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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 29, Number 4
BKCSDE 29(4)
April 20, 2008 

 
Title
Photoresponsive Arylether Dendrimers with Azobenzene Core and Terminal Vinyl Groups
Author
Ji-hye Lee, Daeock Choi*, Ji Eun Park, Eun Ju Shin*
Keywords
Azobenzene, Arylether dendrimer, Isomerization, Absorption spectrum
Abstract
Photoresponsive arylether dendrimers Bis-azo-Gn(3,5) 1a-1c and Bis-azo-Gn(3,4,5) 2a-2c (n = 1-3) with an azobenzene unit at the core and several vinyl groups (3,5-bis(but-3-enyloxy)phenyl groups or 3,4,5-tris(but-3- enyloxy)phenyl groups) at the periphery have been prepared. Their structures and reversible trans-cis isomerization behaviors have been investigated by 1H-NMR, 13C-NMR, MALDI-TOF-Mass, and UV-vis spectra. All six azobenzene-cored dendrimers carried out very fast transcis photoisomerization on irradiation of 350 nm light and reached to the photostationary state within 180 s. During the dark incubation, slow thermal back reversion from cis to trans form is observed for all six dendrimers and is completed within 3 days for 1a-1c and 1 day for 2a-2c. Isomerization efficiency decreases with increasing generation. However, the initial reaction rates of both transcis photochemical isomerization and cistrans thermal isomerization increases significantly with increasing generation for dendrimers for 1a-1c but only slightly for 2a-2c.
Page
761 - 766
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