Comparative Structural Characterization of the Biquaternized N-CH3 and N-BH3 Derivatives of the cis-Cyclen and cis-Cyclam Condensation Products with Glyoxal

Abstract The biquaternized N-CH 3 and N-BH 3 derivatives of the cis -cyclen (1,4,7,10-tetraazacyclododecane) and cis -cyclam (1,4,8,11-tetraazacyclotetradecane) condensation products with glyoxal have been prepared and structurally characterized by NMR spectroscopy and in the case of the BH 3 adducts additionally by X-ray crystallography. A comparison of the structural data between the four compounds and the starting materials permitted: (i) to establish their overall conformation, (ii) to discuss the structural modifications caused by the N-CH 3 and N-BH 3 functional groups and (iii) to understand, why the bialkylated tetraazapolycycles can be reduced to the cross-bridged tetraazamacrocycles, in contrast to the borane adducts.