2DMP

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This study explores a unique class of graphene nanoribbons, the gulf-edged zigzag graphene nanoribbons (ZGNR-Gs), created by introducing bite-like patterns along the zigzag edges. The authors demonstr...

MIL-53(Cr), a flexible “breathing” metal–organic framework (MOF), exhibits exceptional photocatalytic performance in the dehalogenation of aryl halides. Structural flexibility, driven by the interact...

The GW approximation within many-body perturbation theory is the state of the art for computing quasiparticle energies in solids. Typically, Kohn-Sham (KS) eigenvalues and eigenfunctions, obtained fro...

In the search for new magnetic topological insulators with strong spin–orbit coupling, by following conceptual considerations that have already proven to be suitable, the bismuth-rich subiodide Mn[PtBi6I12] was discovered. Single crystals were grown from mixtures of the elements and BiI3 using a temperature program developed on the basis of thermal analyses. Single-crystal X-ray diffraction revealed a rhombohedral structure of the cuboctahedral cluster anions [PtBi6I12]2–, which are linked into chains via octahedrally coordinated Mn2+ cations. Partial substitution of Mn2+ by Bi3+ and vacancy formation are responsible for a phase width represented by the general formula (Mn1–3xBi2x)[PtBi6I12]. Density functional theory-based calculations and measurements of the electrical resistance showed that the compound is a semiconductor with a topologically trivial band gap. Nonstoichiometry of chain fragments, corresponding to n- and p-self-doping, strongly increases the conductivity, especially along the chains. The compound is paramagnetic at room temperature. Electron spin resonance spectra indicate an increase in spin correlations and the buildup of internal fields below 30 K.

ConspectusTriangulene (TRI) and its heterotriangulene (HT) derivatives are planar, triangle-shaped molecules that, via suitable coupling reactions, can form extended organic two-dimensional (2D) crystal (O2DC) structures. While TRI is a diradical, HTs are either closed-shell molecules or monoradicals which can be stabilized in their cationic form.Triangulene-based O2DCs have a characteristic honeycomb-kagome lattice. This structure gives rise to four characteristic electronic bands: two of them form Dirac points, while the other two are flat and sandwich the Dirac bands. Functionalization and heteroatoms are suitable means to engineer this band structure. Heteroatoms like boron and nitrogen shift the Fermi level upward and downward, respectively, while bridging groups and functionalized triangulene edges can introduce a dispersion to the flat bands.The stable backbone architecture makes 2D HT-polymers ideal for photoelectrochemical applications: (i) bridge functionalization can tune the band gap and maximize absorption, (ii) the choice of the center atom (B or N) controls the band occupation and shifts the Fermi level with respect to vacuum, allowing in some cases for overpotential-free photon-driven surface reactions, and (iii) the large surface area allows for a high flux of educts and products.The spin polarization in TRI and in open-shell HTs is maintained when linking them to dimers or extended frameworks with direct coupling or more elaborate bridging groups (acetylene, diacetylene, and phenyl). The dimers have a high spin-polarization energy and some of them are strongly magnetically coupled, resulting in stable high-spin or broken-symmetry (BS) low-spin systems. As O2DCs, some systems become antiferromagnetic Mott insulators with large band gaps, while others show Stoner ferromagnetism, maintaining the characteristic honeycomb-kagome bands but shifting the opposite spin-polarized bands to different energies. For O2DCs based on aza- and boratriangulene (monoradicals as building blocks), the Fermi level is shifted to a spin-polarized Dirac point, and the systems have a Curie temperature of about 250 K. For half-filled (all-carbon) systems, the Ovchinnikov rule or, equivalently, Lieb’s theorem, is sufficient to predict the magnetic ordering of the systems, while the non-half-filled systems (i.e., those with heteroatoms) obey the more involved Goodenough–Kanamori rule to interpret the magnetism on the grounds of fundamental electronic interactions.There remain challenges in experiment and in theory to advance the field of triangulene-based O2DCs: Coupling reactions beyond surface chemistry have to be developed to allow for highly ordered, extended crystals. Multilayer structures, which are unexplored to date, will be inevitable in alternative synthesis approaches. The predictive power of density-functional theory (DFT) within state-of-the-art functionals is limited for the description of magnetic couplings in these systems due to the apparent multireference character and the large spatial extension of the spin centers.