Beitrag zur Konstitution anorganischer Verbindungen. XVIII. Mitteilung. Über Äthylendiam in- und Propylendiaminverbindungen von Salzen zweiwertiger Metalle

The disproportionation of [Ni(tacn)]2+ in Ni2+ and [Ni(tacn)2]2+ crystallographically demonstrated (tacn = 1,4,7-triazacyclononane)

From an EtOH/H2O solution, 0.3 M each of Ni(2+) and cyclic triamine tacn (2; tacn = 1,4,7-triazacyclononane), after 10 min refluxing and cooling at room temperature, copious and comparable amounts of blue crystals (containing the complex [Ni(tacn)(H2O)3](2+)) and pink crystals (containing in the same cell both [Ni(H2O)6](2+) and [Ni(tacn)2](2+)) precipitated. This unusual behaviour is ascribed to the fact that at the refluxing temperature the three species are present at the equilibrium in similar concentrations, which are frozen on cooling, due to the inertness of the macrocyclic complexes [Ni(tacn)(H2O)3](2+) and [Ni(tacn)2](2+).

N-Glycoside Complexes of Nickel(II); Probing Carbohydrate - Transition Metal Interactions

Nickel(ii) complexes prepared from d- and l-arabinose (d-ara and l-ara) and 1,2-diaminoethane (en), [Ni(en-d-ara)2](ClO4)2·2H2O 1 and [Ni(en-l-ara)2](ClO4)2·2H2O 2 (where en-d-ara is 1-((2-aminoethyl)amino)-1-deoxy-d-arabinose) were synthesized and characterized by absorption spectroscopy, circular dichroism (CD), and X-ray crystallography. The CD spectra of 1 and 2 in the d–d transition region indicate a C2 chiral configuration around the metal centre. X-ray crystallography of 1 revealed that two 1-((2-aminoethyl)amino)-1-deoxy-d-arabinose ligands coordinate to the nickel atom in nearly C2 symmetry, through the C(2) hydroxy group of the arabinose moiety and two nitrogen atoms of the diamine in a meridional mode. This results in a Λ-C2-helical configuration around the metal centre. The arabinose ring adopts the rare α-1C4 chair conformation and the carbohydrate–chelate ring conformation is δ.

Antifungal nickel(II) complexes derived from amino sugars against pathogenic yeast, Candida albicans

Nickel(II) complexes containing N-glycosides derived from D-glucosamine (D-GlcN) and ethylenediamine (en) and trimethylenediamine (tn), [Ni(D-GlcN-en)2]Cl2.H2O (1) (D-GlcN-en = 1-¿(2-aminoethyl)amino¿-2-amino-1,2-dideoxy-D-glucose) and [Ni(D-GlcN-tn)2]Cl2.4H2O (2) (D-GlcN-tn = 1-¿(3-aminopropyl)amino¿-2-amino-1,2-dideoxy-D-glucose), are fairly stable in water at room temperature and showed effective antifungal activity against pathogenic yeast, Candida albicans, with the MIC (minimal concentration of inhibition) values of the complexes being 0.25 mM. The results obtained enzyme assays by using preparations of C. albicans chitinase fraction suggested that the sugar complexes 1 and 2 played a role of novel chitinase (chitin-degradation enzyme) inhibitor, where the modes of inhibition were competitive (Ki = 1.3 mM for 1, Ki = 1.8 mM for 2). The newly prepared nickel(II) complex 2 was characterized by elemental analysis, magnetic susceptibility, electronic absorption and circular dichroism spectroscopies, and an X-ray crystallographic analysis.