Structure vs. properties — chirality, optics and shapes — in amphiphilic porphyrin J-aggregates

Zoubir El-Hachemi; Carlos Escudero; Francisco Acosta-Reyes; M. Teresa Casas; Virginia Altoe; Shaul Aloni; Gerard Oncins; Alessandro Sorrenti; Joaquim Crusats; J. Lourdes Campos; Josep M. Ribó

doi:10.1039/C3TC30299G

Structure vs. properties — chirality, optics and shapes — in amphiphilic porphyrin J-aggregates†

Zoubir El-Hachemi,^a Carlos Escudero,‡^b Francisco Acosta-Reyes,^c M. Teresa Casas,^c Virginia Altoe,^d Shaul Aloni,^d Gerard Oncins,^e Alessandro Sorrenti,§^a Joaquim Crusats,^a J. Lourdes Campos^c and Josep M. Ribó*^a

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* Corresponding authors

^a Department of Organic Chemistry, Institute of Cosmos Science, University of Barcelona (IECC-UB), c. Martí i Franquès 1, Barcelona, Catalonia, 08028-Spain
E-mail: jmribo@ub.edu

^b Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, US

^c Department of Chemical Engineering, Polytechnic University of Catalonia (UPC), Av. Diagonal 647, Barcelona, Catalonia, 08028-Spain

^d The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, US

^e Nanometric Techniques Unit. Scientific and Technological Services (CCiTUB), University of Barcelona, c. Lluís Solé i Sabarís 1-3, Barcelona, Catalonia, 08028-Spain

Abstract

The structure of the meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS₄) J-aggregates could be determined by X-ray and electron diffraction methods. A sheet-like architecture reveals the relationship between structure and chirality, optics and shapes of the J-aggregates of the meso 4-sulfonatophenyl- and phenyl-substituted porphyrins. The structure of the J-aggregates of H₄TPPS₄ belongs to the chiral space group P2₁ and includes four porphyrin molecules in its unit cell. The intermolecular stabilization of the zwitterionic units by hydrogen bonding and electrostatic interactions between the positively charged central NH groups and the periphery anionic sulfonato groups results in a structure of porphyrins sheets along the [ [1 with combining macron] 01] plane direction. The structure of the sheet on the [01] plane is already chiral and its molecular architecture explains the simultaneous presence of H- and J-aggregate bands in their absorption spectra. This structure also accounts for the high similarity observed between the absorption spectra of different mesomorphs of the same substance and even between different members of the series of meso-4-sulfonatophenyl- and aryl-substituted diprotonated porphyrins. The possibility, or not, of the sheet-like structure on [ [1 with combining macron] 01] to interact with other layers, either through ionic or hydrophobic interactions, depends on the substitution pattern at the meso-positions of the porphyrin ring. Thus, the different morphologies of the particles [mono- bi- and multilayered] of this series of J-aggregates are explained taking into account the role that the fourth meso-substituent plays in the interlayer stabilization. The results suggest that supramolecular helicity, previously detected in several J-aggregates, is not the explanation of their chirality but would be the expression of the intrinsic chirality of the packing between building blocks.

Journal of Materials Chemistry C

Structure vs. properties — chirality, optics and shapes — in amphiphilic porphyrin J-aggregates†

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Structure vs. properties — chirality, optics and shapes — in amphiphilic porphyrin J-aggregates

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