Structural features of neutral and cationic cyclams

Dicationic compounds of general formula [1,8-R-2-1,4,8,11-tetraazatricyclo[9.3.1.1(4,8)]hexadecane]X-2, where R = H, Me or Bn' and X is a halogen counterion were obtained by reactions of 1,4,8,11-tetraazatricyclo[9.3.1.1(4,8)]hexadecane with different electrophiles. The solid-state molecular structures of the compounds reveal that the hydrogen, methyl or benzyl groups are located on the nitrogen atoms that are not only the less sterically hindered but also have the electron lone pair pointing out of the macrocycle backbone. In all compounds it is observed a bond shortening between the N-C-aminal and the two other C-N bonds that may be attributed to an inductive effect. These compounds afford the corresponding trans-N,N'-disubstituted cyclams upon hydrolysis in basic medium. (C) 2015 Elsevier B.V. All rights reserved.