Porphyrin gels reinforced by sol-gel reaction via the organogel phase

Takanori Kishida, Norifumi Fujita, Kazuki Sada, Seiji Shinkai

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

Porphyrins bearing four urea-linked dodecyl groups (3a) or four urea-linked triethoxysilylpropyl groups (3TEOS) at their peripheral positions were synthesized. 3a tends to assemble into a sheetlike two-dimensional structure due to the predominant hydrogen-bonding interaction among the urea groups and acts as a moderate gelator of organic solvents. On the other hand, its Cu(II) compelx (3a·Cu) tends to assemble into a fibrous one-dimensional structure due to the predominant porphyrin-porphyrin π-π stacking interaction and acts as an excellent gelator of many organic solvents. 3TEOS and 3TEOS·Cu, which also act as gelators, afforded similar superstructures as those of 3a and 3a·Cu, respectively, and as evidenced by SEM and TEM observations and XRD measurements, the original superstructures could be precisely immobilized by in situ sol-gel polycondensation of the triethoxysilyl groups. The TEM images of 3a gels and 3TEOS gels after sol-gel polycondensation showed a fine striped structure, the periodical distance of which was either 2 or 4 nm. X-ray crystallographic analysis of a single crystal obtained from a reference porphyrin bearing four urea-linked butyl groups revealed that there are two different porphyrin-stacked columns in the crystal and both the 2 nm distance and the 4 nm distance can appear, depending on the observation tilting angle. The hybrid gel prepared from 3TEOS·Cu by sol-gel polycondensation showed unique physicochemical properties such as a high sol-gel phase-transition temperature (> 160°C), sufficient elasticity, high mechanical strength, etc. Thus, the present study has established new concepts for molecular design of porphyrin-based gelators on the basis of cooperative and/or competitive actions of hydrogen-bonding and π-π stacking interactions and for immobilization of their superstructures leading to development of new functional organic/inorganic hybrid materials.

Original languageEnglish
Pages (from-to)9432-9439
Number of pages8
JournalLangmuir
Volume21
Issue number21
DOIs
Publication statusPublished - Oct 11 2005

All Science Journal Classification (ASJC) codes

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

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