Coupled spin-crossover complexes in supramolecular systems feature rich spin phases that can exhibit collective behaviors. Here, we report on a molecular-level exploration of the spin phase and collective spin-crossover dynamics in metallo-supramolecular chains. Using scanning tunneling microscopy, spectroscopy, and density functional theory calculations, we identify an antiferroelastic phase in the metal−organic chains, where the Ni atoms coordinated by deprotonated tetrahydroxybenzene linkers on Au(111) are at a low-spin (S = 0) or a high-spin (S = 1) state alternately along the chains. We demonstrate that the spin phase is stabilized by the combined effects of intrachain interactions and substrate commensurability. The stability of the antiferroelastic structure drives the collective spin-state switching of multiple Ni atoms in the same chain in response to electron/hole tunneling to a Ni atom via a domino-like magnetostructural relaxation process. These results provide insights into the magnetostructural dynamics of the supramolecular structures, offering a route toward their spintronic manipulations.

A2 Dm etal-organic framework (2D-MOF) was formed on aCu(111) substrate using benzenehexol molecules. By means of acombination of scanning tunneling microscopy and spectroscopy, X-rayp hotoelectron spectroscopya nd density-functional theory,t he structure of the 2D-MOF is determined to be Cu 3 (C 6 O 6 ), which is stabilized by O-Cu-O bonding motifs.W efind that upon adsorption on Cu(111), the 2D-MOF features asemiconductor band structure with adirect band gap of 1.5 eV.The O-Cu-O bonds offer efficient charge delocalization, which gives rise to ah ighly dispersive conduction band with an effective mass of 0.45 m e at the band bottom, implying ahigh electron mobility in this material. Scheme 1. On-surfacesynthesis of single layer of 2D-MOF Cu 3 (C 6 O 6 ).Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

We report on the design and synthesis of a twodimensional metal−organic framework Fe 3 (HITP) 2 which comprises of a Kagome sublattice of Fe atoms. Density-functional theory calculations reveal that this framework has a ferromagnetic ground state with several topological nontrivial gaps opened due to the spin−orbit coupling, signifying quantum anomalous Hall features. Experimentally, we synthesize this structure by means of on-surface coordination self-assembly on an Au(111) substrate. We resolve its structure at a single-molecule resolution using scanning tunneling microscopy and confirm that the on-surface structure is nearly identical to the free-standing framework. We use scanning tunneling spectroscopy to study its electronic properties. A zero-bias resonance localized at the Fe atoms indicates that a magnetic moment is present at the Kagome lattice. Our results demonstrate the viability of realizing 2D organic quantum anomalous Hall systems.