Bis[<i>N</i>-alkyl-<i>N</i><i>N</i>-di(2-pyridylmethyl)amine]zinc(II) perchlorates display <i>cis-facial</i> stereochemistry in solid state and solution

<div><p><i>N</i>-Alkyl-<i>N</i>,<i>N</i>-di(2-pyridylmethyl)amines are ligands commonly used by supramolecular chemists in molecular recognition and sensing applications. The metal coordination complexes of these ligands, in particular those with 2:1 (ligand:metal) molar ratio, have not been sufficiently characterised in solution. In this work, bis[<i>N</i>-alkyl-<i>N</i>,<i>N</i>-di(2-pyridylmethyl)amine]zinc(II) perchlorates are characterised in both solid and solution phases, using X-ray crystallography and NMR spectroscopy, respectively. Only the <i>cis-facial</i> stereoisomer is observed. Density functional theory calculations support the thermodynamic preference for this stereochemistry, as in one representative case the gas phase energy of the <i>cis-facial</i> configuration is lower than those of the <i>trans-facial</i> and <i>meridional</i> configurations by 4.0 and 4.5 kcal/mol, respectively.</p></div>

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