Differential non-destructive image current detection in a fourier transform quadrupole ion trap

Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd.     

Kupferchalkogenid‐Clusterverbindungen mit nitro‐funktionalisierter Ligandenhülle

Copper Chalcogenide Cluster Compounds with Nitro‐functionalized Ligand Shell Three new copper chalcogenide cluster molecules, [Cu₄(SC₆H₄NO₂)₄(PPh₃)₄] ( 1 ), [Cu₄(SC₆H₄NO₂)₂(OAc)₂(PPh₃)₄] ( 2 ), and [Cu₂₂Se₆(SC₆H₄NO₂)₁₀(PPh₃)₈] ( 3 ), have been synthesized and characterized by single crystal X‐ray structure analysis. 1 and 2 were prepared from the reactions of Cu(OAc) and HSC₆H₄NO₂ in the presence of PPh₃ and have a similar “chair” structure in which two copper atoms are trigonally coordinated and two are tetrahedrally coordinated. The nitro groups of the ligands are not coordinated to any metal atom, but are located on the surface of the organic shell of the cluster molecules. In a further reaction between 2 and Se(SiMe₃)₂, cluster 3 was crystallized. Crystals of 3 include approximately 16.5 molecules THF per formula unit. This synthesis demonstrates the use of these “small” copper chalcogenide clusters as precursor compounds for the synthesis of bigger species. Non‐functionalized compounds similar to 1 and 2 are typically very pale or even colourless crystals. This is in contrast to the clusters presented in this work, which formed intensively orange or red crystals, due to the presence of the nitro groups. To investigate the influence of these nitro groups on the optical properties in more detail we have carried out UV‐VIS spectroscopic measurements.     

Copper(II) and zinc(II) complexes with 2-formylpyridine-derived hydrazones

In the present work 2-formylpyridine-para-chloro-phenyl hydrazone (H2FopClPh) and 2-formylpyridine-para-nitro-phenyl hydrazone (H2FopNO₂Ph) were obtained, as well as their copper(II) and zinc(II) complexes [Cu(H2FopClPh)Cl₂] (1), [Cu(2FopNO₂Ph)Cl] (2), [Zn(H2FopClPh)Cl₂] (3) and [Zn(H2FopNO₂Ph)Cl₂] (4). Upon re-crystallization in DMSO:acetone conversion of 2 into [Cu(2FopNO₂Ph)Cl(DMSO)] (2a) and of 4 into [Zn(2FopNO₂Ph)Cl(DMSO)] (4a) occurred. The crystal structures of 1, 2a, 3 and 4a were determined.     

Structure and stability of BN microclusters: Ab initio calculations for (BN)n (n = 2–4)

Unrestricted Hartree–Fock calcuations coupled with second-order Møller–Plesset correlation correction were performed to study the structures and energetics of microlusters. For (BN)₂, linear and rhombus forms are almost isoenergetic, whereas cyclic forms are preferable for (BN)₃ and (BN)₄ clusters. As a general trend, linear isomers prefer the triplet spin state, whereas cyclic isomers prefer the singlet spin state. Total charge density plots show a strong dominace of the B? N bond, indicating that the extent of its polar character becomes stronger with the increase in the cluster size. The loss of a BN monomer is shown to be the most likely fragmentation channel for both neutral and single-ionized clusters. We find that neutral (BN)_n clusters have the same structural configurations as those of their corresponding C_2n counterparts. This similarity follows the isoelectronic principle and is of importance due to recent interest in the investigations of BN fullerene analogs. © 1994 John Wiley & Sons, Inc.