Cyclen based bis-macrocyclic ligands as phosphates receptors. A potentiometric and NMR study

The host-guest interaction between orthophosphate, pyrophosphate and triphosphate anions and four cyclen based bis-macrocycles ligands possessing ortho-(BOC), meta-(BMC), para-xylenyl (BPC) or 2,6-pyridinyl (BPyC) linker was investigated by potentiometric measurements and NMR spectroscopy. Each ligand gave protonated species in aqueous solution that further formed ternary complexes after binding with anions; these complexes were analyzed as a result of hydrogen bond formation and Coulombic attraction between the organic host and the inorganic guest. The equilibrium constants for all the detected species are reported and the selectivity, illustrated with species distribution diagrams, is discussed. The results unambiguously showed the importance of the distance between the two cyclen cores and underlined, especially for the triphosphate species, the contribution of the nitrogen atom of the pyridinyl spacer as a supplementary anchoring point in acidic medium.     

Protonation et hydrolyse d'enamine. Epimerisation des immoniums intermediaires

At pH 5 (AcOHAcONa) protonation of the enamine of 3,6,6-trimethylnorpinane 2-one (3-methylnopinone) yields the <em>cis</em> immonium ion <strong>6</strong> (X  OAc), which isomerizes to the thermodynamically more stable <em>trans</em> immonium ion <strong>6</strong>′ (X  OAc). Under more strongly acid conditions (aqueous hydrochloric or perchloric acids), the enamonium salts <strong>7</strong> (X  Cl or ClO<sub>4</sub>) are formed; these isomerize, with a rate increasing with decreasing acidity to the <em>cis</em> immonium salts <strong>6</strong>, stable under these conditions. Epimerization of the <em>cis</em> salt <strong>6</strong> (X  Cl), occurs in ethereal hydrogen chloride, the rate increasing also with decreasing acidity. At pH 5, hydrolysis of the enamine yields 3-methylnopinone, the proportion of the less thermodynamically stable <em>trans</em> isomer increasing with a rise in reaction temperature.     

Water adsorption in disordered mesoporous silica (Vycor) at 300 K and 650 K: a Grand Canonical Monte Carlo simulation study of hysteresis

This numerical simulation paper focuses on the adsorption/desorption of water in disordered mesoporous silica glasses (Vycor-like). The numerical adsorbent was previously obtained by off lattice method, and was shown to reproduce quite well the micro- and mesotextural properties of real Vycor, as well as morphological (pore size distribution) and topological (pore interconnections) disorder. The water-water interactions are described by the SPC model while water-silica interactions are calculated in the framework of the PN-TrAZ model. The water adsorption/desorption isotherms and the configurational energies are calculated by the Grand Canonical Monte Carlo simulation method. The low pressure results compare well with experiments, showing the good transferability of the intermolecular potential. It is shown that if the hysteresis loop observed in the adsorption/desorption isotherm is considered as a true phase transition (which is actually still an open question in the case of disordered porous materials), then it is possible to calculate the grand potential by applying the thermodynamic integration scheme. The grand potential is shown to be multivalued for low (subcritical) temperature, and continuous for high (supercritical) temperature. A coexistence point is found within the hysteresis loop, actually close to the vertical desorption line. Below the equilibrium chemical potential, the gaslike branch is stable whereas the liquidlike branch is metastable. The situation is reversed above the coexistence point.     

Thermal investigations on the crystallization of sorbitol

The melting and crystallization of sorbitol were investigated with the DSC method and thermal microscopy. Sorbitol was found to have two crystalline modifications (confirmed by X-ray diffraction) with different melting points, while rapid cooling of molten sorbitol resulted in an amorphous form. The effect of inoculation on the crystallization of the melt was studied too. Powders of both crystalline modifications were used for this purpose. A new technological process for rapid crystallization of molten sorbitol has been worked out on the basis of the thermal analysis results.     

Kinetic study of copper(II) complexation with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone and kinetic-spectrophotometric determination of copper(II)

The kinetics of complexation reaction of Cu(II) with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) has been examined spectrophotometrically. The ligand was synthesized for the first time. The complexation reaction was carried out in a DMF-water medium at 35°C. The complex has maximum absorbance at 393 nm. Kinetic and activation parameters of the complexation reaction were calculated by the Arrhenius and Eyring equations using the data obtained from investigating the effect of temperature on reaction rates under the specified conditions. We also proposed reaction rate equations. Based on the studied complexation reaction, a simple kinetic method for the spectrophotometric determination of copper(II) has been developed. The calibration graphs are linear in the concentration range 0.2–1.9 μg/mL. The species that caused interference were investigated. The text was submitted by the authors in English.     

Thermal analysis of metal complexes,III

On the basis of the thermal investigation of Mpy<sub>n</sub>X<sub> <i>z</i> </sub> mixed complexes (where M=Mn<sup>2+</sup>, Co<sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>; py=pyridine; or<i><img src="/content/l2837g37068k21n3/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-, <img src="/content/l2837g37068k21n3/xxlarge914.gif" alt="Bgr" align="BASELINE" BORDER="0"></i>- and<i><img src="/content/l2837g37068k21n3/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"></i>-picoline; X=Cl<sup>–</sup>, Br<sup>–</sup>, I<sup>–</sup>, OCN<sup>–</sup>, SCN<sup>–</sup>, NO <sub>3</sub> <sup>–</sup> , SO <sub>4</sub> <sup>2–</sup> ; and<i>n</i>=2,3,4,6;<i>z</i>=1,2), factors influencing the stability of the metal-pyridine-N bond have been determined.On the basis of the measured magnetic susceptibilities the symmetry of the coordina tion sphere of the central atom has been established in the intermediate products formed by the thermal decomposition of cobalt(II) complexes.<hr><blockquote>Zusammenfassung Aufgrund derivatographischer Untersuchungen von Mischkomplexen des Typs Mpy<sub>n</sub>X<sub>z</sub> (M=Mn<sup>2+</sup>, Co<sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>; py=Pyridin,<i><img src="/content/l2837g37068k21n3/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">, <img src="/content/l2837g37068k21n3/xxlarge914.gif" alt="Bgr" align="BASELINE" BORDER="0"></i> und<i><img src="/content/l2837g37068k21n3/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"></i> Piccolin; X=Cl<sup>–</sup>, Br<sup>–</sup>, I<sup>–</sup>, OCN<sup>–</sup>, SCN<sup>–</sup>, NO <sub>3</sub> <sup>–</sup> , SO <sub>4</sub> <sup>2–</sup> ;<i>n</i>=2, 3, 4, 6;<i>z</i>=1, 2) wurden die die StabilitÄt der Metall-Pyridin-N Bindung beeinflussenden Faktoren geprüft. Durch Messung der magnetischen SuszeptibilitÄten wurde die Symmetrie der KoordinationssphÄre des Zentralatoms des bei der thermischen Zersetzung entstehenden Kobalt(II)-komplexes ermittelt.</blockquote><hr><blockquote>Résumé On a examiné des complexes du type Mpy<sub> <i>n</i> </sub>X<sub> <i>z</i> </sub> (où M=Mn<sup>2+</sup>, Co<sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>; py=pyridine,<i><img src="/content/l2837g37068k21n3/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-,<img src="/content/l2837g37068k21n3/xxlarge914.gif" alt="Bgr" align="BASELINE" BORDER="0"></i>- et<i><img src="/content/l2837g37068k21n3/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"></i>-piccoline; X=Cl<sup>–</sup>, Br<sup>–</sup>, I<sup>–</sup>, OCN<sup>–</sup>, SCN<sup>–</sup>, NO <sub>3</sub> <sup>–</sup> , SO <sub>4</sub> <sup>2–</sup> ;<i>n</i>=2, 3, 4, 6;<i>z</i>=1, 2) dans le but de déterminer les facteurs ayant une influence sur la stabilité de la liaison métal-pyridine-N. Par mesure des susceptibilités magnétiques, on a pu établir dans la cas des complexes du Co<sup>2+</sup> la sphère de coordination de l'atome central pour les phases intermédiaires produites par décomposition thermique.</blockquote><hr><blockquote><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1078.gif" alt="zhcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1059.gif" alt="Ucy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1075.gif" alt="gcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1060.gif" alt="Fcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1096.gif" alt="shcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1059.gif" alt="Ucy" align="BASELINE" BORDER="0"><sub>n</sub><img src="/content/l2837g37068k21n3/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0"><sub>z</sub> (<img src="/content/l2837g37068k21n3/xxlarge1075.gif" alt="gcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> M=<img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0">n<sup>2+</sup>, <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>; py=<img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0">, <img src="/content/l2837g37068k21n3/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">, <img src="/content/l2837g37068k21n3/xxlarge914.gif" alt="Bgr" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0">; X=Cl<sup>–</sup>, Br<sup>–</sup>, I<sup>–</sup>, OCN<sup>–</sup>, SCN<sup>–</sup>, NO<sub>3</sub> <sup>–</sup>, SO <sub>4</sub> <sup>2–</sup> ; n=2, 3, 4, 6; z=1, 2) <img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1060.gif" alt="Fcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0">, <img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1059.gif" alt="Ucy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1065.gif" alt="SHCHcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1041.gif" alt="Bcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1078.gif" alt="zhcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0">-<img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0">-N. <img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1078.gif" alt="zhcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1075.gif" alt="gcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1063.gif" alt="CHcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1059.gif" alt="Ucy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1059.gif" alt="Ucy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1094.gif" alt="tscy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1060.gif" alt="Fcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1094.gif" alt="tscy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1075.gif" alt="gcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1059.gif" alt="Ucy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0">, <img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1041.gif" alt="Bcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1078.gif" alt="zhcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1053.gif" alt="Ncy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1048.gif" alt="Icy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1056.gif" alt="Rcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1040.gif" alt="Acy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1044.gif" alt="Dcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1052.gif" alt="Mcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1045.gif" alt="IEcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1042.gif" alt="Vcy" align="BASELINE" BORDER="0"> <img src="/content/l2837g37068k21n3/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/l2837g37068k21n3/xxlarge1054.gif" alt="Ocy" align="BASELINE" BORDER="0">(II).</blockquote><hr><hr><p></p>Previous paper of the series: G. Liptay, K. Burger, E. Papp Molnár, Sz. Szebeni, F. Ruff: J. Inorg. Nucl. Chem. 31 (1969) 2359.<hr><p></p>We are indebted to Miss é. Szabó for technical assistance.     

On distribution of molecular weight in anionic polymerizates of caprolactam

Measurement has been made of the dependence of the molecular weight distribution on the ratio of the catalytic system components and on the polymerization time for polycaprolactam obtained by anionic polymerization. A bimodal character of the curves was observed for products made using molar ratios of activator (<em>N</em>-benzoylcaprolactam) to initiator (sodium dihydro-bis(methoxyethoxy)aluminate) of 1:1 and 1:3, when the polymerization times were less than 1 hr. This course is explained by the influence of fast side-reactions, mainly condensations. For a ratio of 3:1 of the components of the catalytic system, smooth integral distribution curves are obtained, accounting for a very fast decrease in the strong base concentration in the initial stages of the polymerization.     

Molecular orbital studies on the conformation of GABA (γ-aminobutyric acid)

In distinction to Extended Hückel Theory which predicts as the most stable conformation of free zwitterionic GABA a totally extended form, PCILO and SCF <i>ab initio</i> studies show that the intrinsically preferred conformation of the isolated molecule is a highly folded one, resulting from strong interactions between the two charged ends. Computations are also carried out for hydrated GABA in the <img src="/content/ukv11w0ww7u53525/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">supermolecule<img src="/content/ukv11w0ww7u53525/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> approach allowing moreover for the flexibility of binding of some of the water molecules of the first hydration shell. They predict the coexistence in solution of a large number of conformations showing different degrees of folding (or extension), a result confirmed by recent NMR studies. This and a number of similar results show that we have to adapt our thinking on the role of conformations in pharmacological activity to this situation, which was frequently obscured by the more abundant results of X-ray crystallography yielding a single conformation.     

Addition of hydroxide to an isoelectronic series of bis-diazineplatinum(II) complex ions

Base hydrolysis of bis-bipyridylplatinum(II) occurs via a 1:1 intermediate adduct with hydroxide ion. The equilibrium constants for this 1:1 addition of hydroxide in<img src="/content/gt542pr8v61x31k3/xxlarge9251.gif" alt="blank" align="MIDDLE" BORDER="0">water to complex ions [PtL2]2+, where L=one of the<img src="/content/gt542pr8v61x31k3/xxlarge9251.gif" alt="blank" align="MIDDLE" BORDER="0">isoelectronic set 2,2<img src="/content/gt542pr8v61x31k3/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-bipyridyl (bpy); 2,2<img src="/content/gt542pr8v61x31k3/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">- bipyrazine (bpz); 3,3<img src="/content/gt542pr8v61x31k3/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-bipyridazine (bpdz) and 2,2<img src="/content/gt542pr8v61x31k3/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">- bipyrimidine (bpym) are respectively (as log10K at 25°C): 4.23; 4.59; 3.82; 6.14. This result is rationalized in terms of addition at the 6–position of the ligand.     

Studies on stereoselective approaches to β-carboline derivatives

Transformation of β-carboline derivatives into optically active entities were studied and the <i>de</i> and <i>ee</i> values of the resulted compounds were detected. Dedicated to Professor Károly Lempert on his 80th birthday.