Long-Range Order in Supramolecular π Assemblies in Discrete Multidecker Naphthalenediimides
Sudhir Kumar Keshri, Tomoya Ishizuka, Takahiko Kojima, Yoshitaka Matsushita, Masayuki Takeuchi
Abstract
We report herein the solution and solid-state studies of conformationally flexible multidecker naphthalenediimides (NDIs) in which the chromophoric NDI units intramolecularly assemble into a series of discrete π-stacks. The X-ray crystallography reveals the existence of exclusively all-syn NDIs orientations in lower congeners while all-anti in a higher congener, suggesting short- to long-range π···π interactions throughout the slipped πNDI chromophoric array. The UV/vis and fluorescence spectra evaluate the discrete π–stacks by remarkable optical changes upon cooling in solution. Furthermore, we carried out a systematic electrochemical investigation to gain an insight into redox properties of the long-range π–stacked structures. The higher congener (5NDI) shows a ten-electron reversible reduction process in a small working potential window (∼0.8 V). To our knowledge, this is an unusual observation in an organic molecular system to undergo up to ten-electron reduction. These results pave the way to design multidecker π-stacks in which structural control with specific electronic properties would be engineered.