Radical-ionic metal-organic frameworks (MOFs) have unique optical, magnetic, and electronic properties. These radical ions, forcibly formed by external stimulus-induced redox processes, are structurally unstable and have short radical lifetimes. Here, we report two naphthalenediimide-based (NDI-based) Ca-MOFs: DGIST-6 and DGIST-7. Neutral DGIST-6, which is generated first during solvothermal synthesis, decomposes and is converted into radical-anionic DGIST-7. Cofacial (NDI) 2 •− and (NDI) 2 2− dimers are effectively stabilized in DGIST-7 by electron delocalization and spin-pairing as well as dimethylammonium counter cations in their pores. Single-crystal x-ray diffractometry was used to visualize redox-associated structural transformations, such as changes in centroid-to-centroid distance. Moreover, the unusual rapid reduction of oxidized DGIST-7 into the radical anion upon infrared irradiation results in effective and reproducible photothermal conversion. This study successfully illustrated the strategic use of in situ prepared cofacial ligand dimers in MOFs that facilitate the stabilization of radical ions.

The recent discovery of chemically reversible isomerization of CdS clusters (Williamson et al. Science2019, 363, 731) shows that the structural transformation of such inorganic clusters has essential characteristics of both small-molecule isomerization and solid−solid transformation. Despite its importance in synthesizing colloidal quantum dots from cluster intermediates (so-called "magic-sized clusters" or MSCs), the underlying mechanism for such inorganic isomerization is not yet understood. Here, using ab initio simulated spectroscopy, we propose a microscopic mechanism for the multiscale isomerization of CdS MSC. When triggered by hydroxyl adsorption, a carboxylate-ligated CdS cluster undergoes a structural transformation through Cd−S bond exchanges at the bond-length scale (molecular isomerization), which induces the change in the stacking sequence of the partially ordered CdS lattice (solid−solid transformation). The creation of the bond-exchange defects in the CdS core and "self-healing" by ligand rearrangements on the surface play a central role in the isomerization. MSCs can be thus made susceptible to forming a particular type of point-like defect (e.g., bond-exchange defect), which provides useful insights into understanding the stability and structural activation of MSCs.

1,2-Diborons with one boron atom each in the allyl and homoallyl positions are of great utility, especially as doubleallylation reagents. However, only a few synthetic methods have been reported to date and have a limited substrate scope. Herein, we developed the Cu-catalyzed regio-and stereoselective synthesis of α-borylmethyl-(E)-allylborons from easily accessible 1-substituted allenols and bis(pinacolato)diboron. Importantly, this method allowed the highly efficient and regioselective formation of doubleallylating diborons with diverse substituents, which would be otherwise cumbersome to synthesize, and could be successfully performed on a gram scale. The synthetic application of α-borylmethyl-(E)-allylborons was demonstrated by the enantio-and (Z)selective allylation of aldehydes via Brønsted acid catalysis. Furthermore, (E)-allyl and (E)-homoallyl diols with excellent diastereoselectivity were generated by the Lewis acid catalyzed diastereo-and (E)-selective allyl transfer of (E)-allyldiborons to aldehydes. Using this strategy, the key intermediate in the construction of the C 7 −C 12 fragment of (−)-discodermolide was also synthesized.

Ultrafast charge transfer in van der Waals (vdW) heterostructures enables efficient control of two-dimensional material properties through strong optical absorption and subsequent carrier transfer. Here, using real-time time-dependent density functional theory coupled to molecular dynamics, we investigated the nonequilibrium dynamics of charge-density-wave (CDW) melting in 1T-TaS2 triggered by ultrafast charge transfer in 1T-TaS2/MoSe2 or WSe2 heterostructures. Despite the fast and sufficient charge transfer from the MoSe2 (or WSe2) “electrode” to the 1T-TaS2 layer, the electronic excitation of the vdW heterostructure does not lead to the nonthermal CDW transition of 1T-TaS2. Instead, the TaS2 lattice is heated by carrier–lattice scattering, leading to thermal CDW melting at high ionic temperatures. The lack of nonthermal melting follows from the fact that the time scale of carrier recombination in 1T-TaS2 is similar to or faster than that of charge transfer. These findings provide physical insights into understanding the CDW melting dynamics in vdW heterostructures under nonequilibrium conditions.

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