Preparation and Unequivocal Identification of Chromophores-Substituted Carbosilane Dendrimers up to 7thGenerations

Abstract

Bis(phenylethynyl)dimethylsilane is branched by the hydrosilation of the phenylethynyl group with dichloromethylsilane, and then the resulting chlorosilane is reacted with lithium phenylacetylide to give the <TEX>$1^{st}$</TEX> generation. The same hydrosilation and alkynylation are repeated to obtain the <TEX>$7^{th}$</TEX> generation. In addition peripheral Si-Cl moiety of the seven kind generation dendrimers are reacted with alcoholic moiety of 9-hydroxymethylanthracene and 2-(2-hydroxyphenyl)benzoxazole group in the presence of TMEDA. Then three kinds of carbosilane dendrimers are prepared from the <TEX>$1^{st}$</TEX> to the <TEX>$7^{th}$</TEX> generations, the <TEX>$7^{th}$</TEX> generation of each dendrimer has 256 phenylethynyl, 256 9-anthracenylmethoxy, or 128 2-(2-phenoxy)benzoxazole groups. Each synthesized dendrimer is unequivocally characterized by <TEX>$^1H\;and\;^{13}C\;NMR$</TEX>, elemental analysis, MALDI-MS, GPC, and PL (photoluminescence). Characteristically PDI (Polydisperse Index) values of the dendrimers’ peak in GPC are in the range of <TEX>$1.00{\sim}1.07$</TEX>, which indicates that each generation of carbosilane is in unified distribution. PL spectra of phenylethynyl and 9- anthracenemethoxy group substituted dendrimers show no significant change with increasing the generation from the <TEX>$1^{st}$</TEX> to the <TEX>$7^{th}$</TEX>. However, the PL spectra of 2-(2-phenoxy)benzoxazole group substituted dendrimers show a blue-shift trend with increasing the generation from the <TEX>$1^{st}$</TEX> to the <TEX>$7^{th}$</TEX>.