1,4,5,8‐Tetraethynylanthracene – Synthesis, UV/Vis Absorption Spectroscopy and its Application as Building Block for Tetradentate Acceptor Molecules

Abstract

1,4,5,8‐Tetraethynylanthracene was synthesised starting from 1,4,5,8‐tetrachloroanthracene‐9,10‐dione. Different reducing agents, namely sodium borohydride, sodium dithionite and zinc, were tested to convert the anthraquinone into the corresponding tetrachloroanthracene. The latter was functionalised in a fourfold Kumada cross‐coupling reaction with (trimethylsilyl)‐ethynyl substituents, followed by cleavage of the protecting groups using potassium carbonate in methanol. UV/Vis absorption spectroscopy was performed for the highly conjugated tetraalkynyl‐substituted anthracenes. In order to demonstrate the usability of 1,4,5,8‐tetraethynylanthracene in the field of organometallic chemistry, silicon‐ and tin‐containing (acceptor‐)substituents were introduced through (hydro)metalation reactions. Most of the new compounds were characterised by X‐ray diffraction experiments.

A Rational Approach to Tetra‐Functional Photo‐Switches

“…The UV/VIS‐absorption spectra of compunds 8 , 9 , 11 and 13 (see Figures S27 and S28, SI) are highly consistent with characteristic p absorption bands located at 320–420 nm, as it is observed for 1,8‐dichloroanthracene . These four bisanthracenes were investigated in UV light induced photo‐cyclomerization experiments (Scheme ).…”

“…Due to the more extended π‐systems, the UV/VIS‐absorption spectra of 19 and 20 (see Figure S30, SI) show bathochromic shifts of about 20 nm for the p absorption bands (340–440 nm), compared to the analogous chloro‐substituted derivatives 9 and 11 . The maxima are located at 423 nm for 19 and 420 nm for 20 , which is considerably red‐shifted compared to simple 1,8‐diethynylanthracene at 405 nm . As for the tetrachlorides 9 and 11 , the products of intramolecular 9,10 : 9’,10’‐cycloaddition 19 PC and 20 PC were obtained upon UV‐light induced photo‐cyclomerization (Scheme ).…”

“…The UV/VIS-absorption spectra of compunds 8, 9, 11 and 13 (see Figures S27 and S28, SI) are highly consistent with characteristic p absorption bands located at 320-420 nm, as it is observed for 1,8-dichloroanthracene. [20] These four bisanthracenes were investigated in UV light induced photo-cyclomerization experiments (Scheme 6). Therefore, small amounts of the yellow solids were dissolved or suspended in degassed deuterated chloroform in an NMR tube and the mixtures were irradiated with UV light (365 nm) for a certain period of time.…”

“…The maxima are located at 423 nm for 19 and 420 nm for 20, which is considerably redshifted compared to simple 1,8-diethynylanthracene at 405 nm. [20] As for the tetrachlorides 9 and 11, the products of intramolecular 9,10 : 9',10'-cycloaddition 19 PC and 20 PC were obtained upon UV-light induced photo-cyclomerization (Scheme 8). In the case of propane 20, traces of an unknown 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 photo-product (probably an intermolecular formed photodimer) were observed in its 1 H NMR spectrum.…”

“…1 General procedure for the syntheses of the trimethylstannylsubstituted compounds 21 and 22: The gas elimination reactions were carried out analogous to a procedure described by Wrackmeyer and co-workers. [20] For that purpose, (dimethylamino)trimethylstannane (ca. 6 eq) was added to a solution of the corresponding tetraalkyne in dry THF.…”