Diaminomalenonitrile Functionalized Gelators in F-/CN- Sensing, Phase-Selective Gelation, Oil Spill Recovery and Dye Removal from Water
Diaminomalenonitrile-based gelators 1 and 2 describing the linking of diaminomalenonitrile as H-bonding site with the cholesterol unit via aromatic linker (naphthalene/benzene) have been synthesized. They form gels from various organic and aq. organic solvents. Aggregation of the gelators occurs due to function of several weak forces (e.g., hydrophobic interaction, H-bonding and π-stacking interactions) in solution. Compound 1 is a superior gelator over 2, capable of forming gels from 15 out of the 20 solvents tested. The gelators show multiple applications. Toluene and 1,2-dichlorobenzene gels of 1 and 2, respectively sense F- and CN- anions by showing gel-to-sol transformation. These ions are distinguished with the aid of Fe3+. In the designs, change in linker group (naphthalene/benzene) influences the gelation behaviors and gel properties (mgc, thermal stability, morphology and mechanical behavior etc.) of the gelators. Naphthyl analogue 1 exhibits self-healing behavior in contrast to the benzene analogue 2. Both 1 and 2 show phase-selective gelation (PSG) from biphasic mixtures of water and hydrocarbons/oils. Toluene gel of 1 serves as excellent injectable material and has been applied in environmental remediation (e.g., oil spill recovery and removal of water soluble toxic dyes).