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Issue 28, 2021
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Ion-pairing π-electronic systems: ordered arrangement and noncovalent interactions of negatively charged porphyrins

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Abstract

In this study, charged π-electronic species are observed to develop stacking structures based on electrostatic and dispersion forces. iπ–iπ Interaction, defined herein, functions for the stacking structures consisting of charged π-electronic species and is in contrast to conventional π–π interaction, which mainly exhibits dispersion force, for electronically neutral π-electronic species. Establishing the concept of iπ–iπ interaction requires the evaluation of interionic interactions for π-electronic ion pairs. Free base (metal-free) and diamagnetic metal complexes of 5-hydroxy-10,15,20-tris(pentafluorophenyl)porphyrin were synthesized, producing π-electronic anions upon the deprotonation of the hydroxy unit. Coexisting cations in the ion pairs with porphyrin anions were introduced as the counter species of the hydroxy anion as a base for commercially available cations and as ion-exchanged species, via Na+ in the intermediate ion pairs, for synthesized π-electronic cations. Solid-state ion-pairing assemblies were constructed for the porphyrin anions in combination with aliphatic tetrabutylammonium (TBA+) and π-electronic 4,8,12-tripropyl-4,8,12-triazatriangulenium (TATA+) cations. The ordered arrangements of charged species, with the contributions of the charge-by-charge and charge-segregated modes, were observed according to the constituent charged building units. The energy decomposition analysis (EDA) of single-crystal packing structures revealed that electrostatic and dispersion forces are important factors in stabilizing the stacking of π-electronic ions. Furthermore, crystal-state absorption spectra of the ion pairs were correlated with the assembling modes. Transient absorption spectroscopy of the single crystals revealed the occurrence of photoinduced electron transfer from the π-electronic anion in the charge-segregated mode.

Graphical abstract: Ion-pairing π-electronic systems: ordered arrangement and noncovalent interactions of negatively charged porphyrins

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Article information


Submitted
23 Apr 2021
Accepted
11 Jun 2021
First published
14 Jun 2021

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2021,12, 9645-9657
Article type
Edge Article

Ion-pairing π-electronic systems: ordered arrangement and noncovalent interactions of negatively charged porphyrins

Y. Sasano, H. Tanaka, Y. Haketa, Y. Kobayashi, Y. Ishibashi, T. Morimoto, R. Sato, Y. Shigeta, N. Yasuda, T. Asahi and H. Maeda, Chem. Sci., 2021, 12, 9645 DOI: 10.1039/D1SC02260A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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