Comparison of thermomagnetic history effects in weakly pinned single crystals of R 3Rh4Sn13 (R=Yb, Ca)

A comparative study of the thermomagnetic memory effects of J _c in two weakly pinned low T _c superconductors, Ca₃Rh₄Sn₁₃ (CaRhSn) and Yb₃Rh₄Sn₁₃ (YbRhSn), is presented. In both the systems, the peak effect (PE) phenomenon appears as an order-disorder transformation through stepwise amorphization of the flux line lattice (FLL). However, in CaRhSn. we can witness another disorder-driven transition (Bragg glass (BG) to a vortex glass (VG) in a distinct manner as in a single crystal of high T _c YBa₂Cu₃O_7-δ for H‖c.     

Simultaneous parallel and antiparallel self-assembly in a triazole/amide macrocycle conformationally homologous to D-,L-α-amino acid based cyclic peptides: NMR and molecular modeling study

A 1,4-linked triazole/amide based peptidomimetic macrocycle, synthesized from a triazole amide oligomer of cis-furanoid sugar triazole amino acids, possesses a conformation resembling the D-,L-α-amino acid based cyclic peptides despite having uniform backbone chirality. It undergoes a unique mode of self-assembly through an antiparallel backbone to backbone intermolecular H-bonding involving amide NH and triazole N2/N3 as well as parallel stacking via amide NH and carbonyl oxygen H-bonding, leading to the formation of a tubular nanostructure.     

Facile Synthesis of 4‐Functionalized Cyclopentenones

1-8-Diazabicyclo[5.4.0]undec-7-ene(DBU)‐catalyzed Michael addition of nitroalkanes to dicyclopentadienone (1) followed by flash vacuum pyrolysis (FVP) provided a high‐yielding synthesis of extremely pure 4‐nitroalkyl cyclopentenones (3). The optimized Nef reaction of the nitro adducts (2) provided 4‐ketoalkyl cyclopentenones (5) in the similar way.     

Annulation of furan-bridged 10-membered rings on N-heterocycles through [8+2] cycloaddition of dienylazaisobenzofurans and dimethyl acetylenedicarboxylate

One-pot three-component coupling of o-alkynylheteroaryl carbonyl derivatives with α,β-unsaturated Fischer carbene complexes and dimethyl acetylenedicarboxylate leading to the synthesis of heterocyclic analogues of furanophane derivatives has been explored. This involves the generation of conformationally flexible dienylazaisobenzofuran intermediate as transient intermediates, which undergo [8+2] cycloaddition reaction with dienophile. In some cases, this intermediate undergoes twofold Diels-Alder reaction to afford heterolignan derivatives in a single step.     

Expedient Access to Enantioenriched 1-Azaspiro Cyclobutanones Enabled by Modified Heyns Rearrangement

Leveraging the unexplored regions of chemical space, the integration of spirocyclic cyclobutane in a molecular scaffold opens up a new vista in modern drug discovery. Despite recent advancements in achieving the synthesis of such motifs, strategies for their asymmetric construction have not been well-recognized and remain a formidable challenge. Herein, for the first time, we have demonstrated a chiral Brønsted acid-catalyzed enantioselective synthesis of 1-azaspiro cyclobutanone enabled by an unusual reactivity of enamine that explore the potentiality of Heyns rearrangement upon electrophilic modification. This design strategy offers viable access to a wide range of cyclobutanone containing spiroindoline and spiropyrrolidine derivatives in good yields with excellent stereoselectivities (up to >99 % ee, >20 : 1 dr). Furthermore, the practicality of this methodology has been shown by a scale-up synthesis of spirocyclic products and their facile post-synthetic modifications.     

Ligand-Mediated Revival of Degraded α-CsPbI3 to Stable Highly Luminescent Perovskite

Although α-CsPbI₃ is regarded as an attractive optical luminophore, it is readily degraded to the optically inactive δ-phase under ambient conditions. Here, we present a simple approach to revive degraded (“optically sick”) α-CsPbI₃ through “medication” with thiol-containing ligands. The effect of different types of thiols is systematically studied through optical spectroscopy. The structural reconstruction of degraded α-CsPbI₃ nanocrystals to cubic crystals in the presence of thiol-containing ligands is visualized through high-resolution transmission electron microscopy and supported by X-ray diffraction analysis. We found that 1-dodecanethiol (DSH) effectively revives degraded CsPbI₃ and results in high immunity towards moisture and oxygen, hitherto unreported. DSH facilitates the passivation of surface defects and etching of degraded Cs₄PbI₆ phase, thus reverting them back to the cubic CsPbI₃ phase, leading to enhanced PL and environmental stability.     

Rearrangement of dicarboranyl methyl cation to icosahedral C3B9H12+: An ab initio dynamics view

Closo-carborane anions are prominent, whereas the cations of the same are less abundant in the literature. As these ions have similar size and are weakly coordinating, the ionic liquids of these two ions could have important applications in many areas of chemistry. In view of limited number of polyhedral carborane cations available, we revisited the rearrangement of dicarboranyl methyl cation (7-CH₂ 7,9-nido-C₂B₉H₁₀⁺) using ab initio molecular dynamics calculations with metadynamics. Our simulations confirmed the concerted mechanism of the rearrangement. We believe this work will resume the interest in its synthesis and carborane cations in general.