M. Spirlet, J. Rebizant, P. Barthelemy
1991
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0
Influential Citations
8
Citations
Journal
Journal of The Chemical Society-dalton Transactions
Abstract
The tetraprotonated form of the macrocyclic ligand teta (1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate) crystallizes in the monoclinic system, space group P21/c, a= 7.816(2), b= 14.656(2), c= 11.647(3)A, β= 102.52(4)°, Z= 2. The structure was refined from diffractometer data to an R value of 0.035 and the hydrogen atoms were located unequivocally. In agreement with previous NMR investigations, H4teta features two protonated nitrogen atoms in the ring and two protonated carboxylate groups. The electrostatic repulsion is thus reduced to a minium. The tetraaza ring adopts a quadrangular [3434] conformation which is one of the most stable geometric arrangements of the 14-membered cycles. The ligand forms no intramolecular hydrogen bonds but it is involved in intermolecular hydrogen bonds with water molecules.