Luísa M D R S Martins

Instituto Superior Técnico, CQE - Coordination Chemistry and Catalysis, Researcher

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Luísa Margarida Martins got her Chemical Engineering degree (1990), Ph.D (1996) and Habilitation in Chemistry (2015) from Instituto Superior Técnico (IST), University of Lisbon, where she is now Associate Professor.From 1996 to 2018 she was Adjunct Professor at the Chemical Engineering Department of Instituto Superior de Engenharia de Lisboa (ISEL), Polytechnic Institute of Lisbon, and Vice-President of the said Department from 2014 to 2018.She is Researcher (Core Member) at Centro de Química Estrutural (Coordination Chemistry and Catalysis Group) of Instituto Superior Técnico, Universidade de Lisboa, since 1992, and member of the Research Core Team and of the Executive Committee of the PhD programme - Catalysis and Sustainability (CATSUS, 2014-2022).She is also member of the Safety Commission of Centro de Química Estrutural of IST. Luísa’s research broadly focuses on the application of green chemistry and engineering principles in the innovative design of products and sustainable processes.Her main interests range over functionalized materials (in particular, involving C-scorpionates), catalysis (homogeneous, supported or nano-catalysis), and electrochemistry.In 2017 Luísa has been awarded the Scientific Excellence Prize IPL-CGD for the Areas of Technology and Engineering in recognition of her scientific productivity and impact along the last three years.She is FRSC, member of ISE and President of the Portuguese Electrochemical Society. (SPE).

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Papers by Luísa M D R S Martins

Supported gold nanoparticles as reusable catalysts for oxidation reactions of industrial significance

by Sónia Carabineiro, Luísa M D R S Martins, Jiawei Wang, B.G.M. Rocha, and F. Maldonado-Hódar

The efficient single-pot oxidative functionalisation of alkanes and alcohols under mild condition... more The efficient single-pot oxidative functionalisation of alkanes and alcohols under mild conditions was catalysed by Au nanoparticles supported on Al2O3, Fe2O3, ZnO and TiO2. The obtained materials were tested for cyclohexane oxidation under mild conditions (60 °C, atmospheric pressure) using an environmentally friendly oxidant (H2O2). The materials were also tested in the oxidation of benzyl alcohol and methylbenzyl alcohol in the presence of tert-butylhydroperoxide as the oxidant under microwave irradiation. With regard to cyclohexane oxidation, all materials were highly selective towards the formation of cyclohexanol and cyclohexanone. No traces of byproducts were detected under the optimised conditions. Au on Fe2O3 led to the best results (13.5 % yield). This system showed an interesting almost exclusive formation of cyclohexanol at 4 h reaction time. Catalyst recycling was tested in up to five cycles, and the catalyst maintained almost the original level of activity after three cycles with no significant leaching. With regard to oxidation of benzyl alcohol and methylbenzyl alcohol, all materials were highly selective towards the formation of benzaldehyde or acetophenone, respectively. No traces of byproducts were detected. Addition of Au increased alcohol conversion from 5 (TiO2) to 91 % (Au/TiO2). The recycling of Au/TiO2 was tested in up to 10 cycles, and the catalytic activity remained high in the first four cycles.

Gold nanoparticles deposited on surface modified carbon xerogels as reusable catalysts for cyclohexane C-H activation in the presence of CO and water

by Sónia Carabineiro, A.P.C. Ribeiro, and Luísa M D R S Martins

The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cycloh... more The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid (up to 55% yield) with CO, water, and peroxodisulfate in a water/acetonitrile medium at circa 50 °C has been achieved in the presence of gold nanoparticles deposited by a colloidal method on a carbon xerogel in its original form (CX), after oxidation with HNO3 (-ox), or after oxidation with HNO3 and subsequent treatment with NaOH (-ox-Na). Au/CX-ox-Na behaves as re-usable catalyst maintaining its initial activity and selectivity for at least seven consecutive cycles. Green metric values of atom economy or carbon efficiency also attest to the improvement brought by this novel catalytic system to the hydrocarboxylation of cyclohexane.

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

by Sónia Carabineiro, Luísa M D R S Martins, and A.P.C. Ribeiro

The highly efficient eco-friendly synthesis of ketones (yields over 99%) from secondary alcohols ... more The highly efficient eco-friendly synthesis of ketones (yields over 99%) from secondary alcohols is achieved by combination of [FeCl2{η3-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.

Oxidovanadium(V) complexes anchored on carbon materials as catalysts for the oxidation of 1-phenylethanol

by Sónia Carabineiro and Luísa M D R S Martins

Six oxidovanadium(V) aroylhydrazone complexes derived from (3,5-di-tert-butyl-2-hydroxybenzyliden... more Six oxidovanadium(V) aroylhydrazone complexes derived from (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H2L1) and (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-aminobenzohydrazide (H2L2), namely, [VOL1(OEt)][VOL1(OEt) (EtOH)] (1), [VOL2(OEt)] (2), [Et3NH][VO2L1] (3), [VO2(HL2)]⋅2 EtOH (4), [(VOL1)2(μ-O)] (5), and [(VOL2)2(μ-O)] (6), were synthesized and characterized by elemental analysis, IR, 1H NMR, and 51V NMR spectroscopies, ESI-MS and, for 1–5, single-crystal XRD. The compounds have VO3+ (1 and 2), VO2+ (3 and 4), and V2O34+ (5 and 6) cores. They are active homogeneous catalysts in the microwave-assisted, solvent-free peroxidative oxidation of 1-phenylethanol to acetophenone by tBuOOH. The immobilization of the oxidovanadium complexes (1, 2, 4, and 5) on oxidized carbon materials improved the oxidation efficiency and allowed catalyst reuse with the preservation of activity.

Gold nanoparticles supported on carbon materials for cyclohexane oxidation with hydrogen peroxide

by Sónia Carabineiro, Luísa M D R S Martins, and J.G. Buijnsters

Gold (1 wt.%) was loaded on several types of carbon materials (activated carbon, polymer based ca... more Gold (1 wt.%) was loaded on several types of carbon materials (activated carbon, polymer based carbon xerogels, multi-walled carbon nanotubes, nanodiamonds, microdiamonds, graphite and silicon carbide) using two different methods (sol immobilisation and double impregnation). Samples were characterised by N2 adsorption at −196 °C, temperature programmed desorption, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging (Z-contrast), X-ray photoelectron spectroscopy and atomic absorption spectroscopy. The obtained Au/carbon materials were used as catalysts for the oxidation of cyclohexane to cyclohexanol and cyclohexanone, with aqueous H2O2, under mild conditions. The most active catalyst was prepared by supporting gold nanoparticles on carbon nanotubes by the sol method, achieving an overall turnover number of ca. 171 and an overall yield of 3.6% after 6 h reaction time. These values are comparable to the industrial process (that uses Co catalysts and high temperature), but were obtained at ambient temperature with considerable low loads of catalyst (Au catalyst to substrate molar ratio always lower than 1 × 10−3), which is of relevance for establishing a greener catalytic process for cyclohexane oxidation. Moreover, a very high selectivity towards the formation of cyclohexanol and cyclohexanone was achieved, since no traces of by-products were detected. The promoting effect of pyrazine carboxylic acid was observed and an optimum peroxide-to-catalyst molar ratio was found to be 2 × 104. Further increase of the oxidant amount results in decreased yield due to overoxidation reactions at higher H2O2 amounts. Catalyst recycling was tested up to six consecutive cycles for the most active catalytic system (gold deposited on carbon nanotubes by sol immobilisation), and it was found that the catalyst maintains almost the original level of activity after several reaction cycles (there was only a 6% drop in activity after the sixth cycle) with a rather high selectivity to cyclohexanol and cyclohexanone and with no catalyst leaching. The differences in activity for the other samples can be explained in terms of gold nanoparticle size and the textural properties of the carbon support.

Trends in properties of para-substituted 3-(phenylhydrazo)pentane-2,4-diones

by Kamran Mahmudov, Telma Silva, Luísa M D R S Martins, and Max Kopylovich

Trends between the Hammett's s p and related normal s n p , inductive s I , resonance s R , negat... more Trends between the Hammett's s p and related normal s n p , inductive s I , resonance s R , negative s S p and positive s R p polar conjugation and Taft's s o p substituent constants and the N-HÁ Á ÁO distance, d N-H NMR chemical shift, oxidation potential (E ox p=2 , measured in this study by cyclic voltammetry (CV)) and thermodynamic parameters (pK, DG 0 , DH 0 and DS 0 ) of the dissociation process of unsubstituted 3-(phenylhydrazo)pentane-2,4-dione (HL 1 ) and its para-substituted chloro (HL 2 ), carboxy (HL 3 ), fluoro (HL 4 ) and nitro (HL 5 ) derivatives were recognized. The best fits were found for s p and/or s S p in the cases of d NÁÁÁO , d N-H and E ox p=2 , showing the importance of resonance and conjugation effects in such properties, whereas for the above thermodynamic properties the inductive effects (s I ) are dominant. HL 2 exists in the hydrazo form in DMSO solution and in the solid state and contains an intramolecular H-bond with the NÁ Á ÁO distance of 2.588(3) Å . It was also established that the dissociation process of HL 1-5 is non-spontaneous, endothermic and entropically unfavourable, and that the increase in the inductive effect (s I ) of para-substitutents (-H < -Cl < -COOH < -F < -NO 2 ) leads to the corresponding growth of the NÁ Á ÁO distance and decrease of the pK and of the changes of Gibbs free energy, of enthalpy and of entropy for the HL 1-5 acid dissociation process. The electrochemical behaviour of HL 1-5 was interpreted using theoretical calculations at the DFT/HF hybrid level, namely in terms of HOMO and LUMO compositions, and of reactivities induced by anodic and cathodic electrontransfers. In the RAHB systems, the proton-donating N-H group is an electron-donor when considered as a substituent (thus with a (wileyonlinelibrary.com) Scheme 1. Possible tautomeric equilibria in azoderivatives of b-diketones HL 1-5

Luísa M D R S Martins

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