Peripheral Modifications of meso-Hydroxyporphyrins: Formation of π-Electronic Anions and Ion-Pairing Assemblies

Phenyl groups were introduced at the β-positions proximal to the meso-hydroxy moiety in hydroxyporphyrin Ni^II complexes by oxidized BINAP Pd^II complexes. Ion-pairing assemblies of deprotonated π-electronic anions, anionic site of which was stabilized by the introduced phenyl moieties with a bulky cation, were formed. They showed charge-by-charge assemblies, assembly modes of which were modulated by the anionic building units.     

Intertwined Detection and Recognition Roles of Tetrazine in Synergistic Anion-π and H-bond Based Anion Receptor

The intrinsic properties of tetrazine as a π-anion receptor and as an on/off recognition probe merged with H-bond ability of an urea motif into a single architecture constitutes a new generation of well-defined anion receptors. Complexation properties directly benefit from the dual and synergistic contribution of tetrazine and urea. In this study, we report on the synthesis and assessment of binding properties to anions of diverse geometries. Association constants have been predicted by theoretical calculations and evaluated by multiple and complementary experimental techniques including electrospray-mass tandem spectroscopy, NMR, UV-visible, steady state fluorescence spectroscopies and time resolved fluorescence. These results provide the basis for a better understanding of both the complexation and the anion-dependent quenching mechanism.     

Electrostatics and Polarization in σ- and π-Hole Noncovalent Interactions: An Overview

The energetics of σ- and π-hole interactions can be described very well in terms of electrostatics and polarization, consistent with their Coulombic natures. When both of these components are taken into account, very good correlations with quantum-chemically computed interaction energies are obtained. If polarization is only minor, as when the interactions are quite weak, then electrostatics can suffice, as represented by the most positive electrostatic potential associated with the σ- or π-hole. For stronger interactions, the combination of electrostatics plus polarization is very effective even for interaction energies considerably greater in magnitude than what is normally considered noncovalent bonding. Several procedures for treating polarization are summarized, including the use of point charges and the direct inclusion of electric fields.     

High sensitive and large dynamic range quasi-distributed sensing system based on slow-light π-phase-shifted fiber Bragg gratings

In this paper, we theoretically analyze the slow-light π-phase-shifted fiber Bragg grating (π-FBG) and its applications for single and multipoint/quasi-distributed sensing. Coupled-mode theory (CMT) and transfer matrix method (TMM) are used to establish the numerical modeling of slow-light π-FBG. The impact of slow-light FBG parameters, such as grating length (L), index change (Δn), and loss coefficient (α) on the spectral properties of π-FBG along with strain and thermal sensitivities are presented. Simulation results show that for the optimum grating parameters L = 50 mm, Δn = 1.5×10⁻⁴, and α = 0.10 m^-1, the proposed slow-light π-FBG is characterized with a peak transmissivity of 0.424, the maximum delay of 31.95 ns, strain sensitivity of 8.380 με^-1, and temperature sensitivity of 91.064 °C^-1. The strain and temperature sensitivity of proposed slow-light π-FBG is the highest as compared to the slow-light sensitivity of apodized FBGs reported in the literature. The proposed grating have the overall full-width at half maximum (FWHM) of 0.2245 nm, and the FWHM of the Bragg wavelength peak transmissivity is of 0.0798 pm. The optimized slow-light π-FBG is used for quasi-distributed sensing applications. For the five-stage strain quasi-distributed sensing network, a high strain dynamic range of value 1469 με is obtained for sensors wavelength spacing as small as 2 nm. In the case of temperature of quasi-distributed sensing network, the obtained dynamic range is of 133 °C. For measurement system with a sufficiently wide spectral range, the π-FBGs wavelength grid can be broadened which results in substantial increase of dynamic range of the system.     

Planarized Phenyldithienylboranes: Effects of the Bridging Moieties and π-Extension on the Photophysical Properties and Lewis Acidity

Two kinds of planarized phenyldithienylboranes, which contain (CH₃)₂C- or CH₂-bridging moieties, were synthesized. The difference of the bridging moieties affects their packing structures and photophysical properties. In particular, the (CH₃)₂C-bridged derivative exhibits a large Stokes shift, unusual for such planarized compounds, that results from a large structural relaxation in the excited state. A series of π-extended derivatives was synthesized, among which a p-(diphenylamino)phenyl-substituted derivative shows large solvatochromism in the fluorescence spectra, while maintaining high quantum yields even in polar solvents. The Lewis acidity of the phenyldithienylborane derivatives was also assessed by titration with pyridine. The Lewis acidity of the boron center is affected not only by the difference in the steric bulk of the bridging moieties, but also by the electronic effect of the substituents introduced at remote positions relative to the boron atom. These results demonstrate the characteristic features of planarized phenyldithienylboranes as building blocks for boron-based π-electron materials.     

Rings whose singular ideals are nil

Abstract

It is well known that when a ring R satisfies ACC on right annihilators of elements, then the right singular ideal of R is nil, in this case, we say R is right nil-singular. Many classes of rings whose singular ideals are nil, but do not satisfy the ACC on right annihilators, are presented and the behavior of them is investigated with respect to various constructions, in particular skew polynomial rings and triangular matrix rings. The class of right nil-singular rings contains π-regular rings and is closed under direct sums. Examples are provided to explain and delimit our results.     

π–π Interactions Between Aromatic Groups in Amphiphilic Molecules: Directing Hierarchical Growth of Porous Zeolites

The development of hierarchical macro- or mesoporous zeolites is essential in zeolite synthesis because the size of the micropores limits mass transport and their use as industrial catalysts for bulky molecules. Although major breakthroughs have been achieved, fabricating crystallographically ordered mesoporous zeolites using a templating strategy is still an unsolved challenge. This minireview highlights our recent efforts on the self-assembly of amphiphilic molecules to obtain ordered hierarchical MFI zeolites by introducing aromatic groups into the hydrophobic tail of the amphiphilic molecules. Owing to the geometric matching between the self-assembled aromatic tails and the MFI framework, a) single-crystalline mesostructured zeolite nanosheets (SCZNs), b) SCZNs with a 90° rotational intergrowth structure, c) a hierarchical MFI zeolite with a two-dimensional square P4mm mesostructure, and d) a single-crystalline mesoporous ZSM-5 with three-dimensional pores and sheetlike mesopores layered along the a-axis were successfully synthesized.     

Highly efficient organic photosensitizer with aggregation-induced emission for imaging-guided photodynamic ablation of cancer cells

We design an organic photosensitizer with a donor-π-acceptor configuration. The photosensitizer exhibits aggregation-induced emission characteristics and efficient singlet oxygen production in the aggregated state. It is then enveloped into the water-soluble micelle to afford a nanoprobe. The water-soluble nanoprobe keeps the photosensitizer in the aggregation state and is used for imaging-guided photodynamic ablation of cancer cells.     

Recent topics on catalytic transformations of aromatic molecules via η6-arene transition metal complexes

The π-complexation of an arene to a transition metal center delivers many useful reactivities to the arene moiety. Although synthetic methodologies that take advantage of such π-coordination have mostly been developed as stoichiometric processes, there have been considerable recent advances in the catalytic transformations of aromatic molecules through their activation in the form of transition metal η⁶-arene complexes. These advances include the π-coordination catalyzed transformations of aryl-heteroatom and side-chain CH and CC bonds and the palladium-catalyzed CH functionalization in pre-formed transition metal η⁶-arene complexes. This digest paper aims to provide a concise view of these recent advances in the area of transition metal η⁶-arene complexes.     

On The Homotopy Type of

We consider the homotopy type of classifying spaces , where is a finite -group, and we study the question whether or not the mod cohomology of , as an algebra over the Steenrod algebra together with the associated Bockstein spectral sequence, determine the homotopy type of . This article is devoted to producing some families of finite 2-groups where cohomological information determines the homotopy type of .