From azo compound

Compounds of the type RN = NX are named by adding diazo to the name of the parent compound followed by the designation of the atom or group X (Rule C-931.2). For historical reasons they are distinguished from azo compounds (see below) by the fact that the group X is not attached to the P-nitrogen atom by a link from a carbon atom (except for the cyanide), e.g. (E )-benzenediazohydroxide,... 

The manifestations of singlet interactions need not be subtle for example, attempts to prepare 1,3-cyclohexadiene photodimers using naphthalene as a sensitizer will give an infinitesimal yield.156 Moreover, the reported159 use of triphenylene to form triplet radical pairs from azo compounds is incorrect since only singlet radical pairs are formed.160... 

The most useful EGB s in organic synthesis are those generated from azo compounds, activated alkenes, and oxygen their application and chemistry is most conveniently discussed according to the type of probase. 

These reactions are important in synthetic organic chemistry, because they lead to highly reactive chemical species called carbenes and nitrenes. A carbene has two unpaired electrons on a carbon atom, a nitrene has two unpaired electrons on a nitrogen atom. They are formed through the elimination of N2 from azo-compounds, RN2, and from azides, RN3 (Figure 4.34b). 

The photoelimination of nitrogen from azo compounds, diazo compounds, and azides is a topic that has been thoroughly reviewed elsewhere. These transformations are found in oxygen and sulfur heterocycles, but as they are not unique to these systems, they will not be discussed in this article. Examples can be found in a review on the photochemistry of nitrogen-containing heterocycles.1... 

By far the most important and widely used metal-complex dyes are derived from azo compounds. Although they deliver a multitude of shades, only a few basic components are necessary to produce metal-complex azo dyes. The most useful starting materials are the amines 1-4, which serve as diazo components for reaction with suitable coupling components to give tridentate azo ligands. In addition, the amines 1 and 2 can be condensed with salicylaldehyde or arylazo-substituted salicylaldehydes to give tridentate azomethine ligands. 

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