基于块相关框架的多参考微扰理论和多参考耦合簇理论

传统单参考电子相关方法已经发展成熟,但很多时候无法正确描述共价键解离、双(多)自由基和激发态等电子之间相关性非常强的体系。近年来发展的多参考微扰理论和多参考耦合簇理论以多个行列式的线性组合为参考波函数,采用不同的方式有效考虑电子之间的动态相关,对强关联体系的描述取得了显著的改进。但根据理论出发点和精度要求的不同发展出了许多多参考理论,仍无一个公认的、令人满意的方案。本文将结合与常见电子相关方法在理论框架和计算精度上的比较,详细阐述块相关理论的基本原理,并介绍基于块相关的"另类"多参考电子相关方法。最后本文还简单展望了多参考电子相关方法今后的发展趋势。     

Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part IV. Derivatives with monodentate ligands and edge-bridging bidentate ligands

The fluxionality of [Ir₄(CO)₈(μ₂-CO)₃L] (L = Br^?, I^?, SCN^?, NO₂^?, P(4-ClC₆H₄)₃, PPh₃, P(4-MeOC₆H₄)₃, P(4-Me₂NC₆H₄)₃), as studied by 2D-¹³C-NMR in solution, is due to two successive scrambling processes: the merry-go-round of six basal CO's and CO bridging to alternative faces of the Ir₄ tetrahedron. The basicity of the ligand L has no significant effect on the activation parameters. The scrambling process of lowest activation energy in [Ir₄(CO)₇(μ₂-CO)₃(PMePh₂)₂] correspond to the two possible synchronous CO bridging about a unique face of the metal tetrahedron swapping the relative axial and radial positions of the ligands L. The disubstituted clusters [Ir₄(CO)₁₀(μ₂-L? L)] with one edge-bridging ligand have a ground-state geometry with three edge-bridging CO's (L? L = bis(diphenylphosphino)methane, bis(diphenylarsino)methane, bis(diphenylphosphino)propane) or with all terminal CO's (L? L = CH₃SCH₂SCH₃). In all cases, the fluxional process of lowest activation energy in the merry-go-round of six CO's about a unique triangular face. For the P and As donor ligands, this process is followed by the rotation of terminal CO's bonded to two Ir-atoms residing on the mirror plane of the unbridged intermediate.     

The role of chemometrics in single and sequential extraction assays: a review. Part II. Cluster analysis, multiple linear regression, mixture resolution, experimental design and other techniques

Single and sequential extraction procedures are used for studying element mobility and availability in solid matrices, like soils, sediments, sludge, and airborne particulate matter. In the first part of this review we reported an overview on these procedures and described the applications of chemometric uni- and bivariate techniques and of multivariate pattern recognition techniques based on variable reduction to the experimental results obtained. The second part of the review deals with the use of chemometrics not only for the visualization and interpretation of data, but also for the investigation of the effects of experimental conditions on the response, the optimization of their values and the calculation of element fractionation. We will describe the principles of the multivariate chemometric techniques considered, the aims for which they were applied and the key findings obtained. The following topics will be critically addressed: pattern recognition by cluster analysis (CA), linear discriminant analysis (LDA) and other less common techniques; modelling by multiple linear regression (MLR); investigation of spatial distribution of variables by geostatistics; calculation of fractionation patterns by a mixture resolution method (Chemometric Identification of Substrates and Element Distributions, CISED); optimization and characterization of extraction procedures by experimental design; other multivariate techniques less commonly applied.     

Isoindole Cycloadditions. Part III: The Synthesis of "Windscreen Wiper" and Other N-Bridged Cavity Systems

The thermal addition of N-carbobenzyloxyisoindole (N-Z isoindole) 11a, generated by the reaction of 3,6-di(2-pyridyl)-s-tetrazine 9 with N-Z 7-azabenzonorbornadiene 8a, onto dimethyl tricyclo[4.2.1.0^2.5]nona-3,7-diene-3,4-dicarboxylate 17 occurred site selectively at the cyclobutene -bond to form a stereoisomeric mixture of 1 : 1-adducts 18 and 19, in which the bent-frame isomer 19 was dominant (ratio 5 : 1). In contrast, N-benzyl tetrafluoroisoindole 11c reacted with 17 only under high-pressure conditions (14 kbar, RT, 4 days) to afford 1 : 1-adducts at the cyclobutene site, in which the extended-frame isomer 18c was dominant and the accompanying bent-frame product 19c reverted to starting materials soon after isolation. These same stereoselectivities were used to prepare "windscreen wiper" compound 28c having two mobile N-benzyl substituents attached to a rigid scaffold by the reaction of N-benzyl tetrafluoroisoindole 11c with tetramethyl tetracyclo[4.4.1.0.^2,5.0^7.10]undeca-3,8-diene-3,4,7,8-tetracarboxylate 23. Cavity bis-(cyclobutene-1,2-diester) 6 reacted with N-benzyl tetrafluoroisoindole 11c twice over to produce cavity structure 36 with two O- and two N-benzyl bridges on the inner face, whereas the narrower cavity bis-alkene 32 stopped at the 1 : 1-addition stage. The dynamics of the Z-group in the dual adducts 26a–28a are discussed briefly and key adducts and cavity systems have been structurally evaluated by X-ray crystallography, VT NMR, and molecular modeling.     

Neutron activation and the JFK assassination, Part II. Extended benefits

The NAA of the bullets and fragments from the JFK assassination not only demonstrated that U.S. President John F. Kennedy and Texas Governor John B. Connally were hit by two and only two bullets, both from Lee Harvey Oswald's rifle, but offered a considerable number of extended benefits for understanding the assassination as well. The NAA eliminated all conspiracy theories that involved additional shooters or planted bullets. The NAA proved that none of the fragments were planted, that the rifle was fired that day (not planted), and that the locations of Kennedy's head wounds and back wound were not needed in order to get the right answer for the assassination. It supported the single-bullet theory and thus helped to provide the best-documented shooting scenario to date. It knits together the core physical evidence into an airtight case against Lee Oswald. It is, thus, the key to resolving the major controversies in the JFK assassination and putting the matter to rest. This revised version was published online in July 2006 with corrections to the Cover Date.     

The determination of some "toxic" metals in human liver as a guide to normal levels in New Zealand. Part II. Arsenic, mercury and selenium.

Results of analyses for arsenic, mercury and selenium in human livers considered to be representative of the population of New Zealand are reported. Procedures are described for the determination of the three elements in liver tissue by colorimetry, flameless atomic absorption spectrometry and spectrofluorimetry respectively.     

Neutron activation and the JFK assassination, Part I. Data and interpretation

Five lead fragments from bullet cores from the assassination of American President John F. Kennedy in 1963 were analyzed twice by NAA, first by the FBI in 1964 and then by Vincent P. Guinn in 1977. Their concentrations of Sb have provided invaluable information about the number and origin of bullets that hit Kennedy and Texas Governor John B. Connally. While both analyses appeared to group the fragments into a body shot and a head shot, the FBI set contained a systematic error and Guinn's results from quarters of test bullets showed that the indicator element Sb varied enough over quarters to potentially merge the groups. The latter problem was resolved by the FBI replicate analyses, which showed that antimony was nearly homogeneos on the small scales of the fragments, and by the mechanism by which jacketed bullets break when hitting bone, which generates tiny fragments from a single break near the middle of the lead core. They collectively meant that the fragments within each group were formed on the scale of subfragments. The two groups were just as they appear because the larger quarter-bullet heterogeneities did not apply. This result substantiates Guinn's original conclusion that two and only two bullets from Lee Harvey Oswald's rifle struck the two men. This revised version was published online in July 2006 with corrections to the Cover Date.     

Simultaneous determination of carbon,hydrogen, and nitrogen. Part II

Summary An analytical procedure is described which allows the simultaneous determination of carbon, hydrogen, and nitrogen in solid organic materials by gas-volumetric techniques. The accuracy is comparable to that obtained with the more conventional methods.On a routine basis, six to ten complete sets of determinations can be made per 8-hour day. The exact number will depend upon the samples being analyzed and the analyst's skill.

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Zusammenfassung Ein Verfahren zur gleichzeitigen gasvolumetrischen Bestimmung von Kohlenstoff, Wasserstoff und Stickstoff in festen organischen Verbindungen wird beschrieben. Die Genauigkeit ist mit jener der üblichen Verbrennungsverfahren vergleichbar.Bei Serienarbeit können in 8 Stunden sechs bis zehn vollständige Analysen ausgeführt werden. Die genaue Zahl hängt von der Art der Proben und von der Geschicklichkeit des Analytikers ab.

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Résumé On décrit un procédé analytique permettant de doser simultanément le carbone, l'hydrogène et l'azote dans les corps organiques solides au moyen de techniques fondées sur une mesure de volume gazeux. La précision est comparable à celle que l'on obtient avec les méthodes plus conventionnelles.On peut réaliser six à dix séries complètes de dosages en une journée de 8 heures, dans un travail de routine. Le nombre exact dépendra des échantillons que l'on analyse et de l'habileté de l'analyste.

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Part I, UCRL-5134, Chem. Abstr.52, 16 118c (1958).

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This work was performed under the auspices of the U. S. Atomic Energy Commission.     

Glyconothio-O-lactones Part II. Cycloaddition to Dienes,Diazomethane, and Carbenoids

The addition of dienes, diazomethane, and carbenoids to the manno- and ribo-configurated thio-γ-O-lactones 1 and 2 was investigated. Thus, 1 (Scheme 1) reacted with 2,3-dimethylbutadiene (→ 4 , 73%), cyclopentadiene (→ 5a/b 1:1, 70%), cyclohexa- 1,3-diene (→ 9a/b 2:3, 92%), and the electron-rich butadiene 6 (→ 7a/b 3:1, 82%). Wheras 5a/b was separated by flash chromatography, 7a/b was desilylated leading to the thiapyranone 8 . Selective hydrolysis of one isopropylidene group of 9a/b and flash chromatography gave 10a and 10b . The structures of the adducts were elucidated by X-ray analysis ( 4 ), by NOE experiments ( 4 , 5a , 5b , 7a/b , 10a , and 10b ), and on the basis of a homoallylic coupling ( 7a/b ). The additions occurred selectively from the ‘exo’ -side of 1 . Only a weak preference for the ‘endo’-adducts was observed. Hydrogenation of 9a/b with Raney-Ni (EtOH, room temperature) gave the thiabicyclo [2.2.2]octane 11 . Under harsher conditions (dioxane, 110°), 9a/b was reduced to the cyclohexyl ß-D C-glycoside 12 which was deprotected to 13 . X-Ray analysis of 13 proved that the desulfuration occurred with inversion of the anomeric configuration. The regioselective addition of the dihydropyridine 14 to 1 (Scheme 2) and the methanolysis of the crude adduct 15 gave the lactams 16a (32%) and 16b (38%). Desilylation of 15 with Bu₄NF · 3H₂O, however, gave the unsaturated piperidinedione 17 (92%) which was deprotected to the tetrol 18 (65%). Similarly, 2 was transformed via 19 (62%) into the triol 20 (74%). The cycloaddition of 1 with CH₂N₂ (Scheme 3) gave a 35:65 mixture of the 2,5-dihydro- 1,3,4-triazole 21 and the crystalline 4,5-dihydro 1,2,3-triazole 22 . Treatment of 21 and 22 with base gave the hydroxytriazoles 23 and 24 , respectively. The structure of 24 was established by X-ray analysis. The triazole mixture 21/22 was separated by prep. HPLC at 5°. At room temperature, 21 already decomposed (half-life 21.6 h) leading in CDCI₃ solution to a complex mixture (containing ca. 20–25% of the spirothiirane 27 and ca. 7–10% of its anomer) and in MeOH solution exclusively to the O,O,S-ortholactone 26 . Crystals of 22 proved be stable at 105°. Upon heating in petroleum ether at 100°, 22 was transformed into a ca. 1:1 mixture of 27 and the enol ether 28 . The reaction of 1 with ethyl diazoacetate (Scheme 4) in the presence of Rh₂(OAc)₄. 2H₂O gave the unsaturated esters 29 (33%) and 30 (26%), whereas the analogous reaction with diethyl diazomalonate afforded the spirothiirane 31 (68%) and the enol ether 32 (29%). Complete transformation of 31 into 32 was achieved by the treatment with P(NEt₂)₃. Similary, 33 (69%) was prepared from 2 .     

Cluster expansion of the wavefunction. Excited states

A method for excited states is given on the basis of the symmetry-adapted-cluster (SAC) expansion method. It is based on the fact that the SAC expansion method gives incidentally a set of excited functions which satisfies the Brillouin theorem with the ground state.     

The RuO4-catalyzed ketohydroxylation. Part 1. Development, scope, and limitation

A new straightforward oxidation of C,C-double bonds to unsymmetrical alpha-hydroxy ketones using catalytic amounts of RuCl(3) and stoichiometric amounts of Oxone under buffered conditions has been developed, a reaction for which we coined the expression "ketohydroxylation". The transformation allows the direct formation of alpha-hydroxy ketones (acyloins) from olefins without intermediate formation of syn-diols. The present paper will provide detailed information starting with the underlying concept and the subsequent development of the reaction. The effect of base, solvent stoichiometry, and temperature will be discussed resulting in an improved mechanistic model that might help to explain the influence of different reaction parameters on reactivity and selectivity in RuO(4)-catalyzed oxidations of C,C-double bonds. Furthermore, an improved workup procedure allows the recovery of the ruthenium catalyst by precipitation while simplifying the overall product purification. The second part of the paper focuses on exploration of scope and limitation. A variety of substituted olefins are oxidized to alpha-hydroxy ketones in good to excellent regioselectivities and yield. Cyclic substrates proved to be problematic to oxidize; however, a careful analysis of temperature effects resulted in the development of a successful protocol for the ketohydroxylation of cyclic substrates by simply decreasing the reaction temperature.     

Microbial metabolism. Part 8. The pyranocoumarin, decursin

Microbial transformation of the cancer chemopreventive agent, decursin (1) with Sepedonium chrysospermem (ATCC 13378) yielded two metabolites, (+)-decursinol (2) and (-)-cis-decursidinol (3). The structures were established by spectroscopic data.     

Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part V. Polysubstituted derivatives of [Ir4(CO)12]

The dynamic behaviour of twelve polysubstituted derivatives of [Ir₄(CO)₁₂] has been investigated in solution, using 2D-EXSY, and VT-³¹P- and ¹³C-NMR. [Ir₄(CO)₆(μ₂-CO)₃(η⁴-diarsine) PPh₃] and [Ir₄(CO)₆(μ₂-CO)₃(η⁴-nor-bornadiene)(PMePh₂)] exhibit two isomeric forms in solution, which interconvert through an intramolecular change of basal face. The related cluster [Ir₄(CO)₆(μ₂-CO)₃(η⁴-norbornadiene)PPh₃] exists as a single isomer in solution. It displays rotation of CO ligands about the apical Ir-atom, followed by two consecutive changes of basal face. The tetrasubstituted clusters with two chelating ligands [Ir₄(CO)₅(μ₂-CO)₃(η⁴-diolefin)₂] also exhibit rotation of apical CO's, the activation energy increases with greater steric hindrance of the radical ligands. A quantitative analysis of the ³¹P- and ¹³C-2D-EXSY spectra followed by simulation of the corresponding VT-NMR spectra of [IR₄(CO)₅(μ₂-CO)₃(μ₂-L)₂] (L = bis(diphenylphosphino)methane and 1,3-bis(diphenylphosphino)propane) revealed a pairwise averaging of the P-atoms, caused by two parallel changes of basal face averaging all CO ligands. In addition, the restricted rotation of ligands about the apical Ir-atom was identified at higher temperatures. The remaining clusters are either rigid on the NMR time scale, or display CO-scrambling about a single Ir-atom.     

Methylpyridylbenzimidazoles. Part I. Mono,bis-quaternary salts and related polymethyne dyes

The reaction of 2-(4-methyl-2-pyridyl)benzimidazole with long chain alkyl halides led to N-alkylation at the imidazole ring. The bases obtained were selectively quaternized at the azine and azole nitrogen atoms. The pyridinium salts gave the corresponding polymethyne dyes. Spectral (nmr and uv) and surface properties are briefly discussed.