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Zn(II) Curcuminate Complexes with 2,2′-bipyridine and Carboxylates

Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
Authors to whom correspondence should be addressed.
Molecules 2019, 24(14), 2540;
Received: 27 June 2019 / Revised: 9 July 2019 / Accepted: 9 July 2019 / Published: 11 July 2019
(This article belongs to the Collection Molecular Structure)
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Two novel zinc(II) compounds with curcuminate (abbreviated as cur), [Zn(CH3COO)(cur)(bpy)](1)·CH3OH·2H2O (bpy = 2,2′-bipyridine) and [Zn(PhCOO)(cur)(bpy)] (2)·CH3OH, have been synthesized and characterized. Their composition has been determined by single-crystal X-ray structure analysis. Complexes 1 and 2 are similar: in both a five-fold coordination environment of zinc(II) consists of a monodentate carboxylate, a chelating bidentate 2,2′-bipyridine, and curcuminate, which is bound via a deprotonated 1,3-dione moiety. In 1, 2,2′-bipyridine nitrogen atoms and curcuminate oxygen atoms form the base of a square pyramid, whereas the acetate oxygen occupies its apex. The O3N2 donor set in 2 defines a polyhedron which more closely resembles a trigonal bipyramid. The packing in the crystal lattices of both compounds is governed by hydrogen-bonds. Complexes 1 and 2 display higher stability than curcumin in buffered media at pH = 7.0, however, the degradation of coordinated cur is comparable to that of yellow pigment curcumin (curH) when the pH is raised to 7.2. Both complexes 1 and 2 in DMSO exhibit fluorescence with Stokes shifts of 5367 and 4634 cm−1, respectively. View Full-Text
Keywords: curcumin; Zn(II) complexes; stability; crystal structures curcumin; Zn(II) complexes; stability; crystal structures

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Grabner, S.; Modec, B. Zn(II) Curcuminate Complexes with 2,2′-bipyridine and Carboxylates. Molecules 2019, 24, 2540.

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