Isofluorindine: The keystone of some novel materials

Various azaacenes have previously been prepared in the hope that the ground state singlets of the molecules might be diradicals, but were instead found to be zwitterionic species. The physical properties of dioctadecylisofluorindine were extensively studied. Ferroelectric monolayers were observed to form at about 90 A2 (5 mN/m) and collapsed at 47 A 2. The monolayers were characterized by striped regions with contrasting light and dark areas. In the solid state, crystalline dioctadecylisofluorindine was observed by differential scanning calorimetry, low and high angle x-ray diffraction and solid state 2H NMR at 122°C. In the amorphous state, the sold to solid transition was observed to occur at 105°C. For each, a solid to liquid crystalline transition occurred at 167°C and a liquid crystalline to isotropic transition at 186°C. Unfortunately, we were unable to obtain a single crystal thick enough to achieve single crystal x-ray diffraction. We were further unable to obtain adequate crystals from both longer and shorter chained dialkylisofluorindines (dibutyl and didocosyl) for single crystal x-ray diffraction.;Increasing chain length of the alkyl portion of the dialkylisofluorindine was observed to lead to a decrease in onset temperature of the liquid crystalline phase, an increase in the liquid crystalline temperature range and a suppression of the isotropic temperature of an isoflourindine material. A solid to liquid crystalline phase transition was not observed for ditetradecylisofluorindine, but the material was observed to become isotropic at 200°C. Dihexadecylisofluorindine was observed to become liquid crystalline at 188°C and isotropic at 195°C. The solid state to liquid crystalline temperature was determined to occur at only 167°C for didocosylisofluorindine which became isotropic at 186°C. Incorporation of oxygen atoms into the aliphatic tails of the dialkylisofluorindine gamma to the zwitterionic azacene moiety was observed to dramatically alter the thermal properties of the material.