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Flexible and more polar receptors tend to aggregate and exhibit inferior extraction qualities. Binding constants in toluene were found to be in the range 10<jats:sup>5<\/jats:sup>\u201310<jats:sup>7<\/jats:sup><jats:sc>\u2009m<\/jats:sc><jats:sup>\u22121<\/jats:sup>, which is significantly higher than in dichloromethane. X\u2010ray analyses indicate the direct participation of a water molecule in the binding process, which may account for the surprisingly small effect of moisture in the solvent on the stability of the complexes.<\/jats:p>","DOI":"10.1002\/chem.200601231","type":"journal-article","created":{"date-parts":[[2007,2,9]],"date-time":"2007-02-09T06:21:23Z","timestamp":1171002083000},"page":"3724-3732","source":"Crossref","is-referenced-by-count":29,"title":["Extraction of Radio\u2010Labelled Xanthine Derivatives by Artificial Receptors: Deep Insight into the Association Behaviour"],"prefix":"10.1002","volume":"13","author":[{"given":"Martin","family":"Bomkamp","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carsten","family":"Siering","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Karin","family":"Landrock","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Holger","family":"Stephan","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Roland","family":"Fr\u00f6hlich","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Siegfried\u2005R.","family":"Waldvogel","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2007,4,19]]},"reference":[{"key":"e_1_2_5_1_2","doi-asserted-by":"publisher","DOI":"10.1002\/3527607439"},{"key":"e_1_2_5_2_2","volume-title":"Supramolecular Chemistry","author":"Steed J. 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Therefore the complex formation is definitely enthalpy driven. However the differences between the receptors will also have entropic contributions. These are a matter of detailed ongoing investigations and will be further discussed in due course."},{"key":"e_1_2_5_25_2","unstructured":"For the water\u2010free binding of caffeine the spiro ketals have to bend towards the triphenylene by approximately 10\u201315\u2009\u00b0."},{"key":"e_1_2_5_26_2","doi-asserted-by":"publisher","DOI":"10.1016\/S1074-5521(96)90164-7"},{"key":"e_1_2_5_26_3","doi-asserted-by":"publisher","DOI":"10.1016\/S0969-2126(00)88333-1"},{"key":"e_1_2_5_26_4","doi-asserted-by":"publisher","DOI":"10.1351\/pac198961071293"},{"key":"e_1_2_5_26_5","doi-asserted-by":"publisher","DOI":"10.1038\/340404a0"},{"key":"e_1_2_5_26_6","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.bi.65.070196.002301"},{"key":"e_1_2_5_26_7","doi-asserted-by":"publisher","DOI":"10.1039\/CS9891800347"},{"key":"e_1_2_5_26_8","doi-asserted-by":"publisher","DOI":"10.1021\/cr940413g"},{"key":"e_1_2_5_27_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00106a029"},{"key":"e_1_2_5_28_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja043037i"},{"key":"e_1_2_5_28_3","doi-asserted-by":"publisher","DOI":"10.1021\/ol0201759"},{"key":"e_1_2_5_29_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0079-6565(97)00012-5"},{"key":"e_1_2_5_30_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja0364165"},{"key":"e_1_2_5_31_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00030a040"},{"key":"e_1_2_5_32_2","unstructured":"For comparison:7\u2009d: 45.9\u2009% caffeine extraction;1\u2009b\u20131\u2009h: >98\u2009% caffeine extraction ([receptor]=0.001\u2009Min toluene; 0.0001\u2009Mcaffeine in HEPES\/NaOH buffer pH\u20057.4)."},{"key":"e_1_2_5_33_2","doi-asserted-by":"publisher","DOI":"10.1016\/0039-9140(85)80238-1"}],"container-title":["Chemistry \u2013 A European Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1002%2Fchem.200601231","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/chemistry-europe.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/chem.200601231","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T15:59:48Z","timestamp":1760284788000},"score":1,"resource":{"primary":{"URL":"https:\/\/chemistry-europe.onlinelibrary.wiley.com\/doi\/10.1002\/chem.200601231"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2007,4,19]]},"references-count":51,"journal-issue":{"issue":"13","published-print":{"date-parts":[[2007,4,27]]}},"alternative-id":["10.1002\/chem.200601231"],"URL":"https:\/\/doi.org\/10.1002\/chem.200601231","archive":["Portico"],"relation":{},"ISSN":["0947-6539","1521-3765"],"issn-type":[{"value":"0947-6539","type":"print"},{"value":"1521-3765","type":"electronic"}],"subject":[],"published":{"date-parts":[[2007,4,19]]}}}