Encapsulation with the Protrusion of Cruciform 9, 10‐Bis(arylethynyl)anthracene Derivatives in a Self‐Assembled Boronic Ester Cavitand Capsule: Photochemical and Photophysical Properties. Issue 5 (25th February 2014)

• Record Type: Journal Article
• Authors: Hirumi, Yohei; Tamaki, Kento; Namikawa, Tomotaka; Kamada, Kenji; Mitsui, Masaaki; Suzuki, Kengo; Kobayashi, Kenji
• Is Part Of: Chemistry, an Asian journal. Volume 9:Issue 5(2014:May)
• Page Start: 1282
• Page End: 1290
• Publication Date: 2014-02-25
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201400042
• Languages: English
• ISSNs: 1861-4728

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The self‐assembled boronic ester cavitand capsule <bold>3</bold> quantitatively and tightly encapsulates 2, 6‐diacetoxy‐9, 10‐bis(arylethynyl)anthracene derivatives <bold>4 a</bold>–<bold>4 c</bold> as highly fluorescent cruciform guests to form complexes <bold>4 a</bold>@<bold>3</bold>, <bold>4 b</bold>@<bold>3</bold>, and <bold>4 c</bold>@(<bold>3</bold>)<sub>2</sub>. The structural features of capsule <bold>3</bold>, which possesses two polar bowl‐shaped aromatic cavity ends and four large equatorial windows connected by dynamic boronic ester bonds, made it possible to encapsulate cruciform <bold>4</bold> with protection of the reactive anthracene core inside the capsule and with two protruding arylethynyl groups, the π‐conjugated arms of compound <bold>4</bold>, through two of the equatorial windows of the capsule. Thus, complexes <bold>4 a</bold>@<bold>3</bold>, <bold>4 b</bold>@<bold>3</bold>, and <bold>4 c</bold>@(<bold>3</bold>)<sub>2</sub> show greater resistance to photochemical reactions in solution and fluorescence quenching in the powder state compared to free guests <bold>4</bold>. In addition to the improved photostability, restriction of the free rotation of the arylethynyl groups of guests <bold>4</bold> upon encapsulation results in sharpening of the UV/Vis absorption peaks with a red‐shift and a significant increase in some of the two‐photon‐absorption peaks of complexes <bold>4 a</bold>@<bold>3</bold>, <bold>4 b</bold>@<bold>3</bold>, and <bold>4 c</bold>@(<bold>3</bold>)<sub>2</sub> compared with free guests <bold>4</bold>.</p> </abstract>