Unusual C–I···O Halogen Bonding in Triazole Derivatives: Gelation Solvents at Two Extremes of Polarity and Formation of Superorganogels

To
investigate the influence of halogen bond (XB) on the gelation
of a one-component organogel system, a new family of 5-iodo-1H-1,2,3-triazole and 1H-1,2,3-triazole
gelators was designed and synthesized. The iodo gelators (1I, 3I) gelled various solvents at low concentrations
and formed many superorganogels, whereas the hydrogenous gelators
(1H, 3H) showed much poorer gelling performance.
An X-ray analysis of the single crystals of two reference compounds
(16I, 16H) reveals that the unusual C–I···O
XB interaction is responsible for this difference. The results of
spectroscopic examinations (XRD, SEM, 1H NMR, and UV) are
well consistent with those of single-crystal analyses. Under the guidance
of the XB interaction and the weak π–π interaction, 1I and 3I self-assemble to hexagonal columnar
aggregations in the gel state, whereas 1H and 3H, driven by CH−π interactions, feature the formation
of gels with a lamellar structure. The mechanical property of iodo
gels is much better than that of hydrogenous gels under the same concentration.
Gels from 1I respond to the stimuli of Hg2+, Cu2+, Zn2+, and Mg2+ as perchlorate
salts, and gels from 1H are selectively responsive to
Hg2+ solely.