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- Fe(III) complexes in cyclohexane oxidation: comparison of catalytic activities under different energy stimuliPublication . Roy Barman, Tannistha; Sutradhar, Manas; Alegria, Elisabete; Silva, M. Fátima C. Guedes Da; Pombeiro, ArmandoIn this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (1) derived from N0 -acetylpyrazine-2-carbohydrazide (H2L) was synthesized and characterized by several physicochemical methods, e.g., elemental analysis, infrared (IR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction analysis. The catalytic performances of 1 and the previously reported complexes [Fe(HL)Cl2] (2) and [Fe(HL)Cl(µ-OMe)]2 (3) towards the peroxidative oxidation of cyclohexane under three different energy stimuli (microwave irradiation, ultrasound, and conventional heating) were compared. 1-3 displayed homogeneous catalytic activity, leading to the formation of cyclohexanol and cyclohexanone as final products, with a high selectivity for the alcohol (up to 95%). Complex 1 exhibited the highest catalytic activity, with a total product yield of 38% (cyclohexanol + cyclohexanone) under optimized microwave-assisted conditions.
- Cd(II) coordination compounds as heterogeneous catalysts for microwave-assisted peroxidative oxidation of toluene and 1-phenylethanolPublication . Sutradhar, Manas; Roy Barman, Tannistha; Alegria, Elisabete; Lapa, Hugo M.; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoThe aroylhydrazone Schiff bases 2-hydroxy(2-hydroxybenzylidene)benzohydrazide (H2L1) and 2-amino(2hydroxybenzylidene)benzohydrazide (H2L2) have been used to synthesize the new Cd(II) coordination polymer [Cd(m-1kONO0:2kO:3kO00-L1)(DMF)]n (1) and the dinuclear complex [Cd(1kONO0:2kO-HL2)(kOO0Ac)]2 2DMF (2). Both 1 and 2 have been characterized by elemental analysis, FT-IR and single crystal X-ray diffraction analysis. The catalytic performances of 1 and 2 were evaluated towards the microwave (MW) assisted peroxidative oxidation (with tert-butylhydroperoxide, TBHP) of toluene and 1-phenylethanol under heterogeneous conditions. The MW-assisted peroxidative oxidation of toluene by a Cd(II) catalytic system is reported for the first time. At 50 1C, the 2/TBHP/MW catalytic system shows good activity for toluene oxidation with a total (benzaldehyde + benzyl alcohol) product yield of 49% in 1 h, in the absence of any additives. In the case of neat solvent-free peroxidative oxidation of 1-phenylethanol the 1/TBHP/MW catalytic system resulted in 24% total yield of acetophenone under optimized conditions. After the catalytic reactions, both 1 and 2 were successfully recovered and reused.
- Catalytic oxidation of a model volatile organic compound (toluene) with tetranuclear Cu(II) complexesPublication . Sutradhar, Manas; Alegria, Elisabete; Roy Barman, Tannistha; Lapa, Hugo; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoA tetranuclear Cu(II) cubane [Cu-2(mu-1 kappa ONO':2 kappa OO':3 kappa O-HL)(mu-1 kappa ONO':2 kappa OO'-HL)](2).4dmf (1) derived form (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) was synthesized at room temperature and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray diffraction. The known tetranuclear Cu(II) open-cubane [Cu(HL)](4).4EtOH (2) was synthesized from the same pro-ligand following a similar method or the reported one. The different tautomeric forms (keto and enol) of the organic ligands in 1 and 2 explain their different structural features. Both complexes were screened as catalysts for the peroxidative oxidation of toluene with tert-butyl hydroperoxide, achieving benzaldehyde and o-cresol as the main products. Complex 1 exhibits the highest activity (maximum product yield of 11%).
- Vanadium(V) complexes supported on porous MIL-100(Fe) as catalysts for the selective oxidation of toluenePublication . Sutradhar, Manas; Marques, Guilherme; Soliman, Mohamed M. A.; Guedes Da Silva, M. Fátima C.; Flores, Daniela S. S.; Granadeiro, Carlos; Balula, Salete; Pombeiro, Armando; Alegria, ElisabeteThe vanadium(V) complexes bearing the aroylhydrazone Schiff base 2-hydroxy-N'-((2-hydroxynaphthalen-1-yl) methylene)benzohydrazide ligand [VO(OMe)L] (1) and [Et3NH][VO2L] (2) were synthesized, characterized and supported on porous MIL-100(Fe) forming the 1@MIL-100(Fe) and 2@MIL-100(Fe) composites. The outcome of such immobilizations was assessed by several characterization techniques, namely powder X-ray diffraction, UV/ Vis, FTIR, SEM-EDS, ICP and BET surface area analysis, confirming the successful heterogenization of both va-nadium complexes. They were screened as catalysts towards the oxidation of toluene, under homogenous (1 and 2) and heterogeneous (1@MIL-100 and 2@MIL-100) conditions. The influence of several parameters, namely the type and amount of catalyst or oxidant, reaction time, temperature, and radical trapping, was studied. The main products obtained were benzaldehyde, benzyl alcohol and benzoic acid. Under the optimized conditions, using 1 and 2 as homogeneous catalysts, total yields of 19 and 23%, respectively, were achieved at 80 degrees C after 6 h. Using 1@MIL100(Fe) and 2@MIL100(Fe) composites under heterogeneous conditions, total yields up to 11% after 24 h, were achieved.
- 1D Copper(II)-aroylhydrazone coordination polymers: magnetic properties and microwave assisted oxidation of a secondary alcoholPublication . Sutradhar, Manas; Alegria, Elisabete; Roy Barman, Tannistha; Guedes Da Silva, M. Fátima C.; Liu, Cai-Ming; Pombeiro, ArmandoThe 1D Cu(II) coordination polymers [Cu-3(L-1)(NO3)(4)(H2O)(2)](n) (1) and [Cu-2(H2L2)(NO3)(H2O)(2)](n)(NO3)(n) (2) have been synthesized using the aroylhyrazone Schiff bases N'(1),N'(2)-bis(pyridin-2-ylmethylene)oxalohydrazide (H2L1) and N'(1),N'(3)-bis(2-hydroxybenzylidene)malonohydrazide (H4L2), respectively. They have been characterized by elemental analysis, infrared (IR) spectroscopy, UV-Vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements (for 2). The ligand (L-1)(2-) coordinates in the iminol form in 1, whereas the amide coordination is observed for (H2L2)(2-) in 2. Either the ligand bridge or the nitrate bridge in 2 mediates weak antiferromagnetic coupling. The catalytic performance of 1 and 2 has been investigated toward the solvent-free microwave-assisted oxidation of a secondary alcohol (1-phenylethanol used as model substrate). At 120 degrees C and in the presence of the nitroxyl radical 2,2,6,6-tetramethylpiperydil-1-oxyl (TEMPO), the complete conversion of 1-phenylethanol into acetophenone occurs with TOFs up to 1,200 h(-1).