Dicopper(II)-EDTA Chelate as a Bicephalic Receptor Model for a Synthetic Adenine Nucleoside

In the extensive field of metal ions, their interactions with nucleic acids, and their constituents, the main aim of this work is to develop a metal chelate suitable to recognize two molecules of an adenine nucleoside. For this purpose, the dinuclear chelate Cu2 (µ-EDTA) (ethylenediaminetetraacetate(4-) ion (EDTA)) is chosen as a bicephalic receptor model for N9-(2-hydroxyethyl)adenine (9heade). A one-pot synthesis is reported to obtain the compound [Cu2 (µ2 -EDTA)(9heade)2 (H2O)4 ]·3H2O, which has been characterized by single-crystal X-ray diffraction and various spectral, thermal, and magnetic methods. The complex unit is a centro-symmetric molecule, where each Cu (II) center is chelated by a half-EDTA, and is further surrounded by an N7-dentate 9heade nucleoside and two non-equivalent trans-O-aqua molecules. The metal chelate-nucleoside molecular recognition is referred to as an efficient cooperation between the Cu-N7(9heade) coordination bond and a (9heade)N6-H···O(carboxyl, EDTA) interligand interaction. Theoretical calculations are also made to account for the relevance of this interaction. The extreme weakness with which each water molecule binds to the metal center disturbs the thermal stability and the infrared (FT-IR) and electron spin resonance (ESR) spectra of the compound.Agencia Estatal de Investigación, Ministerio de Ciencia, Innovación y Universidades (MICIU) from SpainFEDER-EU (project nos. PGC2018-102047-B-I00 and CTQ2017-85821-R)Junta de Andalucía (research group FQM-283)University of Granada (project ref. PPJIA2019-03

Open and closed forms of the interpenetrated [Cu2(Tae)(Bpa)2](NO3)2•nH2O cationic coordination polymer: magnetic properties and high pressure CO2/CH4 gas sorption.

Two closed and one open structural forms of the interpenetrated [Cu2(Tae)(Bpa)2](NO3)2•nH2O (H2Tae= 1,1,2,2-tetraacetylethane, Bpa= 1,2-Bis(4-pyridyl)ethane) cationic coordination polymer have been synthesized. Three crystallographically related interpenetrated “ths” cationic nets encapsulate water molecules and nitrate anions giving rise to the closed structural forms of [Cu2(Tae)(Bpa)2](NO3)2•nH2O. Depending on the location of water molecules and nitrate groups, two different closed forms, with 5.5 and 3.6 crystallization water molecules have been obtained. Thermal activation of the closed structures gives rise to a 29% expansion of the unit cell. This closed to open transformation is reversible, and is triggered by the loss or uptake of solvent. The high pressure gas adsorption experiments show similar selectivity values towards CO2 for CO2/CH4 mixtures than that showed by some metal organic frameworks without unsaturated metal sites, and isosteric heats for CO2 adsorption similar to that for the HKUST-1 compound.Ministerio de Economía y Competitividad (MAT2016-76739-R (AEI/FEDER, EU). Gobierno Vasco (Basque University Research System Group, IT-630-13 and Economic Development and Competitiveness, ACTIMAT (KK-2015/00094) and LISOL (KK-2016/00095) projects, ELKARTEK program)

A Robust Framework Based on Polymeric Octamolybdate Anions and Copper(II) Complexes of Tetradentate N-donor Ligands

A new organic-inorganic compound based on octamolybdate building blocks and copper(II) complexes of tetradentate N-donor ligands has been hydrothermally synthesized, namely [Cu(cyclam)](2)[Mo8O26]center dot 1.5H(2)O (1), (cyclam: 1,4,8,11-tetraazacyclotetradecane). Compound 1 has been chemically (elemental and thermal analyses), spectroscopically (infrared spectroscopy), and structurally (single crystal and powder X-ray diffraction) characterized. The crystal packing of 1 shows a covalent framework structure formed by [Mo8O26](n)(4n-) chains running along the 100 direction which are linked to each other through the coordination spheres of {Cu(cyclam)}(2+) complexes leading to a three-dimensional open network. This structural assembly generates voids that can be described as a succession of cavities communicated through narrow bottlenecks with approximate cross section of 4 x 7 angstrom(2) where the hydration water molecules are hosted. The robust open structure of 1 remains virtually unaltered upon thermal evacuation of guest solvent molecules at 130 degrees C, resulting in the anhydrous phase [Cu(cyclam)](2)[Mo8O26] (1a) with potentially accessible micropores as demonstrated by single-crystal X-ray diffraction measurements. Electron paramagnetic resonance spectroscopy analysis of 1 has also been assessed.This work was funded by UPV/EHU (Grant PPG17/37 and GIU17/050) and University of Tunis El Manar (predoctoral fellowship to N.D., including a three-month stay at Universidad del Pais Vasco, UPV/EHU). B.A. thanks UPV/EHU for a postdoctoral fellowship within the program "Convocatorias de Ayudas para la Especializacion de Personal Investigador". Technical and human support provided by SGIker (UPV/EHU) is gratefully acknowledged

Fast Visible-Light Photopolymerization in the Presence of Multiwalled Carbon Nanotubes: Toward 3D Printing Conducting Nanocomposites

[EN] A new photoinitiator system (PIS) based on riboflavin (Rf), triethanolamine, and multiwalled carbon nanobutes (MWCNTs) is presented for visible-light-induced photopolymerization of acrylic monomers. Using this PIS, photopolymerization of acrylamide and other acrylic monomers was quantitative in seconds. The intervention mechanism of CNTs in the PIS was studied deeply, proposing a surface interaction of MWCNTs with Rf which favors the radical generation and the initiation step. As a result, polyacrylamide/MWCNT hydrogel nanocomposites could be obtained with varying amounts of CNTs showing excellent mechanical, thermal, and electrical properties. The presence of the MWCNTs negatively influences the swelling properties of the hydrogel but significantly improves its mechanical properties (Young modulus values) and electric conductivity. The new PIS was tested for 3D printing in a LCD 3D printer. Due to the fast polymerizations, 3D-printed objects based on the conductive polyacrylamide/CNT nanocomposites could be manufactured in minutes.The authors are thankful for technical and human support provided by IZO-SGI SGIker of UPV/EHU. The authors would like to thank the European Commission for financial support through funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement no. 823989

Metalloporphyrin-based MOFs: new strategies for catalyst immobilization

Comunicacion a congreso (Presentación): ICCC 40. International Conference on Coordination Chemistry. Valencia, September 09-13, 2012Metalloporphyrin systems are one of the cornerstones on which the existence of life is based, as major biochemical, enzymatic and photochemical functions depend on the special properties of the tetrapyrrolic macrocycle. Thus, porphyrin catalysts are well-known to be highly efficient in many catalytic reactions and, during the last years, a great effort has been devoted to the immobilization of distinct types of catalysts on solids . In this sense, recent strategy consists of the immobilization of catalysts in MOFs (metal-organic frameworks). In our group we have started exploring the possibility of using metalloporphyrins both as structural units in MOFs and catalyst, in the same compound. Our preliminary results consist of a series of M-porphyrin-bipy compounds (M= Fe, Co; bipy= 4,4'-bipyridine) that have been structurally characterised. Catalytic activity has also been studied.Ministerio de Ciencia e Innovación (MAT2010-15375) y Gobierno Vasco (Basque University System Research Groups, IT-177-0

Single-Crystal to Single-Crystal Reversible Transformations Induced by Thermal Dehydration in Keggin-Type Polyoxometalates Decorated with Copper(II)-Picolinate Complexes: The Structure Directing Role of Guanidinium

Three new hybrid inorganic-metalorganic compounds containing Keggin-type polyoxometalates, neutral copper(II)-picolinate complexes and guanidinium cations have been synthesized in bench conditions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction: the isostructural [C(NH2)(3)](4)[{XW12O40}{Cu-2(pic)(4)}] . [Cu-2(pic)(4)(H2O)](2) .6H(2)O [X = Si (1), Ge (3)] and [C(NH2)(3)]8[{SiW12O40}(2){Cu(pic)(2)}3{Cu-2(pic)4(H2O)}(2)] .8H(2)O (2). The three compounds show a pronounced two-dimensional character owing to the structure-directing role of guanidinium. In 1 and 3, layers of [{XW12O40}{Cu-2(pic)(4)}] n(4n-) hybrid POM chains and layers of [Cu-2(pic)(4)(H2O)] complexes and [C(NH2)(3)](+) cations pack alternately along the z axis. The hydrogen-bonding network established by guanidinium leads to a trihexagonal tiling arrangement of all copper(II)-picolinate species. In contrast, layers of [C(NH2)(3)](+)-linked [{SiW12O40}(2){Cu(pic)(2)}(3)] n(8n-) double chains where each Keggin cluster displays a {Cu-2(pic)(4)(H2O)} moiety pointing at the intralamellar space are observed in 2. The thermal stability of 1-3 has been studied by thermogravimetric analyses and variable temperature powder X-ray diffraction. Compounds 1 and 3 undergo single-crystal to single-crystal transformations promoted by reversible dehydration processes and the structures of the corresponding anhydrous phases 1a and 3a have been established. Despite the fact that the [Cu-2(pic)(4)(H2O)] dimeric complexes split into [Cu( pic)(2)] monomers upon dehydration, the packing remains almost unaltered thanks to the preservation of the hydrogen-bonding network established by guanidinium and its associated Kagome-type lattice. Splitting of the dimeric complexes has been correlated with the electron paramagnetic resonance spectra.This work was funded by Eusko Jaurlaritza/Gobierno Vasco (grant IT477- 10 and predoctoral fellowship to A. P.), Ministerio de Economia y Competitividad (grant MAT2013-48366-C2-2P) and Universidad del Pais Vasco UPV/EHU (grant UFI11/53). Technical and human support provided by SGIker (UPV/EHU) is gratefully acknowledged

Cationic Mn2+/H+ exchange leading a slow solid-state transformation of a 2D porphyrinic network at ambient conditions

Metalloporphyrins exhibit outstanding chemical, physical and biological properties in dissolution, however, it is a challenge to synthesize them as stable solid frameworks. Long-time stability is crucial for future applications of these materials, and we have detected a slow, solid-state transformation of a 2D MnII-porphyrin at RT. The remarkable point is that this transformation showed up as a result of Electronic Paramagnetic Resonance measurements. Otherwise, the evolution of the system could have remained undetected. Thus, 2D [Mn3(TCPP)(H2O)4]•nD (1) (where TCPP is meso-tetra(4-carboxyphenyl)porphyrin and D is the sovent) has been synthesized hydrothermally, and characterised by means of X-ray diffraction (XRD), Thermogravimetry and X-ray thermodiffractometry (XRTD). This compound slowly transforms into [Mn(H4TCPP)(H2O)2]•nD (2) according to the equilibrium [Mn3(TCPP)]+4H+ ↔ [Mn(H4TCPP)]+2Mn2+. The evolution of the system has been studied through analysis of the distortion (both of the coordination sphere and the tetrapyrrolic macrocycle) and Density Functional Theory (DFT) quantum mechanical calculations.Ministerio de Economia y Competitividad (MAT2013-42092-R), Gobierno Vasco (Basque University System Research Groups, IT-630-13) and UPV/EHU (UFI11/15

Amorphous FeCoCrSiB Ribbons with Tailored Anisotropy for the Development of Magnetic Elements for High Frequency Applications

The ferromagnetic resonance (FMR) in the frequency range of 0.5 to 12.5 GHz has been investigated as a function of external magnetic field for rapidly quenched Fe3Co67Cr3Si15B12 amorphous ribbons with different features of the effective magnetic anisotropy. Three states of the ribbons were considered: as-quenched without any treatment; after relaxation annealing without stress at the temperature of 350 °C during 1 h; and after annealing under specific stress of 230 MPa at the temperature of 350 °C during 1 h. For FMR measurements, we adapted a technique previously proposed and tested for the case of microwires. Here, amorphous ribbons were studied using the sample holder based on a commercial SMA connector. On the basis of the measurements of the reflection coefficient S11, the total impedance including its real and imaginary components was determined to be in the frequency range of 0.5 to 12.5 GHz. In order to confirm the validity of the proposed technique, FMR was also measured by the certified cavity perturbation technique using a commercial Bruker spectrometer operating at X-band frequency of 9.39 GHz. As part of the characterization of the ribbons used for microwave measurements, comparative analysis was performed of X-ray diffraction, optical microscopy, transmission electron microscopy, inductive magnetic hysteresis loops, vibrating sample magnetometry, magneto-optical Kerr effect (including magnetic domains) and magnetoimpedance data for of all samples.The research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) is gratefully acknowledged. Further funding from University of the Basque Country UPV/EHU Research Groups Funding (GMMM) is similarly gratefully acknowledged

Heterogeneous catalytic properties of unprecedented m-O-[FeTCPP]2 dimers (H2TCPP = meso-tetra(4-carboxyphenyl)porphyrin): unusual superhyperfine EPR structure

Articulo científico Dalton TransactionsDuring the past years, a great effort has been devoted to the anchoring of catalysts into solid coordination networks in order to achieve heterogeneous catalysts. In this sense, an innovative approach consists on using the coordination-network synthons both as structural units and as catalysts. Regarding the latter, metalloporphyrins are suitable candidates for synthons. In fact, a few works report on coordination compounds based on metalloporphyrins exhibiting these features. On the other hand, highly distorted di-iron oxo dimers containing electron withdrawing groups rank amongst the most-effective catalyst models. Thus, the aim of this work was obtaining coordination networks based on iron porphyrins exhibiting those characteristics. This way, this work reports on the synthesis and characterisation of the μ-O-[FeTCPP]2•16DMF compound (H2TCPP = meso-tetra(4-carboxyphenyl)porphyrin, DMF = N,N-dimethylformamide). This compound is the first example of an μ-oxo dimer with TCPP. The inter-dimer connections give rise to a laminar structure. The structural, spectroscopic and magnetic properties of this compound are consistent with the presence of high-spin FeIII ions, exhibiting a strong antiferromagnetic coupling in the μ-oxo dimer (J = -132 cm-1). An unusual superhyperfine structure has been observed in EPR that is related to the high accessible volume of the compound. The structural features of the dimers and the accessible network are responsible for the excellent behaviour of the compound as a heterogeneous catalyst for different oxidation of alcohols. Therefore, this compound is a new of the very few examples of metalloporphyrins where structural units play as catalysts.Ministerio de Economia y Competitividad (MAT2013-42092-R, MAT2011-29020-C02-02), Gobierno Vasco (Basque University System Research Groups, IT-630-13) y UPV/EHU (UFI 11/15

Single-Crystal-to-Single-Crystal Cluster Transformation in a Microporous Molybdoarsenate(V)-Metalorganic Framework

[EN]The hybrid compound [Cu(cyclam)(H2O)(2)](0.5)[{Cu(cyclam)}(1.5){B-H2As2Mo6O26(H2O)}].9H(2)O (1) (cyclam = 1,4,8,11- tetraazacyclotetradecane) was synthesized in aqueous solution by reacting the {Cu(cyclam)}(2+) complex with a mixture of heptamolybdate and an arsenate(V) source. Crystal packing of 1 exhibits a supramolecular open-framework built of discrete covalent molybdoarsenate/metalorganic units and additional [Cu(cyclam)-(H2O)(2)](2+) cations, the stacking of which generates squarelike channels parallel to the z axis with an approximate cross section of 10 x 11 A(2) where all the hydration water molecules are hosted. Thermal evacuation of solvent molecules yields a new anhydrous crystalline phase, but compound 1 does not preserve its singlecrystalline nature upon heating. However, when crystals are dehydrated under vacuum, they undergo a structural transformation that proceeds via a single-crystal-to-single-crystal pathway, leading to the anhydrous phase [{Cu(cyclam)}(2)(A-H2As2Mo6O26)] (2). Total dehydration results in important modifications within the inorganic cluster skeleton which reveals an unprecedented solid-state B to A isomerization of the polyoxoanion. This transition also involves changes in the CuII bonding scheme that lead to covalent cluster/metalorganic layers by retaining the open-framework nature of 1. Compound 2 adsorbs ambient moisture upon air exposure, but it does not revert back to 1, and the hydrated phase [{Cu(cyclam)}(2)(A-H2As2Mo6O26)]center dot 6H(2)O (2h) is obtained instead. Structural variations between 1 and 2 are reflected in electron paramagnetic resonance spectroscopy measurements, and the permanent microporosity of 2 provides interesting functionalities to the system such as the selective adsorption of gaseous CO2 over N-2.This work was funded by Eusko Jaurlaritza/Gobierno Vasco (EJ/GV, Grants IT-1291-19 and KK-2020/00008, together with a predoctoral fellowship to E.R.-B.), Ministerio de Economia, Industria y Competitividad (Grant MAT2017-89553-P), and University of Tunis El Manar (predoctoral fellowship to N.D. including a research stay at UPV/EHU)