Template reactions with polynuclear complexes. The reaction of [Mo2(O2CCF3)4(PR3)2] (R = Ph, Et) with 2-aminobenzaldehyde

The binuclear molybdenum(II) complexes [Mo₂(O₂CCF₃)₄(PR₃)₂] (R = Ph, Et) act as templates for the self-condensation of 2-aminobenzaldehyde to give a new class of complexes in which a hydride ion bridges two molybdenum(III) centres, each of which carries a tetradentate macrocyclic ligand (C). The new hydrido complexes [Mo₂(C)₂ (H)(O₂CCF₃)₃(PPh₃)₂] (I), [Mo₂(C)₂(H)₂(O₂CCF₃)₂(PPh₃)₂] (II), and [Mo₂(C)₂ (H)₂(O₂CCF₃)₂(PEt₃)₂]₂ (V) exist in two or more isomeric forms as shown by their IR, ¹H, ³¹P and ¹⁹F NMR spectra. Substitution with thiocyanate, nitrate and tetraphenylborate anions gives the new products [Mo₂(C)₂(H)(CO)(NCS)₃(PPh₃)₂] (III), [Mo₂(C)₂ (H)₂(O₂CCF₃)(NO₃)(PPh₃)₂] (IV), [Mo₂(C)₂(H)(O₂CCF₃)(PPh₃)₂](BPh₄)₂ (VI) and [Mo₂(C)₂(H)₂(O₂CCF₃)(PEt₃)₂](BPh₄) (VII), which also exist in isomeric forms.     

The infrared spectra of imidazole complexes of first transition series metal(ii) nitrates and perchlorates

The IR spectra (4000–4140 cm^?1 ) of the twelve imidazole (Him) complexes [M(Him)₆] (NO₃)₂ (M = Co, Ni, Zn); [M(Him)₆](ClO₄)₂ (M = Mn, Fe, Co, Ni); [Zn(Him)_s](ClO₄)₂; [Cu(Him)₄X₂] (X = NO₃, ClO₄); [Zn(Him)₄(NO₃)₂]; [Zn(Him)₄](ClO₄)₂ and their deuterated analogues are discussed. The ratio between the frequencies of corresponding bands in the deuterated and undeuterated species is used to assign the internal imidazole vibrations. The internal modes of the NO₃^? and ClO₄^? ions are discussed in relation to the known or proposed structures of the complexes. The metal-ligand vibrations are assigned on the grounds of the shifts which occur on imidazole deuteration and metal ion substitution.     

N(2)O(5) reaction on submicron sea salt aerosol: kinetics, products, and the effect of surface active organics

The reaction of N(2)O(5) on sea salt aerosol is a sink for atmospheric nitrogen oxides and a source of the Cl radical. We present room-temperature measurements of the N(2)O(5) loss rate on submicron artificial seawater (ASW) aerosol, performed with an entrained aerosol flow tube coupled to a chemical ionization mass spectrometer, as a function of aerosol phase (aqueous or partially crystalline), liquid water content, and size. We also present an analysis of the product growth kinetics showing that ClNO(2) is produced at a rate equal to N(2)O(5) loss, with an estimated lower limit yield of 50% at 50% relative humidity (RH). The reaction probability for N(2)O(5), gamma(N(2)(O)(5)), depends strongly on the particle phase, being 0.005 +/- 0.004 on partially crystalline ASW aerosol at 30% RH and 0.03 +/- 0.008 on aqueous ASW aerosol at 65% RH. At 50% RH, N(2)O(5) loss is relatively insensitive to particle size for radii greater than 100 nm, and gamma(N(2)(O)(5)) displays a statistically insignificant increase from 0.022 to approximately 0.03 for aqueous ASW aerosol over the RH range of 43-70%. We find that the presence of millimolar levels of hexanoic acid in the aerosol bulk decreases the gamma(N(2)(O)(5)) at 70% RH by a factor of 3-4 from approximately 0.025 to 0.008 +/- 0.004. This reduction is likely due to the partitioning of hexanoic acid to the gas-aerosol interface at a surface coverage that we estimate to be equivalent to a monolayer. This result is the first evidence that a monolayer coating of aqueous organic surfactant can slow the reactive uptake of atmospheric trace gases to aerosol.     

The infrared spectra of imidazole complexes of platinum(II) halides and nitrite

Summary The i.r. spectra (4000-90 cm^–1) of the [Pt(Him)₄]X₂ complexes (Him = imidazole, X = Cl, Br or I) andcis- andtrans-[Pt(Him)₂X₂] (X = Cl, Br, I or NO₂) and their D₃-labelled analogues have been determined. The distinction between the ring and C-H (or N-H) modes of imidazole is based on the relative shifts which these bands undergo on D₃-labelling. Assignments, based on the effects of imidazole deuteriation and halide substitution, are provided for the v(Pt-Him) and v(Pt-X) modes.     

The oxidation of oleate in submicron aqueous salt aerosols: evidence of a surface process

We have studied the oxidation of submicron aqueous aerosols consisting of internal mixtures of sodium oleate (oleic acid proxy), sodium dodecyl sulfate, and inorganic salts by O3, NO3/N2O5, and OH. Experiments were performed using an aerosol flow tube and a continuous flow photochemical reaction chamber coupled to a chemical ionization mass spectrometer (CIMS). The CIMS was fitted with a heated inlet for volatilization and detection of organics in the particle phase simultaneously with the gas phase. A differential mobility analyzer/condensation particle counter was used for determining aerosol size distributions. The oxidation of oleate by O3 follows Langmuir-Hinshelwood kinetics, with gammaO3 approximately 10(-5) calculated from the observed loss rate of oleate in the particle phase. The best fit Langmuir-Hinshelwood parameters are kImax=0.05+/-0.01 s-1 and KO3=4(+/-3)x10(-14) cm3molec-1. These parameters showed no dependence on the ionic composition of the aerosols or on the presence of alkyl surfactants. Several ozone oxidation products were observed to be particle-bound at ambient temperature, including nonanoic acid. We observed efficient processing of oleate by OH (0.1相似文献   

Dynamic combinatorial selection of molecules capable of inhibiting the (CUG) repeat RNA-MBNL1 interaction in vitro: discovery of lead compounds targeting myotonic dystrophy (DM1)

Myotonic dystrophy type 1 (DM1), the most common form of muscular dystrophy in adults, is an RNA-mediated disease. Dramatically expanded (CUG) repeats accumulate in nuclei and sequester RNA-binding proteins such as the splicing regulator MBNL1. We have employed resin-bound dynamic combinatorial chemistry (RBDCC) to identify the first examples of compounds able to inhibit MBNL1 binding to (CUG) repeat RNA. Screening an RBDCL with a theoretical diversity of 11 325 members yielded several molecules with significant selectivity for binding to (CUG) repeat RNA over other sequences. These compounds were also able to inhibit the interaction of GGG-(CUG)(109)-GGG RNA with MBNL1 in vitro, with K(i) values in the low micromolar range.     

Catalytic metallonitrene/alkyne metathesis: a powerful cascade process for the synthesis of nitrogen-containing molecules

A conceptually novel metallonitrene/alkyne metathesis cascade reaction has been developed for the construction of nitrogen-containing compounds from simple alkyne starting materials. Rhodium(II) tetracarboxylate salts are efficient catalysts for this reaction, in which an electrophilic rhodium nitrene is trapped by an alkyne, resulting in the formation of a new C-N bond and the generation of a reactive metallocarbene for cascade reaction. The reaction is tolerant of both alkyl and aryl substituents on the alkyne, and proceeds at room temperature in a variety of common solvents. The modular nature of the reaction allows for the rapid construction of congested bicyclic systems from remarkably simple alkyne starting materials.     

Synchrotron radiation studies of mass-selected Fe nanoclusters deposited in situ

A portable UHV-compatible gas aggregation cluster source, capable of depositing clean mass-selected nanoclusters in situ, has been used at synchrotron radiation facilities to study the magnetic behaviour of exposed and Co-coated Fe clusters in the size range 250 to 540 atoms. X-ray magnetic circular dichroism (XMCD) studies of isolated and exposed 250-atom clusters show a 10% enhancement in the spin magnetic moment and a 75% enhancement in the orbital magnetic moment relative to bulk Fe. The spin moment monotonically approaches the bulk value with increasing cluster size but the orbital moment does not measurably decay till the cluster size is above ∼ 400 atoms. The total magnetic moments for the supported particles though higher than the bulk value are less than those measured in free clusters. Coating the deposited particles with Co in situ increases the spin moment by a further 10% producing a total moment per atom close to the free cluster value. At low coverages the deposited clusters are super-paramagnetic at temperatures above 10 K but a magnetic remanence at higher temperature emerges as the cluster density increases and for cluster films with a thickness greater than 50 ?(i.e. 2-3 layers of clusters) the remanence becomes greater than that of an Fe film of the same thickness produced by a conventional deposition source. Thick cluster-assembled film show a strong in-plane anisotropy. Received 14 December 2000     

Growth of copper and palladium on α-Al2O3(0001)

Non-contact atomic force microscopy (NC-AFM) has been used to image the room-temperature growth of copper and palladium on the (1×1) and terminations of α-Al₂O₃(0001). Three-dimensional (3D) clusters of palladium are observed on both the (1×1) and the terminations, with 3D clusters of copper observed on the reconstructed surface. There is evidence of step-edge-dominated growth of palladium on the termination.     

Bis­[N,N′‐bis(2,4,6‐tri­methyl­phenyl)‐1,2‐ethanediyl­idenedi­amine]copper(I) tetra­fluoro­borate

In the title compound, [Cu(C₂₀H₂₄N₂)₂]BF₄, the complex cation adopts a distorted tetrahedral structure, the dihedral angle between the least‐squares planes of the chelating ligand backbones being 51.1 (2)°. This flattening of the tetrahedral coordination sphere may be driven by the presence of intramolecular π–π stacking interactions between mesityl groups on adjacent ligands.