Reactivity-Selectivity Principle: Phenyl Group in Indazole Makes It More Lucid

Linear free energy relationship (LFER) plots are constructed for the deprotonation equilibriums (pKaH+) of pyrazolium and indazolium (benzopyrazolium) cations. The reaction constants Taft * and Hammett  are found to be 2.75 and 1.32 for deprotonation (pKaH+) of pyrazolium and indazolium cations respectively. Higher value of Taft * than the Hammett  is explained in terms of extra stability of the indazolium cation due to its greater number of resonance structures. This article is an exercise to undergraduate students for writing different resonance structures of indazolium cation.

Benchmark PhotoIonization Cross-Sections of Neutral Scandium from the Ground and Excited States

The B-spline R-matrix method has been used to investigate cross-sections for photoionization of neutral scandium from the ground and excited states in the energy region from the 3d and 4s valence electron ionization thresholds to 25 eV. The initial bound states of Sc and the final residual Sc+ ionic states have been accurately calculated by combining the multiconfiguration Hartree-Fock method with the frozen-core close-coupling approach. The lowest 20 bound states of Sc I belonging to the ground 3d4s2 and excited 3d24s, 3d24p, 3d4s4p, 4s24p, and 3d3 configurations have been considered as initial states. The 81 LS final ionic states of Sc+ belonging to the terms of 3p63d2, 3p63d4l (l = 0–3), 3p63d5l (l = 0–3), 3p63d6s, 3p64s2, 3p64s4l (l = 0–3), 3p64s5l (l = 0–1), and 3p64p2 configurations have been included in the final-state close-coupling expansion. The cross-sections are dominated by complicated resonance structures in the low energy region converging to several Sc+ ionic thresholds. The inclusion of all these final ionic states has been noted to significantly impact the near-threshold resonance structures and background cross-sections. The important scattering channels for leaving the residual ion in various final states have been identified, and the 3d electron ionization channels have been noted to dominate the cross-sections at higher photon energies.

Stable open-shell aromatic nitric acid radicals: accessing highly efficient photothermal conversion with restricted radiative decay

Most of the open-shell radicals are usually thermodynamically or kinetically unstable in air due to their incompletely satisfied valency. As phenol radical without steric hindrance group protection, aromatic nitric acid radical exhibits high electrochemical and thermal stability due to its rich resonance structures including closed-shell nitro-like and open-shell nitroxide structure with unpaired electrons delocalized in conjugated backbones. Herein, a series of star-shaped aromatic nitric acid radical materials were prepared via facile demethylation and consequent oxidation of their phenolic hydroxyl precursors in air. Interestingly, they exhibit extremely high spin concentration and highly enhanced nonradiative decay, which make them exhibit great potential for photothermal conversion. Among them, TPA-TPA-O6 exhibits high photothermal conversion efficiency and negligible photobleaching effect in seawater desalination. Under irradiation of one sunlight, the water evaporation efficiency of TPA-TPA-O6 is recorded as high as 89.41% and the water evaporation rate is 1.293 kg/m2 h, which represent as the top performance in pure organic small molecule photothermal materials.

Resonance structures in kink-antikink collisions in a deformed sine-Gordon model

We study kink-antikink collisions in a model which interpolates smoothly between the completely integrable sine-Gordon theory, the ϕ4 model, and a ϕ6-like model with three degenerate vacua. We find a rich variety of behaviours, including integrability breaking, resonance windows with increasingly irregular patterns, and new types of windows near the ϕ6-like regime. False vacua, extra kink modes and kink fragmentation play important roles in the explanations of these phenomena. Our numerical studies are backed up by detailed analytical considerations.