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- Copper(II) tetrazolato complexes: Role in oxidation catalysis and protein bindingPublication . Saha, Manideepa; Vyas, Komal M.; Martins, Luisa; Martins, Nuno M. R.; Pombeiro, Armando; Mobin, Shaikh M.; Bhattacherjee, D.; Bhabak, Krishna P.; Mukhopadhyay, SumanThree new coordination complexes [Cu-2(phen)(2)(ptz)(4)] (1), [Cu(phen)(pmtz)(2)] (2) and [Cu(phen)(pytz)(2)] (3) (ptz = 5-phenyltetrazolate, pmtz = 5-(2-pyrimidyl)tetrazolate and pytz = 5-(2-pyridyl)tetrazolate) have been synthesized using metal mediated [2+3] cycloaddition reaction between copper bound azide polymer and different organonitriles. All complexes have been structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 shows a dinuclear structure via bridging ptz, while 2 and 3 reveal mononuclear structures. These complexes were explored as homogeneous catalysts for the selective peroxidative (with tBuOOH) oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA oil) under very mild and green (solvent-and additive-free) conditions using microwave irradiation. The catecholase-like activity of the synthesized Cu(II) complexes was investigated by employing 3,5-di-tert-butylcatechol (DTBC) as a convenient model substrate, which showed first order kinetics with respect to the substrate in the oxidation of 3,5-di-tert-butyl catechol (DTBC) to 3,5-di-tertbutyl benzoquinone (DTBQ). Further, the interaction of synthesized Cu(II)-tetrazolato complexes with bovine serum albumin (BSA) was studied experimentally as well as through molecular docking to obtain detailed binding information of the Cu(II) complexes with BSA, which revealed higher binding of complex 1 than 2 and 3
- Greener Selective Cycloalkane Oxidations with Hydrogen Peroxide Catalyzed by Copper-5-(4-pyridyl)tetrazolate Metal-Organic FrameworksPublication . Martins, Luisa; Nasani, Rajendar; Saha, Manideepa; Mobin, Shaikh; Mukhopadhyay, Suman; Pombeiro, ArmandoMicrowave assisted synthesis of the Cu(I) compound [Cu(µ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2]n∙(DMF)2n (2) and [Cu(µ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h−1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1–3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity.
- Copper-organic frameworks assembled from in situ generated 5-(4-pyridyl) tetrazole building blocks: synthesis, structural features, topological analysis and catalytic oxidation of alcoholsPublication . Nasani, Rajendar; Saha, Manideepa; Mobin, Shaikh; Martins, Luisa; Pombeiro, Armando; Kirillov, Alexander M.; Mukhopadhyay, SumanTwo new metal- organic compounds {[Cu-3(mu(3)-4-(p)tz)(4)(mu(2)-N-3)(2)(DMF)(2)](DMF)(2)}(n) (1) and {[Cu(4ptz) (2)(H2O)(2)]}(n) (2) {4-ptz = 5-(4-pyridyl)tetrazolate} with 3D and 2D coordination networks, respectively, have been synthesized while studying the effect of reaction conditions on the coordination modes of 4-pytz by employing the [2 + 3] cycloaddition as a tool for generating in situ the 5-substituted tetrazole ligands from 4-pyridinecarbonitrile and NaN3 in the presence of a copper(II) salt. The obtained compounds have been structurally characterized and the topological analysis of 1 discloses a topologically unique trinodal 3,5,6-connected 3D network which, upon further simplification, results in a uninodal 8-connected underlying net with the bcu (body centred cubic) topology driven by the [Cu-3(mu(2)-N-3)(2)] cluster nodes and mu(3)-4-ptz linkers. In contrast, the 2D metal-organic network in 2 has been classified as a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology assembled from the Cu nodes and mu(2)-4-ptz linkers. The catalytic investigations disclosed that 1 and 2 act as active catalyst precursors towards the microwave-assisted homogeneous oxidation of secondary alcohols (1-phenylethanol, cyclohexanol, 2-hexanol, 3-hexanol, 2-octanol and 3-octanol) with tert-butylhydroperoxide, leading to the yields of the corresponding ketones up to 86% (TOF = 430 h(-1)) and 58% (TOF = 290 h(-1)) in the oxidation of 1-phenylethanol and cyclohexanol, respectively, after 1 h under low power ( 10 W) microwave irradiation, and in the absence of any added solvent or additive.