Strong Electronic Communication in Linearly Elongated Rylenes Featuring Tunable Bridges

A modified synthetic pathway towards perylene-perylene dimers and a facile purification method to obtain the regioisomerically pure syn- and anti-isomers are reported. In addition, a novel perylene-naphthalene heterodimer with 30 conjugated π-electron pairs was designed and synthesized on the basis of a previously described precursor and the resulting regioisomers were separated from each other. Thereby, the opto-electronic properties of the linearly elongated chromophores could be investigated regarding the differences in length of their aromatic system and the configuration of the isomers. Further tuning of their energy gaps was realized via protonation and methylation of the dibenzimidazole-bridging unit. Extraordinary red-shifts of the absorption maxima of 62 nm for the methylated and 92 nm for the protonated perylene-perylene anti-isomer could be achieved. Moreover, the maxima for the syn-isomer could be shifted bathochromically by 87 and 113 nm, respectively.