Synthesis and characterization of highly diluted polyanionic iron(II) spin crossover systems Andrea Moneo-Corcuera, David Nieto-Castro, Jordi Cirera, Verónica Gómez, Jesús Sanjosé-Orduna, Carla Casadevall, Gábor Molnár, Azzedine Bousseksou, Teodor Parella, José María Martínez-Agudo, Julio Lloret-Fillol, Mónica Helvia Pérez-Temprano, Eliseo Ruiz, José Ramón Galán-Mascarós STAR Protocols, 2023 Spin crossover (SCO) complexes, through their reversible spin transition under external stimuli, can work as switchable memory materials. Here, we present a protocol for the synthesis and characterization of a specific polyanionic iron SCO complex and its diluted systems. We describe steps for its synthesis and the determination of crystallographic structure of the SCO complex in diluted systems. We then detail a range of spectroscopic and magnetic techniques employed to monitor the spin state of the SCO complex in both diluted solid- and liquid-state systems. For complete details on the use and execution of this protocol, please refer to Galán-Mascaros et al.1
Molecular memory near room temperature in an iron polyanionic complex Andrea Moneo-Corcuera, David Nieto-Castro, Jordi Cirera, Verónica Gómez, Jesús Sanjosé-Orduna, Carla Casadevall, Gábor Molnár, Azzedine Bousseksou, Teodor Parella, José María Martínez-Agudo, Julio Lloret-Fillol, Mónica Helvia Pérez-Temprano, Eliseo Ruiz, José Ramón Galán-Mascarós Chem, 2023
Synergic Bistability between Spin Transition and Fluorescence in Polyfluorene Composites with Spin Crossover Polymers Irene Sánchez-Molina, David Nieto-Castro, Andrea Moneo-Corcuera, Eugenia Martínez-Ferrero, José Ramon Galán-Mascarós Journal of Physical Chemistry Letters, 2021 In recent years, several examples of materials combining the molecular bistability of spin crossover (SC) and fluorescent moieties have flourished in the literature. Fluorescence is a sensitive probe, and SC may provide modulation of the signal, thus affording systems in which physicochemical changes in the environment of the SC centers could be effectively detected. On the contrary, organic semiconductor polymers are of great interest and, furthermore, have been successfully applied in different optoelectronic devices, such as transistors, solar cells, and light-emitting devices. Herein, we report on the fabrication of composites comprising a fluorescent, organic semiconductor polymer (polyfluorene) and a spin crossover compound, an Fe(II)-triazole coordination polymer. A strong synergy was observed between the spin transition of the Fe(II) compound and variations in the fluorescence of the organic polymer. The fluorescence modulation was shown to be reversible, with an increase of ≤20% with respect to the original value.
Crystal structure and magnetic properties of trinuclear transition metal complexes (Mnii, coii, niii and cuii ) with bridging sulfonate-functionalized 1,2,4-triazole derivatives Andrea Moneo-Corcuera, Breogán Pato-Doldan, Irene Sánchez-Molina, David Nieto-Castro, José Ramón Galán-Mascarós Molecules, 2021 Here we present the synthesis, structure and magnetic properties of complexes of general formula (Mn)(Me2NH2)4][Mn3(μ-L)6(H2O)6] and (Me2NH2)6[M3(μ-L)6(H2O)6] (M = CoII, NiII and CuII); L−2 = 4-(1,2,4-triazol-4-yl) ethanedisulfonate). The trinuclear polyanions were isolated as dimethylammonium salts, and their crystal structures determined by single crystal and powder X-ray diffraction data. The polyanionic part of these salts have the same molecular structure, which consists of a linear array of metal(II) ions linked by triple N1-N2-triazole bridges. In turn, the composition and crystal packing of the MnII salt differs from the rest of the complexes (with six dimethyl ammonia as countercations) in containing one Mn+2 and four dimethyl ammonia as countercations. Magnetic data indicate dominant intramolecular antiferromagnetic interactions stabilizing a paramagnetic ground state. Susceptibility data have been successfully modeled with a simple isotropic Hamiltonian for a centrosymmetric linear trimer, H = −2J (S1S2 + S2S3) with super-exchange parameters J = −0.4 K for MnII, −7.5 K for NiII and −45 K for CuII complex. The magnetic properties of these complexes and their easy processing opens unique possibilities for their incorporation as magnetic molecular probes into such hybrid materials as magnetic/conducting multifunctional materials or as dopant for organic conducting polymers.
Mechanochemical Processing of Highly Conducting Organic/Inorganic Composites Exhibiting Spin Crossover–Induced Memory Effect in Their Transport Properties David Nieto‐Castro, Felipe A. Garcés‐Pineda, Andrea Moneo‐Corcuera, Irene Sánchez‐Molina, José Ramón Galán‐Mascarós Advanced Functional Materials, 2021 Abstract Bistable multifunctional materials have great potential in a large variety of devices, from sensors to information units. However, the direct exploitation of spin crossover (SCO) materials in electronic devices is limited due to their very high electrical resistance (insulators). Beyond their intrinsic properties, SCO materials may also work as probes to confer bistability as switchable components in hybrid materials, as controlled by external stimuli acting upon the SCO spin state. Low resistance conductors with memory effect may be obtained from the incorporation of SCO probes into a conducting organic polymer matrix. This strategy appeared to be limited by the strict synthetic conditions, since polymerization reactions are harsh enough to attack the redox‐unstable SCO component. Because of this, just a few successful examples have been reported. Here a versatile processing protocol is introduced to obtain SCO/conducting polymer composites exploiting a post‐synthetic mechanochemical approach that can be applied to any SCO component and any organic polymer. This new protocol allows highly conducting films of polypyrrole, polyaniline, and poly(3,4‐ethylenedioxythiophene) (PEDOT) to be obtained, with bulk conductivities as high as 1 S·cm −1 , and exhibiting a thermal hysteresis in their electrical conductivity above room temperature.
Redefining the Mechanistic Scenario of Carbon−Sulfur Nucleophilic Coupling via High-Valent Cp*CoIV Species Sara López‐Resano, Sara Martínez de Salinas, Felipe A. Garcés‐Pineda, Andrea Moneo‐Corcuera, José Ramón Galán‐Mascarós, Feliu Maseras, Mónica H. Pérez‐Temprano Angewandte Chemie International Edition, 2021 The potential access to Co IV species for promoting transformations that are particularly challenging at Co III still remains underexploited in the context of Cp*Co-catalyzed C-H functionalization reactions. Herein, we disclose a combined experimental and computational strategy for uncovering the intermediacy of Cp*Co IV species in a Cp*Co-mediated C-S bond-reductive elimination. These studies support the intermediacy of high-valent Cp*Co intermediates in C-H functionalization reactions, under oxidative conditions, when involving nucleophilic coupling partners.
Solvent Effect on the Spin State of an Iron(II)-Triazole Trimer Irene Sánchez‐Molina, Andrea Moneo‐Corcuera, David Nieto‐Castro, Jordi Benet‐Buchholz, José Ramón Galán‐Mascarós European Journal of Inorganic Chemistry, 2021 We report a triazole‐based trinuclear iron(II) compound with bridging 4‐(p‐methylphenyl)‐1,2,4‐triazole ligands with solvatochromic spin crossover (SC) behavior. The magnetic properties of this trimer depend on crystallization solvent molecules. Pink crystals (color suggesting low spin state), showing a triclinic structure can be obtained by slow diffusion of diethyl ether in acetonitrile solution. As in other SC materials, immersion of these crystals in different solvents promote color change. In this case, we have been able to define the microscopic effect of the solvent substitution following the single crystal to single crystal transformation by UV/Vis absorption spectroscopy and X‐ray diffraction. Furthermore, the solvent‐induced switching can be explained by weak intermolecular interactions provoking a variation in the relative orientations of the two aromatic rings in the ligands, which, in turn, determines the ligand field on the central Fe(II), and its SCO behavior. This study brings important details to the origin of solvatochromism in SCO materials, offering alternatives for better control of this switching and, potentially, for their application as colorimetric sensors.
Effect of Mechanochemical Recrystallization on the Thermal Hysteresis of 1D FeII-triazole Spin Crossover Polymers David Nieto-Castro, Felipe A. Garcés-Pineda, Andrea Moneo-Corcuera, Breogán Pato-Doldan, Francesc Gispert-Guirado, Jordi Benet-Buchholz, José Ramón Galán-Mascarós Inorganic Chemistry, 2020 The thermal hysteresis in the cooperative spin crossover (SCO) polymer [Fe(trz)(Htrz)2]n[BF4]n (1) has been tuned by a simple ball milling grinding process. Mechanical treatment affects the size and morphology of the crystallite domains, as confirmed by multiple complementary techniques, including ESEM, DLS, and PXRD data. Upon milling, the regular cubic shape particles recrystallize with slightly different unit cell parameters and preferential orientation. This macroscopic change significantly modifies the thermally induced SCO behavior, studied by temperature-dependent magnetic susceptibility, X-ray diffraction, and DSC analysis. Transition temperatures downshift, closer to room temperature, while hysteresis widens, when particle sizes are actually decreasing. We relate this counterintuitive observation to subtle modifications in the unit cell, offering new alternatives to tune and enhance SCO properties in this class of 1D-cooperative polymers.
Tuning the spin crossover behavior of the polyanion [(H2O)6Fe3(μ-L)6]6-: The case of the cesium salt Andrea Moneo-Corcuera, David Nieto-Castro, Cristina Sáenz de Pipaón, Verónica Gómez, Pilar Maldonado-Illescas, Jose Ramon Galan-Mascaros Dalton Transactions, 2018 Cation exchange transforms the gradual spin transition of the trimer [(H2O)6Fe3(μ-L)6]6– into an abrupt transition with a wide hysteresis above room temperature.
