Synthesis, Structure, and Photochemical Behavior of [5]Heli-viologen Isomers

Abstract

The syntheses of isomeric helical viologens that have potential applications in supramolecular chemistry and catalysis have been developed. The structures of the molecules and their solid-state packing motifs have been determined by X-ray crystallography. Computational studies demonstrate that the magnitude of their racemization barriers is primarily determined by the identity of the helical scaffold and is insensitive to the placement of the viologen functional group. The isomers are similar in their photophysical behavior but very different in their photochemical behavior.

Viologens and Their Application as Functional Materials

“…Two isomeric [5]heli‐viologens were reported (Heli‐1 and Heli‐2) by Zhang et al., exhibiting photophysical similarities, however having significantly different photochemical properties . It should also be mentioned that this viologen derivative is amongst very few viologens that exhibit chirality.…”

“…Twoi someric [ 5]heli-viologensw erer eported (Heli-1 and Heli-2) by Zhang et al,e xhibiting photophysical similarities, however having significantly different photochemical properties. [65] It shoulda lso be mentioned that this viologen derivative is amongst very few viologens that exhibit chirality.I nterestingly, when exposed to ambient light from ah alogen lamp, one of the isomers was photochemically inert, whereas the other reactedi nafew hours to produce an alkyl bridgei nt he molecule (Scheme 9). This transition was easily detectable due to its strongg reen fluorescence, and was predicted to occur due to the 6p conrotatory electrocyclic reaction, which is more stable than the same reactionoccurring with the other species.…”

“…[64][65][66][67][68][69][70] Scheme9.The conrotatary reaction of Heli-2 due to the presence of light. [65] Chem.E ur.J. 2017, 23,16924 -16940 www.chemeurj.org 2017 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim reductions, than those of the parent viologen analogue.…”

Pyridoacridines in the 21st Century

“…In the 21 st century, the ring system has been produced incidentally in studies of helical substances in the context of supramolecular chemistry and catalysis – various [5]heli‐viologen isomers were produced by quaternisations . The construction of precursors 247 for photochemical cyclisations was achieved with a Hiyama–Heck coupling of a 3‐bromoquinoline and vinyltriethoxysilane.…”

Structural flexibilityversusrigidity of the aromatic unit of DNA ligands: binding of aza- and azoniastilbene derivatives to duplex and quadruplex DNA

“…The (E)-1,2-di(quinolin-3-yl)ethane (2a) was prepared according to published procedure 15 and subsequently quaternized by reaction with methyl iodide at high pressure 10a to give the (E)-3,3′-(ethane-1,2-diyl)bis(1-methyl quinolinin-1-ium) (2c) in 70% yield (Scheme 1). The (E)-2-(2-(naphthalen-2-yl)vinyl) quinolizinium (2b) was synthesized in 62% yield by the basecatalyzed Knoevenagel-type reaction of 2-methylquinolizinium (3) 10b with 2-naphthaldehyde (4) (Scheme 1).…”