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

Abstract

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.

Synthesis of the Bacteriostatic Poly(l-Lactide) by Using Zinc (II)[(acac)(L)H2O] (L = Aminoacid-Based Chelate Ligands) as an Effective ROP Initiator

“…For the second complex (Figure 6b), the deformation was not that strong. [37]. The respective lengths of the bonds between zinc and the oxygen or nitrogen atoms as well as the angles in these complexes were very close to the values presented above.…”

“…For Zn[(acac)(LTrp)H 2 O], the lengths of the bonds were as follows: Zn-O1-1.970 Å, ZnO2-1.968 Å, Zn-O3-1.982 Å, Zn-N-2.121 Å, and Zn-O4-2.58 Å; and the angles were as follows: O1-Zn-O2-105.51 • and O3-Zn-N-81.96 • . The calculated geometry was identical to that of many other Zn(II) mononuclear complexes with a similar geometry; for example, Zn(4-dimethylaminopyridyl)(acac) 2 ][36] or Zn[(PhCOO)(cur)(bpy)] contained ligands on curcumin, bipyridine, and benzocarboxylate[37]. The respective lengths of the bonds between zinc and the oxygen or nitrogen…”

Metal–Curcumin Complexes in Therapeutics: An Approach to Enhance Pharmacological Effects of Curcumin

“…It was found that the Zn 2+ -curcumin complex exhibited good stability and higher solubility with better pharmacodynamic effects than free curcumin [104]. It was also observed that Zn 2+ -curcumin displays a higher stability than curcumin in buffered media, but its degradation begins with the increase of pH [105]. A complex of copper and curcumin was synthesized, and to further increase its aqueous solubility, β-cyclodextrin (CD) was included in the complex.…”

Synthesis, characterization, POM analyses and biological evaluation of n-[(2-methoxy-5- nitrophenyl)]-4-oxo-4-[oxy] butenamide based zinc(II) carboxylate complexes

“…In coordination chemistry, Zn is an attractive central metal ion and is an essential part of all enzyme classes. Zinc performs diverse physiological functions in many biological processes, for example, as a structural component, as a catalytic factor, or as a signaling mediator [8]. Curcuminate based zinc(II) complexes having an aromatic spectator ligands displayed in vitro anticancer activity against various cancer cell lines [9].…”