NMR study and quantum mechanical calculations on the 2-[(2-aminoethyl)amino]-ethanol-H2O-CO2 system

13C and 1H NMR spectra were obtained for AEEA (2-[(2-aminoethyl)amino]-ethanol)-H2O-CO2 systems and quantum mechanical calculations were carried out for the different AEEA species. The results suggest that the main AEEA species under the conditions studied are free amine, primary carbamate, and secondary carbamate. There is also some indication that a dicarbamate species is formed, this species does however only appear to be formed in small amounts. Comparison between experimental data and quantum mechanical calculations suggest that most AEEA species take on conforms with some degree of intramolecular hydrogen bonding.     

Solvent Dependence of Photophysical and Photochemical Behaviors of Thioxanthen-9-one

The photophysical and photochemical behaviors of thioxanthen-9-one (TX) in different solvents have been studied using nanosecond transient absorption spectroscopy. A unique absorption of the triplet state \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} is observed, which involves two components, \begin{document}$ ^3 $\end{document}n\begin{document}$ \pi $\end{document}\begin{document}$ ^* $\end{document} and \begin{document}$ ^3 $\end{document}\begin{document}$ \pi\pi^* $\end{document} states. The \begin{document}$ ^3 $\end{document}\begin{document}$ \pi\pi^* $\end{document} component contributes more to the \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} when increasing the solvent polarity. The self-quenching rate constant \begin{document}$ k_{ \rm{sq}} $\end{document} of \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} is decreased in the order of CH\begin{document}$ _3 $\end{document}CN, CH\begin{document}$ _3 $\end{document}CN/CH\begin{document}$ _3 $\end{document}OH (1:1), and CH\begin{document}$ _3 $\end{document}CN/H\begin{document}$ _2 $\end{document}O (1:1), which might be caused by the exciplex formed from hydrogen bond interaction. In the presence of diphenylamine (DPA), the quenching of \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} happens efficiently via electron transfer, producing the TX\begin{document}$ ^\cdot $\end{document}\begin{document}$ ^- $\end{document} anion and DPA\begin{document}$ ^{\cdot} $\end{document}\begin{document}$ ^+ $\end{document} cation radicals. Because of insignificant solvent effects on the electron transfer, the electron affinity of the \begin{document}$ ^3 $\end{document}n\begin{document}$ \pi $\end{document}\begin{document}$ ^* $\end{document} state is proved to be approximately equal to that of the \begin{document}$ ^3 $\end{document}\begin{document}$ \pi\pi^* $\end{document} state. However, a solvent dependence is found in the dynamic decay of TX\begin{document}$^{{ \cdot ^ - }}$\end{document} anion radical. In the strongly acid aqueous acetonitrile (pH = 3.0), a dynamic equilibrium between protonated and unprotonated TX is definitely observed. Once photolysis, \begin{document}$ ^3 $\end{document}TXH\begin{document}$ ^{+*} $\end{document} is produced, which contributes to the new band at 520 nm.     

滴定量热法研究氨基酸羧基质子化反应

氨基酸是典型的两性物质,其羧基质子化常数已有报道,文献结果大都由pH电位法得到,而对氨基酸光学异构体(D、L、DL)的对比研究甚少,为检验光学活性起源理论中提出的D与L分子间的能量差异,我们曾用微量量热技术观察了苯丙氨酸、亮氨酸,蛋氨酸和色氨酸4     

Deprotonation and protonation of hydroxyphenanthroperylenes

Summary Ground and excited state deprotonation and protonationpK _a values of hydroxyanthraquinones, hydroxyanthrones, hydroxyphenanthroperylenes, and the natural pigments hypericin and pseudohypericin were determined by means of spectrophotometric titrations and Förster cycle calculations. It was concluded that there is a strong intramolecular excited state proton transfer in the hydroxyanthraquinones and hydroxyanthrones due to a reversion of acidity and basicity of the hydroxyl and carbonyl groups in the excited state. However, in the hydroxyphenanthroperylene and the natural pigment excited states the order of basicity and acidity of these two functional groups remain unchanged. The site of deprotonation in hypericin and pseudohypericin was deduced by comparison between thepK _a values of suited model compounds and these pigments to be the hydroxyl group in position 3 or 4, respectively.

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Deprotonierung und Protonierung von Hydroxyphenanthroperylenen

Zusammenfassung Die Deprotonierungs- und Protonierungs-pK _a-Werte im Grundzustand und im angeregten Zustand von Hydroxyanthrachinonen, Hydroxyanthronen, Hydroxyphenanthroperylenen und den natürlichen Pigmenten Hypericin und Pseudohypericin wurde durch spektrophotometrische Titrationen und Förster-Zyklus-Rechnungen bestimmt. Bei den Hydroxyanthrachinonen und Hydroxyanthronen wurde auf Grund der Umkehr von Acidität und Basizität der Hydroxy- und Carbonylgruppen im angeregten Zustand auf einen starken intramolekularen Protonentransfer im angeregten Zustand geschlossen. Bei den Hydroxyphenanthroperylenen und den natürlichen Pigmenten bleiben die Aciditäts- und Basizitätsverhältnisse der beiden funktionellen Gruppen jedoch unverändert. Aus dem Vergleich derpK _a-Werte geeigneter Modellverbindungen mit Hypericin und Pseudohypericin wurde auf eine Deprotonierung der Hydroxylgruppe in Position 3 bzw. 4 geschlossen.

     

间氯偶氮安替比林的纯化鉴定及其离解常数和质子化常数的测定

本文研究提出了适合于新显色剂间氯偶氮安替比林的纯化新方法,经该方法纯化后的试剂在纸色谱图上仅有一个斑点,元素分析结果也令人满意。经过元素分析、热重分析和红外吸收光谱的测定,进一步确定了试剂的组成和结构。首次用光度法测定了试剂的离解常数(pKa=7.35±0.03)和质子化常数(1ogKp=-3.50±0.17)。     

Determination of protonation constants of some fluorinated polyamines by means of <Superscript>13</Superscript>C NMR data processed by the new computer program HypNMR2000. Protonation sequence in polyamines

The pK_a values of 6-fluoro-4,8-diazadodecane-1,12-diamine (6-fluorospermine) (1), 6,6-difluoro-4,8-diazadodecane-1,12-diamine (6,6-difluorospermine) (2), 6-fluoro-4-azaoctane-1,8-diamine (6-fluorospermidine) (3) and 6,6-difluoro-4-azaoctane-1,8-diamine (6,6-difluorospermidine) (4) in D₂O solution have been determined at 40 °C from ¹³C NMR chemical shifts data using the new computer program HypNMR2000. The enthalpies of protonation of compounds 1–4 and the parent amines spermine (5) and spermidine (6) have been determined from microcalorimetric titration data. The values of H° were used to derive basicity constants relative to 25 °C. The NMR data have been analysed by two different methods to obtain information on the protonation sequence in the polyamines 1–5. The protonation sequence for spermine is related to its biological activity.Abbreviations PKC Protein kinase C - PS Phosphatidylserine - VB Microsoft Visual BasicPresented at the Spanish-Italian Congress on the Thermodynamics of Metal Complexes, Santiago de Compostela, Spain, June 2–6, 2002     

溶剂中微量水对取代酞菁锌吸收光谱的影响

测定了6种烷氧基取代酞菁锌在不同溶剂中的电子吸收光谱. 在一些溶剂(如甲苯、氯仿和二氯甲烷)中, 除了存在典型的Q带吸收峰外, 在其长波长一侧还可观测到一个新的吸收峰, 结合对其荧光、核磁共振谱、添加强碱性溶剂(吡啶)以及对溶剂除水后的光谱的研究, 证实了新产生的吸收峰与溶剂中的微量水有关, 探讨了该吸收峰产生的原因.     

Protonation constants of some substituted 2-hydroxy-1-naphthalideneanilines in dioxan-water mixtures

The protonation constants of ten Schiff's bases synthesized by the condensation of 2-hydroxy-1-naphthaldehyde with aniline and o-, m-, and p-substituted methylanilines, ethylanilines and methoxyanilines in various dioxan-water mixtures have been determined potentiometrically using an electrode system calibrated in concentration units of the hydrogen ion. The influence of substituents in the molecular structure on the protonation constants is discussed. The log K₂ values relating to the protonation of imine nitrogen atoms are in accordance with the Hammett relationship for all solvent compositions. A reverse relationship is observed between log K₂ for all Schiff's bases and the mole fraction of dioxan. However, the log K₁ values corresponding to the protonation of naphtholate O-ions have been found to increase with the increase in concentration of dioxan. Both electrostatic and non-electrostatic contributions influencing these constants are briefly discussed.     

First reversible protonation of the all-nitrogen 1-aryl pentazole ring

At −40 °C in chlorosulfonic acid 1-aryl pentazoles were protonated at N-3. The N-3 atom showed a ¹⁵N NMR shielding shift of −60 to −62 ppm. The -N₅ ring is the highest member of the azole series.