Photoluminescence Properties of Discrete Conjugated Wires Wrapped within Dendrimeric Envelopes: “Dendrimer Effects” on p-Electronic Conjugation

Conjugated molecular wires with discrete lengths are important for the exploration of physical properties related to the delocalization of p electrons, and have also attracted attention for their potential application in molecular electronics and photonics. Examples of discrete conjugated wires so far reported include derivatives of polyphenylene, polyacetylene, poly(phenylenevinylene), poly(phenyleneethynylene), polythiophene, and polyporphyrin. However, with the exception of only one example, those oligomers are limited in length to tens of nanometers, because of their low solubility and strong tendency to aggregate. From a photochemical point of view, such a strong tendency to aggregate is a major drawback of “naked” nanowires, which results in collisional deactivation of photoexcited states and hinders their potential utilities. A promising approach to solving this problem is to design “isolated” nanowires bearing “insulating” shells. However, such insulated nanowires with discrete molecular lengths are unprecedented.