Complexes between 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) and cucurbit[n]uril hosts modulate the yield and fate of photolytically-generated AAPH radicals†
Angie C. Forero-Girón, Mauricio Oyarzún, Kevin Droguett, Denis Fuentealba, Soledad Gutiérrez-Oliva, Barbara Herrera, Alejandro Toro-Labbé, Eduardo Fuentes-Lemus, Michael J. Davies, Camilo López-Alarcón and Margarita E. Aliaga
{"title":"Complexes between 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) and cucurbit[n]uril hosts modulate the yield and fate of photolytically-generated AAPH radicals†","authors":"Angie C. Forero-Girón, Mauricio Oyarzún, Kevin Droguett, Denis Fuentealba, Soledad Gutiérrez-Oliva, Barbara Herrera, Alejandro Toro-Labbé, Eduardo Fuentes-Lemus, Michael J. Davies, Camilo López-Alarcón and Margarita E. Aliaga","doi":"10.1039/D4RA07150F","DOIUrl":null,"url":null,"abstract":"<p >Using theoretical and experimental tools we investigated the recognition of AAPH (2,2′-azobis(2-methylpropionamidine) dihydrochloride), a well-known water-soluble azo-compound employed as a source of peroxyl radicals, by cucurbit[6]uril (CB[6]), and cucurbit[8]uril (CB[8]). Density functional theory calculations and isothermal titration calorimetry experiments demonstrated that AAPH was not included in the cavity of CB[6], however, an exclusion complex was generated. Inclusion of AAPH in the CB[8] cavity was favored, forming stable inclusion complexes at 1 : 1 and 2 : 1 stoichiometries; AAPH@CB[8] and 2AAPH@CB[8], respectively. Radical formation upon photolytic cleavage of AAPH was examined theoretically, and by spin trapping with electron paramagnetic resonance. The radical yields detected with uncomplexed (free) AAPH and the AAPH-CB[6] (exclusion) complex were identical, whereas a marked decrease was shown for AAPH@CB[8]. Lower decreases were seen with a bimolecular (2 : 1) AAPH-CB[8] inclusion complex (2AAPH@CB[8]). This modulation was corroborated by the consumption of pyrogallol red (PGR), an oxidizable dye that does not associate with CB[6] or CB[8]. AAPH-CB[6] and 2AAPH@CB[8] did not significantly modify the initial consumption rate (Ri) of PGR, whereas AAPH@CB[8] decreased this. The oxidative consumption of free Trp, Gly–Trp and Trp–Gly by radicals derived from AAPH in the presence of CB[8] showed a dependence on the association of the targets with CB[8].</p>","PeriodicalId":102,"journal":{"name":"RSC Advances","volume":null,"pages":null},"PeriodicalIF":3.9000,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/ra/d4ra07150f?page=search","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"RSC Advances","FirstCategoryId":"92","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2024/ra/d4ra07150f","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Using theoretical and experimental tools we investigated the recognition of AAPH (2,2′-azobis(2-methylpropionamidine) dihydrochloride), a well-known water-soluble azo-compound employed as a source of peroxyl radicals, by cucurbit[6]uril (CB[6]), and cucurbit[8]uril (CB[8]). Density functional theory calculations and isothermal titration calorimetry experiments demonstrated that AAPH was not included in the cavity of CB[6], however, an exclusion complex was generated. Inclusion of AAPH in the CB[8] cavity was favored, forming stable inclusion complexes at 1 : 1 and 2 : 1 stoichiometries; AAPH@CB[8] and 2AAPH@CB[8], respectively. Radical formation upon photolytic cleavage of AAPH was examined theoretically, and by spin trapping with electron paramagnetic resonance. The radical yields detected with uncomplexed (free) AAPH and the AAPH-CB[6] (exclusion) complex were identical, whereas a marked decrease was shown for AAPH@CB[8]. Lower decreases were seen with a bimolecular (2 : 1) AAPH-CB[8] inclusion complex (2AAPH@CB[8]). This modulation was corroborated by the consumption of pyrogallol red (PGR), an oxidizable dye that does not associate with CB[6] or CB[8]. AAPH-CB[6] and 2AAPH@CB[8] did not significantly modify the initial consumption rate (Ri) of PGR, whereas AAPH@CB[8] decreased this. The oxidative consumption of free Trp, Gly–Trp and Trp–Gly by radicals derived from AAPH in the presence of CB[8] showed a dependence on the association of the targets with CB[8].
期刊介绍:
An international, peer-reviewed journal covering all of the chemical sciences, including multidisciplinary and emerging areas. RSC Advances is a gold open access journal allowing researchers free access to research articles, and offering an affordable open access publishing option for authors around the world.