Infinitenes as the Most Stable Form of Cycloarenes: The Interplay among π Delocalization, Strain, and π-π Stacking

Electronic Current Density Induced by Uniform Magnetic Fields in Clarenes

Some planar and non-planar clarenes have been studied using maps of magnetically induced quantum-mechanical current density and tools from differential topology to assess their magnetic response in connection with recent results by Du and Wang. Bond current strengths have been computed to estimate quantitative measures. Isosurfaces of the divergence of induced Lorentz force density have been shown to provide useful additional criteria, especially in the case of non-planar clarenes.

Crystal-Rigidifying Strategy in Hybrid Manganese Halide to Achieve Narrow Green Emission and High Structural Stability

Although organic-inorganic hybrid Mn2+ halides have advanced significantly, achieving high stability and narrow-band emission remains enormously challenging owing to the weak ionic nature and soft crystal lattice of the halide structure. To address these issues, we proposed a cationic engineering strategy of long-range cation π···π stacking and C-H···π interactions to simultaneously improve the crystal structural stability and rigidity. Herein, two organic zero-dimensional (0D) manganese halide hybrids of (BACQ)2MnX4 [BACQ = 4-(butylamino)-7-chloroquinolin-1-ium; X = Cl and Br] were synthesized. (BACQ)2MnX4 display strong green-light emissions with the narrowest full width at half-maximum (fwhm) of 39 nm, which is significantly smaller than those of commercial green phosphor β-SiAlON:Eu2+ and most of reported manganese halides. Detailed Hirshfeld surface analyses demonstrate the rigid environment around the [MnX4]2- units originating from the interactions between [BACQ]+. The rigid crystal structure weakens the electron-phonon coupling and renders narrow fwhm of these manganese halides, which is further confirmed by temperature-dependent emission spectra. Remarkably, (BACQ)2MnX4 realizes outstanding structural and luminescence stabilities in various extreme environments. Benefiting from the excellent performance, these Mn2+ halides are used to assemble light-emitting diodes with a wide color gamut of 105% of the National Television System Committee 1931 standard, showcasing the advanced applications in liquid-crystal-display backlighting.

Generalized kekulenes and clarenes as novel families of cycloarenes: structures, stability, and spectroscopic properties

Cycloarenes constitute a captivating class of polycyclic aromatic hydrocarbons with unique structures and properties, but their synthesis represents a challenging task in organic chemistry. Kekulenes and edge-extended kekulenes as classic types of cycloarenes play an important role in the comprehension of π electron distribution, but their sparse molecular diversity considerably limits their further development and application. In this work, we propose two novel classes of cycloarenes, the generalized kekulenes and the clarenes. Using density functional theory, we carry out a comprehensive study of all possible isomers of the generalized kekulenes and clarenes with different sizes. By applying a simple Hückel model, we show that π delocalization plays a crucial role in determining the relative stability of isomers. We also discover that π-π stacking is commonly present in certain larger clarenes and provides a considerable additional stabilization effect, making the corresponding isomers the lowest-energy ones. Among all considered typical looped polyarenes, generalized kekulenes and/or clarenes are revealed to be the energetically most stable forms, suggesting that these novel cycloarenes proposed here would be viable targets for future synthetic work. The simulated 1H NMR spectra and UV-vis absorption spectra provide valuable information about the electronic and optoelectronic properties for the most stable generalized kekulene and clarene species and may support their identification in future synthesis and experimental characterization.

Enumeration, Nomenclature, and Stability Rules of Carbon Nanobelts

With recent breakthroughs and advances in synthetic chemistry, carbon nanobelts (CNBs) have become an emerging hot topic in chemistry and materials science. Owing to their unique molecular structures, CNBs have intriguing properties with applications in synthetic materials, host-guest chemistry, optoelectronics, and so on. Although a considerable number of CNBs with diverse forms have been synthesized, no systematic nomenclature is available yet for this important family of macrocycles. Moreover, little is known about the detailed isomerism of CNBs, which, in fact, exhibits greater complexity than that of carbon nanotubes. The copious variety of CNB isomers, along with the underlying structure-property relationships, bears fundamental relevance to the ongoing design and synthesis of novel nanobelts. In this paper, we propose an elegant approach to systematically enumerate, classify, and name all possible isomers of CNBs. Besides the simplest, standard CNBs defined by chiral indices (n, m), the nonstandard CNBs (n, m, l) involve an additional winding index l. Based on extensive quantum chemical calculations, we present a comprehensive study of the relative isomer stability of CNBs containing up to 30 rings. A simple Hückel-based model with a high predictive power reveals that the relative stability of standard CNBs is governed by the π stabilization and the strain destabilization induced by the cylindrical carbon framework, and the former effect prevails over the latter. For nonstandard CNBs, a third stability factor, the H···H repulsion in the benzo[c]phenanthrene-like motifs, is also shown to be important and can be incorporated into the simple quantitative model. In general, lower-energy CNB isomers have a larger HOMO-LUMO gap, suggesting that their thermodynamic stability coincides with kinetic stability. The most stable CNB isomers determined can be considered the optimal targets for future synthesis. These results lay an initial foundation and provide a useful theoretical tool for further research on CNBs and related analogues.

Advancing Evidence-Based Data Interpretation in UV-Vis and Fluorescence Analysis for Nanomaterials: An Analytical Chemistry Perspective

UV-vis spectrophotometry and spectrofluorometry are indispensable tools in education, research, and industrial process controls with widespread applications in nanoscience encompassing diverse nanomaterials and fields. Nevertheless, the prevailing spectroscopic interpretations and analyses often exhibit ambiguity and errors, particularly evident in the nanoscience literature. This analytical chemistry Perspective focuses on fostering evidence-based data interpretation in experimental studies of materials' UV-vis absorption, scattering, and fluorescence properties. We begin by outlining common issues observed in UV-vis and fluorescence analysis. Subsequently, we provide a summary of recent advances in commercial UV-vis spectrophotometric and spectrofluorometric instruments, emphasizing their potential to enhance scientific rigor in UV-vis and fluorescence analysis. Furthermore, we propose potential avenues for future developments in spectroscopic instrumentation and measurement strategies, aiming to further augment the utility of optical spectroscopy in nano research for samples where optical complexity surpasses existing tools. Through a targeted focus on the critical issues related to UV-vis and fluorescence properties of nanomaterials, this Perspective can serve as a valuable resource for researchers, educators, and practitioners.