Novel Adamantane Asymmetrically Substituted Diketopyrrolopyrroles

The effect of the alkylation and solubilization ethyladamantyl side chains to diketopyrrolopyrroles (DPPs) on the thermal and optical properties was systematically investigated. Nucleophilic substitution of various alkyl chains into the DPP molecule is a powerful tool for increasing solubility and processability of these pigments, leading to their broader applications. Moreover, alkylation can often contribute to solid state packing and structural ordering of DPPs, depending mainly on a character of alkyl chain. In this work, we have synthesized the series containing three derivatives (N,N′-, N,O′- and O,O′-substituted) of alkylated thiophene-DPP derivatives by ethyladamantyl substituents. It was focused on precise separation of all formed DPP derivatives in order to their deeper study. It has been found that the O-substitution leads to worse thermal stability of materials, based on thermogravimetric measurements. On the other hand, ethyladamantyl side chain as rigid alicyclic substituent very effectively contributed to increase of melting point and thermal stability. The new findings provide valuable information about the previously overlooked regioisomers formed during alkylation of the DPP molecule, in particular in terms of thermal stability and optical properties in solution.