DFT STUDY ON THE DISACCHARIDE GLYCOSIDES WITH VARYING ALKYL CHAIN LENGTHS

We performed a DFT calculation using BLY3P/6311G(d) level of theory on six glycosides, octyl-β-maltoside (βMal-C8), octyl-β-cellobioside (βCel-C8), octyl-β-glucoside (βGlc-C8), dodecyl-β-maltoside (βMal-C12), dodecyl-β-cellobioside (βCel-C12), dodecyl-β-glucoside (βGlc-C8), and on their respective sugar units (without alkyl chain) to understand their geometry and electronic properties and rationalize the molecule’s behavior in self-assembly systems. The covalent bond distances in hydroxyl groups almost constant with the increment of the hydrocarbon chain. The energetic values reveals the stability of the lipid molecules are affected by the chain and sugar lengths. Also the increment of dipole moment much influenced by the presence of alkyl chain. Meanwhile, the band gap for lipids with βMal sugar are higher than that of βCel and βGlc, indicates the βMal and its derivatives are more like hard species and lipids with βGlc as headgroup are more like soft species. The intra-molecular hydrogen bonding analysis reveals that the βMal systems have two intra-molecular hydrogen bonds. Meanwhile, the βCel has three intra-molecular hydrogen bonds occurring at HO2⋯O3 , O1⋯HO6´, and C6’H6’⋯O5. Among these the latter (regarded as unusual HB) has longer distance and its strength is weaker compared to the other two and possibly contribute to the lower clearing temperature in the liquid crystalline state.