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Encapsulation with the Protrusion of Cruciform 9,10‐Bis(arylethynyl)anthracene Derivatives in a Self‐Assembled Boronic Ester Cavitand Capsule: Photochemical and Photophysical Properties
Author(s) -
Hirumi Yohei,
Tamaki Kento,
Namikawa Tomotaka,
Kamada Kenji,
Mitsui Masaaki,
Suzuki Kengo,
Kobayashi Kenji
Publication year - 2014
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201400042
Subject(s) - cavitand , anthracene , cruciform , photochemistry , chemistry , capsule , encapsulation (networking) , organic chemistry , materials science , molecule , supramolecular chemistry , computer science , biology , botany , composite material , computer network
Abstract The self‐assembled boronic ester cavitand capsule 3 quantitatively and tightly encapsulates 2,6‐diacetoxy‐9,10‐bis(arylethynyl)anthracene derivatives 4 a – 4 c as highly fluorescent cruciform guests to form complexes 4 a @ 3 , 4 b @ 3 , and 4 c @( 3 ) 2 . The structural features of capsule 3 , 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 4 with protection of the reactive anthracene core inside the capsule and with two protruding arylethynyl groups, the π‐conjugated arms of compound 4 , through two of the equatorial windows of the capsule. Thus, complexes 4 a @ 3 , 4 b @ 3 , and 4 c @( 3 ) 2 show greater resistance to photochemical reactions in solution and fluorescence quenching in the powder state compared to free guests 4 . In addition to the improved photostability, restriction of the free rotation of the arylethynyl groups of guests 4 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 4 a @ 3 , 4 b @ 3 , and 4 c @( 3 ) 2 compared with free guests 4 .