Ahmad S. Abushamleh

Factors affecting the threading of axle molecules through macrocycles: Binding constants for semirotaxane formation

The threading of more or less linear axle molecules through macrocyclic molecules, a fundamental process relating to the formation of interlocked molecular structures, has been investigated through the study in acetone of the equilibrium constants for the formation of pseudorotaxanes by NMR methods. The 30 new axle molecules have in common a secondary ammonium group, present as the thiocyanate salt, and an anthracen-9-ylmethyl group, but are rendered unique by the second amine substituent. All rotaxanes involve the well known polyether macrocycle, benzo[24]crown-8. The constants for the binding of axles having linear groups ranging from 2 to 18 carbon atoms show little variation in binding constant but are divided into two groups by their equilibration rates. Those with less than five methylene groups react rapidly on the NMR timescale, whereas those having more than five methylene groups are slow. Branching inhibits binding, but the effect decreases as the branch is moved away from the amine. Phenyl groups weaken binding when close to the amine but strengthen binding when more remote. Some functional groups decrease pseudorotaxane stability (alcohol functions), whereas others increase binding (carboxylic acid groups).

Synthesis, spectroscopic studies, and crystal structure of 3-(1-hydroxyiminoethyl)-1-phenyl-4-hydro-1,2,4-triazine-5,6-dione methanol solvate

3-(1-Hydroxyiminoethyl)-1-phenyl-4-hydro-1,2,4-triazin-5,6-dione, has been prepared from the chiral 1-phenyl-3-acetyloxime-5-benzyl-4,5-dihydro-1,2,4-triazin-6-one in the presence of organotin(IV) compounds in methanol solution. It crystallizes as a 1:1 methanol solvate in the monoclinic space group P 2 1 /c with the lattice parameters: a = 1517.6(1), b = 563.64(3), c=1500.34(13) pm and β = 90.35(1)°. The molecules, in which the heterocyclic ring is planar, are dimer via strong oxime-methanol and methanol-dione hydrogen bonds and by additional N-H---O bridges linking the heterocyclic rings.

Metal complexes of 1,10-phenanthroline derivatives. XIV: Complexes of 1,10-phenanthrolin-2-yl-(pyridin-2-yl)amine

1,10-Phenanthrolin-2-yl(pyridin-2-yl)amine has been prepared in low yield from 2-chloro-1,10- phenanthroline and pyridin-2-amine. The molecule coordinates as a tridentate chelating agent of the ter-imine type and produces low-spin complexes with iron(II) in both its neutral and anionic forms. The bis(ligand) cobalt(II) complex is high-spin. Although the ligand provides a slightly weaker field than terpyridine, electronic and Mossbauer spectral data indicate a less distorted metal ion environment in its complexes, compared with those of terpyridine. This is correlated with the presence of the six-membered chelate ring.

Transition Metal Complexes of Derivatized Chiral Dihydro-1,2,4-triazin-6-ones, Part IV [1]. Synthesis and Structural Characterization of a Copper(II) Complex of (L)-3-Acetyl-5-benzyl-1-phenyl-4,5-dihydro-1,2,4-triazin-6-one Oxime

Reaction of (L)-3-acetyl-5-benzyl-1-phenyl-4,5,-dihydro-1,2,4-triazine-6-one oxime (1) with copper acetate afforded the complex 5 in high yield. Single crystal X-ray structural analysis of 5 revealed a square-pyramidal geometry around the copper ion where the two oxime ligands are coordinated symmetrically to the Cu atom. The apex of the square-pyramid is occupied by a chloride ligand with the copper atom roofed above the center of the plane of the four coordinating nitrogens by about 0.22 Å . MS-FAB, magnetic and other analytical data are in accord with this solid-state structure.

Metal complexes of 1,10-phenanthroline derivatives. XIII. Denitrogenation in complexes of 2-hydrazino-1,10-phenanthroline

Interaction of 2-hydrazino-1,10-phenanthroline (L) with iron(III) or copper(II) salts results in oxidation of the ligand through loss of nitrogen and complexation of the oxidation product, 1,10-phenanthroline. The mixed iron(II)/iron(III) complex [Fe(phen)3] [FeCl4]2, identified by its magnetic and spectral properties, is formed from the reaction with iron(III) and pure [Cu(phen)2] [BF4]2 is obtained from the reaction with copper(II) fluoroborate. Slow denitrogenation of [FeL2] [BF4]2 has been observed in the solid state.