Valentin V. Novikov

Pure heterometallic [LuCeLu]/[LuLaLu] molecular alloys isolate a Ce ³⁺ qubit from ancillary lanthanide interactions enabling direct solid-state coherence measurements and chemically tunable T _m and T ₁ .

Integration of molecular spin qubits onto superconducting circuits is one of the current proposals to build a hybrid quantum processor, in which their coupling to resonators would allow complex coherent quantum operations. As an alternative to large magnetically dilute crystals or concentrated nanoscale deposits of paramagnetic molecules studied so far, we consider here preformed nanoparticles of a Zr(IV)-based 3D MOF doped with Cu(II) and V(IV)O metalloporphyrin. Highly crystalline, phase-pure nanoparticles are obtained with an adjustable number of spin carriers and a homogeneous size that is adequate for nanoconstrictions in superconducting resonators. Continuous-wave and time-domain EPR spectroscopy show that the Cu(II) and V(IV) spins in these particles are potential qubits and qudits, respectively, with robust quantum coherence. These nanoparticles form good dispersions in methanol-chloroform mixtures, which allows the formation of monolayers of densely packed particles at the air–water interface. These Langmuir films are successfully transferred to very different substrates, including Nb resonators, homogeneously covering their most sensitive areas, i.e., the edges of the superconducting lines. Finally, the quantum coherence of the qubit nodes is maintained in the transferred nanoparticles, thereby demonstrating the viability of the present approach for the development of hybrid quantum processors.

The implementation of lanthanide-based molecular systems in quantum technologies (QTs) requires an accurate and well-designed environment of the spin-bearing lanthanide ion. Lanthanides have become appealing candidates for QTs given their ability to display both slow magnetic relaxation and quantum coherence, in tandem with other properties, which can be achieved through a rational design of the ligand field. This work covers the characterization of a YbIII compound based on phosphine oxide ligand bis(diphenylphosphino)methane oxide (dppmO2). The compound with a structural formula of [Yb(dppmO2)(NO3)3(H2O)]·CH2Cl2 (1) was structurally characterized through X-ray diffraction techniques. Field-induced slow magnetic relaxation was detected through AC SQUID magnetometry. The spin Hamiltonian parameters were evaluated through both continuous wave (CW) and echo-detected field swept (EDFS) electron paramagnetic resonance (EPR). The field and temperature dependence of the phase memory time (Tm) and spin–lattice relaxation (T1) were determined through Hahn echo decays and inversion recovery pulse sequences, respectively. Strong modulations in the Hahn echo decays were rationalized through coupling to 14N nuclei present in the nitrato donors, while Rabi oscillations show the ability of the system to behave as an effective qubit. Theoretical calculations employed at the DFT and CASSCF/NEVPT2 level were performed to elucidate the electronic structure and magnetic properties of 1.

Guest symmetry and directional hydrogen bonding enable SiF ₆ ²⁻ to program the selective self-assembly of distinct Ni( ii ) helicate topologies.

Automatically inferring molecular structure from analytical measurements is a key step toward closing the loop in autonomous chemical research. Yet it remains challenging, because structurally relevant information is distributed across multiple channels, affected by experimental imperfections, and often insufficient to uniquely define a molecular structure. Here, we present BLIND (Bimodal Learning from Imperfect NMR Data), a bimodal transformer that translates 1H and/or 13C NMR data into molecular structures without any chemical priors, such as molecular formula, elemental composition, or possible fragments. Unlike previous approaches, BLIND is trained exclusively on more than 5.5 million experimental spectra extracted from the chemical literature, learning from the inherent heterogeneity of real-world NMR data. Under fully unconstrained, chemistry-ignorant conditions, BLIND correctly infers the molecular structure, including stereochemistry, in more than half of the chemically diverse test cases and otherwise narrows the solution to only a few plausible candidates. On an independent expert-curated dataset acquired under controlled experimental conditions, the prediction accuracy exceeds 80%. BLIND handles various molecular sizes and structural complexity (up to 130 non-hydrogen atoms) and generalizes across a broad chemical space, including compounds with less common elements, multiple stereocentres, and multiple chemical species. These findings demonstrate that experimental data are a valuable source of structural information that should not be blindly replaced by idealized simulated datasets. Trained directly on such data, BLIND enables end-to-end structure elucidation from routine NMR measurements, allowing inferred structures to be fed back into real-time synthetic decisions in autonomous chemical research.

ConspectusThe growing field of coordination supramolecular chemistry constitutes a fruitful avenue for accessing a variety of multifunctional materials with a range of applications. Their versatility is enhanced if they have the ability to encapsulate guest molecules, opening opportunities for host/guest synergies. One of the most paradigmatic categories of such assemblies is coordination supramolecular helicates, which exhibit a central cavity for the potential allocation of small species, provided that their symmetry and volumes are compatible. The presence of noncovalent interactions (NCIs) between host and guest strongly contributes to the thermodynamic stability of these edifices, sometimes giving rise to a template effect. All those features are exploited for the case of triple-stranded helicates, which are predictably obtained from reactions of metal ions that adopt an octahedral coordination geometry with ligands made of two chelating moieties sufficiently separated by a spacer. The properties of the cavity of the helicate can be tuned by adjusting the central spacer of the ligand, which in turn, may incorporate functionalities facilitating NCIs with potential guests, such as hydrogen bonds. In this manner, a collection of pyrazolylpyridine (or -quinoline) ligands (L) has given rise to a large family of (G@[M₂L₃])ⁿ⁺ species (where G represents various guests), in which the encapsulated entities are firmly held in place by [N-H···G] hydrogen bonds. These assemblies can thus be employed for the selective recognition of anions or small coordination complexes, capitalizing on the specific architecture of the ligand strands. Furthermore, they have opened a plethora of possibilities for the investigation of synergic multifunctionality. The host can be made to exhibit molecular switching behavior (for example, spin-crossover, SCO, if M = Fe^II) or single-ion magnet (SIM) behavior (if M = Co^II) while the guest has been exploited to tune these properties or to incorporate new ones. More recently, anionic coordination complexes such as these from the series [M(ox)₃]^3- ("ox" being the oxalate anion and M = Fe, Cr, Al, Ru) have been efficiently trapped inside the metallo-helices. This has unveiled unprecedented phenomena resulting from encapsulation, such as the first manifestation of SIM behavior for Cr^III or the enhancement of the quantum coherence of a molecular qubit when acting as the guest. This family has been expanded with the inclusion of the anilate analogues of oxalates, opening unlimited options for multiproperty explorations (such as photophysical, redox chemistry, radical generation, etc.). More recently, within this group of systems, the guest has been employed as a template to selectively assemble specific combinations of two different ligands in the form of G@[M₂L_xL'_(3-x)]^m+ heteroleptic helicates, thus leading to a further opportunity of function tunability and enhancement. In this Account, we survey this and other related types of host/guest assemblies and place them in the general context of triple-stranded supramolecular helicates while assessing their impact in fields like molecular magnetism, quantum technologies, or anion recognition.

Ferroptosis, a recently described form of regulated, nonapoptotic cell death mechanism, presents significant potential for cancer treatment, particularly when combined with photodynamic therapy (PDT). In this study, we report the synthesis and biological evaluation of a series of Ir-COUBPY complexes as novel photosensitizers (PSs) for effective cancer phototherapy. These complexes exhibit high stability under both dark and light conditions and are capable of photogenerating Type I and Type II reactive oxygen species (ROS), as well as photo-oxidizing NADH. Electron paramagnetic resonance (EPR) spectroscopy provided direct evidence of light-induced superoxide and singlet oxygen generation, confirming dual ROS pathways. Moreover, the Ir-COUBPY complexes preferentially accumulated in the mitochondria of cancer cells, leading to the photogeneration of hydroxyl radicals and hydrogen peroxide. Photocytotoxicity studies on HeLa and A375 cancer cells underscored the role of the COUBPY ligand in enhancing PDT efficiency upon irradiation with both green and red light. Among the Ir-COUBPY complexes, the most effective PS, Ir4a, was encapsulated in polyurethane–polyurea hybrid nanocapsules (NC-Ir4a), resulting in a significant increase in phototoxic index values (e.g., from 64 to 179.6 in A375 cells). Mechanistic studies confirmed ferroptosis as the primary cell death pathway induced by Ir4a, supported by light-dependent lipid peroxidation, glutathione oxidation and depletion, intracellular ATP photodepletion, and the viability-restoring effect of Fer-1. These effects were more pronounced upon nanoencapsulation. Photobiological studies with 3D tumor spheroids of A375 cells further confirmed higher cellular uptake of NC-Ir4a, contributing to improved phototoxic efficiency. Overall, these findings highlight the potential of coumarin-based COUBPY ligands in the design of new Ir­(III)-based PSs that can be activated with light within the phototherapeutic window, operating through nonconventional cell death mechanisms such as ferroptosis.

Photodynamic therapy (PDT) is a promising cancer treatment modality, offering precise spatial and temporal control of drug activation using light. However, clinical translation of current photosensitizers (PSs) is limited by inefficient activation at wavelengths within the phototherapeutic window, especially in the deep-red and near-infrared (NIR) region. NIR light provides advantages such as reduced absorption by endogenous chromophores, minimized tissue photodamage, and improved tissue penetration, highlighting the need for PSs to be activatable in this range. Herein, we report a novel series of ruthenium(II) polypyridyl complexes (Ru4-7) featuring π-extended COUBPY ligands, designed via a vinylogation strategy and synthesized through an innovative postcoordination ligand assembly approach. This structural modification enhances molar absorptivity and red-shifts the absorption bands well into the NIR region without substantially compromising photostability. Complexes Ru4-7 efficiently generate both Type I and Type II reactive oxygen species, and their photodynamic activity, combined with preferential mitochondrial accumulation, leads to potent nanomolar phototoxicity against CT-26 colorectal cancer cells under deep-red and NIR irradiation, even under hypoxia. Notably, the lead complex Ru6 demonstrated strong in vivo phototoxicity in mice bearing subcutaneous CT-26 tumors, achieving significant tumor growth inhibition upon irradiation with 660 and 780 nm light. Ru6 thus represents one of the first Ru(II) polypyridyl complexes to exhibit robust in vivo PDT antitumor activity under one-photon NIR activation. Its broad wavelength activation profile further underscores its potential versatility for treating tumors of varying size and anatomical location depending on specific light penetration requirements. These findings mark a promising step toward next-generation PSs for treating deep-seated and hypoxic tumors.

Spins within molecules benefit from the atomistic control of synthetic chemistry for the realization of qubits. One advantage is that the quantum superpositions of the spin states encoding the qubit can be coherently manipulated using electromagnetic radiation. The main challenge is the fragility of these superpositions when qubits are to partake of solid‐state devices. We address this issue with a supramolecular approach for protecting molecular spin qubits against decoherence. The molecular qubit [Cr(ox)₃]³⁻ has been encapsulated inside the diamagnetic triple‐stranded helicate [Zn₂L₃]⁴⁺ (L is a bis‐pyrazolylpyridine ligand). The quantum coherence of the protected qubit is then analyzed with pulsed EPR spectroscopy and compared with the unprotected qubit, both in solution and in the solid state. Crucially, the spin–spin relaxation in the solid state has been examined within diamagnetic crystal lattices of the isostructural ([Al(ox)₃]@[Zn₂L₃])⁺ or [Al(ox)₃]^3‐ assemblies, respectively, doped with the Cr³⁺ qubit in two different (<10%) concentrations. The study unveils a surprising increase of the phase memory time of the qubit upon encapsulation only in the solid. Spin‐lattice relaxation times also exhibit a significant enhancement, as established from inversion recovery pulse sequences and from slow relaxation of the magnetization of the protected qubit, not featured by the free qubit.

Spins within molecules benefit from the atomistic control of synthetic chemistry for the realization of qubits. One advantage is that the quantum superpositions of the spin states encoding the qubit can be coherently manipulated using electromagnetic radiation. The main challenge is the fragility of these superpositions when qubits are to partake of solid‐state devices. We address this issue with a supramolecular approach for protecting molecular spin qubits against decoherence. The molecular qubit [Cr(ox)₃]³⁻ has been encapsulated inside the diamagnetic triple‐stranded helicate [Zn₂L₃]⁴⁺ (L is a bis‐pyrazolylpyridine ligand). The quantum coherence of the protected qubit is then analyzed with pulsed EPR spectroscopy and compared with the unprotected qubit, both in solution and in the solid state. Crucially, the spin–spin relaxation in the solid state has been examined within diamagnetic crystal lattices of the isostructural ([Al(ox)₃]@[Zn₂L₃])⁺ or [Al(ox)₃]^3‐ assemblies, respectively, doped with the Cr³⁺ qubit in two different (<10%) concentrations. The study unveils a surprising increase of the phase memory time of the qubit upon encapsulation only in the solid. Spin‐lattice relaxation times also exhibit a significant enhancement, as established from inversion recovery pulse sequences and from slow relaxation of the magnetization of the protected qubit, not featured by the free qubit.