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A chemical protocol to design robust hybrid [Fe(Htrz)2(trz)](BF4)@SiO2 nanoparticles (NPs) with sizes as small as 28 nm and ultrathin silica shells below 3 nm has been developed. These NPs present a characteristic abrupt spin transition with a subsequent decrease in the width of the thermal hysteresis upon reducing the NP size. [ABSTRACT FROM AUTHOR]

Assembly of different metal-organic frameworks (MOFs) into hybrid MOF-on-MOF heterostructures has been established as a promising approach to develop synergistic performances for a variety of applications. Here, we explore the performance of a MOF-on-MOF heterostructure by epitaxial growth of MIL-88B(Fe) onto UiO-66(Zr)-NH 2 nanoparticles. The face-selective design and appropriate energy band structure alignment of the selected MOF constituents have permitted its application as an active heterogeneous photocatalyst for solar-driven water splitting. The composite achieves apparent quantum yields for photocatalytic overall water splitting at 400 and 450 nm of about 0.9%, values that compare much favorably with previous analogous reports. Understanding of this high activity has been gained by spectroscopic and electrochemical characterization together with scanning transmission and transmission electron microscopy (STEM, TEM) measurements. This study exemplifies the possibility of developing a MOF-on-MOF heterostructure that operates under a Z-scheme mechanism and exhibits outstanding activity toward photocatalytic water splitting under solar light.

Acquiring spatial control of nanoscopic metal clusters is central to their function as efficient multi-electron catalysts. However, dispersing metal clusters on surfaces or in porous hosts is accompanied by an intrinsic heterogeneity that hampers detailed understanding of the chemical structure and its relation to reactivities. Tethering pre-assembled molecular metal clusters into polymeric, crystalline 2D or 3D networks constitutes an unproven approach to realizing ordered arrays of chemically well-defined metal clusters. Herein, we report the facile synthesis of a {Pd 3 } cluster-based organometallic framework from a molecular triangulo-Pd 3 (CNXyl) 6 (Xyl = xylyl; Pd 3 ) cluster under chemically mild conditions. The formally zero-valent Pd 3 cluster readily engages in a complete ligand exchange when exposed to a similar, ditopic isocyanide ligand, resulting in polymerization into a 2D coordination network (Pd 3 -MOF). The structure of Pd 3 -MOF could be unambiguously determined by continuous rotation 3D electron diffraction (3D-ED) experiments to a resolution of ~1.0 Å (>99% completeness), showcasing the applicability of 3D-ED to nanocrystalline, organometallic polymers. Pd 3 -MOF displays Pd 0 3 cluster nodes, which possess significant thermal and aerobic stability, and activity towards hydrogenation catalysis. Importantly, the realization of Pd 3 -MOF paves the way for the exploitation of metal clusters as building blocks for rigidly interlocked metal nanoparticles at the molecular limit., (© 2024. The Author(s).)

Protein encapsulation by in situ formation of MOFs is a valuable strategy to immobilise and protect these bioentities. However the required biocompatible conditions limits the scope of MOFs under investigation, particularly in the case of hydrolytically unstable MOFs such as HKUST-1. We report alternative synthetic procedures to obtain protein@HKUST-1 biocomposites from related Cu-BTC dense biocomposites. pH dependent dense phase precursors are first obtained and their transformations into HKUST-1 are characterized. Encapsulation efficiency is affected by the protein's nature, and can be modulated by the sequential or simultaneous addition of MOF precursors.

In this work, two ZIF-8-based biocomposites were obtained by entrapping the biomolecules benzaldehyde and methyl anthranilate via direct impregnation with fast encapsulation kinetics and high molecule payloads were achieved. The obtained biocomposites exhibit an enhanced antifungal activity against Penicilium expansum after integration in biopolymeric zein films in comparison with the action of free molecules, making these biomaterials promising candidates for food preservation and packaging applications.

A family of robust and stable molybdenum-based metal-organic cages have been obtained based on the [Mo 2 O 2 (μ 2 -O) 2 ] 2+ secondary building unit. The resulting cages are decorated with different pyrdine derivatives that impart structural stability, resulting in the structural elucidation of the activated cage with single-crystal diffraction. The chemical robustness of the cage is also demonstrated by the post-synthetic modification of the cage, which allows the exchange of the pyridine derivatives without rupture of the cage.

Although Metal-organic frameworks (MOFs) have received attention as drug delivery systems, their application in the delivery of macromolecules is limited by their pore size and opening. Herein, we present the synthesis of nanostructured MUV-2, a hierarchical mesoporous iron-based MOF that can store high payloads of the macromolecular drug paclitaxel ( ca. 23% w/w), increasing its selectivity towards HeLa cancer cells over HEK non-cancerous cells. Moreover, this NanoMUV-2 permits full degradation under simulated physiological conditions while maintaining biocompatibility, and is amenable to specific surface modifications that increase its cell permeation, efficient cytosol delivery and cancer-targeting effect, further intensifying the cancer selectivity of paclitaxel.

Two ultramicroporous 2D and 3D iron-based Metal-Organic Frameworks (MOFs) have been obtained by solvothermal synthesis using different ratios and concentrations of precursors. Their reduced pore space decorated with pendant pyridine from tangling isonicotinic ligands enables the combination of size-exclusion kinetic gas separation, due to their small pores, with thermodynamic separation, resulting from the interaction of the linker with CO 2 molecules. This combined separation results in efficient materials for dynamic breakthrough gas separation with virtually infinite CO 2 /N 2 selectivity in a wide operando range and with complete renewability at room temperature and ambient pressure., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Encapsulation of biomolecules using metal-organic frameworks (MOFs) to form stable biocomposites has been demonstrated to be a valuable strategy for their preservation and controlled release, which has been however restricted to specific electrostatic surface conditions. We present a Lewis-acid-mediated general in situ strategy that promotes the spontaneous MOF growth on a broad variety of proteins, for the first time, regardless of their surface nature. We demonstrate that MOFs based on cations exhibiting considerable inherent acidity such as MIL-100(Fe) enable efficient biomolecule encapsulation, including elusive alkaline proteins previously inaccessible by the well-developed in situ azolate-based MOF encapsulation. Specifically, we prove the MIL-100(Fe) scaffold for the encapsulation of a group of proteins exhibiting very different isoelectric points (5 < pI < 11), allowing triggered release under biocompatible conditions and retaining their activity after exposure to denaturing environments. Finally, we demonstrate the potential of the myoglobin-carrying biocomposite to facilitate the delivery of O 2 into hypoxic human lung carcinoma A549 cells, overcoming hypoxia-associated chemoresistance., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The design of efficient food contact materials that maintain optimal levels of food safety is of paramount relevance to reduce the increasing number of foodborne illnesses. In this work, we develop a smart composite metal-organic framework (MOF)-based material that fosters a unique prolonged antibacterial activity. The composite is obtained by entrapping a natural food preserving molecule, carvacrol, into a mesoporous MIL-100(Fe) material following a direct and biocompatible impregnation method, and obtaining particularly high payloads. By exploiting the intrinsic redox nature of the MIL-100(Fe) material, it is possible to achieve a prolonged activity against Escherichia coli and Listeria innocua due to a triggered two-step carvacrol release from films containing the carvacrol@MOF composite. Essentially, it was discovered that based on the underlying chemical interaction between MIL-100(Fe) and carvacrol, it is possible to undergo a reversible charge-transfer process between the metallic MOF counterpart and carvacrol upon certain chemical stimuli. During this process, the preferred carvacrol binding site was monitored by infrared, Mössbauer, and electron paramagnetic resonance spectroscopies, and the results are supported by theoretical calculations.

In the past few years, the effect of strain on the optical and electronic properties of MoS 2 layers has attracted particular attention as it can improve the performance of optoelectronic and spintronic devices. Although several approaches have been explored, strain is typically externally applied on the two-dimensional material. In this work, we describe the preparation of a reversible 'self-strainable' system in which the strain is generated at the molecular level by one component of a MoS 2 -based composite material. Spin-crossover nanoparticles were covalently grafted onto functionalized layers of semiconducting MoS 2 to form a hybrid heterostructure. Their ability to switch between two spin states on applying an external stimulus (light irradiation or temperature change) serves to generate strain over the MoS 2 layer. A volume change accompanies this spin crossover, and the created strain induces a substantial and reversible change of the electrical and optical properties of the heterostructure., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

With the aim of identifying new cation-phenolate complexes, we herein investigated the reactivity of pyrogallol (H 3 pgal) with vanadium salts. A trimetallic anionic complex was identified, and found to be formed under a broad set of reaction conditions. This complex, with the formula V 3 O 3 (pgal) 3 3- , consists of three oxovanadium(IV) units connected together by three pyrogallate ligands to afford a bowl-shaped species presenting a pseudo 3-fold symmetry axis. Its crystal structure is reported, as well as its characterisation by a broad set of techniques, including powder X-ray diffraction, thermogravimetric analysis, infrared and Raman spectroscopy, and solid state UV-visible diffuse reflectance. Its redox activity both in solution and in the solid state is described, together with its magnetic behavior. Finally, the relevance of this trimetallic unit in the field of phenolic-based biocoatings and Metal Organic Framework (MOF) synthesis is briefly discussed.

We present the covalent coating of chemically exfoliated molybdenum disulfide (MoS 2 ) based on the polymerization of functional acryl molecules. The method relies on the efficient diazonium anchoring reaction to provoke the in situ radical polymerization and covalent adhesion of functional coatings. In particular, we successfully implement hydrophobicity on the exfoliated MoS 2 in a direct, fast, and quantitative synthetic approach. The covalent functionalization is proved by multiple techniques including X-ray photoelectron spectroscopy and TGA-MS. This approach represents a simple and general protocol to reach dense and homogeneous functional coatings on 2D materials.

Herein we report the design of core@shell nanoparticles formed by a metallic Au nanostar core and a spin-crossover shell based on the coordination polymer [Fe(Htrz) 2 (trz)](BF 4 ). This procedure is general and has been extended to other metallic morphologies (nanorods, nanotriangles). Thanks to the photothermal effect arising from the plasmonic properties of the Au nanostar, 60% of iron centers undergo a thermal spin transition inside the thermal hysteresis triggered by a 808 nm laser low intensity irradiation. Compared to other Au morphologies, the great advantage of the nanostar shape arises from the hot spots created at the branches of the nanostar. These hot spots give rise to large NIR absorptions, making them ideal nanostructures for efficiently converting light into heat using low energy light, like that provided by a 808 nm laser., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Carbon capture and storage with porous materials is one of the most promising technologies to minimize CO 2 release into the atmosphere. Here, we report a family of compartmentalized coordination polymers (CCPs) capable of capturing gas molecules in a selective manner based on two novel tetrazole-based ligands. Crystal structures have been modelled theoretically under the Density Functional Theory (DFT) revealing the presence of discrete voids of 380 Å 3 . Single gas adsorption isotherms of N 2 , CH 4 and CO 2 have been measured, obtaining a loading capacity of 0.6, 1.7 and 2.2 molecules/void at 10 bar and at 298 K for the best performing material. Moreover, they present excellent selectivity and regenerability for CO 2 in mixtures with CH 4 and N 2 in comparison with other reported materials, as evidenced by dynamic breakthrough gas experiments. These frameworks are therefore great candidates for separation of gas mixtures in the chemical engineering industry., (© 2020 Wiley-VCH GmbH.)

Metal-organic framework (MOF)-driven synthesis is considered as a promising alternative for the development of new catalytic materials with well-designed active sites. This synthetic approach is used here to gradually transform a new bimetallic MOF, with Pd and Fe as the metal components, by the in situ generation of aniline under mild conditions. This methodology results in a compositionally homogeneous nanocomposite formed by Fe-doped Pd nanoparticles that, in turn, are supported on iron oxide-doped carbon. The nanocomposite has been fully characterized by several techniques such as IR and Raman spectroscopy, TEM, XPS, and XAS. The performance of this nanocomposite as an heterogeneous catalyst for hydrogenation of nitroarenes and nitrobenzene coupling with benzaldehyde has been evaluated, proving it to be an efficient and reusable catalyst., (© 2020 Wiley-VCH GmbH.)

A simple chemical protocol to prepare core-shell gold@spin-crossover (Au@SCO) nanoparticles (NPs) based on the 1D spin-crossover [Fe(Htrz) 2 (trz)](BF 4 ) coordination polymer is reported. The synthesis relies on a two-step approach consisting of a partial surface ligand substitution of the citrate-stabilized Au NPs followed by the controlled growth of a very thin layer of the SCO polymer. As a result, colloidally stable core@shell spherical NPs with a Au core of ca. 12 nm and a thin SCO shell 4 nm thick, are obtained, exhibiting a narrow distribution in sizes. Differential scanning calorimetry proves that a cooperative spin transition in the range 340-360 K is maintained in these Au@SCO NPs, in full agreement with the values reported for pristine 4 nm SCO NPs. Temperature-dependent charge-transport measurements of an electrical device based on assemblies of these Au@SCO NPs also support this spin transition. Thus, a large change in conductance upon spin state switching, as compared with other memory devices based on the pristine SCO NPs, is detected. This results in a large improvement in the sensitivity of the device to the spin transition, with values for the ON/OFF ratio which are an order of magnitude better than the best ones obtained in previous SCO devices., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Rapid intracellular degradation of current drug-delivery nanocarriers presents a challenge for achieving ideal controlled drug-release kinetics. Recent in vivo studies have shown that porous hybrid metal-organic frameworks (MOFs), belonging to the Materials of Institute Lavoisier (MIL) family, display prolonged biodegradation behavior. In this study, we investigated stability of these materials in Kupffer cells, a relevant target for the treatment of several life-threatening immune-mediated liver diseases. For this aim, we selected fluorescently labeled microporous MOF particles of MIL88A and MIL88B-NH 2 , built from trimers of Fe(III) octahedra, as an inorganic component, and fumarate (MIL88A) or 2-amino terephthalate (MIL88B-NH 2 ), as an organic linker. Cell uptake inhibition analysis of MOF particles by a Kupffer cell line (KUP5) has shown that phagocytosis is the major endocytic pathway involved in MIL88B-NH 2 internalization. Investigation of MOF interaction with KUP5 cells by real-time microscopy indicated that the structure of MIL88B-NH 2 MOFs stays intact up to 15 min after uptake, followed by MOF accumulation in acidic cell compartments and slow degradation, reaching a minimum of 10-15% decomposition over 24 h. MIL88A particles demonstrated similar degradation kinetics. Analysis of the mechanisms of MOF degradation has shown that inhibition of phagosome acidification as well as protease activity does not prevent decomposition of MIL88B-NH 2 particles. Thus, our study demonstrates the relative stability of the MOF structure in the phagolysosomal environment of Kupffer cells, revealing potential use of these materials for controlled drug delivery in a case of immune-mediated liver diseases.

Herein we report the synthesis of an elusive metal-organic framework, the iron(II) analogue of ZIF-8 with the formula Fe(2-methylimidazolate) 2 , here denoted as MUV-3. The preparation of this highly interesting porous material, inaccessible by common synthetic procedures, occurs in a solvent-free reaction upon addition of an easily detachable template molecule, yielding single crystals of MUV-3. This methodology can be extended to other metals and imidazolate derivatives, allowing the preparation of ZIF-8, ZIF-67, and the unprecedented iron(II) ZIFs Fe(2-ethylimidazolate) 2 and Fe(2-methylbenzimidazolate) 2 . The different performance of MUV-3 toward NO sorption, in comparison to ZIF-8, results from the chemisorption of NO molecules, which also causes a gate-opening behavior. Finally, the controlled pyrolysis of MUV-3 results in a N-doped graphitic nanocomposite that exhibits extraordinary performance for the oxygen evolution reaction (OER), with low overpotential at different current densities (316 mV at 10 mA cm -2 ), low Tafel slope (37 mV per decade), high maximum current density (710 mA cm -2 at 2.0 V vs RHE), and great durability (15 h).

We use the electrodeless time-resolved microwave conductivity (TRMC) technique to characterize spin-crossover (SCO) nanoparticles. We show that TRMC is a simple and accurate means for simultaneously assessing the magnetic state of SCO compounds and charge transport information on the nanometer length scale. In the low-spin state from liquid nitrogen temperature up to 360 K the TRMC measurements present two well-defined regimes in the mobility and in the half-life times, in which the former transition temperature T R occurs near 225 K. Below T R , we propose that an activationless regime taking place associated with short lifetimes of the charge carriers points at the presence of shallow-trap states. Above T R , these states are thermally released, yielding a thermally activated hopping regime where longer hops increase the mobility and, concomitantly, the barrier energy. The activation energy could originate not only from intricate contributions such as polaronic self-localizations but also from dynamic disorder due to phonons and/or thermal fluctuations of SCO moieties.

Controlling the outer surface of nanometric metal-organic frameworks (nanoMOFs) and further understanding the in vivo effect of the coated material are crucial for the convenient biomedical applications of MOFs. However, in most studies, the surface modification protocol is often associated with significant toxicity and/or lack of selectivity. As an alternative, how the highly selective and general grafting GraftFast method leads, through a green and simple process, to the successful attachment of multifunctional biopolymers (polyethylene glycol (PEG) and hyaluronic acid) on the external surface of nanoMOFs is reported. In particular, effectively PEGylated iron trimesate MIL-100(Fe) nanoparticles (NPs) exhibit suitable grafting stability and superior chemical and colloidal stability in different biofluids, while conserving full porosity and allowing the adsorption of bioactive molecules (cosmetic and antitumor agents). Furthermore, the nature of the MOF-PEG interaction is deeply investigated using high-resolution soft X-ray spectroscopy. Finally, a cell penetration study using the radio-labeled antitumor agent gemcitabine monophosphate ( 3 H-GMP)-loaded MIL-100(Fe)@PEG NPs shows reduced macrophage phagocytosis, confirming a significant in vitro PEG furtiveness., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Despite high morbidity and mortality associated with lung diseases, addressing drugs towards lung tissue remains a pending task. Particle lung filtration has been proposed for passive lung targeting and drug delivery. However, toxicity issues derived from the long-term presence of the particles must be overcome. By exploiting some of the ignored properties of nanosized metal-organic frameworks it is possible to achieve impressive antitumoral effects on experimental lung tumors, even without the need to engineer the surface of the material. In fact, it was discovered that, based on unique pH-responsiveness and reversible aggregation behaviors, nanoMOF was capable of targeting lung tissue. At the neutral pH of the blood, the nanoMOFs form aggregates with the adequate size to be retained in lung capillaries. Within 24 h they then disaggregate and release their drug payload. This phenomenon was compatible with lung tissue physiology., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The use of a 5,10,15,20-tetrakis(3,4,5-trihydroxyphenyl)porphyrin has yielded a new MOF based on M-1,2,3-trioxobenzene chains that can be made of M = Zr(iv) or RE(iii) (RE = rare earth), showing a very high and limited chemical stability, respectively. The robust metallated Zr-analogue, Co-MIL-173(Zr), has proven to be a heme-like heterogeneous catalyst suitable for aerobic oxidation of hydrocarbons.

Discrimination between different gases is an essential aspect for industrial and environmental applications involving sensing and separation. Several classes of porous materials have been used in this context, including zeolites and more recently MOFs. However, to reach high selectivities for the separation of gas mixtures is a challenging task that often requires the understanding of the specific interactions established between the porous framework and the gases. Here we propose an approach to obtain an enhanced selectivity based on the use of compartmentalized coordination polymers, named CCP-1 and CCP-2 , which are crystalline materials comprising isolated discrete cavities. These compartmentalized materials are excellent candidates for the selective separation of CO 2 from methane and nitrogen. A complete understanding of the sorption process is accomplished with the use of complementary experimental techniques including X-ray diffraction, adsorption studies, inelastic- and quasi-elastic neutron scattering, magnetic measurements and molecular dynamics calculations.

The charge transport properties of SCO [Fe(Htrz)2 (trz)](BF4 ) NPs covered with a silica shell placed in between single-layer graphene electrodes are reported. A reproducible thermal hysteresis loop in the conductance above room-temperature is evidenced. This bistability combined with the versatility of graphene represents a promising scenario for a variety of technological applications but also for future sophisticated fundamental studies., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new magnetic coordination polymer, [Fe(bipy)(im)2] (bipy = 4,4-bipyridine and im = imidazole), has been synthesized in a solvent-free reaction. Structural analysis reveals a pillared 3D coordination polymer composed by neutral layers, formed by iron(II) and imidazolate linkers, interconnected by bipy ligands which serve as pillars. Magnetic measurements show that the material magnetically orders at low temperatures (Tc = 14.5 K) as a weak ferromagnet, likely due to a spin canting.

A systematic study of the key synthetic parameters that control the growth of spin-crossover (SCO) nanoparticles (NPs) using the reverse micelle technique has been undertaken in the system [Fe(Htrz) 2 (trz)](BF 4 )·H 2 O, (Htrz = 1,2,4-triazole). This has permitted us to modulate the physical properties of the NPs in a controlled and reproducible manner. In particular, a control over the size of the NPs (in the range 4 to 16 nm) has been achieved by varying the water to surfactant molar ratio. The consequences of this size variation on the cooperativity of the spin transition are discussed. Finally, this approach has been extended to the chemical alloy [Fe(Htrz) 2.95 (NH 2 trz) 0.05 ](ClO 4 ) 2 in order to prepare NPs exhibiting a cooperative and hysteretic spin transition centred closer to room temperature.

Two-dimensional assemblies of triazole-based spin-crossover nanoparticles (SCO NPs) presenting different morphologies are prepared and electrically characterized. The thermal hysteresis loop in the electrical conductance near room temperature correlates with the NP morphologies and their 2D organization. The unprecedentedly large difference - up to two orders of magnitude - in the electrical conductance of the two spin states is of interest for applications., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The formation of a metal-organic framework (MOF) with nodes that have single-molecule magnet (SMM) behaviour has been achieved by using mononuclear lanthanoid analogues, also known as single-ion magnets (SIMs), which enormously simplifies the challenging issue of making SMM-MOFs. Here we present a rational design of a family of MOFs, [Ln(bipyNO)4](TfO)3⋅x solvent (Ln=Tb (1); Dy (2); Ho (3); Er (4); TfO=triflate), in which the lanthanoid centres have an square-antiprismatic coordination environment suitable for SIM behaviour. Magnetic measurements confirm the existence of slow magnetic relaxation typical of SMMs, which has been rationalised by means of a radial effective charge model. In addition, we have explored the incorporation of bulky polyoxometalates (POMs) into the cavities of the SIM-MOF by anion exchange, finding that they do not interfere with the slow magnetic relaxation. This demonstrates the robustness of the frameworks and opens the possibility of incorporating non-innocent anions., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, we present a family of Fe(II) coordination polymers of general formula [Fe(btzx)(3-3x)(btix)(3x)](ClO4)2 with interesting spin-crossover properties. These coordination polymers have been synthesized using chemical mixtures of two different but closely related ligands, 1,4-bis(tetrazol-1-ylmethyl)benzene (btzx) and 1,4-bis(triazol-1-ylmethyl)benzene (btix), and the effect of a gradual substitution of the ligand in the spin transition temperature has been investigated. Several chemical mixtures have been structurally characterized by X-ray powder diffraction indicating a clear critical amount in the composition of the mixture after which mixed phases rather than a single phase comprising mixed components are observed. Importantly, this approach causes the appearance of a new transition at lower temperatures that is not present in the pure [Fe(L)3](ClO4)2 systems.

We present a spin-crossover Fe(II) coordination polymer with no permanent channels that selectively sorbs CO2 over N2. The one-dimensional chains display internal voids of ∼9 Å diameter, each being capable to accept one molecule of CO2 at 1 bar and 273 K. X-ray diffraction provides direct structural evidence of the location of the gas molecules and reveals the formation of O═C═O(δ(-))···π interactions. This physisorption modifies the spin transition, producing a 9 K increase in T1/2.

The restacking of charged TaS2 nanosheets with molecular counterparts has so far allowed for the combination of superconductivity with a manifold of other molecule-intrinsic properties. Yet, a hybrid compound that blends superconductivity with spin crossover switching has still not been reported. Here we continue to exploit the solid-state/molecule-based hybrid approach for the synthesis of a layered TaS2-based material that hosts Fe(2+) complexes with a spin switching behavior. The chemical design and synthetic aspects of the exfoliation/restacking approach are discussed, highlighting how the material can be conveniently obtained in the form of highly oriented easy-to-handle flakes. Finally, proof of the presence of both phenomena is provided by the use of a variety of physical characterization techniques. The likely sensitivity of the intercalated Fe(2+) complexes to external stimuli such as light opens the door for the study of synergistic effects between the superconductivity and the spin crossover switching at low temperatures.

A three-dimensional coordination polymer, [Cu(btix)(2)(BF(4))(2)](n) [btix = 1,4-bis(triazol-1-ylmethyl)benzene], with antiferromagnetic interactions occurring via the organic ligand, has been prepared and characterized. It has been shown to permit the exchange of anionic species in the crystalline network with modification of the magnetic properties. Coordinated BF(4)(-) can be reversibly exchanged by different anions with (NO(3)(-) and Cl(-)) or without (PF(6)(-) and ClO(4)(-)) dynamic response of the organic ligand, which acts as the only linker between the metal centers. Interestingly, an irreversible exchange occurs with N(3)(-) anions to generate a new coordination polymer, [Cu(btix)(N(3))(2)](n), whose structure has been determined ab initio by powder X-ray diffraction, revealing a totally different connectivity between the Cu(II) centers. These structural transformations are accompanied by a change of the magnetic properties, which have been detected by electron paramagnetic resonance and magnetic susceptibility measurements.

New manganese compounds [Mn(HphpzMe)(2)(H(2)phpzMe)(HCO(2))] (1), [Mn(2)(phpzMe)(2)(HphpzMe)(2)(OCH(3))]·2CH(3)OH (2), Na{[Mn(HphpzPh)(phpzPh)(MeOH)(2)](2)}(HCO(2)) (3), [Mn(HphpzPh)(2)(EtOH)(2)]ClO(4)·2EtOH (4) and [Mn(HphpzPh)(2)N(3)] (5) were synthesized and characterized with various techniques. 1, 4 and 5 are mononuclear manganese(III) compounds, 2 is a mixed-valence dinuclear manganese(III/IV) compound, and 3 is a trinuclear compound containing two manganese(III) ions and a sodium(I) ion. A remarkable feature is the spontaneous formation of the formate ion as a result of the methanol or methoxide oxidation in compounds 1 and 3. Using ethanol precludes the formation of the formate and compound 4 is obtained. The molecular structure of all compounds is stabilized by supramolecular interactions, including strong hydrogen bonding and π-π interactions.

Responsive materials for which physical or chemical properties can be tuned by applying an external stimulus are attracting considerable interest in view of their potential applications as chemical switches or molecular sensors. A potential source of such materials is metal-organic frameworks. These porous coordination polymers permit the physisorption of guest molecules that can provoke subtle changes in their porous structure, thus affecting their physical properties. Here we show that the chemisorption of gaseous HCl molecules by a non-porous one-dimensional coordination polymer instigates drastic modifications in the magnetic properties of the material. These changes result from profound structural changes, involving cleavage and formation of covalent bonds, but with no disruption of crystallinity.

Two families of coordination polymers, {[M(btix)(2)(OH(2))(2)]·2NO(3)·2H(2)O}(n) [M = Co (1), Zn (2), Co-Zn (3); btix = 1,4-bis(triazol-1-ylmethyl)benzene] and {[M(btix)(2)(NO(3))(2)]}(n) [M = Co (4), Zn (5), Co-Zn (6)], have been synthesized and characterized. The two conformations of the ligand, syn and anti, lead to one-dimensional (1D) cationic chains or two-dimensional (2D) neutral grids. Extrusion of the water molecules of the 1D compounds results in an irreversible transformation into the 2D compounds, which involves a change in conformation of the btix ligands and a rearrangement in the metal environment with cleavage and reformation of covalent bonds. This structural transformation has been followed by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements to monitor the minor modifications that the metal centers suffer.