
%0 Journal Article
%A Wilkes, Eric N. 
%A Hambley, Trevor W. 
%A Lawrance, Geoffrey A. 
%A Maeder, Marcel 
%T Characterization of the Minor <emph type="2">cis</emph> Isomer of a Dipendant Polyamino Acid Macrocycle as a Dimeric Nickel(II) Complex
%J Australian Journal of Chemistry
%D 2000/09/01
%V 53
%N 6
%P 517-521
%K Macrocycle; pendant arm; nickel(II); X-ray crystal structure.
%R https://doi.org/10.1071/CH00012
%U https://www.publish.csiro.au/paper/CH00012 
%X The dipendant-arm polyamino acid macrocycle 13-amino-13-methyl-1,4,8,11-tetraazacyclotetradecane-6-carboxylate (acammac), characterized earlier as the major trans isomer (3), has been isolated as the minor cis isomer (4) by crystallization as the &#91;Ni(4)&#93;(ClO4) complex. The complex has been examined by an X-ray crystal structure analysis, and the cation exists as a dimer with each carboxylate group bound both to its &#8216;parent&#8217; nickel atom and bridging to the adjacent nickel atom. The macrocycle adopts a folded geometry, each nickel atom appearing as a cis-NiN4O2 chromophore. The pendant primary amine group and three of the four secondary amine groups are also coordinated, whereas the fourth secondary amine group is not coordinated but stabilized by a proton bridging within a superbase between the uncoordinated amine and one of the coordinated amines. 
