Inclusion of nickel(<Emphasis Type="SmallCaps">II</Emphasis>) and copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with aliphatic polyamines in cucurbit[8]uril

The inclusion compound of macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex containing the tetraazamacrocyclic ligand cyclam, {[Ni(cyclam)]@CB[8]}Cl₂··16H₂O (1), and the inclusion compounds of CB[8] with the copper(II) bis-ethylene-diamine complex, {trans-[Cu(en)₂(H₂O)₂]@CB[8]}Cl₂·{CB[8]}·42H₂O (2a) and {trans-[Cu(en)₂(H₂O)₂]@CB[8]}Cl₂·17H₂O (2b), were synthesized and characterized by X-ray diffraction analysis, IR and ESR spectroscopy, and electrospray mass spectrometry. Guest—host inclusion compounds can be directly synthesized starting from a metal complex and cucurbit[8]uril, as was exemplified by the preparation of compounds 2a and 2b.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2414–2419, November, 2004.     

The effects of sample preparation methods on the variability of the electrospray ionization response for model drug compounds

A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd.     

Thermal transformations of the supramolecular compound of cucurbit[8]uril with cobalt(III) complex {<Emphasis Type="Italic">trans</Emphasis>-[Co(en)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>]@CB[8]}Cl·17 H<Subscript>2</Subscript>O

The thermal decomposition of hydrated cucurbit[8]uril C₄₈H₄₈N₃₂O₁₆·20H₂O (CB[8]) and the inclusion compound of cucurbit[8]uril with cobalt(III) complex {trans-[Co(en)₂Cl₂]@CB[8]}Cl·17 H₂O was studied in the inert atmosphere by TG, TM, and DSC methods. The dehydration of (C₄₈H₄₈N₃₂O₁₆)·20H₂O (at 320–390 K), and the decomposition of cucurbituril itself (at 620–720 K) are accompanied by a decrease in the sample volume. The inclusion compound loses water molecules at 320–380 K; dehydration is accompanied by an increase in the sample volume. The decomposition (pyrolisis) of the anhydrous compound takes place at 620–720 K; the decomposition is forestalled by a continued increase in the sample volume with an endothermic peak (490–600 K), and only the mass loss (620–720 K) is accompanied by a decrease in the sample volume. The included guest complex does not lose amines until the decomposition process is complete; the previously observed increase in the sample volume is explained by the expansion of cavitand molecules due to a distortion of the included [Co(en)₂Cl₂]⁺ complex on heating.     

5<Emphasis Type="Italic">p</Emphasis>-4<Emphasis Type="Italic">d</Emphasis> Emission spectrum with a cascade decay of the 3<Emphasis Type="Italic">d</Emphasis> vacancy in the Xe atom

The 5p-4d emission spectrum, obtained during cascade de-excitation of the initial deep 3d vacancy in the Xe atom, was calculated by directly constructing a decay tree in a stepwise manner. The cascade decay tree was constructed with allowance for all radiative and nonradiative channels of decay for the initial and all intermediate ionic configurations of the cascade. The probabilities of branching and transition energies were calculated in a one-electron approximation with averaging over configurations. The 5p-4d cascade emission spectrum has a complex structure with many components, which reflects the transitions from the wide variety of the many-hole intermediate configurations generated by the cascade. The calculated data agree well with the experiment.     

Distinctive unimolecular gas-phase reactivity of [M(en)2]2+ (M=Ni, Cu) dications and their inclusion complexes with the macrocyclic cavitand Cucurbit[8]uril

Electrospray ionization mass spectrometry makes it possible to generate gas-phase bis-ethylenediamine nickel and copper dications, [M(en)(2)](2+) (M = Ni, 1; M = Cu, 2), as well as their {[M(en)(2)]@cuc[8]}(2+) inclusion complexes with the macrocyclic cavitand cucurbit[8]uril (cuc[8]). The unimolecular gas-phase reactivity of these species has been investigated by electrospray ionization tandem mass spectrometry with a quadrupole-time-of-flight configuration. Distinctive fragmentation pathways have been observed for the free and encapsulated [M(en)(2)](2+) (M = Ni, Cu) dications under collision-induced dissociation (CID) conditions. The dications [M(en)(2)](2+) (M = Ni, Cu) dissociate according to several competitive pathways that involve intra-complex hydrogen or electron-transfer processes. Most of these channels are suppressed after encapsulation inside the cucurbit[8]uril macrocycle and, as a consequence, a simplification of the {[M(en)(2)]@cuc[8]}(2+) fragmentation pattern is observed. The results obtained demonstrate that the encapsulation of a coordination complex inside a host molecule can be used to alter the nature of the product ions generated under CID conditions.     

Jørgensen complex within a molecular container: selective encapsulation of trans-[Co(en)2Cl2]+ into cucurbit[8]uril and influence of inclusion on guest's properties

The unprecedented selective encapsulation of trans-[Co(en)2Cl2]+ from the mixture of trans and cis isomers into the cavity of macrocyclic cavitand cucurbit[8]uril (C48H48N32O16, CB[8]) leads to the inclusion compound {trans-[Co(en)2Cl2]@CB[8]}Cl.17H2O (1). Single-crystal X-ray analysis, 1H NMR, and ESI-MS spectra confirm the formation of host-guest complex 1 in both solid state and solution. The geometry of the complex cation alters significantly upon inclusion, which causes appreciable hypsochromic shifts of the absorption bands of the guest complex. According to TGA data, inclusion of trans-[Co(en)2Cl2]+ dramatically stabilizes the complex toward thermal decomposition. Encapsulation of trans-[Co(en)2Cl2]+ into the CB[8] cavity also increases the stability of the metal complex toward isomerization into the cis form. The supramolecular adduct {cis-[Co(en)2(H2O)2](CB[8])6}Cl3.ca109.5H2O (2) was isolated only after prolonged heating of an aqueous solution of 1 at 120 degrees C in an evacuated tube; it was characterized by X-ray crystallography, IR, and elemental analysis.     

Synthesis and guest exchange reactions of inclusion compounds of cucurbit[8]uril with nickel(II) and copper(II) complexes

Inclusion compounds of the macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex, {trans-[Ni(en)₂(H₂O)₂]@CB[8]}Cl₂ · 23.5H₂O, the copper(II) complex, {2[Cu(dien)(bipy)(H₂O)]@CB[8]}(ClO₄)₄ · 11H₂O, and the organic molecules, 2(pyCN)@CB[8]} · 16H₂O and {2(bpe)@CB[8]} · 17H₂O, where bipy is 4,4′-bipyridyl, pyCN is 4-cyanopyridine, and bpe is trans-1,2-bis(4-pyridyl)ethylene, were synthesized. The inclusion compounds with organic molecules were synthesized starting from inclusion compounds of cucurbit[8]uril with cyclam and ethylenediamine complexes of copper(II) and nickel(II) by the guest exchange method, which is based on the replacement of one guest with another in the cavity of the cavitand The resulting compounds were characterized by X-ray diffraction, ESR, ¹H NMR, IR, and electronic absorption spectroscopy, and electrospray mass spectrometry. Photochemically induced [2+2]-cycloaddition of two 1,2-bis(4-pyridyl)ethylene molecules included in cucurbit[8]uril was studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 25–34, January, 2006.     

关于单位园周上阶梯函数的性质

Ｔ．Ｓｈｅｉｌ－Ｓｍａｌｌ［１］讨论了阶梯函数的Ｆｏｕｒｉｅｒ级数。本文对［１］中所涉及到一些阶梯函数的性质进行了详细讨论，并给出了详细证明。     

极限方程有奇性的一类六阶椭圆型方程混合边值问题解的渐近式

该文研究极限方程在部分边界上为退缩椭圆型(椭圆-抛物)的一类六阶椭圆型方程混合边值问题的奇摄动,在适当的假设下,应用改进了的多重尺度法,求得其解包括边界层和套层在内除了半圆域的两个角点外,在整个半圆域中有任意阶的一致有效的渐近展开式.