The effect of core delocalization on intermolecular interactions in conjugated dendrimers

Four generations of conjugated dendrimers that contain 1,3,5-tris(distyrylbenzenyl)benzene cores, stilbene dendrons, and t-butyl surface groups have been synthesized. The dendrimers were synthesized by coupling benzylphosphonate-focused dendrons with 1,3,5-tris(4-formylstilbenyl)benzene to give the dendrimers in yields in the range 60-82 %. We have probed the optoelectronic properties of the dendrimers by electrochemistry, photoluminescence, and in light-emitting device structures. we have found that the degree of aggregation is strongly generation dependent. We compared the properties of these benzene-centered dendrimers with an equivalent family of dendrimers that differs only in having a nitrogen atom as the central unit. We found that the aggregation of dendrimers was strongly dependent on the degree of delocalization across the central unit. the dendrimers with the benzene central unit, which have three localized distyrylbenzene chromophores, were found to aggregate more strongly in the solid state that those with nitrogen as the central unit. In the latter case the electroactive component is comprised of all three distyrylbenzene units and the nitrogen atom.