Control of the Stereochemistry of Four-co-ordinate Copper(II) Complexes by Pyridinecarboxamide Ligands: Crystal Structure, Spectral and Redox Properties

Article abstract of DOI:10.1039/DT9940000965

Three copper(II) complexes 1>*H2O 1, 22> 2 and 32> 3 1 = N,N'-o-phenylenebis(pyridine-2-carboxamide); HL² = N-phenylpyridine-2-carboxamide; HL³ = N-2,4,5-trichlorophenylpyridine-2-carboxamide> have beenn prepared and their stereochemical properties investigated.Complex 2 has been characterized by X-ray crystallography: space group P2₁/n, a = 10.853(4), b = 19.015(6), c = 10.293(3) Angstroem, β = 105.22(3) deg, Z = 4, R = 0.030, R' = 0.034 for 2938 observed reflections.Compared to the known square-pyramidal structure of 1 it is revealed that the deprotonated bidentate ligand L² exerts a measureable degree of geometric control over the co-ordination sphere of 2 (distorted towards tetrahedral).Similar effects are also observed from absorption and EPR spectral results.The Cu(II)-Cu(I) redox potentials in dimethylformamide solution have been determined by cyclic voltammetry.Upon replacement of the tetradentate L¹ ligand by two uninegative bidentate L² or L³ ligands, of similar donor set, a marked positive shift (ca. 0.6-0.7 V) was observed, implying the predominance of structural effects.

Full text of DOI:10.1039/DT9940000965

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