A sensitive fluorescent chemosensor for anions based on a styryl-boradiazaindacene framework

Long wavelength emitting, extended conjugation boradiazaindacenes are novel dyes with considerable ICT character. By appending a dipicolylaminylethylamine group, the parent compound was transformed into a fluorescent dye with a strong chelating ability for Zn(II) ions. The zinc complex which has bright orange fluorescence, reversibly signals anions with very large changes in both the absorption and the emission spectra. The remarkable change in the emission intensity is explained in relation to the electron donating capacity of the substituent on the styryl functionality.     

Subpicosecond electro-optic measurement of relativistic electron pulses

Time-resolved measurements of the transverse electric field associated with relativistic electron bunches are presented. Using an ultrafast electro-optic sensor close to the electron beam, the longitudinal profile of the electric field was measured with subpicosecond time resolution and without time-reversal ambiguity. Results are shown for two cases: inside the vacuum beam line in the presence of wake fields, and in air behind a beryllium window, effectively probing the near-field transition radiation. Especially in the latter case, reconstruction of the longitudinal electron bunch shape is straightforward.     

A reverse donor-acceptor bistable [2]catenane

A [2]catenane, composed of a pi-electron-rich bis-1,5-dioxynaphthalene[38]crown10 (BDNP38C10) ring, mechanically interlocked with a large macrocycle containing two disubstituted tetraarylmethane "speed bumps" and two different pi-electron-deficient units--namely, naphthalene dimide (NpI) and bipyridinium (BIPY(2+)) units--has been synthesized from a [2]rotaxane, containing the former recognition unit, after performing two sequential Cu(I)-catalyzed azide-alkyne cycloadditions with a linker containing the latter recognition unit. The product, which exists as a single co-conformer, wherein the BDNP38C10 ring encircles the NpI unit, undergoes equilibration to give approximately equal amounts of the other co-conformer in which the BDNP38C10 ring encircles the BIPY(2+) unit.     

Eutectic Molten Salt Synthesis of Highly Microporous Macrocyclic Porous Organic Polymers for CO2 Capture

The development of porous materials is of great interest for the capture of CO₂ from various emission sources, which is essential to mitigate its detrimental environmental impact. In this direction, porous organic polymers (POPs) have emerged as prime candidates owing to their structural tunability, physiochemical stability and high surface areas. In an effort to transfer an intrinsic property of a cyclotetrabenzoin-derived macrocycle – its high CO₂ affinity – into porous networks, herein we report the synthesis of three-dimensional (3D) macrocycle-based POPs through the polycondensation of an octaketone macrocycle with phenazine-2,3,7,8-tetraamine hydrochloride. This polycondensation was performed under ionothermal conditions, using a eutectic salt mixture in the temperature range of 200 to 300 °C. The resulting polymers, named 3D-mmPOPs, showed reaction temperature-dependent surface areas and gas uptake properties. 3D-mmPOP-250 synthesized at 250 °C exhibited a surface area of 752 m² g⁻¹ and high microporosity originating from the macrocyclic units, thus resulting in an excellent CO₂ binding enthalpy of 40.6 kJ mol⁻¹ and CO₂ uptake capacity of 3.51 mmol g⁻¹ at 273 K, 1.1 bar.     

Tailoring Electrochemical CO2 Reduction on Copper by Reactive Ionic Liquid and Native Hydrogen Bond Donors

Electrochemical CO₂ reduction (CO₂RR) on copper (Cu) shows promise for higher-value products beyond CO. However, challenges such as the limited CO₂ solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion-CO₂ adducts and a hydrogen bond donor (HBD) upon CO₂ absorption to modulate CO₂RR on Cu in a non-aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface-enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum-mechanical/molecular mechanics (IC-QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO₂ availability, reduced overpotential, and suppressed HER where C₄ products are obtained. This study deepens the understanding of electrolyte effects in CO₂RR and the role of IL ions towards electrocatalytic microenvironment design.     

A finite differences method for a two-dimensional nonlinear hyperbolic equation in a class of discontinuous functions

A numerical scheme is proposed for a scalar two-dimensional nonlinear first-order wave equation with both continuous and piecewise continuous initial conditions. It is typical of such problems to assume formal solutions with discontinuities at unknown locations, which justifies the search for a scheme that does not rely on the regularity of the solution. To this end, an auxiliary problem which is equivalent to, but has more advantages then, the original system is formulated and shown that regularity of the solution of the auxiliary problem is higher than that of the original system. An efficient numerical algorithm based on the auxiliary problem is derived. Furthermore, some results of numerical experiments of physical interest are presented.