Lev Kantorovich

Controlling crystalline‐to‐glassy transitions represents a vibrant frontier in supramolecular chemistry and condensed matter physics, providing fundamental insights into non‐equilibrium dynamics and enabling functional tunability for elasticity electronics and phase‐change devices. Conventional two‐dimensional (2D) supramolecular assembly follows an enthalpy‐dominated thermodynamic paradigm, restricting the exploration of non‐equilibrium supramolecular glasses (SMGs). Herein, we report the controlled construction of a non‐equilibrium SMG on Ag(111) using in situ‐generated triradical triphenyl‐triazine molecules. The electrophilic triazine core enriches charge density at radical sites and strengthens molecule–substrate interfacial coupling, imposing pronounced kinetic constraints at the surface. Upon thermal activation, the system follows a non‐monotonic, four‐phase evolution that involves a thermodynamically uphill transformation. Rather than directly relaxing to the global thermodynamic minimum, it is kinetically arrested into a metastable glassy state with short‐range order and long‐range disorder. This work revises the conventional enthalpy‐dominated view of supramolecular assembly and establishes a backbone‐modulated radical kinetic strategy for rational fabrication of disorder‐tunable 2D supramolecular materials.

Controlling crystalline‐to‐glassy transitions represents a vibrant frontier in supramolecular chemistry and condensed matter physics, providing fundamental insights into non‐equilibrium dynamics and enabling functional tunability for elasticity electronics and phase‐change devices. Conventional two‐dimensional (2D) supramolecular assembly follows an enthalpy‐dominated thermodynamic paradigm, restricting the exploration of non‐equilibrium supramolecular glasses (SMGs). Herein, we report the controlled construction of a non‐equilibrium SMG on Ag(111) using in situ‐generated triradical triphenyl‐triazine molecules. The electrophilic triazine core enriches charge density at radical sites and strengthens molecule–substrate interfacial coupling, imposing pronounced kinetic constraints at the surface. Upon thermal activation, the system follows a non‐monotonic, four‐phase evolution that involves a thermodynamically uphill transformation. Rather than directly relaxing to the global thermodynamic minimum, it is kinetically arrested into a metastable glassy state with short‐range order and long‐range disorder. This work revises the conventional enthalpy‐dominated view of supramolecular assembly and establishes a backbone‐modulated radical kinetic strategy for rational fabrication of disorder‐tunable 2D supramolecular materials.

We investigate the low-temperature (40 K) oxidation behavior of size-selected molybdenum clusters supported on epitaxial graphene. By combining high-resolution X-ray photoelectron spectroscopy with first-principles density functional theory, we demonstrate that subnanometric clusters can break the stoichiometric ceiling of bulk transition-metal oxides. Quantitative agreement between experiment and theory is achieved only when the clusters accommodate an unusually high oxygen content, with metal-to-oxygen ratios reaching up to Mo:O = 1:5, far exceeding the 1:3 limit of bulk oxide MoO3. This superstoichiometric regime is a consequence of coordination plasticity, where the molybdenum framework undergoes pronounced structural expansion to stable tetrahedral MoO4 motifs that are energetically inaccessible in extended solids. We provide compelling evidence that this process is mediated by photon-driven structural fluxionality: with kinetic energies exceeding 10 eV, secondary electrons generated during photoemission represent the only source to provide the vibrational excitations necessary to overcome the thermal constraint for structural transformation, allowing the clusters to disrupt the atomic connectivity and reach low-energy isomer configurations characterized by large structural expansion. Furthermore, atomic valence, rather than formal oxidation state, provides a physically meaningful and transferable descriptor for interpreting the main trend in core electron binding energy shifts in nanoscale disordered systems. These findings reveal a fundamentally non-bulk oxidation mechanism governed by non-thermal energy-activated structural dynamics, outlining a strategy for engineering oxygen-rich reactive sites at the ultimate size limit.

The photoinduced semiconductor-to-metal transition (PSMT) unveils crucial photodynamic mechanisms and holds great promise for information storage, sensing, optoelectronics, optical switches, etc. All previously reported PSMTs have occurred between two structural phases of the same material, lacking real-space evidence at the atomic or molecular level. Herein, we report atomic-scale observations of a photoinduced ‘face changing’: light irradiation transforms a semiconductor copper selenide (Cu₂Se) surface layer on Cu(111) into a well-defined metallic Cu layer. Se atoms sink to form a new Cu₂Se sublayer, while the original subsurface Cu atoms are lifted to the top layer. The Cu₂Se-to-Cu transition barrier is significantly lower in the excited state compared to the ground state. Thermoactivation enables the reverse transition. The photoinduced Cu₂Se-to-Cu and thermoactivated Cu-to-Cu₂Se transitions are highly reversible. This work, which demonstrates PSMT between two distinct materials and photo-driven interlayer atom migration, unlocks an unconventional and intriguing route for PSMT and surface modification technologies.

The development of novel subnanometer clusters (SNCs) catalysts with superior catalytic performance depends on the precise control of clusters' atomistic sizes, shapes, and accurate deposition onto surfaces. The intrinsic complexity of the adsorption process complicates the ability to achieve an atomistic understanding of the most relevant structure-reactivity relationships hampering the rational design of novel catalytic materials. In most cases, existing computational approaches rely on just a few structures to draw conclusions on clusters' reactivity thereby neglecting the complexity of the existing energy landscapes thus leading to insufficient sampling and, most likely, unreliable predictions. Moreover, modeling of the actual experimental procedure that is responsible for the deposition of SNCs on surfaces is often not done even though in some cases this procedure may enhance the significance of certain (e.g., metastable) adsorption geometries. This study proposes a novel systematic approach that utilizes global search techniques, specifically, the particle swarm optimization (PSO) method, in conjunction with ab initio calculations, to simulate all stages in the beam experiments, from predicting the most relevant SNCs structures in the beam and on a surface, to their reactivity. To illustrate the main steps of our approach, we consider the deposition of Molybdenum SNC of 6 Mo atoms on a free-standing graphene surface, as well as their catalytic properties with respect to the CO molecule dissociation reaction. Even though our calculations are not exhaustive and serve only to produce an illustration of the method, they are still able to provide insight into the complicated energy landscape of Mo SNCs on graphene demonstrating the catalytic activity of Mo SNCs and the importance of performing statistical sampling of available configurations. This study establishes a reliable procedure for performing theoretical rational design predictions.

Functionalized porphyrins by introducing exotic atoms into their central cavities have significant applications across various fields. As unique nanographenes, porphyrins functionalized with monoboron are intriguing, yet their synthesis remains highly challenging. Herein, we present the first on-surface boronation of porphyrin, bonding a single boron atom into the porphyrin's cavity. The boronation is selective, being observed exclusively in molecules featuring a specific aromatic ring-fused structure (ARFS*), not the pristine porphyrin molecule or its other ARFS forms. The boron's bonding geometry is noncentered, transforming the boronated porphyrin into a molecular dipole and imparting a markedly varied electronic structure. Well-ordered two-dimensional dipole arrays are achieved. Upon elevated thermoactivation, intermolecular O-B-O bonds provide robustness and flexibility to the molecular chains. This work demonstrates the high selectivity of on-surface porphyrin boronation and provides an effective strategy for tailoring molecules' electronic structure, producing molecular dipoles, and promoting the robustness and flexibility of molecular chains.