NEW FACILE AND CONVENIENT SYNTHESIS OF BISPOLYAZAMACROCYCLES USING BOC PROTECTION - DETERMINATION OF GEOMETRIC PARAMETERS OF DINUCLEAR COPPER(II) COMPLEXES USING ESR SPECTROSCOPY AND MOLECULAR MECHANICS CALCULATIONS

A new facile and convenient synthetic route has been designed for the preparation of bispolyazamacrocycles in high yields by direct condensa tion of the readily available intermediate N,N'-diboctriazamacrocycle or N,N',N ''-triboctetraazamacrocycles with aromatic biselectrophiles, ie, o-, m-, p-xylyl and anthracenyl derivatives. The use of a versati le group, such as tert-butyloxycarbonyl (Boc), which is easily removed within 1 h by treatment with 6 M HCl or TFA, leads to polyazamacrocyc les in which one nitrogen is discriminated from the others. The anthra cenyl and o-xylyl dimers were synthesized by reacting diacyl chloride to give the corresponding diamides. Further reduction of the amide gro ups and elimination of the protecting Boc moieties were carried in a o ne-pot reaction with BH3-THF followed by acid treatment. In parallel, exclusive mono-N-alkylation of the available secondary amine of the sa me protected macrocycle with the corresponding dibromoxylene gave the meta and para dimers; the protecting moieties were eliminated in a sim ilar way. ESR measurements of spin-spin distances of the dicopper comp lexes were determined from the ratio of the intensity of the forbidden transition to the intensity of the allowed transitions. Molecular mec hanics calculations were also undertaken in order to evaluate the Cu-C u distance by using a new rule-based force field.