@article {46718, title = {Vinylogous michael addition of 3-alkylidene-2-oxindoles to beta,gamma-unsaturated alpha-keto esters by bifunctional cinchona alkaloids}, journal = {European Journal of Organic Chemistry}, volume = {2020}, year = {2020}, month = {SEP }, pages = {5690-5694}, type = {Article}, abstract = {

A highly enantioselective vinylogous Michael addition of 3-alkylidene-2-oxindoles with beta,gamma-unsaturated alpha-keto esters using a bifunctional tertiary-amine thiourea catalyst is demontsrated. The challenging Michael reaction with the beta,gamma-unsaturated alpha-keto esters has been accomplished due to the synchronized H-bond guided dual activation of vinylogous nucleophile and electrophile by catalyst. The reaction afforded product in high yield while resulting in excellent stereocontrol (\> 19:1E/Zand upto 99 \%ee).

}, keywords = {3-Alkylidene-2-oxindoles, Asymmetric synthesis, beta, gamma-Unsaturated alpha-keto esters, Michael adduct, Vinylogous Michael addition}, issn = {1434-193X}, doi = {10.1002/ejoc.202000835, Early Access Date = SEP 2020}, author = {Jaiswal, Manish K. and Kumar, Rajesh and Singh, Sanjay and Jain, Shailija and Vanka, Kumar and Singh, Ravi P.} } @article {47751, title = {Ionic conductivity of Na3Al2P3O12 glass electrolytes role of charge compensators}, journal = {Inorganic Chemistry}, volume = {60}, year = {2021}, month = {SEP }, pages = {12893-12905}, type = {Article}, abstract = {In glasses, a sodium ion (Na+) is a significant mobile cation that takes up a dual role, that is, as a charge compensator and also as a network modifier. As a network modifier, Na+ cations modify the structural distributions and create nonbridging oxygens. As a charge compensator, Na+ cations provide imbalanced charge for oxygen that is linked between two network-forming tetrahedra. However, the factors controlling the mobility of Na+ ions in glasses, which in turn affects the ionic conductivity, remain unclear. In the current work, using high-fidelity experiments and atomistic simulations, we demonstrate that the ionic conductivity of the Na3Al2P3O12 (Si0) glass material is dependent not only on the concentration of Na+ charge carriers but also on the number of charge-compensated oxygens within its first coordination sphere. To investigate, we chose a series of glasses formulated by the substitution of Si for P in Si0 glass based on the hypothesis that Si substitution in the presence of Na+ cations increases the number of SiOAl bonds, which enhances the role of Na as a charge compensator. The structural and conductivity properties of bulk glass materials are evaluated by molecular dynamics (MD) simulations, magic angle spinning-nuclear magnetic resonance, Raman spectroscopy, and impedance spectroscopy. We observe that the increasing number of charge-imbalanced bridging oxygens (BOs) with the substitution of Si for P in Si0 glass enhances the ionic conductivity by an order of magnitudefrom 3.7 x 10(-8) S.cm(-1) to 3.3 x 10(7) S.cm(-1) at 100 degrees C. By rigorously quantifying the channel regions in the glass structure, using MD simulations, we demonstrate that the enhanced ionic conductivity can be attributed to the increased connectivity of Na-rich channels because of the increased charge-compensated BOs around the Na atoms. Overall, this study provides new insights for designing next-generation glass-based electrolytes with superior ionic conductivity for Na-ion batteries}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.1c01280}, author = {Keshri, Shweta R. and Ganisetti, Sudheer and Kumar, Rajesh and Gaddam, Anuraag and Illath, Kavya and Ajithkumar, Thalasseril G. and Balaji, Sathravada and Annapurna, K. and Nasani, Narendar and Krishnan, N. M. Anoop and Allu, Amarnath R.} } @article {48229, title = {Elucidating the influence of structure and Ag+ -Na+ ion-exchange on crack-resistance and ionic conductivity of Na3Al1.8Si1.65 P-1.8 O-12 glass electrolyte}, journal = {Acta Materialia}, volume = {227}, year = {2022}, month = {APR }, pages = {117745}, type = {Article}, abstract = {

Glasses are emerging as promising and efficient solid electrolytes for all-solid-state sodium-ion batteries. However, they still suffer from poor ionic conductivity and crack-resistance, which need to be improved for better battery performance, reliability, and service life. The current study shows a significant enhancement in crack resistance (from 11.3 N to 32.9 N) for Na3Al (1.8) Si-1.65 P1.8O12 glass (Ag-0 glass) upon Na+ -Ag+ ion-exchange (IE) due to compressive stresses generated in the glass surface while the ionic conductivity values (similar to 10(-5) S/cm at 473 K) were retained. In this study, magic angle spinning-nuclear magnetic resonance (MAS-NMR), molecular dynamics (MD) simulations, Vickers micro hardness, and impedance spectroscopic techniques were used to evaluate the intermediate-range structure, atomic structure, crack resistance and conductivity of the glass. MAS-NMR and MD simulations confirm the presence of Si-OAl-O-P groups in the glass, thus enabling formation of Na percolated channel regions. AC-conductivity analysis for Ag-0 and ion-exchanged Ag-0 glass suggests that the mobility of Na+ ion increases with increasing temperature. It is observed that the measured mean square displacement (root \< R-2(t(p))\>) for sodium cations using AC-conductivity isotherms is nearly constant up to 448 K and then increases with increasing temperature up to 523 K. From the impedance spectra for ion-exchanged Ag-0 glass, it is identified that the increase in root \< R-2 (t(nu))\> and thereby, the mobility of sodium-ions for Ag-0 glass is due to the structural variations in the Ag-0 glass with increasing the temperature. Overall, the mechanisms presented in this article helps in formulating better glass based electrolyte materials for room temperature or high temperature sodium-ion batteries. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

}, keywords = {amorphous, Ion-exchange, Ionic-conductivity, MD simulations, Mechanical property}, issn = {1359-6454}, doi = {10.1016/j.actamat.2022.117745}, author = {Keshri, Shweta R. and Mandal, Indrajeet and Ganisetti, Sudheer and Kasimuthumaniyan, S. and Kumar, Rajesh and Gaddam, Anuraag and Shelke, Ankita and Ajithkumar, Thalasseril G. and Gosvami, Nitya Nand and Krishnan, N. M. Anoop and Allu, Amarnath R.} } @article {50083, title = {Fast self-healing in a layered molecular crystal mediated by stress-induced symmetry breaking}, journal = {Nature Communications}, volume = {17}, year = {2026}, month = {FEB}, pages = {2525}, type = {Article}, abstract = {

In recent years, symmetry-breaking has emerged as a powerful tool for significantly altering various physical properties in 2D layered materials. However, the breaking of symmetry by means of mechanical stress in organic crystals remains elusive. Here, we demonstrate a simple approach to engineer symmetry-breaking through mechanical stress fields in a layered molecular crystal, resulting in autonomous and fast self-healing under ambient temperature and pressure conditions. Fracture mechanics analysis reveals that the crystal adheres to an elasto-plastic model, with formation of a plastic zone at the crack tip, which prevents further crack propagation, facilitating the self-healing process. Spatially resolved Raman mapping reveals that the crack formation is accompanied by a distinct symmetry-breaking mechanism at the microstructural level. A six-fold increase in non-linear second harmonic (SH) activity, triggered by mechanical perturbation, further validates the local symmetry breaking in an otherwise centrosymmetric crystal. Furthermore, symmetry is restored following successful healing, as evidenced by the disappearance of the SH signal in the healed regions. This study not only broadens the scope of self-healing mechanisms viable in molecular materials but also offers key insights into the role of symmetry breaking and its potential for related technological applications.

}, doi = {10.1038/s41467-026-68987-z}, author = {Ghosh, Ishita and Biswas, Rabindra and Tanwar, Manushree and Bhunia, Surojit and Das, Kaustav and Torris, Arun and Mondal, Amit and Raghunathan, Varun and Kumar, Rajesh and Reddy, C. Malla} }