Mn(IV), Co(II) and Ni(II) complexes of the Schiff bases of 2-hydroxy-naphthaldehyde with amino alcohols: synthesis, characterization and electrochemical study; DFT study and Catecholase activity of Mn(IV) complex

Abstract

Four new mononuclear complexes, [Mn^IV(L¹)₂] (1), [Co^II(HL¹)₂] (2), [Ni^II(HL¹)₂] (3), and [Ni^II(HL²)₂] (4), with ligands H₂L¹ (2-hydroxyethylimino)methylnaphthol) and H₂L² (3-hydroxy propylimino)methylnaphthol) have been synthesized, characterized, and their catecholase activities have been studied. Single-crystal X-ray diffraction study shows that 1 crystallizes in P4₃2₁2 space group and adopts an octahedral geometry in meridional fashion, whereas 4 with a square planar geometry crystallizes in P2₁/n space group. The catecholase activity has been investigated in acetonitrile by UV-Vis spectrophotometric technique. The kinetic study revealed that 1 has a moderate catecholase activity (k_cat = 812 h⁻¹), whereas 2–4 are inactive. Electronic structure of 1 and 4 has been established by theoretical calculation. Structures of both complexes have been optimized by DFT. Experimental electronic spectra of the complexes have been corroborated by TD-DFT analysis.

Graphical Abstract

Keywords:

• Catechol oxidase (CO)
• DFT and TD-DFT
• electrochemical analysis
• enzymatic parameters (k_cat
• K_M
• and V_max)
• single-crystal X-ray diffraction

Acknowledgements

S.N. also acknowledges the NMR spectral facility 242/2012. Different analytical services were obtained from CIF, BIT-Mesra.

Disclosure statement

There is no conflict of interest to declare.

Additional information

Funding

S.N. thanks CSIR, New Delhi, Govt. of India for funding this work through the CSIR Project (No. 01(2577)/12/EMR-II, 03/04/2013). S.S. acknowledges Birla Institute of Technology-Mesra for fellowship.