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RESEARCH PRODUCT

Coordination behaviour of sulfanilamide derivatives.

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Abstract Hg(II), Cd(II) and Zn(II) complexes with the ligands sulfadimethoxine, sulfamethoxypyridazine, sulfadiazine, sulfamerazine, sulfadimidine and sulfamethoxazole have been prepared and characterised by spectral data. 1H and 13C NMR have been used to interpret the structural characteristics of the complexes in solution. The X-ray crystal structures of [Hg(sulfamethoxypyridazinato)2] (2a), [Cd(sulfadimidinato)2(H2O)]·2H2O (4b) and [Zn(sulfamethoxazolato)2(py)2(H2O)2] (6d) have been determined. In complex 2a the Hg(II) ion lies on an inversion centre and exhibits linear coordination by two sulfonamidic nitrogen atoms [Hg–N(1)=2.071(4) A] of the two deprotonated sulfamethoxypyridazinato ligands. The polymeric Cd(II) complex (4b) exhibits a high distorted-octahedral geometry, involving the sulfonamidic nitrogen [Cd–N(1)=2.328(6); Cd–N(1′)=2.326(6) A] and the heterocyclic N(3)/N(2′) [Cd–N(3)=2.307(6) A; Cd–N(2′)=2.426(6) A] of two bidentate sulfadimidine ligands, the terminal amino N(4′b) [Cd–N(4′b)=2.379(7) A] of a third sulfadimidine which is bonded to an adjacent Cd(II), and the O(3) atom of a coordinated water molecule [Cd–O(3)=2.334(6) A]. In complex 6d the geometry around the Zn(II) ion can be described as a slightly distorted compressed octahedron. Two pyridine [Zn–N(16)=2.1841(17) A] and two isoxazole N atoms [Zn–N(2)=2.1736(15) A] are located in the equatorial plane and two oxygen atoms of two water molecules [Zn–O(4)=2.0984(14) A] are placed in the apical positions. IR and NMR spectral studies suggest a similar behaviour of the Cd(II) and Zn(II) complexes, both in solid state and solution, and different to the corresponding Hg(II) complexes. Thus 1H and 13C NMR spectra, in DMSO-d6, of Cd(II) and Zn(II) compounds show coordination mainly through the heterocyclic nitrogen while the corresponding Hg(II) derivatives seem to be coordinated through the sulfonamidic nitrogen.