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151.
Pentacarbonyl-rhenate and -manganate react with the cationic complexes [cpMo(CO)2(diene)]+, [cpMo(CO)2(cyclopentadiene]+, [cpMo(CO)2(cyclohexadiene)]+, [cpMo(CO)2(trimethylenemethane]+, [(OC)3Mo(η7-C7H7)]+, [cp(OC)-(Ph3P)Mo(alkyne)]+ to give the corresponding heteronuclear hydrocarbon-bridged complexes. 相似文献
152.
Gadolinium dicyanamide dihydrate Gd[N(CN)2]3 · 2 H2O was prepared by ion exchange in aqueous solution followed by evaporation of the solvent at room temperature. Gd[N(CN)2]3 · 2 H2O was characterized by single‐crystal structure analysis, FTIR spectroscopy and DSC analysis. In the crystal there are three crystallographically independent [N(CN)2]? ions and Gd3+ which are coordinated by six N atoms from six different [N(CN)2]? ions and two O atoms from two water molecules forming an irregular quadratic antiprism. Four H bonds have been identified in the structure of Gd[N(CN)2]3 · 2 H2O, two of them running to terminal N atoms and two to the bridging N atoms of dicyanamide ions (Gd[N(CN)2]3 · 2 H2O: P21/n (no. 14), a = 7.4845(15) Å, b = 11.529(2) Å, c = 13.941(3) Å, β = 93.98(3)°, Z = 4, 1948 reflections, 175 parameters, R1 = 0.0493). The DSC analysis indicates that Gd[N(CN)2]3 · 2 H2O looses the crystal water at temperatures around 130 – 140 °C forming anhydrous Gd[N(CN)2]3, the structure of which has been refined by the Rietveld method based on X‐ray powder diffraction data. Gd[N(CN)2]3 was found to be isotypic with Ln[N(CN)2]3 (Ln = La, Ce, Pr, Nd, Sm and Eu) which previously have been described in the literature. 相似文献
153.
Patra S Sarkar B Ghumaan S Patil MP Mobin SM Sunoj RB Kaim W Lahiri GK 《Dalton transactions (Cambridge, England : 2003)》2005,(7):1188-1194
The isomeric title complexes were obtained in almost equimolar ratio from the reaction of Ru(trpy)Cl3 and L. Crystal structure analyses of the perchlorate hemihydrates, electrochemical and spectroscopic (NMR, UV/VIS, EPR) studies, supported by DFT calculations, reveal distinct differences between the isomeric redox series [1]n+(tetrazine-Nt trans to Cl) and [2]n+(pyrazolyl-Np trans to Cl; n= 0, 1, 2). The latter system with the pi acceptors trpy and tetrazine in the equatorial plane and the pyrazolyl and chloride donors in the axial positions exhibits facilitated oxidation, lower energy MLCT transitions, more balanced chelate coordination, and a higher g anisotropy in the oxidised (RuIII) state. According to partially resolved EPR spectra of one-electron reduced neutral compounds and they have the unpaired electron predominantly in the tetrazine ring of L. 相似文献
154.
Intermolecular Diels-Alder additions of the readily available dienamides to various dienophiles proceeded in a regio- and stereoselective manner, allowing the preparation of complex anilides (), cyclohexenyl amides (, ) and bridged heterocycles (). 相似文献
155.
Alexander Kaiser Klaus K. Mayer Andreas Sellmer Wolfgang Wiegrebe 《Monatshefte für Chemie / Chemical Monthly》2003,43(11):343-354
The molecular ion 1 of N-(n-propoxy)benzaldimine I rearranges by an 1,5-H-shift to the δ-distonic ion 2 which subsequently cyclizes to the α-distonic ion 3. Homolytic cleavage of the N–O bond in 3 results in the δ-distonic ion 4 which expels CH2O leading to the β-distonic ion 5. Ion 5 is also formed from the molecular ions of tetrahydrooxazines II and III and from M+• of phenylazetidine IVa. In a subsequent step, ion 5 cyclizes to the N-protonated 3,4-dihydroisoquinolinium ion 6. The syntheses of II–IV and their derivatives are described. 相似文献
156.
Haiss W Raisch P Schiffrin DJ Bitsch L Nichols RJ 《Faraday discussions》2002,(121):167-80; discussion 229-51
In situ FTIR spectroscopy has been used in the attenuated total reflectance (ATR) mode to investigate the surface chemistry of etching Si(100) surfaces in aqueous KOH. The effect of solution concentration and electrode potential on the Si-H vibrations has been explored and the experimental results compared with density functional theory calculations. In addition. the kinetics of surface passivation of n-Si(100) has been investigated using FTIR spectroscopy. 相似文献
157.
Su X Wu YJ Robelek R Knoll W 《Langmuir : the ACS journal of surfaces and colloids》2005,21(1):348-353
Surface plasmon resonance (SPR) spectroscopy is employed for the study of biotinylated DNA assembly on streptavidin modified gold surfaces for target DNA hybridization. Two immobilization strategies are involved for constructing streptavidin films, namely, (1) physical adsorption on biotin-containing thiol treated surfaces through biotin-streptavidin links and (2) covalent attachment to 11-mercaptoundecanoic acid (MUA) treated surfaces through amine coupling. To understand the structural properties of the streptavidin films, a quartz crystal microbalance with energy dissipation monitoring (QCM-D) is used to monitor the streptavidin immobilization procedures. The simultaneously measured frequency (Deltaf) and dissipation factor (DeltaD) changes, together with the SPR angle shifts (Deltatheta), suggest that the streptavidin film assembled on the biotin-containing surface is highly rigid with a well-ordered structure while the streptavidin film formed through amine coupling is highly dissipative and less structured. The subsequent biotinylated DNA (biotin-DNA) assembly and target hybridization results show that the streptavidin film structure has distinct effects on the biotin-DNA binding amount. On the streptavidin matrix, not only the probe DNA density but also the strand orientation mediated by the streptavidin films has distinct effects on hybridization efficiency. Particularly, the molecularly ordered streptavidin films formed on the biotin-containing surfaces ensure a well-ordered DNA assembly, which in turn allows for a higher efficiency in target DNA capture and for a higher sensitivity in the hybridization analysis when compared to the biotin-DNA assembled on the less structured streptavidin films formed through amine coupling. 相似文献
158.
Reversed-phase LC-MS/MS is used to determine major estrogenic alkylphenol ethoxylates (APEOs) and their biotransformation products. It allows the simultaneous analysis of eight APEOs, alkylphenoxy carboxylates (APECs) and alkylphenols (APs) in sewage treatment plant (STP) effluents in the same extract after solid-phase enrichment on polymeric Oasis HLB. As precursor ions, [APEO + NH4]+, [APEC - H]- and [AP - H]- were monitored. Instrumental limits of detection (LOD) were 2-600 pg, corresponding to sample concentrations of 0.04-12 ng l(-1), without correction for overall method recoveries. Matrix-induced signal suppression during electrospray ionisation (ESI) and extraction as well as overall method recoveries were assessed and the suitability of deuterated surrogates as internal standards was evaluated. 相似文献
159.
On the Synthesis of Derivatives of Pyrido[1,2-a]lazepine The conjugated pyridinium ylides of type 4 undergo 8π -electrocyclisation affording the heterobicyclic allenes 5 which, in the presence of H2O and H2O2, are subsequently transformed into the substituted pyrido[1,2-a]-azepinones 6, a novel heterocyclic system. The chemical behaviour of 6a,b is dominated by cleavage of the lactam bond and subsequent reaction to pyridinc and isoquinoline derivatives, respectively; e.g. reaction of 6a, b with 4,5-dihydro-4-methyl-3H-1,2,4-triazole-3,5-dione affords the cycloadducts 11 and 12 almost quantitatively. The successful transformation of 6b into 15 is described, the latter being the first representative of the presently unknown, potentially antiaromatic pyrido[1,2-a]azepine ( 1 ). 相似文献
160.
Rotational spectra of eight isotopomers of the weakly bound van der Waals complex CO-CH4 were recorded in the frequency range from 4 to 19 GHz using a pulsed molecular beam Fourier transform microwave spectrometer. For the isotopomers containing methane monomers of Td symmetry, namely, 12C16O-12CH4, 12C16O-13CH4, 12C16O-12CD4, 13C16O-12CH4, and 13C18O-12CH4, three rotational progressions were observed that correlate to the jm=0, 1, and 2 rotational levels of free methane. For those containing partially deuterated methane monomers with C3V symmetry, namely, 12C16O-12CH3D and 12C16O-12CHD3, only two progressions were recorded, correlating to the jk=0(0) and 1(1) rotational levels of free CH3D and CHD3, respectively. The van der Waals bond distance R, intermolecular stretching frequency nus, and the corresponding stretching force constant ks were derived from the obtained spectroscopic results. The results obtained for the jm=0 ground state are compared to the previous infrared and millimeter wave data. A 17O nuclear quadrupole coupling constant was determined from the resolved hyperfine structure of 13C17O-12CH4 and was used to obtain angular information about the carbon monoxide subunit. A Coriolis interaction was deduced from the irregular spectral pattern involving levels with jm=1. Qualitative information about the extent of the perturbation was obtained from a comparison of spectroscopic constants of different isotopomers. 相似文献