Crown ether styryl dyes

Cyanines during the 1990s: A Review

“…The dissociation of dimer to the trans isomer leads to high regio- and stereoselective products. The styryl dyes containing 15-crown-5-ether and N -sulfobenzyl spacer on complexation with Mg 2+ in acetonitrile give dimeric product which on photolysis undergoes cis isomer formation leading to stereospecific [2+2]-autocycloaddition to give cyclobutane derivative.

…”

Design principles for optical molecular sensors and photocontrolled receptors based on crown ethers

“…It is noteworthy that 2 : 2 complexes of trans-isomers 52a ± c with Mg 2+ cations undergo, apart from photoisomerisation, stereospecific [2+2]-autophotocycloaddition (PCA). 190,191 The quantum yield of PCA was relatively low. UV irradiation of PCA products (cyclobutane derivatives) induces the back reaction, retro-PCA.…”

“…In the complex of dye trans-52d with the Mg 2+ cation, no PCA reaction occurs. 191 It was shown experimentally 185 ± 192 that 1 : 1 complexes of cis-isomers 52a ± d with Mg 2+ exist in the anion-`capped' form, i.e., these complexes have an intramolecular coordination bond between the sulfonate group of the N-substituent and the metal cation located in the crown ether cavity.…”

Photoswitchable molecular pincers: synthesis, self-assembly into sandwich complexes and ion-selective intramolecular [2+2]-photocycloaddition of an unsaturated bis-15-crown-5 ether

“…3) and for the corresponding cyclobutanes 6aؒBa 2ϩ and 6bؒBa 2ϩ were determined with the PCMODEL 3.2 program using the MMX force field according to a previously described procedure. 17 For each of the conformations, the relative heat of formation was calculated (Scheme 5) (in relation to that of [(E,E)-2b]ؒBa 2ϩ , which was taken to be zero). For both complexes, cycloaddition is to a substantial extent an endothermic process, which partially accounts for the low quantum yield of PCA and the high quantum yield of the retroPCA.…”