Chiral Bis(tyrosinol) and Bis(p-hydroxyphenylglycinol) Oxalamide Gelators. Influence of Aromatic Groups and Hydrogen Bonding on Gelation Properties

Enantiomerically pure R,R-bis(4-hydroxyphenylglycinol) oxalamides 3 and S,S-bis(tyrosinol) oxalamides 4 were prepared and tested for their gelling properties toward organic solvents, water and aqueous mixtures with polar organic solvents. It was found that oxalamide compounds with aryl substituted phenolic hydroxy groups are efficient organogelators of highly polar solvent systems while the derivatives with free phenolic hydroxy groups tend to crystallize. The revealed different behaviour is explained on the basis of specific hydrogen bonding motifs found in the crystal structures.