Chiral Water-Soluble Perylenediimides

For the first time the synthesis of covalently linked very water-soluble chiral perylenediimides (PDIs) is presented. The PDIs carry the amino acids alanine or lysine as imide substituents, respectively, which are coupled to Newkome-type dendrimers acting as hydrophilic groups. The tert-butyl-protected precursors 5 as well as its water-soluble free acid compounds 6 were investigated by absorption, fluorescence and circular dichroism (CD) spectroscopy. Except for the sterically most crowded 2(nd) generation alanine compounds 5f and 6f all chiral dyes show bisignate CD effects which indicate helical aggregation. The 1(st) generation alanine compound 6b shows the greatest CD effects in buffer solution and its aggregation behaviour was also directly proven by the use of cryogenic transmission electron microscopy. Furthermore, the formation of chiral superstructures of 6b was found to be pH- and concentration-dependent. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)