Synthesis, characterization, reactivity, and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Abstract

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂] · nH₂O (where A = py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN = bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.

Keywords:

• “EPR of Mn (IV)” complexes
• Bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone
• Magnetic moment
• Electrochemical studies
• Spectral studies

Acknowledgments

The authors are grateful to the Head, SAIF, North-Eastern Hill University, Shillong-793022, Meghalaya, India for elemental analyses and mass spectral studies, the Head, SAIF, CDRI, Lucknow, Uttar Pradesh, India for FAB mass spectral data, and the Head, SAIF, IIT Mumbai, India for EPR spectroscopic studies.