A rapid route to carbazole containing dendrons and phosphorescent dendrimers

Abstract

A convergent strategy for the synthesis of three generations of dendrons comprised of carbazole moieties is described. The procedure to build the dendrons involves an iterative palladium catalysed amination-debenzylation sequence using N-benzyl-3,6-dibromocarbazole. The three carbazolyl focussed dendrons are then attached to a reactive fac-tris[2-phenylpyridyl]iridium(III) core by a palladium catalysed amination to give the dendrimers. The three generations of dendrons have one, three, and seven carbazole units leading to dendrimers with fac-tris[2-phenylpyridyl]iridium(III) cores and three, nine and twenty one carbazole units. The use of 9,9 0 -dialkylfluorenyl surface groups gave the dendrimers excellent solubility. The attachment of the carbazolyl-based dendrons did not change the emission colour significantly with the dendrimers emitting green phosphorescence. The dendrimers were highly luminescent with solution photoluminescence quantum yields of the order of 70%. Ground state molecular orbital calculations showed that while the ''LUMO'' was concentrated on the core iridium(III) complex the ''HOMO'' was delocalised across the core and each of the dendrons. This was reflected in the oxidation properties of the dendrimers whereby the increased carbazolyl character of the ''HOMO'' resulted in the first oxidation being moved to more positive potentials. Results and discussion SynthesisWhen developing the strategies for the preparation of dendrimers we have focussed on minimising the reaction types and steps for the formation of the different generations of

Solution‐Processible Phosphorescent Blue Dendrimers Based on Biphenyl‐Dendrons and Fac‐tris(phenyltriazolyl)iridium(III) Cores

“…[12] Scheme 1 outlines the synthetic pathways for the formation of the four new dendrimers. Different strategies [21,22] were employed for the formation of the ''monodendronized'' (one dendron per ligand) and ''doubly dendronized'' (two dendrons per ligand) iridium(III) complexes. For the monodendronized dendrimers the iridium(III) complexes were first synthesized and then three dendrons were added in the final step to give dendrimers 2 and 5.…”

Control of Charge Transport in Iridium(III) Complex‐Cored Carbazole Dendrimers by Generation and Structural Modification

“…[29] In these materials there is one dendron per ligand of the core. We refer to them as ''single dendron'' materials and their structures are shown in Figure 1(a-c).…”

Charge transport properties of carbazole dendrimers in organic field-effect transistors

“…In a previous report on dendrimers with fac-tris(2-phenylpyridyl)iridium(III) cores and the same dendrons it was found that the hole mobility (measured by time-of-flight) increased with increasing generation. 14 We were therefore motivated to determine whether the same affect would be observed in an OFET architecture where transport in the channel is dictated by the planar morphology, packing and hopping dynamics.…”