In-Situ Monitoring of Sol-Gel Transition by Temperature-dependent VCD Method: Signal Enhancement Induced by Gelation

Temperature-dependent vibrational circular dichroism (VCD) measurements were performed in situ during the sol-gel transformation of a chiral low-molecular weight gelator, N,N′-diperfluoroheptanoyl-1,2(R,R)- or -1,2(S,S)-diaminocyclohexane in CD3CN. No VCD signal was detected for an isotropic acetonitrile solution of the gelator above 45 °C, while clear peaks appeared on the onset of gelation below 45 °C. They were assigned to the C=O stretching, NH bending and stretching vibrations related to perfluoroalkyl groups. The signal enhancement induced by gelation was ascribed to the occurrence of intermolecular vibrational coupling among the gelator molecules asymmetrically arranged within a fibril.