Gelation-induced enhanced fluorescence emission from organogels of salicylanilide-containing compounds exhibiting excited-state intramolecular proton transfer: synthesis and self-assembly.
Self-assembly structure, stability, hydrogen-bonding interaction, and optical properties of a new class of low molecular weight organogelators (LMOGs) formed by salicylanilides 3 and 4 have been investigated by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV/Vis absorption and photoluminescence, as well as theoretical studies by DFT and semiempirical calculations with CI (AM1/PECI=8) methods. It was found that salicylanilides form gels in nonpolar solvents due to pi-stacking interaction complemented by the presence of both inter- and intramolecular hydrogen bonding. The supramolecular arrangement in these organogels predicted by XRD shows lamellar and hexagonal columnar structures for gelators 3 and 4, respectively. Of particular interest is the observation of significant fluorescence enhancement accompanying gelation, which was ascribed to the formation of J-aggregates and inhibition of intramolecular rotation in the gel state.
Nayak
Manoj Kumar
MK
Department of Chemistry, Texas A&M University at Qatar, PO Box 23874, Doha, Qatar.
Kim
Byung-Hwa
BH
Kwon
Ji Eon
JE
Park
Sanghyuk
S
Seo
Jangwon
J
Chung
Jong Won
JW
Park
Soo Young
SY