M ammonium chloride solution as an eluent, single separation factor, , 1.068 (⁶Li/⁷Li)_resin/(⁶Li/⁷Li)_solution was obtained by theGlueckauf method from the elution curve and isotope ratios.     

Investigation of Structures and Stabilities of AlmPn and AlmP(m+n=2～6)Clusters by DFT

The geometries,electronic states and energies of Alm Pn （ m + n = 2 ～ 6）neutral and anionic clusters have been investigated using the density functional theory（DFT）method of Becke’s three-parameter hybrid exchange functional with the nonlocal correlation of B3LYP. Structural optimization and frequency analyses are performed with the basis of 6-311G（ d）. The calculations predict the existence of a number of previously unknown isomers（i. e. ,Al3P_ and AlmPn （ m + n.5））. The calculations have also predicted that small AlP and（AlP）2 clusters adopt two-and three-dimensional structures characteristic of Si2 and Si4 clusters,while the structures of the larger AlP clusters are different completely from those of Sin clusters with the same electrons. The results show that the structures with the singlet have higher symmetries,while those with the doublet have lower symmetries. The vertical detachment energy of AlmPn （ m + n = 2 ～ 6）are also discused and the adiabatic electron affinities of AlmPn（m + n = 2 ～ 6）and also discussed at the same level. The results agree satisfactorily with the anion photoelectron spectroscopy of aluminum phosphide clusters reported recently by Gomez et al.     

Structurally nonrigid molecular complexes (HF)n(H2O)m (n + m ≥ 2) and their spectroscopic features

The problem of the formation and stability of structurally nonrigid, donor—acceptor molecular complexes is considered. These complexes are formed between the molecules of water and hydrogen fluoride, the latter being the hydrolysis product of the chemical, radiochemical, and metallurgical industrial wastes. Based on the results of ab initio quantum-chemical calculations of the potential energy surfaces by the Hartree—Fock—Roothaan method, the equilibrium configurations of the (H₂O) _n (HF) _m complexes (n : m = 1 : 1; 1 : 2; 2 : 1; 2 : 2; and 3 : 3) were determined. These configurations are necessary for correct interpretation of the IR absorption spectra and for routine remote monitoring of such environmentally hazardous complexes in the Earth atmosphere. The harmonic vibrational frequencies of the (H₂O) _n (HF) _m complexes (n + m 2) were calculated and the interaction energies between the monomers were found. The influence of UV radiation on the (H₂O) _n (HF) _n complexes (n = 1—3) upon the transition from the ground to the lowest excited singlet electronic state was studied. Characteristic spectroscopic features of the (H₂O) _n (HF) _m complexes were established.     

Joint photoelectron and theoretical study of (Rh(m)Co(n))⁻ (m=1-5, n=1-2) cluster anions and their neutral counterparts

Anion photoelectron spectroscopic experiments and calculations based on density functional theory have been used to investigate and uniquely identify the structural, electronic, and magnetic properties of both neutral and anionic (Rh(m)Co(n)) and (Rh(m)Co(n))(-) (m=1-5, n=1-2) clusters, respectively. Negative ion photoelectron spectra are presented for electron binding energies up to 3.493 eV. The calculated electron affinities and vertical detachment energies are in good agreement with the measured values. Computational results for geometric structures and magnetic moments of both cluster anions and their neutrals are presented.     

Formation of [M − nH + mNa](m−n)+ and [M − nH + mK](m−n)+ ions in electrospray mass spectrometry of peptides and proteins

The [M - nH + mNa](m-n)+ and [M - nH + mK](m-n)+ ions are common in the electrospray mass spectra of proteins and peptides. The feasibility of forming these ions in the gas phase via collision activation and/or ion-molecule reaction is investigated. Sodium and potassium affinities of the N-methylacetamide anion, the acetate anion, and the 1-propanamide anion have been calculated using density functional theory at the B3LYP/6-311+ +G(d,p) level of theory. These anions were chosen as models for the functional groups on a protein or peptide. These affinity values are then used to calculate reaction enthalpies of alkali hydroxides, chlorides, and hydrates with N-methylacetamide, acetic acid, the acetate anion, and 1-propanamine, model reactions that may lead to formation of the [M - nH + mNa](m-n) and [M - nH + mK](m-n)+ ions. It is found that a number of these reactions are exothermic or slightly endothermic (deltaH(o) < + 20 kcal/mol) and are accessible after collision activation in the lens region. The potential energy hypersurfaces of model reactions between NaOH and formamide as well as NaCl and formamide show relatively flat surfaces devoid of significant barriers.