An odd–even relationship which appears in the aggregation modes of ‘gemini’-type cholesterol-based gelators and their transcription into silica gel

Abstract

Four ‘gemini’-type cholesterol-based gelators 1_nnn were synthesized. They acted as versatile gelators of organic fluids. The xerogels showed a lamellar structure for 1₂22 and 1₄44 and a fiber structure for 1₃3 and 1₅5 according to whether the number of methylene units between the two nitrogens was even or odd. The difference in these organogel supramolecular structures has successfully been transcribed into silica structures by sol–gel polymerization of tetraethoxysilane (TEOS) in the gel phase. These results indicate that the novel silica structures can be created by transcription of various superstructures in organogels as a template through hydrogen-bonding interaction. Nitrogen adsorption–desorption isotherms were measured by a BET method. The silica obtained from 1₂22 and 1₃3 had a BET surface area of 698 and 525 m² g⁻¹, respectively. To deposit metals inside the silica structure, sol–gel polymerization was carried out in the presence of metal salts. The metal ions bound to the diamine moiety were thereby deposited inside the silica wall. It is certain that metal-deposited silica will be applicable as catalysts to various reactions, which require a size recognition ability.