Zhang, Yan published the artcileThe photochromic behaviour of two viologen salts modulated by the distances between the halide anions and the cationic N atoms of viologen, COA of Formula: C8H6ClN, the publication is Acta Crystallographica, Section C: Structural Chemistry (2019), 75(12), 1628-1634, database is CAplus and MEDLINE.
In recent years, viologens and their derivatives have received much attention due to their various potential applications, ranging from electro- or photochromic devices to clean energy. Generally, viologen compounds exhibit a color change upon being subjected to an external stimulus. However, the chromic mechanism is still ambiguous, because there are many electron-transfer pathways for a chromic compound that need to be considered. Thus, exploring new chromic viologen-based compounds with one pathway should be important and meaningful. In this article, two new viologen-based derivatives, namely 1-(2-cyanobenzyl)-4,4′-bipyridinium chloride (o-CBbpy·Cl), C18H14N3+·Cl– (1), and 1-(2-cyanobenzyl)-4,4′-bipyridinium bromide (o-CBbpy·Br), C18H14N3+·Br– (2), have been synthesized and characterized. Interestingly, both isomorphic compounds possess only one electron-transfer pathway, in which 1-(2-cyanobenzyl)-4,4′-bipyridinium cations (o-CBbpy) and halide anions are employed as electron donors and acceptors, resp. Salts 1 and 2 consist of o-CBbpy cations involved in p-p interactions and hydrogen-bond interactions, and halide anions weakly hydrogen bonded to the viologen cations. The salts show different photoresponsive characteristics under identical conditions, which should be mainly related to the distances between the halide cations and the cationic N atoms of o-CBbpy but not the electronegativities of the halogen atoms. These results should not only help in understanding that the distance of the electron-transfer pathway plays an important role in viologen-based photochromism, but should also guide the design and synthesis of addnl. photochromic materials.
Acta Crystallographica, Section C: Structural Chemistry published new progress about 612-13-5. 612-13-5 belongs to nitriles-buliding-blocks, auxiliary class Organic Pigment, name is 2-(Chloromethyl)benzonitrile, and the molecular formula is C18H28B2O4, COA of Formula: C8H6ClN.
Referemce:
https://en.wikipedia.org/wiki/Nitrile,
Nitriles – Chemistry LibreTexts