Hydrogen Bond, pi¿pi, and CH¿pi Interactions Governing the Supramolecular Assembly of Some Hydrazone Ligands and Their Mn(II) Complexes ¿ Structural and Theoretical Interpretation

Abstract

[eng] The hydrazone Schiff base ligands (E)-N -(2-hydroxybenzylidene) acetohydrazide (HL1) and (E)-N -(2,3-dihydroxybenzylidene) acetohydrazide (H2L2) with a functional group variation in the aromatic moiety have been synthesized. The ligands have been used to synthesize the following MnII complexes: the mononuclear complex [Mn(HL1)2]- [ClO4]2·2H2O (1), the cocrystallized discrete dinuclear complex {[Mn(HL1)2]·[Mn(L1)2]}[ClO4]2 (2), and the phenoxidobridged dinuclear complex [Mn(μ-HL2)(H2O)]2[ClO4]2 (3). The ligands and the complexes were characterized by FTIR and UV/Vis spectroscopic techniques, and their crystal structures were determined by single-crystal X-ray diffraction analysis. 1H and 13C NMR spectroscopy shows evidence of keto-enol tautomerism of the ligands in solution. All of the compounds develop hydrogen-bonded assemblies of different dimensionalities and architectures. CH-π and π-π interactions also contribute significantly to the overall binding energies of the supramolecular assemblies. The supramolecular interaction energies have been computed at the BP86- D3/def2-TZVPD level of theory.