NDLI: Unveiling the effects of the <i>in situ</i> generated arene anion radical and imine radical on catecholase like activity: a DFT supported experimental investigation

Content Provider	Royal Society of Chemistry (RSC)
Author	Das, Debasis Adhikary, Jaydeep Bauza, Antonio Dasgupta, Sanchari Frontera, Antonio Giri, Sanjib
Copyright Year	2017
Abstract	Two new dinuclear nickel(II) complexes namely [Ni2(L1)2(OAc)2(H2O)2]·CH3CN (1) and [Ni2(L2)2(SCN)2(CH3OH)2]·CH3OH (2) have been synthesized from the designed Schiff-base ligand 4-bromo-2-[(2-hydroxy-1,1-dimethyl-ethylimino)-methyl]-phenol (HL1) and its reduced analogue 4-bromo-2-[(2-hydroxy-1,1-dimethyl-ethylamino)-methyl]-phenol (HL2), respectively. Both 1 and 2 have been characterised by usual physicochemical techniques (UV-Vis, FT-IR, ESI-MS study and single crystal XRD) and their variable temperature magnetic study has been performed. The nickel(II) centres in the dinuclear complexes 1 and 2 are antiferromagnetically coupled through participation of the bridging phenoxyl oxygen. In acetonitrile solution both 1 and 2 retain their dinuclear structural integrity as is evident from the ESI-MS study. The catecholase-like activity of 1 and 2 has been performed in acetonitrile medium using 3,5-di-tert-butylcatechol (3,5-DTBC) as a model substrate. Complex 1 shows a higher catalytic activity than that of complex 2. The ESI-MS study suggests that dinuclear species undergo cleaving into a mononuclear entity in the presence of 3,5-DTBC and that mononuclear species are supposed to act as active catalysts in the catalytic cycle. The EPR study of catalytic reactions confirms that organic radicals have been generated during catalysis in both cases. However, in the case of complex 1 catalyzed reaction a single isotropic signal at g = 1.97 is obtained which is most likely due to imine radical formation. On the other hand, for complex 2 catalyzed reaction the spectrum shows a signal with hyperfine splitting (g = 2.11, 2.05 and 1.9), thereby suggesting the generation of a new radical i.e. an arene anion radical in this study on catecholase activity. Extensive DFT calculations have been performed to support the experimental observation and thus to put forward the most probable mechanistic pathways operating in the two cases. The higher efficiency of the imine radical pathway over the arene anion radical has been rationalized by DFT calculations.
Starting Page	5888
Ending Page	5900
Page Count	13
File Format	HTM / HTML PDF
ISSN	14779226
Volume Number	46
Issue Number	18
Journal	Dalton Transactions
DOI	10.1039/c7dt00733g
Language	English
Publisher	Royal Society of Chemistry
Access Restriction	Open
Subject Keyword	EPR Nickel Water Acetonitrile Ligand Phenol Hamble River H.L.1 Seaplane Fourier-transform infrared spectroscopy X-ray crystallography Antiferromagnetism Alkoxy group Nucleophile Catalytic cycle Isotropy Imine Hyperfine structure Ion
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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