high catalytic activity towards the model “click” reaction between benzylazide and
phenylacetylene, obtaining conversions of 71% in the first 3 h of reaction and in the
presence of 1 mol% catalyst.
Cholesterol-appended benzimidazole 8 (Scheme 3.2) shows selective gelation
ability with silver perchlorate in DMF-H 2 O (1:1, v/v) [9]. The gelators aggregate
via p–p stacking and hydrophobic interaction (Scheme 3.2). Silver ion-specific
gelation highlights compound 8 as an excellent visual detector of Ag
+ ions over a
series of other metal ions. The detection limit for Ag
+ was estimated to be
4.31 Â 10
−5 M in DMF-H 2 O. Silver-induced gel of 8 shows thermally activated
ionic conductivity due to the movement of Ag
+ ions within the gel network
(Scheme 3.3).
3.1.2 Metal–Organic Gelators with Chelate Ligands
8-quinolinol chelate motifs have been incorporated in metal–organic gels [10].
Shinkai and co-workers reported that a square-planar Pt(II) bis-quinolinol complex
(9, Scheme 3.4) functionalized via amide linkages with long chains formed gels in a
Fig. 3.2 Formation of Pd-containing rotaxanes and gels. Reprinted with permission from [6].
Copyright © 2013 The Chemical Society of Japan
3.1 Discrete Gelators
65