Thiourea-based low molecular-mass organogelators from (+)-dehydroabietylamine

Abstract

Three new thiourea-based thermo-reversible, low molecular weight organogelators (LMOGs) 3-5 have been synthesized using (+)-Dehydroabietylamine (DAA, a tricyclic diterpene) employing DLS (Diterpene-Linker-spacer) strategy. (+) DAA was converted into isothiocynates through a cascade of reactions and cross-coupled with primary amines to furnish thiourea 3-5 with respective spacers. The structures of gelators 3-5 were confirmed through 1H-NMR and 13C-NMR spectroscopy, high-resolution electron spray ionization mass spectrometry (HRESI–MS, positive mode) and FTIR spectroscopy. Gelation potential of gelators 3-5 was investigated through inverted test tube method and sol–gel transition measured by ball-dropping method. The results revealed that unbranched alkyl groups furnish gelation and their gelation ability increases with increasing spacer length. Gelator 5 with dodecyl chain found to be excellent gelator that can gelate hexane (spontaneously), toluene, methanol, ethanol, petrol, and diesel. Morphology of gels was studied though scanning electron microscopy exhibiting fibrillar to lamellar structure with a thickness in the range of 9.5 nm to 5.0 μm with increasing length of spacer.