Supramolecular assemblies based on intermolecular hydrogen bonding (H bonding) have been intensively investigated to develop functional materials. Along this line, we have developed supramolecular assemblies using protonated and saddle-distorted porphyrins as H-bonding electron acceptors to gain unique photofunctionality of the assemblies.¹ In order to expand the possibility of structures and components of the assemblies, it is required to develop a strategy to construct H-bonded supramolecular assemblies involving different components. Herein, we present selective formation of unusual H-bonded hetero-triads.

We examined formation of hydrogen-bonded supramolecular assemblies using dodecaphenylporphyrin (H­₂DPP) with various acids including carboxylic acids, sulfonic acids, and carboxylic acids with positively charged moieties. It was revealed that the stability of homo-assembly (H₄DPPX₂; X = conjugate base of an acid) can be controlled by the strength of the H bonding depending on the acidity of an acid used to protonate H₂DPP and the electrostatic repulsion between the H₄DPP²⁺ cation and the positively charged moiety of an acid used.² By employing a carboxylic acid with a pyridinium moiety, the PF₆^- salt of N-benzyl-4-carboxyphenylpyridinium (BnPy⁺-COOH•PF₆^-) to react with H₄DPPCl₂ in chloroform, we succeeded in the formation and crystal structure determination of a supramolecular hetero-triad, [H₄DPP²⁺(Cl^–)(BnPy⁺-PhCOO^–)](PF₆^–).

1. S. Fukuzumi, T. Honda, T. Kojima, Coord. Chem. Rev. 2012, 256, 2488-2502.
2. W. Suzuki, H. Kotani, T. Ishizuka, Y. Shiota, K. Yoshizawa, T. Kojima, Chem. Commun. 2017, 53, 6359.