A new diaza heteroaromatic crown of 3,5-disubstituted 1H-pyrazole which forms solid dinuclear complexes with lipophilic phenethylamines

The cyclic stannoxane obtained from N-methyldiethanolamine and dibutyltin o xide reacts with 1H-pyrazole-3,5-dicarbonyl dichloride to afford the new 26 -membered diaza tetraester crown 3. In neutral medium, the above crown Form s 1:2 solid dinuclear complexes with phenethylamine (3a) and homoveratrylam ine (3b), which, after crystallization From acetonitrile, were isolated in high yield (90% and 85%, respectively). The 3, 3a, and 3b structures were i dentified from their analytical and spectroscopic (H-1, C-13 NMR, and MS (F AB)) data. The spectroscopic properties of 3a and 3b are demonstrating that , in each complexation centre, simultaneously to the strong participation o f the four pyrazole nitrogens, an additional weaker interaction between the aliphatic nitrogen of the side chain and the amine is involved. Comparison of the total interaction energies calculated (GenMol software) for pheneth ylamine-derived complex (3a) and homoveratrylamine-derived one (3b) suggest s that the o-dimethoxy substitution of the guest aromatic ring could be imp roving the stability of 3b in relation to 3a.