Ordered Arrangement of Charged Porphyrins in π-Electronic Ion-Pairing Assemblies

Abstract

π-Electronic ions with appropriate geometries and peripheral substituents provide assemblies through the interactions between charged building subunits, resulting in fascinating electronic properties. Structures and properties of the assemblies can be controlled by the combined negatively and positively charged species in the assemblies. Thus far, diverse π-electronic ions along with ion-responsive π-electronic systems have afforded dimension-controlled ion-pairing assemblies as crystals, supramolecular gels, and thermotropic liquid crystals.[1] Highly ordered arrangement of charged species has been found to be a key factor to exhibit the enhanced performance as fascinating electronic materials. In fact, ion pairs of porphyrin–AuIII complexes as π-electronic cations, prepared with the combination of various anions including π-electronic anions, formed dimension-controlled assemblies as thermotropic liquid crystals, whose ionic components were highly organized by i π– i π interactions (mainly electrostatic and dispersion forces).[2] Furthermore, π-electronic ion pairs comprising porphyrin-based π-electronic anions[3] have exhibited characteristic assembling modes via i π– i π interactions and resulting electronic properties such as solid-state absorption, which was correlated with the arrangement of constituent charged π-systems, and photoinduced electron transfer.[4]References[1] Recent reviews: (a) Haketa, Y. et al. Mol. Syst. Des. Eng. 2020, 5, 757; (b) Yamasumi, K. et al. Bull. Chem. Soc. Jpn. 2021, 94, 2252. [2](a) Haketa, H. et al. iScience 2019, 14, 241; (b) Tanaka, H. et al. Chem. Asian J. 2019, 14, 2129; (c) Tanaka, H. et al. Chem. Asian J. 2020, 15, 494; (d) Fumuto, N. et al. Org. Lett. 2021, 23, 3897; (e) Kuno, A. et al. Chem. Eur. J. 2021, 27, 10068. [3](a) Sasano, Y. et al. Dalton Trans. 2017, 46, 8924. (b) Sasano, Y. et al. Chem. Eur. J. 2019, 25, 6712. [4] Sasano, Y.; Tanaka, H. et al. Chem. Sci. 2021, 12, 9645.