Elena Bartolomé

Coumarin-based Nd( iii ) single-ion magnets integrating NIR luminescence and field-induced slow magnetic relaxation are reported, with ancillary-ligand variation enabling modulation of their bifunctional magneto-optical response.

Ce/Er carborane-based metal–organic frameworks (MOFs) provide compositionally programmable multifunctional platforms integrating slow magnetic relaxation, magnetocaloric response, and dual visible-NIR luminescence.

We report the synthesis, structural and magnetothermal characterization down to sub-Kelvin temperatures of the polymeric complex {Ho(α-fur)3}n (α-fur = C4H3OCOO−). The α-furoate ligands bridge Ho(III) ions into one-dimensional zigzag chains running along the crystallographic c-axis. Two slightly distinct coordination environments, denoted Ho(A) and Ho(B), arise from positional disorder of one furoate ligand. Ab initio calculations were performed to estimate the zero-field splittings of both Ho at A and B sites. Magnetic susceptibility and heat capacity measurements show that at low temperatures, the compound behaves as an assembly of antiferromagnetically coupled S* = 1/2 Ising-like chains (J*/kB ≈ −0.4 K) of Ho ions with transverse anisotropy. The low-temperature susceptibility further reveals a small concentration of chain defects. Zero-field ac susceptibility measurements evidence slow relaxation of the magnetization assigned to defect-enabled single-chain magnet (SCM) dynamics in the two chain types, with activation energies EA,SCM = 2.9(3) K and EB,SCM = 4(3) K. Below 0.4 K, a crossover to a coherent quantum tunneling of the magnetization regime, assisted by hyperfine interactions, is observed. The relaxation behavior is discussed in comparison with the related compounds {Ln(α-fur)3}n (Ln = Dy, Tb) and {Ho2Ba(α-fur)8}n, highlighting the interplay between Kramers versus non-Kramers ion character, hyperfine interactions, and magnetic exchange topology in governing the low-temperature dynamics.

Multifunctional Gd- and Dy-based CPs built from silane-bridged dicarboxylate ligand: SMM and magnetocaloric properties for different dimensionalities.

Multi-lanthanide metal-organic frameworks (MOFs) provide a versatile platform for designing materials with tailored multifunctional properties. Here, we report the synthesis and full characterization of novel carborane-based MOFs of formula {[(Nd_yYb_1-y)₃ (mCB-L)₄ (NO₃)(DMF)_x] _n •Solv}, including homometallic Nd (y = 1), Yb (y = 0) compounds and the mixed Nd/Yb analogue (y = 0.44). Magneto-thermal and optical properties were investigated using dc and ac Magnetometry, X-ray Absorption Spectroscopy (XAS), X-ray Magnetic Circular Dichroism (XMCD), and Luminescence measurements. The two Kramers ions, Nd³⁺ and Yb³⁺, yield multifunctional MOFs combining slow relaxation of the magnetization (U/k B ~ 19 K), magnetocaloric effects (-ΔSm ~ 1.6 R at 5 T, 1.8 K) and near-infrared (NIR) luminescence. In particular, the mixed Nd/Yb MOF exhibits NIR emission at 998 nm and 1060 nm arising from partial Nd → Yb energy transfer. Our findings illustrate how carborane-based ligands can engineer multi-lanthanide frameworks with tailored properties, highlighting the potential of {Nd/Yb} MOFs as multifunctional materials for quantum technologies, optical communication, and cryogenic cooling.

The controlled deposition of organized molecular materials on technologically relevant substrates is crucial for the development of innovative magneto-optical devices. In this work, we report the growth of lanthanoid-based 2D metal–organic frameworks (MOFs) with formula unit [Ln(MeCOO)(PhCOO)₂] (Ln = Dy, Tb) on Si(100) wafers functionalized by silanization. The thickness, morphology and composition of the grown material was assessed using a combination of ellipsometry, contact angle measurements, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The on-surface grown terbium 2D MOFs exhibit green luminescence, like the bulk. Furthermore, chemisorbed Dy and Tb 2D MOFs retain a significant magnetic moment, as demonstrated by X-ray magnetic circular dichroism (XMCD) measurements conducted at the M_4,5 edge of the two lanthanoids. Our work paves the way for the preparation of magneto-optical devices and organized arrays of single-molecule magnets (SMMs) and qubits on surfaces for high-density information storage and quantum computing applications.

Three novel coordination polymers – [LnLNO₃(o-Phen)] (Ln: Eu(III) (1), Sm(III) (2)) and [Eu₂L₃EtOH(H₂O)₃]·1.5EtOH·H₂O (3) – were synthesized by reacting the respective lanthanide nitrates with the organosilane dicarboxylic acid bis(p-carboxyphenyl)diphenylsilane (H₂L) with or without o-phenanthroline (o-Phen) as coligand. The o-Phen-assisted route yielded isostructural one-dimensional coordination polymers (CP) 1 and 2, incorporating both ligands and the nitrate anion. These ribbon-like chains assemble into hydrogen-bonded 2D networks that further stack into 3D architectures through non-covalent interactions. In contrast the o-Phen-free conditions produced the 3D CP 3, based solely on H₂L, with ethanol and water molecules retained in the lattice. All three architectures are highly dense, with free volumes of only 2.7% (1, 2) and 11.0% (3). Photophysical studies reveal an exceptional quantum yield of 67% for Eu-based complex 1 attributed to complete ligand-to-Eu energy transfer. In contrast, the Sm-based compound 2 achieves a modest 2% quantum yield, while compound 3 reaches 8%. Magnetic measurements confirm typical Van Vleck paramagnetism for Eu³⁺ in 1 and 3, with spin–orbit coupling constants of Λ = 379 and 352 cm⁻¹, respectively. The magnetism of the Sm-based CP 2 is governed by its ground ⁶H_5/2 and first excited ⁶H_7/2 multiplets (Λ = 310 cm⁻¹), and notably displays field-induced slow magnetic relaxation. Remarkably, Eu-based CP 1 affords exfoliation by sonication into nanometric flakes that retain a high quantum yield of 57% upon deposition, opening up exciting opportunities for surface-integrated sensing, photonic, and quantum applications.

Metal–organic frameworks (MOFs) incorporating arrays of molecular spin qubits (quMOFs) offer a promising pathway toward scalable quantum computing. In this work, we introduce a novel quMOF, {[(Gd)3(mCB-L)4(NO3)(DMF)x]n·Solv}, constructed with a carborane linker and Gd(III) ions at three distinct coordination sites. We thoroughly characterize its magneto-thermal properties using dc/ac magnetometry, X-ray absorption spectroscopy, X-ray magnetic circular dichroism, and heat capacity measurements. The quantum computing potential is demonstrated through ab initio calculations and pulsed electron paramagnetic resonance on GdY-diluted analogues, revealing Tm= 0.7 μs and Rabi oscillations persisting up to 50 K. Each of the three isolated Gd(i) sites in GdY-MOFs functions as an 8-level qudit, accessible via X-band transitions. Notably, the triple-site Gd3 quMOF provides an unprecedented qudit with d = (2S + 1)3 = 512 states, capable of encoding up to 9 qubits, marking a significant advance in the scalability of molecular-based quantum computing systems.

One-dimensional (1D) antiferromagnetic chains are fascinating because of their exotic quantum phenomena. However, isolating large-spin S chains remains challenging as even minimal interchain interaction J’ tends to drive unwanted long-range ordering. Here, we report on the synthesis, crystal structure, magnetism, optical, and electronic properties of two isostructural metal-organic frameworks (MOFs), [M₂ (mCB-L)₂(μ₂-H₂O)₂(DMF)₄]ₙ∙solv (M = Co(II) (mCB-Co) or Ni(II) (mCB-Ni)), which feature water-bridged Co (S = 3/2) or Ni (S = 1) spin chains that are effectively separated by bulky carborane linkers (1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane, mCBLH₂). The temperature-dependent susceptibility reveals strong antiferromagnetic interactions with significant intrachain coupling, J_Co/k_B= -4.65 K (mCB-Co) and J_Ni/k_B= -23.36 K (mCB-Ni), yet confirm the absence of long-range order down to 0.3 K due to negligible interchain interactions, as corroborated by specific heat data. This indicates extremely small J’, with J’/J < 4.7 × 10−4 (3.7 × 10−5) for Co (Ni) MOFs, making these new materials nearly ideal 1D antiferromagnets. Additionally, optical band gaps were estimated via the Kubelka-Munk method, yielding an increase from 3.83 eV for mCB-Co to 4.20 eV for mCB-Ni, showcasing tunable electronic properties across the two MOFs.

Didactic models are invaluable resources for teaching Machines and Mechanisms, a crucial subject in the Engineering curriculum. This work investigates the impact of various types of models on learning outcomes across different instructional approaches, from traditional to active and inquiry-based learning methods. We analyzed a range of didactic models used in a second-year Theory of Machines and Mechanism (TMM) course at EUSS School of Engineering in Barcelona over the past decade, including: i) mechanical models built with “Meccano” parts, 3D-printed models, and kits simulating “fairground attractions”, introduced in traditional teaching settings; ii) real machines and student-developed models used in in TMM courses based on the “Study and Research Path” (SRP) approach, and iii) advanced didactic machines, created by fourth-year students. We discuss the educational benefits provided by these models, considering aspects like the theoretical concepts they mobilize, their construction (by teachers or students), design flexibility, materials used, complexity, and realism. Additionally, we examine how these models enrich the Media and Milieu dialectics, promote the development of both technical and transversal skills, and present a range of advantages and challenges in each TMM context. Our findings offer valuable insights into how models enhance the teaching and learning experience in Machines and Mechanisms, guiding instructors in selecting appropriate models and instructional strategies based on course objectives, student characteristics, and contextual constraints.