Claire Roiland

Cold-region ecosystems are highly sensitive to climate change, yet the geochemical processes shaping their future remain poorly understood. Here, we show that ice systematically enhances mineral dissolution through freeze concentration into microscale reactive hot spots. Using goethite nanoparticles as a model iron oxide and environmentally relevant inorganic anions common in soils, waters, and aerosols (chloride, fluoride, sulfate), we demonstrate that ligand-promoted dissolution rates under mildly acidic conditions scale with binding affinity in both ice and liquid water, with ice enhancing rates across all reactive ligands. Fluoride, the strongest complexing agent, increased dissolution more than fourfold in ice, while weakly binding perchlorate produced no measurable dissolution in either phase. Reactions persisted well below the eutectic temperature, mediated by minute volumes of liquid-like water stabilized within networks of micron-sized mineral aggregates. Our findings highlight ice as a dynamic medium driving iron release, with implications for nutrient availability, carbon cycling, and biogeochemical feedbacks in rapidly warming polar and alpine regions.

Reactions in water at ambient temperature and pressure between a lanthanide ion and benzene-1,3,5-tricarboxylate (or trimesate) lead to two series of iso-structural coordination polymers. Their general chemical formula is [Ln(tma)(H₂O)₆]_∞ for the lightest lanthanide ions (Ln = La-Dy except Pm), while it is [Ln(tma)(H₂O)₅·3.5H₂O]_∞ for the heaviest ones (Ho-Lu plus Y). For the heaviest lanthanide ions, reactions at 50 °C lead to a third structural family with the general chemical formula [Ln(tma)(H₂O)₃·1.5H₂O]_∞ with Ln = Ho-Lu plus Y. Homo-lanthanide coordination polymers that belong to the latter two families do not exhibit luminescence in the visible region. Therefore, we used a phase induction strategy to obtain molecular alloys that belong to these structural families and show sizeable emission. The random distribution of the lanthanide ions over the metallic sites has been investigated using ⁸⁹Y and ¹³⁹La solid-state NMR spectroscopy experiments. Luminescent properties of homo- and hetero-nuclear coordination polymers based on Eu³⁺ and Tb³⁺ have been studied in detail and compared. As a result, this study strongly suggests that exchange-based intermetallic energy transfer mechanisms play an important role in these systems. It also suggests the presence of an intermetallic exchange pathway through π-stacking interactions.

The Raman modes of α-quartz-type boron phosphate were found to be extremely stable in frequency over a large temperature range from 300–1000 K. In order to determine the origin of this behavior, the material was also studied at high pressure up to 6 GPa. Upon compression, a classical behavior was observed with mode Grüneisen parameters ranging from −0.08(2) to 3.0(1). The present results indicate that the high temperature behavior in this material is an example of an unusual compensation effect between phonon–phonon interactions and implicit contributions due to thermal expansion. Phonon stability is of utmost importance for materials properties that are dependent on it such as dielectric and piezoelectric properties, for example. Boron phosphate belongs to the important class of α-quartz-type piezoelectric materials for which temperature stability is of primordial importance for resonator and sensor applications.

Dynamics of confined molecules within porous materials is equally important as local structural order, and it is necessary to quantify it and to reveal the microscopic mechanisms ruling it for better control of adsorption applications. In this study, molecular dynamics simulations were carried out to investigate the translational and the rotational dynamics of methanol trapped into the flexible NH₂-MIL-53(Al) metal–organics framework (MOF). Indeed, atomistic simulation is nowadays a relevant tool to explore matter at the nanoscale. Very recently it has been shown that the NH₂-MIL-53(Al) MOF material was capable to undergo a reversible structural transition (breathing phenomenon) by combining adsorption and thermal stimuli. This flexibility can drastically affect the dynamics of confined molecules and therefore the successful conduct of adsorption applications such as gas storage and separation. Rotational and translational dynamics of confined methanol through nanoporous flexible NH₂-MIL-53(Al) MOF were then deeply investigated by exploring a broad range of dynamical properties to extract the molecular mechanisms ruling them. This study allowed us to shed light on the interplay of dynamics of confined fluids and flexibility of porous material and to highlight the physical insights in diffusion mechanisms of confined molecules. Anomalous translational diffusion was evidenced due to a dynamical heterogeneity caused by a combination of a localized dynamics at the subnanometric scale and translational jumps between nanodomains in a zigzag scheme between the hydroxide group of the NH₂-MIL-53(Al). Actually, the non-Fickian dynamics of methanol is the result of the specific host–guest interactions and the MOF flexibility involving the pore opening. Eventually, decoupling between both rotational and translational dynamics related to breaking in the Stokes–Einstein relation was highlighted.

Isostructural lanthanide-based coordination polymers that are obtained by reactions in water of a lanthanide chloride and the sodium salt of 5-methoxyisophthalate (mip^2–) have the general chemical formula [Ln₂(mip)₃(H₂O)₈·4H₂O]_∞ with Ln = Nd–Er except Pm plus Y (symbolized by [Ln₂(mip)₃]_∞). Some of these homo-lanthanide compounds present very high luminescence brightness. The weak intermetallic energy transfer between lanthanide ions observed in these compounds allows the design of hetero-lanthanide coordination polymers with tunable luminescence properties. A molecular alloy that involved six different lanthanide ions (Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺) has been prepared and its luminescent properties have been studied. This compound, under a unique irradiation wavelength (λ_exc = 325 nm), exhibits almost 20 emission peaks in both the visible and the NIR regions at room temperature. This unprecedented richness of the emission spectrum could be of great interest as far as luminescent bar-codes are targeted.

Two new supramolecular fluorescent hybrid materials, combining for the first time [M₆O₁₉]²⁻ (M=Mo, W) polyoxometalates (POMs) and aggregation‐induced emission (AIE)‐active 1‐methyl‐1,2,3,4,5‐pentaphenyl‐phospholium (1⁺), were successfully synthesized. This novel molecular self‐assembling strategy allows designing efficient solid‐state emitters, such as (1)₂[W₆O₁₉], by directing favorably the balance between the AIE and aggregation‐caused quenching (ACQ) effects using both anion‐π⁺ and H‐bonding interactions in the solid state. Combined single‐crystal X‐ray diffraction, Raman, UV‐vis and photoluminescence analyses highlighted that the nucleophilic oxygen‐enriched POM surfaces strengthened the rigidity of the phospholium via strong C−H⋅⋅⋅O contacts, thereby exalting its solid‐state luminescence. Besides, the bulky POM anions prevented π–π stacking interactions between the luminophores, blocking detrimental self‐quenching effects.

Crown ethers and their derivatives are versatile building blocks for the design of supramolecular materials. They can be functionalized at will and are well known for their abilities to complex with alkali cations. Here, we show that emissive lanthanide free hybrid materials can be generated by using such building blocks. The organic tribenzo[18]crown-6 central core was functionalized via six-fold Suzuki cross-coupling as a key reaction with three o-terphenyl units which could be converted into their corresponding triphenylenes by the Scholl reaction, leading to novel liquid-crystalline columnar materials. Selected tribenzo[18]crown-6 o-terphenyls could interact with emissive ternary metal cluster compound salts to generate hybrid materials combining the properties of both moieties. Due to synergistic effects and despite the anisometry of the cluster compounds, individual properties such as liquid-crystalline phase stability of the organic part and emission abilities of its inorganic counter-part are enhanced in the hybrid compounds.

Replacing pure inorganic materials by functional organic–inorganic hybrid ones to lower production costs has become a major challenge, in particular for the optoelectronic industry. Adding nanostructuration abilities meanwhile preserving homogeneity is even more challenging for this class of new materials. Here we show that red‐NIR emissive ternary molybdenum cluster salts can be assembled to liquid crystalline 15C5 crown ethers. The resulting hybrids are homogeneous and stable up to high temperature despite the weakness of the supramolecular interactions binding both components. These are illustrated by ¹³³Cs MAS NMR. All hybrids show hexagonal columnar arrangements and strong red‐NIR emission. Surprisingly, when chlorinated clusters are used instead of brominated ones, the mesophase stability is largely enhanced.