S. du Pré

Abstract: 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.

Abstract: The nature of the peptide seems to be a very important factor for the reactivity of copper(II) peptide complexes with bioligands. Thus, although we have tried to obtain all the ternary complexes derived from the dipeptides l -ala-gly, gly- l -tyr and gly- l -trp with benzimidazole and creatinine, only four new ternary Cu(II) peptide complexes have been obtained: [Cu(gly- l -tyr)(benzimidazole)] · H2O (1), [Cu( l -ala-gly)(benzimidazole)] · 3H2O (2), [Cu(gly- l -trp) (creatinine)] · 1.25H2O (4) and [Cu( l -ala-gly)(H2O)(creatinine)] · 2H2O (5). Compounds 1, 2 and 4 exist as slightly distorted square planar complexes with the four coordination sites occupied by the tridentate peptide dianion and a nitrogen of the ligand, while compound 5 present a square pyramidal co-ordination in which the axial position is occupied by a water molecule. In the ternary benzimidazole complexes the lateral chain of the peptide moiety seems to determine the relative orientation of the ligand. In contrast, in the creatinine complexes the presence of two important intramolecular hydrogen bonds, involving the exocyclic NH2 and CO groups of the creatinine molecule, yield a nearly co-planar system which is independent of the nature of the peptidic lateral chain. These compounds do not present catalase-like activity nor remarkable SOD-like activity but the values of IC50 permit to distinguish a different behavior between benzimidazole and creatinine ternary complexes. Thus, benzimidazole compounds show lower IC50 (similar to free Cu(II)) values than creatinine ones.

Abstract: Preparation, crystal and molecular structure of creatininium tetrachlorocuprate(II) is described. The structure was solved by X-ray diffraction studies and was refined by least-squares methods to R = 0.041 for 1344 reflections. The compound is monoclinic, space group, P21/c. The unit cell parameters are a = 8.080(3), b = 7.831(2), c = 13.922(3) A, β = 113.77(2)°, V = 806.2 A3, dc = 1.786, dm = 1.77(1) g cm−3, Z = 2. The [CuCl4]2− ion is centrosymmetric and the copper atom is surrounded by four Cl atoms (CuCl1 2.233(1), CuCl2 2.268(1)) in a square planar arrangement. The creatininium cation is almost planar and each cation is linked to [CuCl4]2− units through hydrogen bonding involving the amino and imino nitrogen atoms.

Abstract: 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.

Abstract: Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV–vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV–visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu–Crn–urea heteroligand complex at different solute concentrations have been analyzed and the complex is found to be rigid and stable in its monomeric form at very low concentrations.