engleski

Donor abilities of heterocyclic neutral Lewis bases in Ni(II) salicylaldehyde 4-phenylthiosemicarbazonato coordination environment

The eight mononuclear [Ni(sal 4-Phtsc)•D] thiosemicarbazonato complexes [sal 4-Phtsc = salicylaldehyde 4-phenyl thiosemicarbazonato ligand ; D = imidazole (1), methylimidazole (2), pyridine (3), 4-aminopyridine (4), 4-methylpyridine (6), morpholine (7), thiomorpholine (8), 2-aminophenol (9)] and one dinuclear {; ; ; ; [Ni(sal 4-Phtsc)]2D}; ; ; ; •2DMSO [D = 4, 4’-bipyridine (5)] have been prepared by adding of corresponding Lewis base to the methanol suspension of the parent complex [Ni(sal 4-Phtsc)(H2sal 4-Phtsc)]•CH3OH. The exchange of neutral salicylaldehyde 4-phenyl thiosemicarbazone (H2sal 4-Phtsc) ligand in the parent complex by appropriate Lewis base has been confirmed by IR spectroscopy and powder X-ray diffraction (PXRD) in the solid state. Single crystal X-ray diffraction of seven complexes 1 and 3 – 8 confirmed formation of the complexes with Ni(II) ion coordinated via O, N, S donor atoms from dibasic salicylaldehyde 4-phenyl thiosemicarbazonato ligand and endocyclic N donor atom from neutral ligand D in a form of a distorted square-planar coordination. NMR spectroscopy in DMF or DMSO and quantum mechanical calculations have been performed in order to explain and compare the stability of complexes in solution depending on the polarity of solvents in the context of donor properties and nucleofility of heterocyclic Lewis base, while single crystal X-ray data enables comparison with calculated standard Gibbs energies of binding in the context of crystal packing forces leading to a general conclusion that stability of mononuclear complexes results in formation of more stable hydrogen bonded cyclic dimers as crystal packing pattern.

thiosemicarbazonato complexes / nickel(II) / heterocyclic neutral Lewis bases

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