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Microwave-assisted peroxidative oxidation of toluene and 1-phenylethanol with monomeric keto and polymeric enol aroylhydrazone Cu(II) complexes

Publication . Sutradhar, Manas; Alegria, Elisabete; Roy Barman, Tannistha; Scorcelletti, Francesco; Guedes Da Silva, M. Fátima C.; Fatima, C.; Pombeiro, Armando

Cu(II) complexes in two different tautomeric forms (keto and enol) derived from the aroylhydrazone Schiff base 2-hydroxy(2-hydroxybenzylidene)benzohydrazide (H2L) have been synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray crystallography. While the compound with the enol form of the ligand exists as the 1D polymer [Cu(kappa KNOO',2 kappa O',3 kappa O"-L)](n) (1), that with the keto form of the ligand occurs as the monomer [Cu(KNOO'-HL)CI(CH3OH)] (2). Both complexes act as good catalysts for the microwave-assisted peroxidative oxidation of toluene and 1-phenylethanol with tert-butyl hydroperoxide. Complex 2 exhibits the highest activity in both reactions, leading selectively to,a maximum product yield of 39 and 92%, respectively.

2017-10Journal article

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Highly efficient and reusable CNT supported iron(II) catalyst for microwave assisted alcohol oxidation

Publication . Martins, Luisa; Ribeiro, A. P. C.; Carabineiro, S. A. C.; Figueiredo, J. L.; Pombeiro, Armando

The highly efficient eco-friendly synthesis of ketones (yields over 99%) from secondary alcohols is achieved by combination of [FeCl2{eta(3)-HC(pz)(3)}] (pz = pyrazol-1-yl) supported on functionalized multi-walled carbon nanotubes and microwave irradiation, in a solvent-free medium. The carbon homoscorpionate iron(II) complex is the first one of this class to be used as catalyst for the oxidation of alcohols.

2016Journal article

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Aroylhydrazone Cu(II) complexes in keto form: structural characterization and catalytic activity towards cyclohexane oxidation

Publication . Sutradhar, Manas; Alegria, Elisabete; Guedes Da Silva, M. Fátima C.; Martins, Luisa; Pombeiro, Armando

The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) with a copper(II) salt of a base of a strong acid, i.e., nitrate, chloride or sulphate, yielded the mononuclear complexes [Cu(H2L)(NO3)(H2O)] (1), [Cu(H2L)Cl]center dot 2MeOH (2) and the binuclear complex [{Cu(H2L)}(2)(mu-SO4)]center dot 2MeOH (3), respectively, with H2L- in the keto form. Compounds 1-3 were characterized by elemental analysis, Infrared (IR) spectroscopy, Electrospray Ionisation-Mass Spectrometry (ESI-MS) and single crystal X-ray crystallography. All compounds act as efficient catalysts towards the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, under mild conditions. In the presence of an acid promoter, overall yields (based on the alkane) up to 25% and a turnover number (TON) of 250 (TOF of 42 h(-1)) after 6 h, were achieved.

2016-04Journal article

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Supported C-Scorpionate Vanadium(IV) Complexes as Reusable Catalysts for Xylene Oxidation

Publication . Wang, Jiawei; Martins, Luisa; Da Costa Ribeiro, Ana Paula; Carabineiro, Sonia Alexandra Correia; Figueiredo, José L.; Pombeiro, Armando

C-Scorpionate vanadium(IV) [VOxCl3-x{k(3)-RC(pz)(3)}] [pz = pyrazol-1-yl; x=0, R = SO3 (1); x = 1, R= CH2OH (2) or CH2OSO2Me (3)] complexes supported on functionalized carbon nanotubes (CNTs) are the first V-scorpionate catalysts used so far for the neat oxidation of o-, m- or p-xylene, with TBHP (70% aqueous solution), to the corresponding toluic acids (main products), tolualdehydes and methylbenzyl alcohols. Remarkably, a p-toluic acid yield of 43% (73% selectivity, TON = 1.34 V 10(3)) was obtained with 2@CNT in a simple microwave-assisted mild oxidation procedure, using a very low catalyst charge (3.2 x 10(-2) mol% vs. substrate). Further, this occurred in the absence of any bromine source, what is significant towards the development of a greener and more sustainable process for oxidation of xylenes. Moreover, reuse of catalysts with preservation of their activity was found for up to six consecutive cycles. The effects of reaction parameters, such as reaction time, temperature, amount of catalyst or type of heating source, on the performance of the above catalytic systems are reported and discussed.

2017-10Journal article

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Copper(II) tetrazolato complexes: Role in oxidation catalysis and protein binding

Publication . Saha, Manideepa; Vyas, Komal M.; Martins, Luisa; Martins, Nuno M. R.; Pombeiro, Armando; Mobin, Shaikh M.; Bhattacherjee, D.; Bhabak, Krishna P.; Mukhopadhyay, Suman

Three 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

2017-08Journal article

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