ABSTRACT
Nickel-rich (Ni-rich) layered oxides are considered as the most promising cathode candidates for lithium-ion cells owing to their high theoretical specific capacity. However, the higher nickel content endows structural deformation through unwanted phase transitions and parasitic side reactions that lead to capacity fading upon prolonged cycling. Hence, a deep understanding of the chemistry and structural behaviour is essential for developing Ni-rich Lithium Nickel Cobalt Manganese oxide (NCM) cathode-based high-energy batteries. The present review focuses on the different challenges associated with Ni-rich NCM materials and surface modification as a strategy to solve the issues associated with NCM materials, assessment of several coating materials, and the recent developments in the surface modification of Ni-rich NCMs, with an in-depth discussion on the impact of coating on the degradation mechanism.
ABSTRACT
We report a nonparallel stacked arrangement of donoracceptor (DA) pairs for prolonging the lifetime of photoinduced charge-separated states. Hydrogenhydrogen steric repulsion in naphthalimide-naphthalene (NIN) dyad destabilizes the planar geometry between the constituent units in solution/ground state. Sterically imposed nonplanar geometry of the dyad allows the access of nonparallel arrangement of the donor and acceptor stacks having triclinic space group in the crystalline state. Antiparallel trajectory of excitons in nonparallel DA stacks can result in lower probability of geminate charge recombination, upon photoexcitation, thereby resulting in a long-lived charge-separated state. Upon photoexcitation of the NIN dyad, electron transfer from naphthalene to the singlet excited state of naphthalimide moiety results in radical ion pair intermediates that survive >10,000-fold longer in the aggregated state (τcra > 1.2 ns) as compared to that of monomeric dyad (τcrm < 110 fs), monitored using femtosecond transient absorption spectroscopy.
ABSTRACT
Tetraarylpyrazoles are synthesized from commercially available materials in three steps and found to exhibit Aggregation Induced Emission Enhancement (AIEE) characteristics. Removing one aryl unit from tetraarylpyrazole leads to Aggregation Caused Quenching (ACQ), thus the number of aryl groups plays an important role in exploring such a phenomenon.
ABSTRACT
The syntheses and spectral and structural characterization of hitherto unknown p-benzene incorporated normal, expanded, strapped and N-confused calixbenzophyrins are achieved; altogether five new macrocycles from a single starting material are reported. The binding studies of the strapped macrocycle revealed that the molecule is selective towards Fe(III) ions.
ABSTRACT
Fluorine interaction assisted AIEE characteristic in an expanded calixbenzophyrin is presented by single-crystal X-ray-diffraction analysis and molecular modelling approaches. Selective exposure to volatile organic compounds such as ketones and esters results in the breaking of fluorine interaction, leading to enhanced monomer emission.
Subject(s)
Calixarenes/chemistry , Esters/chemistry , Fluorine/chemistry , Ketones/chemistry , Luminescence , Porphyrins/chemistry , Crystallography, X-Ray , Models, Molecular , Molecular StructureABSTRACT
Synthesis, spectral and structural characterization of a pyrroloindolizine derivative having structural similarity with calix[2]pyrrole is described. Here, two pyrrole rings are connected with two meso-carbon atoms having an N,α-linkage and an α,ß-linkage to afford the smallest analogue in the calixpyrrole family. Detailed NMR spectroscopic studies along with single crystal X-ray analysis confirm the assigned structure of the molecule.
