Fast atom bombardment mass spectrometry of new polydentate schiff bases. 2. The case of mono- and bisaldimines containing pyridine groups

The mass spectrometric behaviour of seven polydentate Schiff bases derived from the condensation of formyl or diformyl precursors (2,3-dihydroxy- or 2,5-dihydroxy-benzaldehyde, 3-metoxy- or 3-ethoxy-salicylaldehyde, 3-formyl-salicyclic acid, 4-methoxy- or 4-chloro-2,6-diformylphenol) with 2-aminomethylpyridine have been investigated by fast atom bombardment mass spectrometry and metastable ion studies.     

Heterodinuclear Ln[bond]Na complexes with an asymmetrical macrocyclic compartmental Schiff base

Heterodinuclear lanthanide(III)-sodium(I) complexes [LnNa(L)(Cl)(2)(CH(3)OH)] (Ln=La[bond]Nd, Sm[bond]Lu), where H(2)L is a [1+1] asymmetric compartmental macrocyclic ligand containing a N(3)O(2) Schiff base and a O(3)O(2) crown-ether-like coordination site, have been prepared and characterized by IR, (1)H, (13)C, and (23)Na NMR spectroscopy, mass spectrometry, and electron microscopy. In the solid state, the lanthanide(III) ions coordinate the Schiff-base N(3)O(2) site, and the sodium ion occupies the O(3)O(2) crownlike cavity, as shown by the X-ray crystal structures of the Nd, Eu, Gd, and Yb derivatives. In these complexes, the lanthanide(III) ion is coordinated by two chlorine atoms in the trans position and by three nitrogen and two negatively charged phenol oxygen atoms of the Schiff base, and the ion is heptacoordinated with a pentagonal bipyramidal geometry. The sodium ion is coordinated by three etheric oxygen atoms and the two phenolic oxygens that act as a bridge. A methanol molecule is also coordinated in the apical position of the resulting pentagonal pyramidal polyhedron. A detailed (1)H and (13)C NMR study was carried out in CD(3)OD for both diamagnetic and paramagnetic heterodinuclear complexes [LnNa(L)(Cl)(2)(CH(3)OH)]. The complexes are also isostructural in solution, and their structures parallel those found in the solid state. Moreover, some significative distances determined in the solid state and in solution are comparable. Finally, the potential use of these complexes as molecular probes for the selective recognition of specific metal ions has been tested. In particular, their ability to act as shift reagents and the selectivity of the O(3)O(2) site towards Li(+), Ca(2+), and K(+) were investigated by (23)Na NMR spectroscopy.     

Generation of some orthogonal groups by a set of three involutions

Lavoro eseguito con il finanziamento del M.P.I.     

Separation and Quantitative Determination of Aldoses and Alditols by Over-Pressured Layer Chromatography (OPLC)

JPC – Journal of Planar Chromatography – Modern TLC - Anew OPLC method has been established for separation and quantitative determination of three alditols (d-xylitol, L-arabitol, and...     

Constructive (2,3)-generation: A permutational approach

A groupG is said to be (2,3)-generated if it can be generated by two elements of respective orders 2 and 3. The class of these groups has recently received a lot of attention by several authors: a brief survey of the results in this area is given in the introduction. In this paper we show that, ifR is a ring generated by one element of finite multiplicative order, then the analogues of classical groups overR are (2,3)-generated, provided that their rank is sufficiently large. Our lower bound for the rank improves previous results.     

Fermentation Monitoring Based on HPTLC-OPLC. The Effect of a Complex Biological Matrix on Quantitative Performance

JPC – Journal of Planar Chromatography – Modern TLC - An OPLC method has been established for separation and quantification of eight carbohydrates (glucose, fructose, galactose,...     

Mass spectrometric investigation of some macrocyclic and macroacyclic compartmental schiff bases

The mass spectrometric behaviour of four macroacyclic and five macrocyclic Schiff bases using two ionization methods (electron impact and fast atom bombardment) was studied in detail with the aid of mass-analysed ion kinetic energy (MIKE) spectrometry. It was possible to propose a common electron impact-induced decomposition pattern for the acyclic compounds, whereas for the cyclic compounds, analysed by fast atom bombardment, peculiar fragmentation routes occurred, which were strongly dependent on the macrocyclic structure and on the different side-chains.     

Some remarks on the degrees of faithful irreducible representations

We study a class of finite p-groups admitting faithful irreducible complex representations of distinct degrees. In particular, for every prime p, we produce an example of such a p-group having minimal order p ⁸.Dedicated to A. Wagner on the occasion of his 60th birthdayLavoro eseguito nell'ambito dei finanziamenti M.U.R.S.T.