Physical Image vs. Structure Relation. Part 3 [1]. Basic Properties and Protonation Mechanism of Some Tetraaza Macrocyclic Ligands

The protonation constants, log K, for 1,4,7,11-tetraazacyclotetradecane (isocyclam, 2), 1-(2-aminoethyl)-1,4,8,11-tetraazacyclotetradecane (scorpiand, 3), 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane (Me₂cyclam, 4) and 5,5,7,12,14,14-hexamethyl-1,4,8,11- tetraazacyclotetradecane (Me₆cyclam, 5) were determined pH-metrically. Attempts of correlation of the calculated enthalpy of protonation in the gas phase (AM1 method) with experimental values of the protonation constants for ligands 1, 2, 4–7 were done 1,4,8,11-tetraazacyclotetradecane, cyclam, 1; 1,4,7,10-tetraazacyclotetradecane, cyclen, 6; 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, (N-Me)₄cyclam, 7. Extensive NMR pH-titrations, i.e., determination of pH vs. chemical shifts (¹H and/or ¹³C) plots, (_X = f(pH), allowed to suggest the most likely protonation schemes of all nitrogen atoms in the cyclic polyamines 1–3. The possibility of the formation-breaking of the intramolecular hydrogen bonds, as well as the change of conformation of these polybasic macrocycles during protonation-deprotonation steps, has been considered on the basis of the supplementary theoretical calculations (MMX/STO-3G study).     

A Direct Kinematical Derivation of the Relativistic Sagnac Effect for Light or Matter Beams

The Sagnac time delay and the corresponding Sagnac phase shift, for relativistic matter and electromagnetic beams counter-propagating in a rotating interferometer, are deduced on the ground of relativistic kinematics. This purely kinematical approach allows to explain the universality of the effect, namely the fact that the Sagnac time difference does not depend on the physical nature of the interfering beams. The only prime requirement is that the counter-propagating beams have the same velocity with respect to any Einstein synchronized local co-moving inertial frame.     

The Minimal Subgroup of a Random Walk

It is proved that for each random walk (S _n ) _n0 on ^d there exists a smallest measurable subgroup of ^d , called minimal subgroup of (S _n ) _n0, such that P(S _n )=1 for all n1. can be defined as the set of all x ^d for which the difference of the time averages n ^{–1 n} _k=1 P(S _k ) and n ^{–1 n} _k=1 P(S _k +x) converges to 0 in total variation norm as n. The related subgroup * consisting of all x ^d for which lim _n P(S _n )–P(S _n +x)=0 is also considered and shown to be the minimal subgroup of the symmetrization of (S _n ) _n0. In the final section we consider quasi-invariance and admissible shifts of probability measures on ^d . The main result shows that, up to regular linear transformations, the only subgroups of ^d admitting a quasi-invariant measure are those of the form ₁×...× _k × ^l–k ×{0} ^d–l , 0kld, with ₁,..., _k being countable subgroups of . The proof is based on a result recently proved by Kharazishvili⁽³⁾ which states no uncountable proper subgroup of admits a quasi-invariant measure.     

手性位移试剂Eu(dcm)~3的一个改进合成方法

我们对H(dcm)的Whitesides合成路线的关键步骤龙脑酰甲烷的合成和缩合反应进行了重要的改进。     

羰基硼化合物(BCO)n(n==1～12)的理论研究

运用HF/3-21G方法和密度泛函理论(DFT)的B3LYP/6-31G*方法, 对羰基硼化合物(BCO)n(n=1~12)的各种可能结构进行了优化, 对在B3LYP/6-31G*水平上得到的几何构型、电子态、结合能、振动频率、核独立化学位移(NICS)、能量二次差分和热力学性质进行了理论研究, 得到了(BCO)n(n=1~12)结构的稳定性信息. 十二种基态结构都是端配位(μ1-CO), (BCO)n(n=1~3, 5, 6) 的基态是线型或平面结构, (BCO)n(n=4, 7~12)的基态是笼状结构; B—C平均键能呈现奇偶交替现象, 偶数的结构比奇数稳定; 能量二次差分得到同样的结论；羰基的振动频率与实验值非常吻合; 热力学性质的研究对实验具有重要的指导意义.     

蛋氨酸稀土配合物构象的^13CNMR研究

本文测量了在7种不同稀土离子(La~(3 )、Pr~(3 )、Nd~(3 )、Dy~(3 )、Ho~(3 )、Er~(3 )和Tm~(3 ))的水溶液中蛋氨酸~(13)C稀土诱导位移。利用稀土诱导位移对蛋氨酸稀土配合物构象的模拟结果表明,蛋氨酸通过离子化的羧基与稀土离子配位,Ln~(3 )—O长度为2.7A在配合物中,蛋氨酸以伸展状态存在,C_0-C_α-C_β-C_γ和C_α-C_β-C_γ-S成反式构象,C_β-C_γ-S-C_δ成旁式构象。根据稀土诱导位移方法建立的构象模型符合~1H邻位质子偶合常数和~(13)C顺磁弛豫速率的结果。     

Substituent Effect on Mercury-199 Chemical Shifts in Some Bisarylmercurials and Aryl(2-benzothiazolylthio) mercurials

The present paper covers the 199 Hg NMR chemical shifts of 24 substituted diphenylmercurials and phenyl(2-benzothiazolylthio)mercurials. There is a good linear relationship between the chemical shift and the Hammett constant of the substituents for both series of compounds, and electron donating substituents cause the chemical shift towards downfield.     

偶极-偶极相互作用的探讨(I)

用增强拉曼光谱和电势调节红外光谱探讨偶极－偶极相互作用时，吸附带强度变化比频率位移更为重要．因为其它因素，如吸附物位置不均匀，通过金属表面的诱导作用等也能引起频率的稍微位移，但这些因素均不能解释强度转移效应．分子间的振动相互作用主要通过它们的偶极场，吸附分子吸收峰强度的转移与它们的电子极化率的屏蔽作用密切相关，相关势近似（CPA，CoherentPotentialApproximation）已广泛用于讨论分子间的振动相互作用［1］．本文用CPA方法计算了C（ZXZP’CN一、“CN丫All（100）体系的吸收光谱，并与吸附在粗化金电极上的…     

Measurement of hyperfine structures and isotope shifts in 4f5d6s and 4f6s6p of Sm I

We report the first observation of hyperfine structures (HFSs) and isotope shifts (ISs) of Sm I in the range of 540–560 nm using an atomic beam resonance–fluorescence technique. The least square fitting was used to determine hyperfine constants in 4f⁵5d6s² and 4f⁶6s6p of atomic samarium (Sm I). The isotope shifts of 18 transition lines were also determined and analyzed by the King plot.     

Spectroscopy of sodium atom in liquid helium cluster: a symmetry adapted cluster-configuration interaction (SAC-CI) study

Excitation line shift of the principal resonance line of sodium atom embedded in liquid helium is estimated using symmetry adapted cluster-configuration interaction (SAC-CI) method with a reasonably good choice of basis set. The effect of the liquid surroundings is considered by taking only the nearest neighbor interaction using several model clusters of helium atoms with a centrally located isolated sodium atom. The transition wavelength of the ²P ← ²S line of Na is estimated both for the free Na and for the Na atom centrally located inside a model helium cluster. The shift depends obviously on the model cluster and the distance of the central Na atom from the surrounding He atom. With a physically realizable structure, SAC-CI calculation correctly predicts the theoretical results obtained previously on such estimates.