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The octadentate ligand H4DOTA (H4DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N",N′′′-tetraacetic acid) forms the most stable calcium complexes known. The overall solid state structure of the title complex {poly[triaqua-μ-(1,4,7,10-tetraazacyclododecane)-N,N',N",N′′′-tetraacetato)-dicalcium 7.7-hydrate], [Ca2(C16H24N4O8)(H2O)3].7.7H2O} contains two independent eight-coordinate Ca2+ ions on a twofold crystallographic axis with the Ca2+ ions bound to four of the eight O atoms [mean Ca-O = 2.45 (3) Å] and the four N atoms [mean Ca-N = 2.59 (2) Å] of the DOTA ligand. The coordination geometry of the Ca atom encapsulated by the DOTA ligand is distorted square antiprismatic. Carboxylate bridges link [Ca(DOTA)]2− anions to [Ca(OH2)3]2+ counterions (on general positions related by the twofold symmetry) to form a neutral tetranuclear unit, which in turn bridges to surrounding units through a carboxylate O atom and generates a one-dimensional chain.

Supporting information

cif

Crystallographic Information File (CIF)
Contains datablock cado

fcf

Structure factor file (CIF format)
Contains datablock cado

CCDC reference: 124363

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