Pentameric circular iron(II) double helicates and a molecular pentafoil knot

We report on the synthesis of 11 pentameric cyclic helicates formed by imine condensation of alkyl monoamines with a common bis(formylpyridine)bipyridyl-derived building block and iron(II) and chloride ions. The cyclic double-stranded helicates were characterized by NMR spectroscopy, mass spectrometry, and in the case of a 2,4-dimethoxybenzylamine-derived pentameric cyclic helicate, X-ray crystallography. The factors influencing the assembly process (reactant stoichiometry, concentration, solvent, nature and amount of anion) were studied in detail: the role of chloride in the assembly process appears not to be limited to that of a simple template, and larger circular helicates observed with related tris(bipyridine) ligands with different iron salts are not produced with the imine ligands. Using certain chiral amines, pentameric cyclic helices of single handedness could be isolated and the stereochemistry of the helix determined by circular dichroism. By employing a particular diamine, a closed-loop molecular pentafoil knot was prepared. The pentafoil knot was characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography, confirming the topology and providing insights into the reasons for its formation.     

Precision Mass Measurements beyond ^{132}Sn: Anomalous Behavior of Odd-Even Staggering of Binding Energies

Atomic masses of the neutron-rich isotopes ^{121-128}Cd, ^{129,131}In, ^{130-135}Sn, ^{131-136}Sb, and ^{132-140}Te have been measured with high precision (10?ppb) using the Penning-trap mass spectrometer JYFLTRAP. Among these, the masses of four r-process nuclei ^{135}Sn, ^{136}Sb, and ^{139,140}Te were measured for the first time. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across N=82 for Sn, with a Z dependence that is unexplainable by the current theoretical models.     

Selective derivatisations of resorcarenes - 2. Multiple regioselective ring closure reactions

The condensation of the C-pentyl resorcarene 1 with long chain aliphatic diamines 3a-d and excess formaldehyde leads under high dilution conditions to tetrabenzoxazine derivatives 4a-d in which pairs of adjacent oxazine rings are connected by an aliphatic chain. Six new rings are formed per resorcarene molecule during this reaction in a regioselective way. For one example (4a) the chiral cleft-like structure with C₂ symmetry was proved by single crystal X-ray analysis. Hydrolysis of the oxazine rings gives the secondary amine derivatives 5a,b with C_2v symmetry in high yield.     

Quark interpretation of the combinatorial hierarchy

We propose a physical interpretation of the second level of the combinatorial hierarchy in terms of three quarks, three antiquarks, and the vacuum. This interpretation allows us to introduce a new quantum number, which measures electromagnetic mass splitting of the quarks. We extend our argument by analog to baryons, and find someSU(3) and some new mass formulas for baryons. The generalization of our approach to other hierarchy levels is discussed. We present also an empirical mass formula for baryons, which seems to be loosely connected with the combinatorial hierarchy.     

A comparison of one-electron properties calculated from Gaussian SCF and CI wavefunctions

Ground state LCAO-MO-SCF single- and multiconfiguration wavefunctions of NH₃ and CH ₃ ^– , constructed from a large contracted Gaussian basis set, have been analyzed in terms of one-electron expectation values.Both sets of values agree fairly well with the experimental data in the case of NH₃. It is expected therefore that the results obtained for CH ₃ ^– are also reliable.

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Zusammenfassung Einfach- und Mehrfachdeterminanten-LCAO-MO-SCF-Funktionen für NH₃ und CH ₃ ^– wurden zur Berechnung von Einelektroneneigenschaften herangezogen. Die Übereinstimmung ist in beiden Fällen bei NH₃ gut, man darf daher für CH ₃ ^– dasselbe erwarten.