Porphyrin-based organogels

Control of the aggregation mode by a pyridine-carboxylic acid interaction

Satoshi Tanaka, Michihiro Shirakawa, Kenji Kaneko, Masayuki Takeuchi, Seiji Shinkai

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

To find a new strategy for designing porphyrin-based organogelators, hydrogen-bond-donating (carboxylic acid)/accepting (pyridine) substituants or electron-donating (dialkylamino)/withdrawing (pyridine) substituents were introduced into peripheral positions of a porphyrin (1cp or 1ep, respectively), and the gelation properties were compared with those of symmetrical reference compounds bearing two pyridyl substituents or two ester groups (1pp or 1ee, respectively). It was found that the symmetrical molecules show a solubility that is quite inferior to that of 1cp and 1ep having a dipole moment and precipitate from most organic solvents. 1cp, 1ep, and 1ee formed gels with cyclohexane, methylcyclohexane, and several alcoholic solvents, but scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that their superstructures constructed in the organogels are very different. In cyclohexane, 1cp resulted in a sheetlike structure, whereas 1ep and 1ee resulted in a fiberlike structure. The difference is attributed to the two-dimensional interactive forces in 1cp consisting of the porphyrin-porphyrin π-π stacking and the carboxylic acid-pyridine hydrogen bonding. In fact, when the hydrogen-bonding interaction was weakened by alcoholic solvents or by adding pyridine or N,N-(dimethylamino)-pyridine, the sheetlike structure was transfigured to the fiberlike structure. Further detailed analyses of their aggregation modes were conducted by spectroscopic methods such as ultraviolet-visible (UV-vis) absorption, Fourier transform infrared (FT-IR), and X-ray diffraction (XRD). On the basis of these findings, the influence of these peripheral substituents on the gel formation and the aggregation mode was discussed.

Original languageEnglish
Pages (from-to)2163-2172
Number of pages10
JournalLangmuir
Volume21
Issue number6
DOIs
Publication statusPublished - Mar 15 2005

Fingerprint

Porphyrins
Carboxylic Acids
Carboxylic acids
carboxylic acids
porphyrins
Pyridine
pyridines
Agglomeration
Hydrogen bonds
Cyclohexane
cyclohexane
interactions
Bearings (structural)
Gels
gels
Dipole moment
gelation
hydrogen
Gelation
Organic solvents

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Porphyrin-based organogels : Control of the aggregation mode by a pyridine-carboxylic acid interaction. / Tanaka, Satoshi; Shirakawa, Michihiro; Kaneko, Kenji; Takeuchi, Masayuki; Shinkai, Seiji.

In: Langmuir, Vol. 21, No. 6, 15.03.2005, p. 2163-2172.

Research output: Contribution to journalArticle

Tanaka, Satoshi ; Shirakawa, Michihiro ; Kaneko, Kenji ; Takeuchi, Masayuki ; Shinkai, Seiji. / Porphyrin-based organogels : Control of the aggregation mode by a pyridine-carboxylic acid interaction. In: Langmuir. 2005 ; Vol. 21, No. 6. pp. 2163-2172.
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