2,1,3‐Benzothiadiazole (BTD) is one of the most important nuclei used in the chemistry of photoluminescent compounds and applicable for light technology. The understanding of its properties and reactions is fundamental for the design and application of these derivatives in molecular organic electronic devices and for other technologies. As a result of their potential as constituents of organic light‐emitting diodes, solar cells, liquid crystals, dyes, photovoltaic cells, and many others, attention has been focused on BTD π‐extended derivatives with potential use in this exciting area. Herein, we describe their syntheses, properties, reactions, and selected examples of applications in light technology using by BTD (small molecules) as the core.

This Account describes the origins, features, importance, and trends of the use of fluorescent small-molecule 2,1,3-benzothiadiazole (BTD) derivatives as a new class of bioprobes applied to bioimaging analyses of several (live and fixed) cell types. BTDs have been successfully used as probes for a plethora of biological analyses for only a few years, and the impressive responses obtained by using this important class of heterocycle are fostering the development of new fluorescent BTDs and expanding the biological applications of such derivatives. The first use of a fluorescent small-molecule BTD derivative as a selective cellular probe dates back to 2010, and since then impressive advances have been described by us and others. The well-known limitations of classical scaffolds urged the development of new classes of bioprobes. Although great developments have been achieved by using classical scaffolds such as coumarins, BODIPYs, fluoresceins, rhodamines, cyanines, and phenoxazines, there is still much to be done, and BTDs aim to succeed where these dyes have shown their limitations. Important organelles and cell components such as nuclear DNA, mitochondria, lipid droplets, and others have already been successfully labeled by fluorescent small-molecule BTD derivatives. New technological systems that use BTDs as the fluorophores for bioimaging experiments have been described in recent scientific literature. The successful application of BTDs as selective bioprobes has led some groups to explore their potential for use in studying membrane pores or tumor cells under hypoxic conditions. Finally, BTDs have also been used as fluorescent tags to investigate the action mechanism of some antitumor compounds. The attractive photophysical data typically observed for π-extended BTD derivatives is fostering interest in the use of this new class of bioprobes. Large Stokes shifts, large molar extinction coefficients, high quantum yields, high stability when stored in solution or as pure solids, no fading even after long periods of irradiation, bright emissions with no blinking, good signal-to-noise ratios, efficiency to transpose the cell membrane, and irradiation preferentially in the visible-light region are just some features noted by using BTDs. As the pioneering group in the use of fluorescent small-molecule BTDs for bioimaging purposes, we feel pleased to share our experience, results, advances, and personal perspectives with the readers of this Account. The readers will clearly note the huge advantages of using fluorescent BTDs over classical scaffolds, and hopefully they will be inspired and motivated to further BTD technology in the fields of molecular and cellular biology.

The current manuscript describes the importance, mechanism propositions, evidence and controversies associated with multicomponent reactions (MCRs). The following multicomponent reactions are presented and critically evaluated: The Biginelli, Hantzsch, Mannich, Passerini and Ugi reactions. The aim of this review is to highlight what we already know about the mechanisms associated with these MCRs and the evidence supporting the proposed reaction pathways. Controversies and prospects are also discussed herein.

Photoluminescent lanthanide-organic frameworks (Ln-MOFs) were printed onto plastic and paper foils with a conventional inkjet printer. Ln-MOF inks were used to reproduce color images that can only be observed under UV light irradiation. This approach opens a new window for exploring Ln-MOF materials in technological applications, such as optical devices (e.g., lab-on-a-chip), as proof of authenticity for official documents.

In the present overview, we describe the bases of intercalation of small molecules (cationic and polar neutral compounds) in DNA. We briefly describe the importance of DNA structure and principles of intercalation. Selected syntheses, possibilities and applications are shown to exemplify the importance, drawbacks and challenges in this pertinent, new, and exciting research area. Additionally, some clinical applications (molecular processes, cancer therapy and others) and trends are described.

The synthesis of a new series of photoluminescent compounds, namely 5,8-diaryl quinoxaline derivatives (aryl = phenyl, 4-fluorophenyl, 4-methoxyphenyl, and 4-cyanophenyl), was achieved by a direct Suzuki cross-coupling reaction with the employment of a NCP-pincer palladacycle. The electrochemical and photophysical properties of these compounds were also investigated. Four new 4,8-diaryl-2,1,3-benzothiadiazoles were also synthesized in order to enable a comparison between the two types of nitrogen-containing π-extended heterocycles. The substitution of a hydrogen atom at the 4-position of the aryl that is groups attached to the quinoxaline or benzothiadiazole base by either elec-

The mechanism of the Ugi four-component reaction has been investigated by electrospray ionization (tandem) mass spectrometry using charge-tagged reagents (a carboxylic acid or an amine) to favour detection. Key intermediates were transferred directly via ESI(+) from the reaction solution to the gas phase and characterized by MS measurements and MS/MS collision induced dissociation. The Mumm rearrangement (final step) was also investigated by both travelling wave ion mobility mass spectrometry and DFT calculations. The data seem to consolidate the amazingly selective mechanism of this intricate four-component reaction.

The present manuscript describes the importance of small mitochondrion-specific fluorescent markers to study mitochondrial dynamics and related processes. The importance of mitochondria, their dynamic cellular processes, the use of fluorescent selective probes, limitations of selected commercially available fluorescent systems and recent developments on the synthesis and applications of small fluorescent probes and trends are discussed.