The photochemical isomerization of cross-linked 1,3,5-tristyrylbenzene dendrimer with hula-twist mechanism

High-Boron-Content Porphyrin-Cored Aryl Ether Dendrimers: Controlled Synthesis, Characterization, and Photophysical Properties

“…50−53 From the reaction of 3,5-dihydroxybenzylic alcohol and Br-dendron-1, a second derivative of benzylic alcohol was obtained and submitted to a second halogenation to give Br-dendron-2. 54,55 The spectroscopic data for dendrons and intermediates are in agreement with those reported in the literature. The reaction of porphyrins lb or 2b with allyl bromide, Br-dendron-1, or Br-dendron-2 in acetone in the presence of K 2 CO 3 and KI leads to the formation of dendrimers with 4 (1c), 56 the aim of obtaining high-boron-rich porphyrin-cored dendrimers, we have selected some of these dendritic structures, either free base or zinc porphyrins, to be functionalized with carboranyl derivatives via catalytic hydrosilylation reactions.…”

“…On the other hand, Fréchet dendron types, Br-dendron-1 and Br-dendron-2 , with allyl groups at the periphery were prepared by esterification of 3,5-dihydroxybenzoic acid in methanol and H 2 SO 4 , followed by coupling with allyl bromide in the presence of K 2 CO 3 , KI, and acetone. The subsequent reduction of the ester with LiAlH 4 in tetrahydrofuran gave benzylic alcohol, which was treated with SOCl 2 and pyridine to generate Br-dendron-1 . − From the reaction of 3,5-dihydroxybenzylic alcohol and Br-dendron-1 , a second derivative of benzylic alcohol was obtained and submitted to a second halogenation to give Br-dendron-2 . , The spectroscopic data for dendrons and intermediates are in agreement with those reported in the literature. The reaction of porphyrins lb or 2b with allyl bromide, Br-dendron-1 , or Br-dendron-2 in acetone in the presence of K 2 CO 3 and KI leads to the formation of dendrimers with 4 ( 1c ), 8 ( 1d and 2c ), 16 ( 1e and 2d ), and 32 ( 2e ) allyl groups at the periphery (Scheme ).…”

“…The n -BuLi solution (1.6 M in hexanes) and 1-(CH 3 )-2-[CH 2 CH 2 CH 2 Si­(CH 3 ) 2 H]-1,2- closo -C 2 B 10 H 10 were prepared according to the literature . Compounds 1a , 2a , 1b , 2b , Br-dendron-1 , − and Br-dendron-2 , , were prepared following literature processes; in some specific cases, little modification was done (see the SI). UV–vis spectroscopic data for all of these are in agreement with the data reported in the literature.…”

“…IR spectra were measured on PerkinElmer Spectrum 400 FT-IR/FT-FIR and Shimadzu FTIR-ATR-8300 spectrophotometers (units are reciprocal centimeters). 1 H NMR (300.13 and 400 MHz) and 13 54,55 were prepared following literature processes; in some specific cases, little modification was done (see the SI). UV−vis spectroscopic data for all of these are in agreement with the data reported in the literature.…”

Enhancement of the Large Stokes-Shifted Fluorescence Emission from the 2-(2‘-Hydroxyphenyl)benzoxazole Core in a Dendrimer

“…In a previous study, 12a, we have reported that the isomerization efficiency in the stilbene dendrimers in organic solvents was generation independent, probably because there are two different competing isomerization modes for stilbenes, one-bond flip (OBF) and hula-twist (HT) mechanisms. When the isomerization with the OBF mechanism is inhibited by bulky dendrons, another isomerization mechanism (HT) can be operative, resulting in similar isomerization efficiencies . Liu et al proposed that a H atom is needed on the CC double bond to induce HT isomerization .…”