Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

Thermodynamic studies of clathrate hydrates

Thermodynamic studies of clathrate hydrates, mainly of structures I and II, are considered in this review which is based on 147 references. There are two main subjects. The first is the host lattice energy and the guest-host interaction energy, both of these quantities being related to the enthalpy of dissociation and composition of the hydrates. The second subject concerns orientational ordering phenomena occurring in both host and guest, as reflected in the low temperature heat capacity. The classical theoretical treatment of clathrate formation has been reconsidered on the basis of recent experimental results. Particular emphasis has been given to orientational ordering since this topic is undoubtedly central to clarifying the nature of clathrate hydrates.Ausgehend von 147 Literaturangaben wurden in diesem Review thermodynamische Untersuchungen von Klathrathydraten hauptsächlich der Struktur I und II betrachtet. Es gibt zwei Hauptaugenmerke. Als erstes die Wirtsgitterenergie und die Gast-Wirt-Wechselwirkungsenergie, beide bezogen auf die Dissoziationsenthalpie und die Bildungsenthalpie der Hydrate. Das zweite Hauptaugenmerk betrifft Orientierungs-Konditionierungserscheinungen sowohl in Wirt als auch Gast, wie in den Wärmekapazitäten bei niedrigen Temperaturen widergespiegelt wird. Auf der Basis jüngster experimenteller Ergebnisse wurde die klassische theoretische Betrachtung über die Bildung von Klathraten überprüft. Der Orientierung-Konditionierung wurde besonderer Nachdruck verliehen, da dies zweifellos eine entscheidende Rolle bei der Klärung der Natur der Klathrathydrate spielt. 147 I II. . «» « — », . «» « », . . , .

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Contribution No. 155 from the Chemical Thermodynamics Laboratory.     

Rapid separation of phenylthiohydantoin amino acids: ambient pressure ion-mobility mass spectrometry (IMMS)

An electrospray ionization (ESI) ambient pressure ion-mobility spectrometer (APIMS) interfaced to an orthogonal reflector time-of-flight mass spectrometer (TOFMS) was evaluated for the first time as a detector for the identification of phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. The drift and flight times of the twenty common PTH amino acids were characterized by a well-defined 2-D mobility/mass spectral pattern. The combination of mobility/mass modes of analysis gave rise to a unique trend-line formation for the series of PTH amino acids. In addition, each PTH amino acid had a unique reduced mobility constant K(o), thus enabling the differentiation of all the amino acid derivatives including the PTH-leucine and PTH-isoleucine isomers. More importantly it was shown that it was possible to resolve a complete reference mixture of PTH amino acids in a single experimental run in less than 1 min. Detection limits for the PTH amino acids were found to range from 1.04 to 3.52 ng; indicating that the limits of detection were less than 17.0 pmol for all of the PTH amino acids.     

Synthesis,crystal structure and luminescent property of a novel H<Subscript>2</Subscript>O-bridged cobalt(II) polymer with one-dimensional chain structure

The coordination compound [Co(C₁₀H₇COO)₂(H₂O)₃]_2n · 4nH₂O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions. The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can be assigned to the intraligand electronic transfer.     

Conversion of 3-benzoyl-1-methyl-4-phenyl-γ-piperidol by arylamines and arylhydrazines. Synthesis of 3-arylamino-1-oxo-1-phenylpropanes and 1,3-diarylpyrazoles and their fragmentation under electron impact

It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007.     

The Effect of Alkane Chain Length on the Liquid–Liquid Critical Temperatures of Oligostyrene/Linear-Alkane Mixtures

Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N ₁=5) to pentacontane (N ₁=50)) with an oligostyrene (1241amu, N ₂=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains.     

Preliminary calculations on excited states of the oxygen molecule

It is well known that the energy interval separating ³ _u ^– and ³ _u ⁺ states of O₂, as given by the conventional ASMO method, is too large. In order to resolve this difficulty, removal of the equivalence restrictions usually employed in the orbital theory is proposed. Thus the orbital exponent of one antibonding _g MO is allowed to take a different value from the other _g's. Variational calculations show that the resulting outermost orbital is much more diffuse than the others. This model of a single diffuse orbital brings about a considerable energy lowering for the ³ _u ^– state and thus the agreement of the ³ _u ^– - ³ _u ⁺ interval with experiment is improved.

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Zusammenfassung Die konventionelle ASMO-Theorie liefert bekanntlich eine viel zu große Differenz der Terme ³ _u ^– und ³ _u ⁺ von O₂, weswegen der Vorschlag gemacht wird, die üblicherweise vorgenommene Äquivalenz-Einschränkung fallen zu lassen. Der Orbital-Exponent eines lockernden MO's kann von dem der übrigen _g's abweichen. Rechnungen zeigen, daß das äußerste MO viel diffuser als die anderen ist und daß die Energie des ³ _u ^– -Zustandes beträchtlich erniedrigt wird.

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Résumé La séparation entre les états ³ _u ^{– 3} _u ⁺ de O₂ donnée par la méthode ASMO conventionnelle est connue pour être trop grande. Afin de résoudre cette difficulté la levée des restrictions d'équivalence ordinairement utilisées est proposée. Ainsi l'exposant orbital d'une des orbitales moléculaires antiliantes _g peut prendre une valeur différente de celui de l'autre orbitale antiliante _g. Des calculs variationnels montrent que l'orbitale la plus haute ainsi obtenue est beaucoup plus diffuse que les autres. Ceci a pour effet de diminuer considérablement l'énergie de l'état ³ _u ^– , améliorant la séparation entre les états ³ _u ^– et ³ _u ⁺ .

     

Formulation study for lansoprazole fast-disintegrating tablet. II. Effect of triethyl citrate on the quality of the products

The purpose of this study was to develop enteric-coated microgranules for the lansoprazole fast-disintegrating tablet (LFDT), which is a rapidly disintegrating tablet containing enteric-coated microgranules. In our previous study, it was clarified that sufficient flexibility of the enteric layer was achieved by the optimized combined ratio of methacrylic acid copolymer dispersion to ethyl acrylate-methyl methacrylate copolymer dispersion and adding the optimized concentration of triethyl citrate to reduce the damage during the compression process. However, since triethyl citrate has an unpleasant bitter taste and is especially incompatible with lansoprazole, it adversely affects the taste and stability of lansoprazole in the enteric-coated microgranules. The enteric layer containing macrogol 6000 was proven useful to improve the unpleasant bitter taste and stability of lansoprazole, because macrogol 6000 does not have an unpleasant bitter taste and is more compatible than triethyl citerate. By covering the inner (first enteric layer) and outer side (third enteric layer) of the enteric layer containing triethyl citrate (second enteric layer) with the enteric layer containing macrogol 6000, we resolved the stability problem of lansoprazole and the unpleasant bitter taste. Finally, we developed enteric-coated microgranules comprising seven layers: 1) core, 2) active compound layer, 3) intermediate layer, 4) first enteric layer, 5) second enteric layer, 6) third enteric layer, and 7) over coating layer. The enteric-coated microgranules have the multiple functions of reducing the damage to the enteric layer during the compression process, improving the stability of lansoprazole, and masking the unpleasant bitter taste.     

Experiments in Solving Mixed Integer Programming Problems on a Small Array of Transputers

The time-consuming process of solving large-scale Mixed Integer Programming problems using the branch-and-bound technique can be speeded up by introducing a degree of parallelism into the basic algorithm. This paper describes the development and implementation of a parallel branch-and-bound algorithm created by adapting a commercial MIP solver. Inherent in the design of this software are certain ad hoc methods, the use of which are necessary in the effective solution of real problems. The extent to which these ad hoc methods can successfully be transferred to a parallel environment, in this case an array of at most nine transputers, is discussed. Computational results on a variety of real integer programming problems are reported.     

The microwave spectrum of thioformaldehyde,CD2S,and CH2S: Average structure,dipole moments,and 33S quadrupole coupling

Microwave transitions up to J = 53 in the ground vibrational state of deuterothioformaldehyde, CD₂S, were studied between 8 and 40 GHz. A detailed centrifugal distortion analysis yields accurate constants for comparison with force field values. The isotopic species ¹³CH₂S, CH₂³⁴S, CH₂³³S, ¹³CD₂S, CD₂³⁴S, and CD₂³³S were studied in natural abundance. Accurate average zero-point structures were determined for both CD₂S and CH₂S:

$\text{CH}{}_2\text{S}\text{CS}\text{=1.6138(4)}\text{CH}\text{= 1.0962(6)}\text{A}\text{?}\text{∠}\text{HCH}\text{=116° 16(6)′,}\text{CD}{}_2\text{S}\text{CS}\text{=1.6136(4)}\text{CD}\text{= 1.0931(4)}\text{A}\text{?}\text{∠}\text{DCD}\text{=116° 25(5)′}$

Changes in the zero-point geometry for deuterium substitution were established. Quadrupole fine structure arising from the ³³S nucleus has been measured in CH₂³³S and CD₂³³S. Analysis gives the following coupling constants (for both molecules) as χ_aa = ?11.7 and χ_bb - χ_cc = 88.1 MHz. The dipole moment of CD₂S was measured to be 1.6588(8)D and an accurate comparison with CH₂S was made; the ratio of dipole moments $\text{CD}{}_2\text{S}\text{CH}{}_2\text{S}$ was found to be 1.0062(4). The spectroscopic and bonding properties of CH₂S will be compared with formaldehyde and other molecules.