Synthesis of novel diketopyrrolopyrrole-based luminophores showing crystallization-induced emission enhancement properties

A series of diketopyrrolopyrrole-based luminophores were synthesized and characterized. Their photoluminescent properties were affected significantly by the change of pi-conjugated units and alkyl groups linked to the diketopyrrolopyrrole-ring. 2,5-Dialkyl-3,6-bis(4-((10-oxoanthracen-9(10H)-ylidene)methyl) phenyl)pyrrolo[3,4-c]pyrrole-1,4-dione showed aggregate-induced emission enhancement and crystallization-induced emission enhancement properties while 3,6-bis(4-[1,3]dioxolan-2-yl-phenyl)-2,5-dialkylpyrrolo[3,4-c]pyrrole-1,4-dione, 2,5-dialkyl-3,6-bis(4-formylphenyl)pyrrolo[3,4-c]pyrrole-1,4-dione, and 2,5-dioctyl-3,6-bis{4-[2-(4-bromophenyl)-2-cyanovinyl]-phenyl}pyrrolo[3,4-c]pyrrole-1,4-dione did not exhibit these properties. The results showed that emission enhancements of the luminophores depended on the competition between the restriction of intramolecular rotation and pi-pi aggregation with the former causing emission enhancement and the latter inducing fluorescence quenching. (C) 2011 Elsevier Ltd. All rights reserved.