Mechanistic insights into the electrochemical reduction of CO2 to CO on Ni(salphen) complexes

LA/P/0056/2020. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC). FCT is acknowledged for PTDCQUI-QIN0252_2021 (PNM). The CARISMA COST action CM1205 is acknowledged. MJC thanks N. A. G. Bandeira for technical assistance. The CATSUS doctoral programme is also acknowledged. Publisher Copyright: © 2023 The Royal Society of Chemistry.Cyclic voltammetry and bulk electrolysis showed that [Ni(ii)(salphen)] [1], [Ni(ii)(tBu-salphen)] [2], and a binuclear Ni(ii) compound combining salphen and tBu-salphen [3] react with CO2 to yield a metal-carbonyl species that is stable under an oxygen free atmosphere. Upon exposure to air, a stoichiometric amount of CO is released (detected by gas chromatography) and protonation regenerates the initial complex. To shed light on the mechanism of CO2 reduction and O2-dependent CO release by [1], UV-vis, EPR and SEC-IR spectroscopy studies complemented with DFT calculations were performed. It is proposed that the mono reduced [Ni(i)(salphen)]−, 2[1]−, formed a CO2 complex, 2[1(CO2)]−, which was then further reduced to 3[1(CO2)]2−. After addition of two protons, the coordinated CO2 was reduced to CO and released, regenerating 1[1]. Alternatively, 2[1(CO2)]− is protonated and then reduced to the same intermediate as before, continuing the same way. In the second cycle, the CO released competed with CO2 and coordinated to 2[1]− much more strongly, thereby deactivating the system. The new 2[1(CO)]− was reduced to 3[1(CO)]2− which was identified by comparison of experimental spectroscopic (UV-vis, EPR, SEC-IR) data with DFT calculated parameters.publishersversionpublishe

Click-Derived Triazoles and Triazolylidenes of Manganese for Electrocatalytic Reduction of CO2

022162, CEECIND/00509/2017, PTDC/QUI-QIN/28151/2017, RECI/BBB-BEP/0124/2012, SFRH/BD/131955/2017, UIDB/00100/2020, UIDB/04378/2020, UIDB/04612/2020, UIDP/00100/2020, UIDP/04046/2020, UIDP/04378/2020, UIDP/50006/2020, UIPD/04612/2020 Funding Information: This research was funded by FUNDA??O DE CI?NCIA E TECNOLOGIA, FCT, grant numbers: PTDC/QUI-QIN/28151/2017, SFRH/BD/131955/2017, CEECIND/00509/2017. The MOSTMICRO-ITQB was funded by UIDB/04612/2020 and UIPD/04612/2020. The NMR spectrome-ters at CERMAX were funded by 022162. LAQV and UCIBIO were funded by UIDB/50006/2020, UIDP/50006/2020, UIDB/04378/2020, and UIDP/04378/2020. The X-ray infrastructure was funded by RECI/BBB-BEP/0124/2012. The BioISI was funded by UIDB/04046/2020, UIDP/04046/2020, UIDB/00100/2020, and UIDP/00100/2020. We thank C. Almeida for elemental analysis at ITQB laboratories. Funding Information: Funding: This research was funded by FUNDAÇÃO DE CIÊNCIA E TECNOLOGIA, FCT, grant numbers: PTDC/QUI-QIN/28151/2017, SFRH/BD/131955/2017, CEECIND/00509/2017. The MOSTMICRO-ITQB was funded by UIDB/04612/2020 and UIPD/04612/2020. The NMR spectrometers at CERMAX were funded by 022162. LAQV and UCIBIO were funded by UIDB/50006/2020, UIDP/50006/2020, UIDB/04378/2020, and UIDP/04378/2020. The X-ray infrastructure was funded by RECI/BBB-BEP/0124/2012. The BioISI was funded by UIDB/04046/2020, UIDP/04046/2020, UIDB/00100/2020, and UIDP/00100/2020. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.A series of new fac-[Mn(L)(CO)3 Br] complexes where L is a bidentate chelating ligand containing mixed mesoionic triazolylidene-pyridine (MICˆpy, 1), triazolylidene-triazole (MICˆtrz, 2), and triazole-pyridine (trzˆpy, 3) ligands have been prepared and fully characterized, including the single crystal X-ray diffraction studies of 1 and 2. The abilities of 1–3 and complex fac-[Mn(MICˆMIC)(CO)3 Br] (4) to catalyze the electroreduction of CO2 has been assessed for the first time. It was found that all complexes displayed a current increase under CO2 atmosphere, being 3 and 4 the most active complexes. Complex 3, bearing a NˆN-based ligand exhibited a good efficiency and an excellent selectivity for reducing CO2 to CO in the presence of 1.0 M of water, at low overpotential. Interestingly, complex 4 containing the strongly electron donating di-imidazolylidene ligand exhibited comparable activity to 3, when the experiments were performed in neat acetonitrile at slightly higher overpotential (−1.86 vs. −2.14 V).publishersversionpublishe

Self-Assembly Properties of Amphiphilic Iron(III) Spin Crossover Complexes in Water and at the Air–Water Interface

The assembly properties of three known spin crossover iron(III) complexes 1⁻3, at the air⁻water interface, are reported. All three complexes are amphiphiles, each bearing a pair of Cn alkyl chains on the polyamino Schiff base sal2trien ligand (n = 6, 12, or 18). Complex 1 is water-soluble but complexes 2 and 3 form Langmuir films, and attempts were made to transfer the film of the C18 complex 3 to a glass surface. The nature of the assembly of more concentrated solutions of 3 in water was investigated by light scattering, cryo-SEM (scanning electron microscopy), and TEM (transmission electron microscopy), all of which indicated nanoparticle formation. Lyophilization of the assembly of complex 3 in water yielded a powder with a markedly different magnetic profile from the powder recovered from the initial synthesis, notably, the spin crossover was almost completely quenched, and the thermal behavior was predominantly low spin, suggesting that nanoparticle formation traps the system in one spin state

The influence of molecular mobility on the properties of networks of gold nanoparticles and organic ligands

We prepare and investigate two-dimensional (2D) single-layer arrays and multilayered networks of gold nanoparticles derivatized with conjugated hetero-aromatic molecules, i.e., S-(4-{[2,6-bipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)thiolate (herein S-BPP), as capping ligands. These structures are fabricated by a combination of self-assembly and microcontact printing techniques, and are characterized by electron microscopy, UV–visible spectroscopy and Raman spectroscopy. Selective binding of the S-BPP molecules to the gold nanoparticles through Au–S bonds is found, with no evidence for the formation of N–Au bonds between the pyridine or pyrazole groups of BPP and the gold surface. Subtle, but significant shifts with temperature of specific Raman S-BPP modes are also observed. We attribute these to dynamic changes in the orientation and/or increased mobility of the molecules on the gold nanoparticle facets. As for their conductance, the temperature-dependence for S-BPP networks differs significantly from standard alkanethiol-capped networks, especially above 220 K. Relating the latter two observations, we propose that dynamic changes in the molecular layers effectively lower the molecular tunnel barrier for BPP-based arrays at higher temperatures

The Halogen Effect on the Magnetic Behaviour of Dimethylformamide Solvates in [Fe(halide-salEen)2]BPh4

Funding Research was funded by Fundação para a Ciência e a Tecnologia (FCT): projects UIDB/00100/2020, UIDP/00100/2020, LA/P/0056/2020, UIDB/04046/2020, UIDP/04046/2020, UIDB/50006/2020, UIDP/50006/2020 and LA/P/0008/2020, UIDB/04378/2020, UIDP/04378/2020, and LA/P/0140/2020, PTDC/QUI-QFI/29236/2017, PTDCQUI-QIN0252_2021, CEECIND/00509/2017; Fonds de la Recherche Scientifique (FNRS): PDR T.0095.21); Portugal2020: CENTRO-01-0145-FEDER-000018; Royal Society of Chemistry (RSC): R21-7511142525. Acknowledgments Centro de Química Estrutural (CQE) and Institute of Molecular Sciences (IMS) acknowledge the financial support of Fundação para a Ciência e a Tecnologia (FCT): Projects UIDB/00100/2020, UIDP/00100/2020, and LA/P/0056/2020, respectively. BioISI acknowledges FCT for financial support (UIDB/04046/2020, UIDP/04046/2020). This work was supported by the FNRS (PDR T.0095.21). Clara S. B. Gomes acknowledges the Associate Laboratory for Green Chemistry—LAQV, the Applied Molecular Biosciences Unit—UCIBIO and Associated Laboratory i4HB, which are financed by national funds from FCT (UIDB/50006/2020, UIDP/50006/2020 and LA/P/0008/2020, UIDB/04378/2020 and UIDP/04378/2020, and LA/P/0140/2020, respectively). Sónia Barroso thanks project SmartBioR for financial support (CENTRO-01-0145-FEDER-000018)and Centro de Química Estrutural for the access to crystallography facilities. Nuno A. G. Bandeira gratefully acknowledges the NanoBioSolutions FCT grant PTDC/QUI-QFI/29236/2017 for the computational infrastructure. Paulo N. Martinho thanks FCT and RSC for financial support (grants PTDCQUI-QIN0252_2021 and R21-7511142525). Paulo N. Martinho also thanks FCT for the contract CEECIND/00509/2017.Complexes [Fe(X-salEen)2]BPh4·DMF, with X = Br (1), Cl (2), and F (3), were crystallised from N,N′-dimethylformamide with the aim of understanding the role of a high boiling point N,N′-dimethylformamide solvate in the spin crossover phenomenon. The counter ion was chosen for only being able to participate in weak intermolecular interactions. The compounds were structurally characterised by single crystal X-ray diffraction. Complex 1 crystallised in the orthorhombic space group P212121, and complexes 2 and 3 in the monoclinic space group P21/n. Even at room temperature, low spin was the predominant form, although complex 2 exhibited the largest proportion of the high-spin species according to both the magnetisation measurements and the Mössbauer spectra. Density Functional Theory calculations were performed both on the periodic solids and on molecular models for complexes 1–3 and the iodide analogue 4. While all approaches reproduced the experimental structures very well, the energy balance between the high-spin and low-spin forms was harder to reproduce, though some calculations pointed to the easier spin crossover of complex 2, as observed. Periodic calculations with the functional PBE led to very similar ΔEHS-LS values for all complexes but showed a preference for the low-spin form. However, the single-point calculations with B3LYP* showed, for the model without solvate, that the Cl complex should undergo spin crossover more easily. The molecular calculations also reflected this fact, which was more clearly defined when the cation–anion–solvate model was used. In the other models there was not much difference between the Cl, Br, and I complexes.publishersversionpublishe

Downregulation of RKIP Is Associated with Poor Outcome and Malignant Progression in Gliomas

Malignant gliomas are highly infiltrative and invasive tumors, which precludes the few treatment options available. Therefore, there is an urgent need to elucidate the molecular mechanisms underlying gliomas aggressive phenotype and poor prognosis. The Raf Kinase Inhibitory protein (RKIP), besides regulating important intracellular signaling cascades, was described to be associated with progression, metastasis and prognosis in several human neoplasms. Its role in the prognosis and tumourigenesis of gliomas remains unclear

Large orbital moment of two coupled spin-half Co ions in a complex on gold

The magnetic properties of transition-metal ions are generally described by the atomic spins of the ions and their exchange coupling. The orbital moment, usually largely quenched due the ligand field, is then seen as a perturbation. In such a scheme, S = 1/2 ions are predicted to be isotropic. We investigate a Co(II) complex with two antiferromagnetically coupled 1/2 spins on Au(111) using low-temperature scanning tunneling microscopy, X-ray magnetic circular dichroism, and density functional theory. We find that each of the Co ions has an orbital moment comparable to that of the spin, leading to magnetic anisotropy, with the spins preferentially oriented along the Co–Co axis. The orbital moment and the associated magnetic anisotropy is tuned by varying the electronic coupling of the molecule to the substrate and the microscope tip. These findings show the need to consider the orbital moment even in systems with strong ligand fields. As a consequence, the description of S = 1/2 ions becomes strongly modified, which have important consequences for these prototypical systems for quantum operations.We acknowledge financial support from the European Union’s Horizon 2020 program, grant number 766726. C.L. thanks the Alexander von Humboldt Foundation for a Research Fellowship for Postdoctoral Researchers and also acknowledges support from Kiel Nano, Surface and Interface Science (KiNSIS). M.G. acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG; Project-ID 278162697 - CRC 1242, Project A08). R.R. and N.L. acknowledge financial support from the European Union project ESiM 101046364 and the Spanish State Research Agency grant (Project No. PID2021-127917NB-I00) funded by MCIN/AEI/10.13039/50110001103; they are grateful for the computer resources at Finisterrae II and the technical support provided by CESGA. Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them. Centro de Química Estrutural (CQE) and Institute of Molecular Sciences (IMS) acknowledge the financial support of Fundação para a Ciência e Tecnologia (FCT) (Projects UIDB/00100/2020, UIDP/00100/2020, and LA/P/0056/2020, respectively). P.N.M. and S.Re. thank FTC for the research contracts CEEC-IND/00509/2017 and 2020.02134.CEECIND. S.Ru. acknowledges funding from the Swiss National Science Foundation (grant number 200021_175941).Peer reviewe

Including cognitive aspects in multiple criteria decision analysis

"First Online: 21 December 2016"Many Multiple Criteria Decision Analysis (MCDA) methods have been proposed over the last decades. Some of the most known methods share some similarities in the way they are used and configured. However, we live in a time of change and nowadays the decision-making process (especially when done in group) is even more demanding and dynamic. In this work, we propose a Multiple Criteria Decision Analysis method that includes cognitive aspects (Cognitive Analytic Process). By taking advantage of aspects such as expertise level, credibility and behaviour style of the decision-makers, we propose a method that relates these aspects with problem configurations (alternatives and criteria preferences) done by each decision-maker. In this work, we evaluated the Cognitive Analytic Process (CAP) in terms of configuration costs and the capability to enhance the quality of the decision. We have used the satisfaction level as a metric to compare our method with other known MCDA methods in literature (Utility function, AHP and TOPSIS). Our method proved to be capable to achieve higher satisfaction levels compared to other MCDA methods, especially when the decision suggested by CAP is different from the one proposed by those methods.This work was supported by COMPETE Programme (operational programme for competitiveness) within project POCI-01-0145-FEDER-007043, by National Funds through the FCT – Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within the Projects UID/CEC/00319/2013, UID/EEA/00760/2013, and the João Carneiro PhD grant with the reference SFRH/BD/89697/2012.info:eu-repo/semantics/publishedVersio

Euphol, a tetracyclic triterpene, from Euphorbia tirucalli induces autophagy and sensitizes temozolomide cytotoxicity on glioblastoma cells

Glioblastoma (GBM) is the most frequent and aggressive type of brain tumor. There are limited therapeutic options for GBM so that new and effective agents are urgently needed. Euphol is a tetracyclic triterpene alcohol, and it is the main constituent of the sap of the medicinal plant Euphorbia tirucalli. We previously identified anti-cancer activity in euphol based on the cytotoxicity screening of 73 human cancer cells. We now expand the toxicological screening of the inhibitory effect and bioactivity of euphol using two additional glioma primary cultures. Euphol exposure showed similar cytotoxicity against primary glioma cultures compared to commercial glioma cells. Euphol has concentration-dependent cytotoxic effects on cancer cell lines, with more than a five-fold difference in the IC50 values in some cell lines. Euphol treatment had a higher selective cytotoxicity index (0.64-3.36) than temozolomide (0.11-1.13) and reduced both proliferation and cell motility. However, no effect was found on cell cycle distribution, invasion and colony formation. Importantly, the expression of the autophagy-associated protein LC3-II and acidic vesicular organelle formation were markedly increased, with Bafilomycin A1 potentiating cytotoxicity. Finally, euphol also exhibited antitumoral and antiangiogenic activity in vivo, using the chicken chorioallantoic membrane assay, with synergistic temozolomide interactions in most cell lines. In conclusion, euphol exerted in vitro and in vivo cytotoxicity against glioma cells, through several cancer pathways, including the activation of autophagy-associated cell death. These findings provide experimental support for further development of euphol as a novel therapeutic agent for GBM, either alone or in combination chemotherapy.The work was supported by the Amazonia Fitomedicamentos (FITO05/2012) Ltda. and Barretos Cancer Hospital, all from Brazil