Tuning the Au–Au interactions by varying the degree of polymerisation in linear polymeric Au(i) N-heterocyclic carbene complexes

Abstract

Gold(I) N-heterocyclic carbene (Au(I) NHC) polymers were successfully synthesised with alkyl and alkoxy spacers, wherein polymers with different degrees of polymerisation were isolated for the first time by varying the reaction time. The structure–property relationships of the newly synthesised luminescent Au(I) NHC polymeric complexes were examined from the viewpoint of material applications. In particular, we investigated the effect of controlling the Au–Au interactions by varying the degree of polymerisation and introducing spacers into the complexes. An emission study of the polymers suggested that increasing the degree of polymerisation decreases the number of Au–Au interactions. The structures of the molecular aggregates were affected by the degree of polymerisation as well as the spacer between the two carbenes, and all complexes exhibited a high thermal stability (>300 °C). Moreover, we found that the polymer bearing an alkoxy spacer and with a low degree of polymerisation exhibited white room-temperature phosphorescence, thereby indicating that the luminescence behaviour depends mainly on the molecular aggregate structure. These results suggest that various material properties, such as the luminescence colour and thermal stability, can be controlled independently by tuning the structures of molecules and molecular aggregates using alkyl/alkoxy spacers with different degrees of polymerisation.