2‐(4′‐Pyridyl‐N‐oxide)‐Substituted Hemithioindigos as Photoresponsive Guests for a Super Aryl‐Extended Calix[4]pyrrole Receptor. Issue 12 (23rd May 2018)

• Record Type: Journal Article
• Authors: Moncelsi, Giulia; Escobar, Luis; Dube, Henry; Ballester, Pablo
• Is Part Of: Chemistry, an Asian journal. Volume 13:Issue 12(2018)
• Page Start: 1632
• Page End: 1639
• Publication Date: 2018-05-23
• Subjects: calixarenes -- hemithioindigos -- molecular recognition -- photoisomerization -- supramolecular chemistry; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201800463
• Languages: English
• ISSNs: 1861-4728

Abstract

Abstract: We report the synthesis of two 2‐(4′‐pyridyl‐ N ‐oxide)‐substituted hemithioindigos (HTIs). We probed their photoisomerization by using UV/Vis and 1 H NMR spectroscopy techniques. Light irradiation at λ =450 nm provoked the isomerization of the HTI Z isomer to the E counterpart to a large extent (≈80 % at the photostationary state). 1 H NMR titration experiments revealed the formation of thermodynamically and kinetically stable 1:1 inclusion complexes of the ( Z )‐HTI isomers with a super aryl‐extended host (association constant>10 4 m −1 ). Photoirradiation at λ =450 nm of the inclusion complexes induced the isomerization of the bound HTI N ‐oxide to afford the ( E )‐HTI⊂calix[4]pyrrole complex. We determined accurate association constant values for the 1:1 inclusion complexes of the ( Z )‐ and ( E )‐HTI isomers by using isothermal titration calorimetry experiments. The results showed that the stability constants of the ( E )‐HTI complexes were 2.2–2.8‐fold lower than those of the ( Z )‐HTI counterparts, which explains the lack of light‐induced release of the former to the bulk solution. Abstract : Include me in : Two 2‐(4′‐pyridyl‐ N ‐oxide)‐substituted hemithioindigos (HTIs) are investigated as photoresponsive guests to modulate the binding stability of their inclusion complexes with a super aryl‐extended calix[4]pyrrole. Moderate changes in the stability constant values of the deep‐inclusion complexes produced with the Z and E isomers are assessed by using isothermal titration calorimetry experiments.