Naslov
Chiral bis(amino alcohol) oxalyl amide gelators-gelation properties and supramolecular organization. Racemate vs pure enantiomer gelation

Autori
Makarević, Janja ; Jokić, Milan ; Raza, Zlata ; Štefanić, Zoran ; Kojić-Prodić, Biserka ; Žinić, Mladen

Izvornik
Chemistry - A European Journal (0947-6539) 9 (2003); 5567-5580

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
gel; supramolecular chemistry; self-assembly; racemate; bilayer

Sažetak
Chiral bis(leucinol, valinol, phenylglycinol and phenylalaninol) oxalamides (1-4) have been prepared as new low molecular weight organic gelators. Their gelation properties towards various organic solvents and their mixtures were determined and compared to related bis(amino acid) oxalamide gelators. Spectroscopic (FTIR, 1H-NMR) and X-ray diffraction studies revealed formation of inversed bilayers by (S, S)-1 and rac.-1 in lipophilic solvents as the primary organization motif. X-Ray crystal structure of (S, S)-1 shows bilayer type of organization. In the crystal of rac.-2 meso-bilayers of hydrogen bonded aggregates are observed. In the bilayers formed, the gelator molecules are connected by cooperative hydrogen bonding between oxalamide units and OH groups while the interbilayer interactions are realized through lipophilic interactions between i-Bu groups of leucinol. Meso-1 lacks any gelation ability and crystallizes as monolayers. With dichloromethane rac.-1 forms unstable gel prone to crystallization due to formation of symmetrical meso-bilayers. In contrast, with aromatic solvents rac.-1 forms stable gels that indicates formation of enatiomeric bilayers. Rac.-1 is capable of gelling a 3 times larger volume of toluene then (S, S)-1. TEM investigation of rac.-1 and (S, S)-1 toluene gels reveals the presence of thinner fibers in the former gel and hence a more compact network which is capable of immobilizing a larger volume of the solvent. The self-assembly of this type of gelator molecules into bilayers and subsequent formation of fibrous aggregates can be explained by consideration of the strength and directionality of aggregation forces (supramolecular vectors) in 3D space

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA