Synthesis Characterization and Molecular Structures of someBismuth(III) Complexes with Thiosemicarbazones andDithiocarbazonic Acid Methylester Derivatives with Activityagainst Helicobacter Pylori

摘要

The reactions of bismuth(III) nitrate pentahydrate and bismuth(III) chloride with heterocyclic thiosemicarbazones and derivatives of dithiocarbazonic acid methylester were used to synthesize the respective bismuth(III) complexes, which could be divided into five groups D-H because of their stoichiometrical properties and their molecular structures. The molecular structure and the near coordination sphere of the bismuth(III) central atom of four representative compounds were determined by single-crystal X-ray studies. Bis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N′,N³,S]bismuth(III) nitrate (5) belongs to group D. The two tridentate ligands and the nitrate ion surround the bismuth atom. The best description of the coordination sphere appears to be that of a distorted trigonal dodecahedron with one position occupied by the lone pair of the bismuth atom. Bis[1-azepanyl-4-(2-thienyl)-2,3-diazapenta-1,3-diene-1-thiolato-N³,S]bismuth(III) nitrate (9) is assigned to complex type E. Here, two deprotonated ligand molecules are coordinated to the bismuth(III) central atom as bidentate ligands. The structure of this complex can best be described as a distorted trigonal antiprism with a five-coordinated central atom. The two triangular faces are formed by the atoms S(4), N(6), O(11) and S(3), N(4) and the lone pair of the central atom. The two chelate rings are almost perpendicular to each other. Complex molecules of group F form dimeric units with bichloro-bridged bismuth atoms. The structure of di-μ-chlorobis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N′,N³,S-chloro]dibismuth(III) (15) can be described as two six-coordinated bismuth atoms, which are bound together via two bridging chlorine atoms. The two bismuth atoms Bi(1) and Bi(1a) and the two bridging chlorine atomsCl(2) and Cl(2a) form the Bi2Cl2 plane. The two tridentate ligand molecules coordinate via thesame atoms as shown in complex 5. In addition, they form two parallel planes, which are perpendicularto the Bi2Cl2 plane. With regard to the center of the Bi(1)-Bi(2) axis they are centralpoint symmetrical, i.e. one pyridine ring lies above and the other beneath the Bi2Cl2 plane. Bismuth(III) chloride and pyridine-2-carboxaldehydethiosemicarbazone 1 b or 2-acetylpyridine-thiosemicarbazone1 c form complexes of group G. Three chlorine atoms and a bidentate ligandare coordinated to the bismuth(III) central atom. The bidentate ligand bound to thecentral atom through the N(3) atom and the sulfur atom of the thioketo group. The structureof 18 is completely different from the structures of the bismuth(III) complexes discussed sofar and was therefore assigned to group H. The bismuth central atom is coordinated with twoligands, which are bound in different ways. One of them is deprotonated. This ligand is boundto the central atom via the sulfur atom S(3) of the thiolate group and the N(5) atom. An interactionbetween the sulfur atom of the thiophene ring and the bismuth atom is not possible.The other ligand molecule is not deprotonated. This ligand is bound to the bismuth(III) cationmerely via the sulfur atom S(1) of the thioketo group. The best description of the coordinationsphere of the bismuth atom is that of a distorted square bipyramidal polyhedron. The squareface is formed by the atoms S(3), N(5), Cl(1), the lone pair and the bismuth atom within. Theaxial positions are occupied by the atoms S(1) and Cl(2). The bond angle between S(1), Bi(1)and Cl(2) differs by about eight degrees from the value determined for a regular squarebipyramidal polyhedron of 180 degrees.Some of the newly synthesized bismuth complexes and three ligands have been testedagainst several strains of Helicobacter pylori bacteria in an agar dilution test. Almost all of thelisted bismuth complexes show excellent inhibitory properties with regard to growth of H. pylori already at low concentrations.