Boron-doped polycyclic aromatic hydrocarbons (PAHs) have emerged as a prominent class of compounds due to the unique properties that can be achieved through the incorporation of boron, often paired with another heteroatom, a combination that makes them attractive for a range of applications. The benefit of doping with these heteroatoms is also evident in 1,2-azaboroles, a subclass of B-containing compounds, consisting of five-membered unsaturated heterocycles with dative boron-nitrogen bonds. The donation of electron density from nitrogen to boron renders the molecule electronically saturated and endows it with the stability that is a prerequisite for its application in organic electronics, photovoltaics or bioimaging. The development of these compounds, first described in the 1960s, has been particularly intensive over the past two decades, driven by their photoresponsive and luminescent properties. This review aims to provide a comprehensive overview of the synthetic methodologies employed in the construction of 1,2-azaboroles. In addition to classical approaches, such as nitrogen-directed electrophilic C-H borylation or lithiation-transmetalation of pre-functionalized substrates, we discuss less commonly used methods and protocols that are limited to specific starting materials, thus demonstrating a large available repertoire of synthetic tools to access these compounds.

Despite the proliferation of multiple resonance (MR) emitters with rigid 1,4-borazine-based skeletons, the straightforward and efficient incorporation of nonhexagonal rings, especially for heptagons, to avoid notorious aggregation-induced quenching effect remains elusive. Here, a green-yellow emitter consisting of two azepines was designed and synthesized via a palladium-catalyzed one-pot twofold [5+2]-annulation reaction with high selectivity and efficiency. The tetrabenzene-fused benzo[1,2-b:5,4-b']bis(azepine) (TBBBA) core induced a highly twisted and dynamically helical rim for the novel MR-skeleton, which reduced Π-Π stacking in the solid state. Moreover, the nonalternant topology facilitated the delocalization of frontier molecular orbitals (FMO) within the twisted geometry, thus achieving red-shifted narrow emission. Our work provides a new synthetic strategy towards nonalternant extension of MR-emitters and gives insights into the electronic effects of multiple azepination on FMO distribution.

This short review demonstrates how MO-theoretical considerations can support the tailor-made design of new dye scaffolds, specifically the recently introduced BOIMPY class of fluorophores. Starting with historical and structural foundations, the influence of canonical streptocyanines on the electronic features of diarylmethenes and rhodamines is examined and the BODIPY scaffold is introduced as the primary structural inspiration for our work. The attachment of five-membered ring heterocycles at the meso position of the BODIPY core enables a relaxation into a co-planar and twofold chelating triarylmethene system. After introduction of two electron-withdrawing BF2 units, efficient rigidity is achieved since hindered rotation prevents non-radiative dissipation of energy via excited state relaxation. Hence, a lowered LUMO level allows the combination of a large red shift with high quantum efficiencies. The synthetic approach to BOIMPYs is straightforward and analogous to BODIPY syntheses starting from benzimidazole or tetrazole carbaldehydes. Cyclic voltammetric measurements prove that BOIMPYs are able to easily accept two electrons and might act as efficient photoredox catalysts.

The synthesis of circumazulene, a nonalternant isomer of circumnaphthalene, and its π-expanded derivatives poses a considerable challenge due to the lack of a suitable synthetic strategy. In this work, we present our efforts toward achieving tetrabenzo-fused circumazulene (1) through both solution and on-surface syntheses. In the case of in-solution synthesis, we obtained a product (P) with the desired target mass, but the structural verification proved to be challenging owing to the presence of various structural isomers. In the on-surface synthesis approach, a series of unexpected azulene-embedded nanographenes were obtained, including a molecule with an additional pentagonal ring (U1) based on the backbone of 1. Furthermore, theoretical calculations were conducted to shed light on these unexpected structures and to investigate their aromaticity. This work opens a new avenue for the design and synthesis of novel nonalternant graphene nanostructures incorporating circumarene.

Two-dimensional conductive metal–organic frameworks (2D c-MOFs) have attracted research attention, benefitting from their unique properties such as superior electronic conductivity, designable topologies, and well-defined catalytic/redox-active sites. These advantages enable 2D c-MOFs as promising candidates in electrochemical energy applications, including supercapacitors, batteries and electrocatalysts. This mini-review mainly highlights recent advancements of 2D c-MOFs in the utilization for electrochemical energy storage, as well as the forward-looking perspective on the future prospects of 2D c-MOFs in the field of electrochemical energy.Table of content:1 Introduction2 Design Principles of 2D c-MOFs3 Synthesis of 2D c-MOFs4 2D c-MOFs for Electrochemical Energy Storage4.1 Supercapacitors4.2 Metallic Batteries4.2.1 Lithium-Ion Batteries4.2.2 Sodium-Ion Batteries4.2.3 Zinc-Ion Batteries4.2.4 Sodium–Iodine Batteries4.2.5 Lithium–Sulfur Batteries4.2.6 Potassium-Ion Batteries5 2D c-MOFs for Electrochemical Energy Conversion6 Conclusions and Outlook

The development of new reaction chemistry is highly desirable to construct new structural and functional covalent organic frameworks (COFs). Benefiting from the extremely large database of metal-catalyzed reaction database, we herein develop a new synthetic strategy that can generate quinoline-linked COFs via a silver-catalyzed three-component one-pot reaction and achieve functionalization by the simple replacement of alcohols. This metal-catalyzed approach to the construction of robust COF structures characterized by extended π-conjugation holds the potential to pave a novel pathway in the synthesis of COF materials endowed with both heightened stability and functionality.