Formation of Hydrogen-Bonded Supramolecular Hetero-Triads with a Diprotonated Porphyrin

Abstract

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