An artificial receptor has been designed to bind creatinine with a color change (chromogenic response) caused by proton transfer from one end of the receptor to the other. The receptor was synthesized and found to extract creatinine from water into chlorocarbon solvents. The color change in the organic layer is specific for creatinine relative to other organic solutes, and it is selective for creatinine relative to sodium, potassium, and ammonium ions. The chromogenic mechanism is revealed by x-ray crystal structures of creatinine, the free receptor, and the complex, showing "induced fit" binding resulting from electronic complementarity between host and guest.

https://science.sciencemag.org/content/sci/269/5224/671.full.pdf

Detection of creatinine by a designed receptor

Reactivity of copper(II) peptide complexes with bioligands (benzimidazole and creatinine)

Crystal and molecular structure of creatininium tetrachlorocuprate(II)

Aromatic acids and creatinine, an important blood metabolite, form well-defined crystalline ionic complexes. Their supramolecular architecture is formed not only by simple proton transfer and ionic interaction but also by other very important noncovalent interactions, especially the hydrogen bonds. The supramolecular behavior of the complexes is varied with the acidity and structural difference of aromatic acids. Creatinine interestingly generated creatine monohydrate during crystallization of creatinine with glacial acetic acid and the supramolecular array of creatine monohydrate is also reported.

H. Mendel

Papers

The crystal structure of creatinine