Calcium acamprosate: a triclinic polymorph.

Area of Science:

• Crystallography
• Materials Science
• Coordination Chemistry

Background:

• The study investigates poly[bis-(4-acetamido-propane-sulfonato)-calcium], a coordination polymer.
• A monoclinic polymorph of this compound was previously reported by Toffoli et al. (1988).

Purpose of the Study:

• To characterize a novel triclinic polymorph of poly[bis-(4-acetamido-propane-sulfonato)-calcium].
• To elucidate the structural differences between the triclinic and monoclinic polymorphs.
• To understand the coordination environment of the calcium cation and the intermolecular interactions within the crystal structure.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the crystal structure.
• The crystal structure was solved and refined, accounting for non-merohedral twinning.

Main Results:

• The triclinic polymorph exhibits an all-trans configuration of the acetamido-propane chain.
• The calcium cation (Ca(2+)) is hexa-coordinated in a distorted octahedral geometry, situated on an inversion center.
• A layered structure parallel to (011) was observed, with layers connected by N-H⋯O hydrogen bonds and C-H⋯O interactions.
• The crystal structure was successfully determined despite being twinned by non-merohedry.

Conclusions:

• The discovery of the triclinic polymorph provides new insights into the structural polymorphism of this calcium coordination compound.
• The distinct chain configuration and layered structure highlight the versatility of crystal packing in this material.
• The detailed structural analysis contributes to the understanding of calcium coordination polymers and their intermolecular interactions.