Polymorphism in an unexpected caesium complex of 5-hydroxyhydurilic acid

Area of Science:

• Crystal engineering
• Coordination chemistry
• Supramolecular chemistry

Background:

• Barbituric acid derivatives are versatile building blocks in coordination chemistry.
• Polymorphism in metal-organic complexes can significantly influence material properties.
• Understanding crystal packing is crucial for designing novel functional materials.

Purpose of the Study:

• To synthesize and characterize a novel caesium complex of 5-hydroxyhydurilic acid.
• To investigate the formation of different polymorphic forms of the complex.
• To elucidate the structural differences between the observed polymorphs.

Main Methods:

• Reaction of barbituric acid with caesium hydroxide in water.
• Single-crystal X-ray diffraction analysis.
• Crystallographic studies to determine space groups and molecular arrangements.

Main Results:

• A new coordination polymer, poly[[caesium-mu5-5-hydroxyhydurilato] hemihydrate], {[Cs(C8H5N4O7)].0.5H2O}n, was successfully synthesized.
• Two distinct polymorphic forms (orthorhombic and monoclinic) were obtained, dependent on crystallization conditions.
• Both polymorphs feature nine-coordinate caesium centers and exhibit differences in crystal packing and cavity morphology.

Conclusions:

• The synthesis yielded a novel caesium-5-hydroxyhydurilate complex with potential for diverse applications.
• The study highlights the influence of crystallization methods on the formation of distinct polymorphs.
• Structural analysis revealed subtle yet significant differences in the arrangement of components and cavity shapes between the two crystalline forms.