Open Access
Monokristal-monokristal eraldaketak polioxometalatoetan oinarritutako sistemetan: termikoki aktibatutako zenbait adibide
(Universidad del País Vasco, 2019) Fernández Navarro, Leticia; Ruiz Bilbao, Estíbaliz; Artetxe, Beñat; San Felices, Leire; Iturrospe, Amaia; Reinoso, Santiago; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Kanpo-estimuluen bitartez aktibatutako fase-trantsizioak, eta haien artean kristal bakun izaera mantentzen duten kasuak, hots monokristal-monokristal (MKMK) eraldaketak, interes handikoak dira; izan ere, gai dira i) ezaugarri berriak dituzten produktuak emateko eta ii) materialaren propietateetan gertatzen diren aldaketak, egitura kristalinoak jasaten dituenekin erlazionatzeko. Polioxometalatoen (POMen) kasuan bezala, egiturei zurruntasuna ematen dieten oinarrizko unitateak erabiltzea bide egokia da prozesuan zehar gerta litekeen kristalinitatearen galera saihesteko. Gaur egun POMetan oinarritutako sistemetan aurki daitezkeen MKMK eraldaketa urrien artean, aipatzekoak dira termikoki aktibatutako adibideak. Lan honetan azken hauek laburbilduko dira eta bereziki gure ikerketa taldean prestatutako konposatuak eta haien erabilerak (katalisia eta gasen xurgapen selektiboa) goraipatuko ditugu.
Open Access
A simple approach to develop tailored mesoporosity in nanostructured heteropolysalts
(Wiley, 2017) Alcañiz Monge, Juan; Trautwein, Guido; El Bakkali, Bouchra; Reinoso, Santiago; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
In this study, we describe a very simple approach to the development of tailored mesoporosity in any nanostructured heteropolysalt with control over both the mesoporous volume and the pore size. This approach, which consists in the treatment of a solid microporous precursor with a basic agent, has been tested on the ammonium salt of the Keggin‐type [PMo12O40]3− heteropolyanion and constitutes a novel procedure for the preparation of mesoporous solids with no precedents. The results obtained in this study allow two main conclusions to be drawn: 1) the micro‐ and mesoporous structures in the heteropolysalt nanoparticles are independent from each other and 2) the development of mesoporosity in the solid material must be related to a process of alkaline degradation within the core of the nanocrystals that aggregate into the particles. These results afford valuable additional information to the present model of porosity that has been established for heteropolysalts.
Open Access
In situ synthesis of SERS-active Au@POM nanostructures in a microfluidic device for real-time detection of water pollutants
(American Chemical Society, 2020) Lafuente Adiego, Marta; Pellejero, Ismael; Clemente, Alberto; Urbiztondo, Miguel A.; Mallada, Reyes; Reinoso, Santiago; Pina, María del Pilar; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a simple, versatile and low-cost approach for the preparation of SERS-active regions within a microfluidic channel 50 cm in length. The approach involves the UV-light-driven formation of polyoxometalate-decorated gold nanostructures, Au@POM (POM: H3PW12O40 (PW) and H3PMo12O40 (PMo)), that self-assemble in situ on the surface of the PDMS microchannels without any extra functionalization procedure. The fabricated LoCs were characterized by SEM, UV-Vis, Raman, XRD and XPS techniques. The SERS activity of the resulting Au@POM–coated lab-on-a-chip (LoC) devices was evaluated in both static and flow conditions using Rhodamine R6G. The SERS response of Au@PW–based LoCs was found superior to Au@PMo counterparts and outstanding when compared to reported data on metal@POM nanocomposites. We demonstrate the potentialities of both Au@POM–coated LoCs as analytical platforms for real time detection of the organophosphorous pesticide Paraoxon-methyl at 10-6 M concentration level.
Open Access
Polioxometalatoak: elhuyar anaien ametsak bizirik dirau!
(Universidad del País Vasco, 2017) Artetxe, Beñat; Reinoso, Santiago; Gutiérrez Zorrilla, Juan M.; Institute for Advanced Materials and Mathematics - INAMAT2
Polioxometalatoak (POMak) kimika ez-organikoaren munduan ezagunak diren metalez eta oxigenoz osatutako kluster anionikoak dira. Azaldu ohi duten forma, konposizio eta propietate aniztasunaren ondorioz, POMek aplikazio ugari dituzte teknologiari, ekonomiari edo ingurugiroari lotutako arlo ezberdinetan. Nahiz eta aspaldidanik aplikazio katalitikoetan erabili, gaur egun etorkizunerako garrantzitsuak izango diren esparru oso ezberdinetarako ikertzen ari dira, besteak beste, hondakin-uren tratamenduan, medikuntzan, konputazio kuantikoan, energia-iturri berriztagarrietan edota sentsore kimiko lumineszenteetan. Horrengatik guztiagatik, polioxometalatoen kimika, etorkizun handiko kimika ezorganikoaren alorreko esparru dinamikoenetariko bat dela baiezta genezake.
Open Access
The effects of halogen substituents on the catalytic oxidation of benzylalcohols in the presence of dinuclear oxidovanadium(IV) complex
(Elsevier, 2017) Bikas, Rahman; Shahmoradi, Elaheh; Noshiranzadeh, Nader; Emami, Marzieh; Reinoso, Santiago; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
A new dinuclear complex of oxidovanadium(IV), namely [(VO)2(HL)(l-O)] (1), has been synthesized by the reaction of VO(acac)2 with the heptadentate N4O3-donor Schiff base ligand, 2-(5-Bromo-2-hydroxyphenyl)-1,3-bis(2-(5-bromo-2-hydroxybenzylideneamino)ethyl)imidazolidine (H3L). The complex has been characterized by elemental analysis, spectroscopic methods and single-crystal X-ray diffraction. The latter technique revealed that the vanadium ions have distorted octahedral geometry and are connected together by oxido and phenolic oxygen atoms. The bridging oxido ligand shares the equatorial positions of the two metal centers while the oxygen atom of the bridging phenol group connects the axial positions. The catalytic activity of this complex has been tested for the oxidation of some benzyl alcohol derivatives by using H2O2 as a green oxidant. In order to maximize the yields, the effects of various influential parameters in catalytic reactions such as the oxidant-to-substrate molar ratio, the temperature and the solvent, were studied. Moreover, the electronic and steric effects of halogen substituents on the phenyl group of the substrate were also explored by analyzing the oxidation of benzyl alcohol derivatives with F, Cl and Br atoms in the relative para-position (electronic effect), and of another set of substrates with a Cl substituent in relative ortho-, meta, and para-positions (steric effect). The results of these catalytic studies show that complex 1 catalyzes the oxidation of benzyl alcohol derivatives to the corresponding benzaldehydes with little amounts of the benzoic acid being detectable in the reaction mixture. Both the reaction conditions and the substituents on the phenyl group of the benzyl alcohols affect the selectivity and the activity of this catalytic system.
Open Access
Consecutive single-crystal-to-single-crystal isomerization of novel octamolybdate anions within a microporous hybrid framework with robust water sorption properties
(Wiley, 2023) Ruiz Bilbao, Estíbaliz; Iturrospe, Amaia; Reinoso, Santiago; Artetxe, Beñat; Beobide, Garikoitz; San Felices, Leire; Lezama, Luis; Gutiérrez Zorrilla, Juan M.; Darwish, Shaza; Sensharma, Debobroto; Zaworotko, Michael J.; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
The 3D hybrid framework [{Cu(cyclam)}3(kMo8O27)]· 14H2O (1) (cyclam=1,4,8,11-tetraazacyclotetradecane) undergoes sequential single-crystal-to-singlecrystal transformations upon heating to afford two different anhydrous phases (2 a and 3a). These transitions modify the framework dimensionality and enable the isomerization of k-octamolybdate (k-Mo8) anions into λ (2 a) and μ (3 a) forms through metal migration. Hydration of 3 a involves condensation of one water molecule to the cluster to afford the γ-Mo8 isomer in 4, which dehydrates back into 3a through the 6a intermediate. In contrast, 2a reversibly hydrates to form 5, exhibiting the same Mo8 cluster as that of 1. It is remarkable that three of the Mo8 clusters (k, λ and μ) are new and that up to three different microporous phases can be isolated from 1 (2 a, 3a, and 6a). Water vapor sorption analyses show high recyclability and the highest uptake values for POM-based systems. The isotherms display an abrupt step at low humidity level desirable for humidity control devices or water harvesting in drylands.
Open Access
Electrical conduction mechanism in carbon-ceramic composites
(Elsevier, 2023) Alcañiz Monge, Juan; Gil-Muñoz, Gema; Trautwein, Guido; Reinoso, Santiago; Institute for Advanced Materials and Mathematics - INAMAT2
Carbon-ceramic composites (C/Cer) have been prepared by chemical vapor deposition of coal tar pitch onto clay substrates and characterized by thermogravimetric analyses, powder X-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopies (SEM and TEM). The study of the dc electrical conductivity, together with the determination of the Hall voltage sign, proves that such C/Cer composites are n-type semiconductors. Our results demonstrate that: 1) the mechanism of electrical conduction of C/Cer semiconductors proceeds through the pathways expected for amorphous solids (ie. variable-range hopping and heat-activated pathways at low and high temperatures, respectively); and 2) their transport properties are strongly dependent on the clay components, as evidenced by microscopy experiments.
Open Access
Crystal-to-crystal polymerisation of monosubstituted [PW11O39Cu(H2O)]5- Keggin-type anions
(Royal Society of Chemistry, 2024) Ruiz Bilbao, Estíbaliz; Pache, Aroa; Barrenechea, Unai; Reinoso, Santiago; San Felices, Leire; Vivanco, Maria dM.; Lezama, Luis; Artetxe, Beñat; Gutiérrez Zorrilla, Juan M.; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
The reaction between neutral bis(picolinate)copper(ii) complexes and copper(ii)-monosubstituted Keggin-type phosphotungstate anions formed in situ leads to the formation of the hybrid [C(NH2)3]10[{PW11O39Cu(H2O)}2{Cu(pic)2}]·10H2O compound (1, pic = picolinate) in the presence of structure-directing guanidinium cations. Single-crystal X-ray diffraction studies demonstrate that 1 contains dimeric {PW11O39Cu(H2O)}2{Cu(pic)2} molecular species constituted by two Keggin-type anions linked by one {Cu(pic)2} octahedral complex through axial coordination to their terminal oxygen atoms. The extensive hydrogen-bonding network established by guanidium cations and Keggin clusters plays a key role in retaining the crystallinity of the system throughout dehydration to allow a single-crystal-to-single-crystal (SCSC) transformation into the anhydrous [C(NH2)3]10[{PW11O39Cu}2{Cu(pic)2}] (2a) at 170 °C. Structural modifications involve the re-orientation, shifting in ca. 1.5 Å and condensation of all the {PW11O39Cu} units to result in {PW11O39Cu}n chains in an unprecedented solid-state polymerisation. This phase transition also implies the cleavage of Cu-O bonds induced by the rotation and translation of Keggin-type anions, in such a way that hybrid dimeric units in 1 are dismantled and {Cu(pic)2} complexes become square planar. The irreversibility of the phase transition has been confirmed by combined thermal and diffractometric analyses, which evidence that the anhydrous phase adsorbs only one water molecule per cluster to become the [C(NH2)3]10[{PW11O39Cu}2{Cu(pic)2}]·2H2O (2h) hydrated derivative without any significant alteration in its cell parameters, nor in its crystalline structure. Phase transformations have been monitored by electron paramagnetic resonance spectroscopy.
Open Access
The effect of the orientation of the Jahn-Teller distortion on the magnetic interactions of trinuclear mixed-valence Mn(II)/Mn(III) complexes
(Royal Society of Chemistry, 2019) Bikas, Rahman; Shahmoradi, Elaheh; Reinoso, Santiago; Emami, Marzieh; Lezama, Luis; Sanchiz, Joaquín; Noshiranzadeh, Nader; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Two new trinuclear manganese complexes, [Mn3(L1)(μ-OCH3)2(N3)2]·CH3OH (1) and [Mn3(L2)(μ-OCH3)2(N3)2]·CH3OH (2), have been obtained from the reaction of Mn(OAc)2 4H2O, NaN3 and the preformed N6O4-donor H4L1 or H4L2 compartmental ligands, which are synthesized via Schiff base condensation of pentaethylenehexamine with 2-hydroxybenzaldehyde or 2-hydroxy-3-methoxybenzaldehye, respectively. Complexes 1 and 2 have been characterized by spectroscopic methods and single-crystal X-ray analysis. The structural studies indicate that both 1 and 2 are mixed-valence complexes containing angular Mn(III)-Mn(II)-Mn(III) cores in which the metal centers are connected to each other by phenoxido and methoxido bridging groups. The coordination environment around the manganese ions is analogous in both complexes, but for a change in the direction of the Jahn-Teller distortion around the external Mn(III) ions when going from 1 to 2, which is mainly attributed to the steric effect of different substituents on the phenyl rings of the ligands. The analysis of the magnetic susceptibility data indicates the presence of antiferromagnetic intramolecular coupling in both complexes, but the interaction in 1 was found to be nearly one order of magnitude weaker than that in 2. This fact is rationalized on the basis of the different orientation of the Jahn-Teller distortion, which modifies the magnetic exchange pathway through the phenoxido bridges from the equatorial-axial connection type observed in 1 to the axial-axial linkages displayed by 2.
Open Access
Determination of hazardous vapors from the thermal decomposition of organochlorinated silica xerogels with adsorptive properties
(Elsevier, 2024) Rosales Reina, María Beatriz; Cruz Quesada, Guillermo; Pujol, Pablo; Reinoso, Santiago; Elosúa Aguado, César; Arzamendi Manterola, Gurutze; López Ramón, María Victoria; Garrido Segovia, Julián José; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
The incorporation of organic groups into sol-gel silica materials is known to have a noticeable impact on the properties and structure of the resulting xerogels due to the combination of the properties inherent to the organic fragments (functionality and flexibility) with the mechanical and structural stability of the inorganic matrix. However, the reduction of the inorganic content in the materials could be detrimental to their thermal stability properties, limiting the range of their potential applications. Therefore, this work aims to evaluate the thermal stability of hybrid inorganic-organic silica xerogels prepared from mixtures of tetraethoxysilane and organochlorinated triethoxysilane precursors. To this end, a series of four materials with a molar percentage of organochlorinated precursor fixed at 10%, but differing in the type of organic group (chloroalkyls varying in the alkyl-chain length and chlorophenyl), has been selected as model case study. The gases and vapors released during the thermal decomposition of the samples under N2 atmosphere have been analyzed and their components determined and quantified using a thermogravimetric analyzer coupled to a Fourier-transform infrared spectrophotometer and to a gas chromatography-mass spectrometry unit. These analyses have allowed to identify up to three different thermal events for the pyrolysis of the organochlorinated xerogel materials and to elucidate the reaction pathways associated with such processes. These mechanisms have been found to be strongly dependent on the specific nature of the organic group.

Reinoso, Santiago

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