Synthesis and optical properties of water-soluble NIR absorbing star polypeptides based on functional rylene dyes

In this contribution, the synthesis of two novel amino-functionalized terrylene and quaterrylene diimide derivatives is described. These chromophores have been used as initiators for the ring-opening polymerization of N€-benzyloxycarbonyl-L-lysine N-carboxyanhydride. 4-Arm star polypeptides were obtained with number average chain lengths of 50 and 100 units. Removal of the N€-benzyloxycarbonyl side-chain protective groups afforded unprecedented water-soluble terrylene and quaterrylene based star polypeptides that combined high extinction coefficients in the NIR range with very good chemical and photostability.