1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 z Inorganic Chemistry Role of Electronegative Atom Present on Ligand Backbone and Substrate Binding Mode on Catecholase- and Phosphatase-Like Activities of Dinuclear Ni II Complexes: A Theoretical Support Jaydeep Adhikary,* [a, b] Ishani Majumdar, [b] Priyanka Kundu, [b] Haya Kornweitz, [a] Hulya Kara, [c, d] and Debasis Das* [b] The reaction of two pentadentate compartmental ligands HL 1 and HL 2 [ HL 1 = 2,6-bis((E)-(2-morpholinoethylimino)methyl)-4- tert-butylphenol; HL 2 = 2,6-bis((E)-(2-(piperidin-1-yl)ethylimino) methyl)-4-tert-butylphenol] with nickel acetate followed by addition of NaSCN afforded two discrete dinuclear complexes, [Ni 2 L 1 (CH 3 COO) 2 (SCN)] . (H 2 O) 2 . (0.5CH 3 OH) (1) and [Ni 2 L 2 (CH 3 COO)(SCN) 2 (CH 3 OH)] . (CH 3 OH) (2). Single crystal structure reveals that the complexes are Ni II dimer with triple-mixed phenoxo and acetate/isothiocyanate bridges. Variable-temper- ature (3-300 K) magnetic studies have been performed and data analyses reveal that the dinuclear nickel(II) units show a weak ferromagnetic coupling in complex 1 (J =+ 3.70) and a weak antiferromagnetic coupling in complex 2 (J =- 0.87 cm –1 ). The catalytic promiscuity of the complexes in terms of two different bio-relevant catalytic activities like oxidation (catecho- lase) and hydroxylation (phosphatase) has been thoroughly explored. Role of an auxiliary electronegative atom present on the ligand backbone and binding approach of the substrate to the metal centres during the catalytic activities have been scrutinized by DFT calculation. Several experimental techniques have been utilised to evaluate the mechanistic interpretation of catecholase like activity. And finally, mechanistic pathway of both the bio activities are demonstrated. Introduction During the last few years, much of the information regarding the role of metals in dinuclear oxidative and hydrolytic metal- loenzymes, such as catechol oxidases and phosphatases is gained through comparative studies on metalloenzymes and synthetic model metal complexes. [1] Studies with model complexes have been described, aiming to mimic the structural and/or functional properties of these metalloenzymes, such as the intermetallic distance, [2] asymmetry, [3] and geometry around each metal center, [4] with the presence of labile sites essential for binding of the substrate and/or available nucleophiles to initiate the catalytic process. [5] Our laboratory has been actively engaged to access the mechanistic pathway of catechol oxidase as well as phospha- tase activity for the last few years. We have recently reported the role of solvent in catecholase and phosphates like activities. [6] We have also succeeded to expose the role of the para substituent group present in the end-off ligand on these bio mimicking studies. [7] In those cases, we took phenolic aldehyde with different substitution on their para position to -OH group and followed by the condensation with amine to prepare the ligand. The ligands having different substitution on the para position were considered for the preparation of metal complexes and followed by the study on their catecholase and phosphatase like activity. Very recently we have explored the effect of Lewis acidity of group 12 metal on phosphatase like activity. [8] However, the role of auxiliary electronegative atom present in the amine part was not investigated over these catalytic processes. Our group has recently investigated the effect auxiliary atoms [9] in overall coordination chemistry in terms of structural and solid-state phenomenon but the effect on catalytic efficiencies have not been yet explored. These deficiencies therefore motivated us towards our current investigation. Consequently, in the present project two Ni II complexes, namely, [Ni 2 L 1 (CH 3 COO) 2 (SCN)] . (H 2 O) 2 . (0.5CH 3 OH) (1) and [Ni 2 L 2 (CH 3 COO)(SCN) 2 (CH 3 OH)] . (CH 3 OH) (2) have been syn- [a] Dr. J. Adhikary, Prof. H. Kornweitz Department of Chemical Sciences Ariel University Ariel 40700, Israel E-mail: adhikaryj86@gmail.com [b] Dr. J. Adhikary, I. Majumdar, Dr. P. Kundu, Prof. D. Das Department of Chemistry University of Calcutta 92, A. P. C. Road, Kolkata – 700009, India E-mail: dasdebasis2001@yahoo.com [c] Prof. H. Kara Department of Physics Faculty of Science and Art Balikesir University Balikesir, Turkey [d] Prof. H. Kara Department of Physics Faculty of Science Mugla Sıtkı Koc ¸man University Mugla, Turkey Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201702861 Full Papers DOI: 10.1002/slct.201702861 1445 ChemistrySelect 2018, 3, 1445 – 1454  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim