Abstract
The asymmetric unit of the title compound, [Co(C12H8N2)2(H2O)2]2[Ge(C6H5O7)2](NO3)2, features two complex [(C12H8N2)2(H2O)2Co]2+ cations, two NO3 - anions as well as one centrosymmetric [(C6H5O7)2Ge]2- anion. Two HCit ligands (Cit = citrate, C6H4O7) each coordinate via three different oxygen atoms (hy-droxy-late, α-carboxyl-ate, β-carboxyl-ate) to the Ge atom, forming a slightly distorted octa-hedron. The coordination polyhedron of the Co atom is also octa-hedral, formed by coordination of four nitro-gen atoms from two phenanthroline mol-ecules and two water oxygen atoms. In the crystal, the cations and anions are linked by hydrogen bonds and form layers parallel to the bc plane. The structure exhibits disorder of the NO3 - anion [disorder ratio 0.688 (9) to 0.312 (9)]. There are also highly disordered solvent mol-ecules (presumably water and/or ethanol) in the crystal structure; explicit refinement of these mol-ecules was not possible, and the content of the voids was instead taken into account using reverse Fourier transform methods [SQUEEZE procedure in PLATON; Spek (2015 ▸). Acta Cryst. C71, 9-18]. The given chemical formula and other crystal data do not take into account the unknown solvent mol-ecule(s).
Highlights
Citric acid (H4Cit) is an essential component of the Krebs cycle and a universal intermediate in plant and animal metabolism
The authors reported that the anion of the cobalt salt affects the composition and structure of the complex and results in the formation of cation– anionic compounds such as [Co(phen)3][Ge(HCit)2]Á2H2O (Seifullina et al, 2017a) or [Co(H2O)2(phen)2]2[Ge(Cit)2]Á4H2O (Martsinko et al, 2018a,b)
The third carboxylic group of the citric acid is deprotonated, which leads to a change of the charge of the anion and of the molar Co:Ge ratio, while the coordination polyhedron of the germanium atom remains the same: distorted octahedral, formed by six oxygen atoms of three types of oxygen atoms from two tridentate chelating citrate ligands
Summary
Citric acid (H4Cit) is an essential component of the Krebs cycle and a universal intermediate in plant and animal metabolism. In this compound, the third carboxylic group of the citric acid is deprotonated, which leads to a change of the charge of the anion and of the molar Co:Ge ratio, while the coordination polyhedron of the germanium atom remains the same: distorted octahedral, formed by six oxygen atoms of three types of oxygen atoms from two tridentate chelating citrate ligands. We report the synthesis and structural analysis of a new complex, [Co(H2O)2(phen)2]2[Ge(HCit)2(NO3)2], which was synthesized by changing the anion of the initial cobalt(II) salt to nitrate. This study is important for establishing the effect that the anion of the 3d metal salt has on the composition and structure of heterometal bis(citrato)germanates with 1,10-phenanthroline, as well as for the creation of new bioactive compounds
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