engleski

N-(2-ethylpyridine) -2-oxy-1-naphthaldimine. Dimerization by three-centre intermolecular hydrogen bond

As a part of our comprehensive study on Schiff bases derived from 2-hydroxy-1- naphthaldehyde with as bulky as possible aryl amines a potential tridentate ligand with pyridine-2-ethylamine was prepared and structurally characterized by the X-ray analysis. The practical interest in this type of compounds arises from their possible use as excellent coordinating agents for transition metals. Besides, the choice of N-substituents can effect to the sterochemistry of the chelate ring i.e. to the sort of intramolecular hydrogen bond. Although two kinds of hydrogen bridge are possible in this class of compounds (N-H…O versus N…H-O) the majority of Schiff base ligands derived from 2-OH-naphthaldehyde investigated so far contains hydrogen atom bonded to nitrogen i.e. bidentate ligands appear as a rule in the form of keto-amine tautomer. On the contrary corresponding 2-OH-salicylaldimines prefer the O-H…N, enol-imine tautomeric form. Sometimes, as was established in this structure determination H-bond hydrogen atom can be involved in intermolecular hydrogen bridging. The presence of four stereomers in the unit cell and a non-centrosymmetric space group were established during the structural determination in the P-1 space group. The crystals are built up of discrete dimer molecules linked mutually with normal van der Waals attractive forces only. Four single molecules have combined in two dimers by three-centre intermolecular hydrogen bond. The monomer molecules themselves are in the form of a keto-amine tautomer. The presence of the inversion centre in the middle of the dimer is just an illusion. The N-substituent ethylpyridine hetero atom predetermines pseudo symmetry. The refinement procedure is in progress.

three-centre hydrogen bond; Schiff base dimer molecules; X-ray structure determination

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