Spin-site exchange system constructed from endohedral metallofullerenes and organic donors

Complexation behavior of the paramagnetic La@C82 metallofullerene with organic donor molecules (D) in solution is investigated. It is revealed that La@C82 and D form a 1:1 complex as a result of electron transfer. La@C82 and D are in equilibrium with [La@C82]-/[D]*+ in solution, which is readily controllable by changing the temperature and solvent.     

Simultaneous analysis of cationic, anionic, and neutral compounds using monolithic CEC columns

A new capillary electrochromatography (CEC) column for the simultaneous analysis of cationic, neutral, and anionic compounds using CEC-ESI-MS is described. Three different silica monolith columns were prepared by changing the poly(ethylene glycol) (PEG) contents for comparison of the separation property of these columns. Different separation programs were used for the simultaneous separation of different charged compounds under the same conditions. The column prepared with 80 mg of PEG separated typical compounds within 15 min using 1 M formic acid as the electrolyte. The analytes migrated in the order of cationic, neutral, and anionic compounds, which means that the migration order was mainly determined by the electrophoresis. The hydrodynamic flow by pressure from the inlet side was significant for a stable analysis to be achieved. The effect of the composition of the sheath liquid was also examined. All analytes (14 amino acids, thiourea, urea, citric acid, and ATP) were detectable when 1% acetic acid in 50% (v/v) methanol was used as the sheath liquid.     

Optimum hole-opening condition for Cisplatin incorporation in single-wall carbon nanohorns and its release

We enclosed cisplatin (CDDP), an anticancer drug, inside single-wall carbon nanohorns (SWNH) with holes opened by being heated from room temperature to a target temperature (475-580 degrees C) in flowing dry air, with an increase rate of 1 degrees C/min. The optimum target temperature was found to be 500 degrees C, in terms of the least amount of CDDP deposited outside the SWNH, when the quantity of CDDP encapsulated inside the SWNH was 12 wt %. The incorporated CDDP was slowly released from the SWNH in phosphate buffer saline, and the released quantity was 80%, which was greatly improved from the previous value of 15%. This indicated that a CDDP-containing SWNH could become more potentially useful for biological applications.     

Synthesis of novel macromonomers and telechelics of poly(2-alkyl-2-oxazoline)s

Novel macromonomers and telechelics of poly(2-alkyl-2-oxazoline) (PROZO) were syn-thesized by utilizing termination of propagating species (2-oxazolinium ions) in the living polymerization of 2-alkyl-2-oxazoline (ROZO) with suitable nucleophiles. Two types of p-vinylbenzyl–type macromonomers were obtained by terminating living PROZO with sodium p-vinylbenzyl alkoxide or with sodium p-vinylbenzyl mercaptide. The synthesis of telechelics having a functional group (SH, COOH) on both ends of PROZO was achieved by using a bis(2-oxazolinium salt) initiator. The PROZO dithiol was synthesized by two methods: (1) termination of the living species on both ends with NaSH, and (2) aminolysis of PROZO bis(O-ethyldithiocarbonate) given by treatment of the living PROZO with potassium O-ethyldithiocarbonate. Termination of the living PROZO with the sodium salt of di-t-butyl malonate yielded a PROZO with di-t-butyl malonate moieties on both polymer ends, from which the PROZO dicarboxylic acid was derived via free tetracarboxylic acid. © 1995 John Wiley & Sons, Inc.     

Pd(II) acts simultaneously as a Lewis acid and as a transition-metal catalyst: synthesis of cyclic alkenyl ethers from acetylenic aldehydes

The reaction of carbon-tethered acetylenic aldehydes with alcohols in the presence of a catalytic amount of Pd(OAc)2 in 1,4-dioxane at room temperature gave the 5- or 6-membered acetal products in high yields. The 13C NMR studies suggested that a Pd(II) catalyst exhibited dual roles in the present reaction; the attack of ROH to aldehyde is catalyzed by Lewis acidic Pd(OAc)2, and the nucleophilic oxygen of the resulting hemiacetal reacts with alkyne complexed by Pd(II), giving the alkenyl ethers.     

Cyclophane porphyrins and their metal complexes: Biomimetic study on receptor site of hemoprotein oxygen binding

A new symmetric porphyrin, 7,8,17,18-tetraethyl-3,13-dimethylporphyrin-2, 12-dipropionic acid and its derivatives were synthesized by the a,c-biladiene route. Condensation of the dipropionic acid with diamine, [H₂N(CH₂)_nNH₂, n= 6,7,8,9,10,12, and14], afforded the corresponding cyclophane porphyrins. The bridged groups were characterized by the ¹H-NMR spectra of their zinc complexes. The spin state of the Fe(III) complexes of the cyclophane porphyrins was investigated by changing the size of the bridged chain or size of axial ligand. The cyclophane-porphyrinato (III) perchlorate complexes in a mixture of MeOH and CHCl₃, with 4-benzylpyridine provide a model for methemoproteins. Steric constraint between an axial ligand and the bridge group, [-CH₂CH₂CONH(CH₂)_nNHCOCH₂CH₂]at the bridged face determines the ratio of the penta- and hexa-coordinated ferric complexes. The rate of O-binding to the Co(II) cyclophane porphyrins is mar present result indicates that removal of a solvent molecule or sixth axial ligand from the near proximity of the Co(II) complex increases the rate of O- binding.     

Effect of an "ionic liquid" cation, 1-butyl-3-methylimidazolium, on the molecular organization of H2O

The excess partial molar enthalpy of 1-propanol (1P), , was measured at 28 degrees C in the ternary mixture of 1P-1-butyl-3-methylimidazolium chloride ([bmim]Cl)-H(2)O in the H(2)O-rich composition range. From these data we evaluated what we call the 1P-1P enthalpic interaction function, . Its changes induced by addition of [bmim]Cl of the pattern of were used as a probe to elucidate the effect of [bmim]Cl on the molecular organization of H(2)O. It was found that the effect of Cl(-) was not conspicuous within this methodology, and the observed dependence is predominantly due to the hydration of [bmim](+). The changes in the x(1P)-dependence of were compared with those brought about by temperature increase, or by the addition of fructose or glycerol. It was found that the effect of [bmim](+) is similar to that of fructose or increased temperature. We speculate that in the H(2)O-rich composition region a number of H(2)O molecules are attracted to the delocalized positive charge of the imidazolium ring and the bulk of H(2)O is influenced in such a manner that the global hydrogen bond probability is reduced.     

Synthesis of allenes from allylic alcohol derivatives bearing a bromine atom using a palladium(0)/diethylzinc system

A general and efficient synthesis of allenes using a palladium(0)/diethylzinc system is described. Treatment of mesylates or trichloroacetates of (E)- or (Z)-2-bromoalk-2-en-1-ols with diethylzinc in the presence of a catalytic amount of palladium(0) affords allenes bearing an aminoalkyl, alkyl, or aryl substituent(s) in good to high yields. No transfer of chirality from the stereogenic center carrying the mesyloxy group to the allene was observed.     

Heteroepitaxial growth of a zeolite film with a patterned surface-texture

We focus on the eteroepitaxial growth of trigonal chabazite with voids of three-dimensional intersection structures. The differences in the structures originate from the stacking sequences of the six-membered rings. Sodalite along 111 is constructed by an "abcabc" stacking sequence, while chabazite along [111] is constructed by "abab". Therefore, chabazite can grow heteroepitaxially on a sodalite substrate while keeping the relation of chabazite (111)//sodalite {111}. In this Communication, we report on the first success of the heteroepitaxial growth of a continuous zeolite (chabazite) film with a unique patterned surface-texture on a millimeter-sized sodalite single crystal. We have found that the unique texture of chabazite films is rationalized by the heteroepitaxial growth of chabazite on sodalite and the subsequent twin formation of chabazite.