Recent Advances in the Synthesis of Aromatic Azo Compounds

Abstract

Aromatic azo compounds have -N=N- double bonds as well as a larger π electron conjugation system, which endows aromatic azo compounds with wide applications in the fields of functional materials. The properties of aromatic azo compounds are closely related to the substituents on their aromatic rings. However, traditional synthesis methods, such as the coupling of diazo salts, have a significant limitation with respect to the structural design of aromatic azo compounds. Therefore, many scientists have devoted their efforts to developing new synthetic methods. Moreover, recent advances in the synthesis of aromatic azo compounds have led to improvements in the design and preparation of light-response materials at the molecular level. This review summarizes the important synthetic progress of aromatic azo compounds in recent years, with an emphasis on the pioneering contribution of functional nanomaterials to the field.

Recent Advances in Catalytic Nitrogen–Nitrogen Bond Formation Reactions

“…Construction of the NN bond normally results in the synthesis of aromatic azo compounds, which are widely used as organic dyes, indicators, food additives, radical reaction initiators, nonlinear optics, and therapeutic agents. Traditionally, these compounds have been prepared through reduction of nitroarenes, oxidation of anilines, diazo coupling of a diazonium salt with the corresponding active methylene compound, oxidation of hydrazines, reduction of azoxybenzenes, and coupling of primary anilines with aromatic nitroso compounds. − …”

In‐situ Oxidation and Coupling of Anilines towards Unsymmetric Azobenzenes Using Flow Chemistry

“…[9] This isomerization process not only changes the geometry of the molecule from an extended planar (E)-AB to a twisted (Z)-AB, but also modifies its physical properties, including dipole moment and polarity. [10] Various methods for the synthesis of ABs have been reported in literature over time, [11,12] making the choice of the most suitable synthetic approach dependent on the required substitution pattern. Traditionally, ABs are synthesized through azo coupling reactions, which involve the electrophilic aromatic substitution of a diazonium compounds with an electron rich aromatic system.…”

Comparative Investigation of Ultrafast Excited-State Electron Transfer in Both Polyfluorene-Graphene Carboxylate and Polyfluorene-DCB Interfaces

“…Recently, polyfluorene with azide derivatives has been covalently linked with graphene flakes, and the produced materials have been demonstrated to have low bandgaps and high charge carrier mobility, and they are potential materials for solar cells [23]. It is therefore an interesting challenge to explore the electron or energy transfers in non-covalent polyfluorene associations, which can provide a unique study of the bimolecular electron transfer reactions of polyfluorene in the solution phase [24,25]. Like in the case of the photoexcitation dynamics of small molecules, vertical excitation of the electron donor-acceptor system would also induce electron or energy transfer [21], and the rate of the photoinduced electron transfer (PET), charges separation (CS), and charge recombination (CR) can be related to the quenching mechanism [26].…”