π-Electronic ion pairs are of interest for fabricating electronic materials that use intermolecular interactions based on electrostatic and dispersion forces, defined as i π− i π interactions, to provide dimension-controlled assemblies. Porphyrin ions, whose charge is delocalized in the core units, are suitable for ordered arrangement and assemblies by ion pairing. Herein, charged porphyrins were found to form solid-state assemblies and solution-state stacked ion pairs according to the peripheral electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). The concentration-dependent 1 H NMR signal shifts of a porphyrin ion pair, comprising a meso-EWG cation and a meso-EWG anion, provided a hetero-dimerization constant of 2.8 × 10 5 M −1 in CD 2 Cl 2 at 20 °C. In the ion pair of a meso-EWG cation and a meso-EDG anion, the electron transfer in the steady and excited states according to solvent polarity and photoexcitation, respectively, produced the radical pairs. The electron spin resonance analysis in frozen toluene revealed the formation of a heterodiradical in a closely stacked structure by the antiferromagnetic dipolar interaction and temperature-dependent spin transfer behavior.

The optical property of an ionic metal nanocluster (NC) is affected by the ionic interaction with counter ions. Here, we report that the modification of trianionic [Ag 29 (BDT) 12 (TPP) 4 ] 3− NC (BDT: 1.3-benzenedithiol; TPP: triphenylphosphine) with silver(I) complexes led to the intense photoluminescence (PL) in the near-infrared (NIR) region. The binding of silver(I) complexes to the peripheral region of Ag 29 NC is confirmed by the single-crystal X-ray diffraction (SCXRD) measurement, which is further supported by electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy. The change of excited-state dynamics by the binding of silver(I) complexes is discussed based on the results of a transient absorption study as well as temperature-dependent PL spectra and PL lifetime measurements. The modification of Ag 29 NCs with cationic silver(I) complexes is considered to give rise to a triplet excited state responsible for the intense NIR PL. These findings also afford important insights into the origin of the PL mechanism as well as the possible light-driven motion in Ag 29 -based NCs.

Dithienylnitrophenols were synthesized as precursors of π-electronic anions, which were stabilized by intramolecular chalcogen bonding, forming various ion pairs in combination with cations. The modes of solid-state charge-by-charge assemblies, along with solution-state stacking and photoinduced electron transfer behaviors, were modulated by the constituent ionic species.

Various combinations of charged porphyrins with controlled electronic states were achieved by ion‐pair metathesis based on the HSAB theory. The transient absorption spectra of the porphyrin ion pairs revealed photoinduced electron transfer from the anion to the cation through substituent‐dependent photoexcitation processes. More information can be found in the Research Article by Y. Kobayashi, H. Maeda, and co‐workers (DOI: 10.1002/chem.202203957).

Porphyrin ion pairs, the charge of which is delocalized in core units, form tightly associated structures through i π-i π interactions. 5,10,15-Triphenyl-substituted porphyrin-Au III complex, which is favorable for forming stacked structures in the form of a stable ion, has been synthesized. Ion-pair metathesis based on the hard and soft acids and bases theory enabled combination with porphyrin anions possessing electronic states controlled by electron-donating and electron-withdrawing groups. Transient absorption spectroscopy suggested that the lifetimes of the radical pairs generated by photoinduced electron transfer of the ion pairs could be controlled by a judicious combination of the anions and cations.