Mn(III) and Cu(II) complexes of 1-((3-(dimethylamino)propylimino)methyl) naphthalen-2-ol): Synthesis, characterization, catecholase and phenoxazinone synthase activity and DFT-TDDFT study

Abstract

Two new complexes, [MnL₂](ClO₄) (1) and [CuL₂] (2) (where LH = (E)-1-((3-(dimethylamino)propylimino)methyl)naphthalen-2-ol), have been synthesized and characterized by spectroscopic techniques and their molecular structures are established by single-crystal X-ray diffraction study. Complex 1 adopts an octahedral geometry around the central manganese atom which is in + 3 oxidation state, whereas in complex 2, the Cu⁺² ion preferred a square pyramidal environment around it through the ligand donor atoms. Both complexes were tested for catecholase and phenoxazinone synthase activity. Complex 1 catalyzes the oxidation of 3,5-ditertiary-butyl catechol with a k_cat value of 6.8424 × 10² h⁻¹ in acetonitrile whereas the same for complex 2 is 3.7485 × 10² h⁻¹ in methanol. Phenoxazinone synthase activity was shown only by complex 2 having k_cat = 74.225 h⁻¹. Structures of both the title complexes have been optimized by means of DFT calculations. Experimental electronic spectra of the complexes have been corroborated by TDDFT analysis. Electrochemical investigations by means of cyclic voltammetry have been carried out to study the electron transfer processes in the complexes.

Keywords:

• Metal complex
• catecholase
• phenoxazinone synthase
• DFT

Acknowledgements

S N thanks CSIR, New Delhi, Government of India for funding this work through the CSIR Project (No. 01(2577)/12/EMR-II, 03/04/2013). SN is grateful to AICTE, New Delhi, Government of India for sanctioning a UV–vis-NIR spectrophotometer through AICTE-RPS Project (No. 8023/RID/RPS-10/Pvt (II Policy)/2011–2012). S N also acknowledges the NMR spectral facility established in the Chemistry Dept. BIT-Mesra through the DST FIST Program (SR/FST/CSI-242/2012). Different analytical services obtained from CIF, BIT-Mesra are greatly acknowledged.