Materials chemistry: Design, Synthesis and Functionality

The need to synthesise new materials is driven by the need for materials with specific functionality, which is in turn driven by the intended final application. In this talk we will explore the design of materials based on the application for which they are intended and the ways in which they can be synthesised and characterised. From the materials perspective we will focus on inorganic–organic hybrid materials, metal phosphonates and metal oxides, and discuss how we can make such materials which exhibit properties of luminescence and antimicrobial activity. Characterisation of materials using crystallography, photoluminescence and adsorption spectroscopies, and how the biological activity of materials is determined will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Materials chemistry: design and synthesis of luminescent and biologically active materials

The need to synthesise new materials is driven by the need for materials with specific properties. Those properties are determined by the final application. In this talk we will explore the design of materials which are used in Luminescent and Anti-microbial applications. From the materials perspective we will focus on inorganic–organic hybrid materials, metal phosphonates and metal oxides, and discuss how we can make such materials. We will consider how the choice of metal changes the luminescent response and how materials can be constructed by design at the atomic level. considering antimicrobial materials we will discuss how structure influences the release of active species and can result in materials which are therapeutic but not toxic.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Tunable crystal structure and proton conductivity of lanthanide nitrilotrismethylphosphonates

Metal phosphonates are multifunctional solids with remarkable stability and proton conducting properties owing to their structure is usually composed of extended hydrogen-bond networks that favor proton transfer pathways [1]. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3]. In this communication, a new family of isostructural 2D layered compounds based on lanthanide nitrilotris-methylphosphonates is reported. These compounds have been isolated at room temperature and have the general formula Ln[N(CH2)3(PO3H2)2(PO3H)(H2O)]SO4·2H2O (Ln= Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb). The coordination environment of Ln3+ is composed by eight oxygen atoms from three different ligands and two oxygens from bound waters. This connectivity creates positive charged layers connected to sulfate ions through hydrogen-bonds. These compounds show promising proton conductivity with values ranging between 7.6·10-2 and 3.8·10-2 S·cm-1 at 80 °C and 95% RH and low activation energy corresponding to Grotthuss-type proton transfer mechanism. In addition, a structural transformation occurs at T > 70 °C accompanied by a remarkable enhanced conductivity. Studies on the structure-properties relationships will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO: MAT2016-77648-R Junta Andalucía: P12-FQM-1656 y FQM-11

Proton conductivity and luminiscence properties of lanthanide aminotriphosphonates

Metal phosphonates are multifunctional solids with tunable properties, such as internal H-bond networks, and high chemical and thermal stability [1]. In the present work, we describe the synthesis, structural characterization, luminescent properties and proton conduction performance of a new family of isostructural cationic compounds with general formula [Ln(H4NMP)(H2O)2]Cl·2H2O [Ln = La3+, Pr3+, Sm3+, Gd3+, Tb3+, Dy3+, Ho3+, H6NMP = nitrilotris(methylphosphonic acid)]. These solids are formed by positively charge layers, which consist of isolated LnO8 polyhedra and bridge chelating NMP2- ligands, held apart by chloride ions and water molecules. This arrangement result in extended interlayer hydrogen networks with possible proton transfer pathways. The proton conductivity of Gd3+ sample, selected as prototype of the series, was measured. In the range between range 25º and 80 ºC, the conductivity increase with the temperature up to a maximum value of 3.10-4 S·cm-1, at relative humidity of 95 %. The activation energy obtained from the Arrhenius plot (Figure 1) is in the range corresponding to a Grotthuss transfer mechanism.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. FQM-1656; MAT2013-41836-R

Synthesis and antibacterial activity of bimetallic carboxyphosphonates

As a class of coordination polymers (CPs), metal phosphonates (MPs) are constructed by coordination bonds connecting metal sites and phosphonate (RPO3 2−) ligands, where the metal sites are dispersed uniformly at the atomic level. The synthetic chemistry of phosphonates is well developed, so phosphonic acids can be obtained through simple, well-known reactions, enabling the synthesis of phosphonate derivatives of non-steroidal anti-inflammatory drugs (NSAIDs) to be carried out. We report here, general characteristics of a new series of isostructural compounds resulting from the combination of the multifunctional R,S-hydroxyphophonoacetic acid (HPAA) with transition metal ions, AgMII[HO3PCH(OH)COO] (MII= Co or Zn), AgMHPAA. Both compounds were synthesized under hydrothermal conditions and their crystal structures were solved from single crystal diffraction data. The antibacterial activity of AgZnHPAA and AgCoHPAA was evaluated using three different bacterial strains: Staphylococcus aureus (NCIMB 6571), Escherichia coli K12 W-T (W1485 Cardiff Collection) and Pseudomonas aeruginosa (NCIMB 8295). Preliminary results regarding their antibacterial properties will be presented and discussed.Universidad de Málaga. Campus de Excelencia Interna Andalucía Tech. Proyectos nacionales MAT2016-77648-R y PID2019-110249RB-I00ciona

Proton Conductivity in Sulfate-Containing Lanthanide Nitrilotris-methylphosphonates

Multifunctional metal phosphonates are coordination polymers (CPs) whose structures are usually composed of extended hydrogen-bond networks and thus making them potential candidates as proton conductors [1]. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3]. In this communication, isostructural 2D layered compounds based on lanthanide nitrilotrismethylphosphonates are studied. In series 1 compounds, Ln[(ATMP)(H2O)2]HSO4·2H2O (Ln= Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Yb3+), uncoordinated HSO4- acts as the counterion of positively charged layers creating an extended hydrogen-bond networks together with the lattice water molecules, while the lanthanide ions are octacoordinated by two water molecules and six oxygen from four different ligands. This phase transforms to other structures by dehydration or by exposing the samples at 80 ºC and 95% relative humidity. Under wet conditions, the solids experience partial (Ln= Pr3+, Eu3+, Tb3+) or full loss (Ln= Yb3+) of HSO4-, accompanied by a structural reorganization that influence the proton conductivity properties. In series 2, Ln[(ATMP)(H2O)](SO4)·H2O (Ln= Pr3+, Eu3+, Gd3+ and Tb3+), the octacoordinated environment of lanthanide ions in the layer structure is composed of six phosphonate oxygen atoms and two oxygen from two sulfate ions which acts as a bridge ligands. This structural variability allows obtaining solids with conductivities ranging between 3.5·10-2 and 1.0·10-3 S·cm-1 (80 ºC and 95% RH) and activation energies corresponding to a Grotthuss-type proton transfer mechanism.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MAT2016-77648-R, Junta de Andalucía-FQM-11

Temperature dependent characteristics of La2O2S: Ln [Ln = Eu,Tb] with various Ln concentrations over 5-60 ºC

This research is aimed at developing an optical sensor for remotely measuring human skin temperature in electromagnetically hostile environments, such as within a magnetic resonance imaging (MRI) scanner. In this feasibility study, various concentrations of europium doped lanthanum oxysulphide (La2O2S: Eu- 0.1-15 mol % (m/o)) and terbium doped lanthanum oxysulphide (La2O2S: Tb - 0.005-50 m/o) have been investigated in terms of crystallinity, photoluminescent (PL) spectral and decay time characteristics. For both phosphors, X-ray diffraction (XRD) has shown that as dopancy increases, the (100) and (002) reflections merge and there is a reduction in the c-axis parameter as well as the crystallite size. Photoluminescent characterisation (337 nm excitation) has also shown a dependency to dopant concentration through variance of peak intensity. Temperature dependent decay time measurements were carried out over a low temperature range of 5 to 60 °C. Optimum brightness of these temperature dependent lines is achieved at concentrations of 1 and 10 m/o for La2O2S: Eu and La2O2S: Tb respectively. However, optimum temperature dependency is achieved at lower concentration for La2O2S: Eu, specifically at 0.1 m/o. In comparison to conventional phosphor temperature dependent characteristic, La2O2S: Tb showed an increase in decay time with respect to temperature for concentrations above 2 m/o

Luminescent and Proton Conducting Lanthanide Coordination Networks Based On a Zwitterionic Tripodal Triphosphonate

The synthesis, structural characterization, luminescence properties, and proton conduction performance of a new family of isostructural cationic 2D layered compounds are reported. These have the general formula [Ln(H4NMP)- (H2O)2]Cl·2H2O [Ln = La3+, Pr3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, H6NMP = nitrilotris(methylphosphonic acid)], and contain Cl− as the counterion. In the case of Ce3+, a 1D derivative, [Ce2(H3NMP)2(H2O)4]·4.5H2O, isostructural with the known lanthanum compound has been isolated by simply crystallization at room temperature. The octa-coordinated environment of Ln3+ in 2D compounds is composed by six oxygen atoms from three different ligands and two oxygens from each bound water. Two of the three phosphonate groups act as both chelating and bridging linkers, while the third phosphonate group acts solely as a bridging moiety. The materials are stable at low relative humidity at less at 170 °C. However, at high relative humidity transform to other chloride-free phases, including the 1D structure. The proton conductivity of the 1D materials varies in a wide range, the highest values corresponding to the La derivative (σ ≈ 2 × 10−3 S·cm−1 at RH 95% and 80 °C). A lower proton conductivity, 3 × 10−4 S·cm−1, was measured for [Gd(H4NMP)(H2O)2]Cl·2H2O at 80 °C, which remains stable under the work conditions used. Absorption and luminescence spectra were recorded for selected [Ln(H4NMP)(H2O)2]Cl·2H2O compounds. In all of them, the observed transitions are attributed solely to f−f transitions of the lanthanide ions present, as the H4NMP2− organic group has no measurable absorption or luminescence properties.Proyecto nacional MAT2013-41836-R (MINECO) y Proyecto de la Junta de Andalucía P12-FQM-165

Phase Transformation Dynamics in Sulfate-Loaded Lanthanide Triphosphonates. Proton Conductivity and Application as Fillers in PEMFCs

Phase transformation dynamics and proton conduction properties are reported for cationic layer-featured coordination polymers derived from the combination of lanthanide ions (Ln3+) with nitrilo-tris(methylenephosphonic acid) (H6NMP) in the presence of sulfate ions. Two families of materials are isolated and structurally characterized, i.e., [Ln2(H4NMP)2(H2O)4](HSO4)2·nH2O (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Er, Yb; n = 4−5, Series I) and [Ln(H5NMP)]SO4· 2H2O (Ln = Pr, Nd, Eu, Gd, Tb; Series II). Eu/Tb bimetallic solid solutions are also prepared for photoluminescence studies. Members of families I and II display high proton conductivity (10−3 and 10−2 S·cm−1 at 80 °C and 95% relative humidity) and are studied as fillers for Nafion-based composite membranes in PEMFCs, under operating conditions. Composite membranes exhibit higher power and current densities than the pristine Nafion membrane working in the range of 70−90 °C and 100% relative humidity and with similar proton conductivity.Proyectos de Ministero de Ciencia e Innovación MAT2016-77648-R (MICINN/FEDER); PID2019-110249RB-I00 (MICINN/FEDER) y la Junta de Andalucía (FQM113). Funding for open access change: Universidad de Málaga/ CBU

Divalent Metal Vinylphosphonate Layered Materials: Compositional Variability, Structural Peculiarities, Dehydration Behavior, and Photoluminescent Properties

A family of M-VP (M = Ni, Co, Cd, Mn, Zn, Fe, Cu, Pb; VP = vinylphosphonate) and M-PVP (M = Co, Cd; PVP = phenylvinylphosphonate) materials have been synthesized by hydrothermal methods and characterized by FTIR, elemental analysis, and thermogravimetric analysis (TGA). Their structures were determined either by single crystal X-ray crystallography or from laboratory X-ray powder diffraction data. The crystal structure of some M-VP and M-PVP materials is two-dimensional (2D) layered, with the organic groups (vinyl or phenylvinyl) protruding into the interlamellar space. However, the Pb-VP and Cu-VP materials show dramatically different structural features. The porous, three-dimensional (3D) structure of Pb-VP contains the Pb center in a pentagonal pyramid. A Cu-VP variant of the common 2D layered structure shows a very peculiar structure. The structure of the material is 2D with the layers based upon three crystallographically distinct Cu atoms; an octahedrally coordinated Cu2+ atom, a square planar Cu2+ atom and a Cu+ atom. The latter has an unusual co-ordination environment as it is 3-coordinated to two oxygen atoms with the third bond across the double bond of the vinyl group. Metal-coordinated water loss was studied by TGA and thermodiffractometry. The rehydration of the anhydrous phases to give the initial phase takes place rapidly for Cd-PVP but it takes several days for Co-PVP. The M-VP materials exhibit variable dehydration-rehydration behavior, with most of them losing crystallinity during the process.Proyecto nacional MAT2010-15175 (MICINN, España