Self-assembly and molecular dynamics studies of an excimer emissive hexacatenar derivative in helical columnar crystalline and liquid crystalline phases

Herein, the temperature-dependent fluorescence properties of a hexacatenar liquid crystalline (LC) molecule composed of naphthalenyl and 1,2,3-triazolyl linkers are reported. This molecule exhibited a bluish emission in its crystalline and LC phases under UV-irradiation. According to the obtained photoluminescence (PL) and lifetime data, the emission originated from excimer formation of the naphthalenyl units. Morphological analyses indicated the face-to-face stacking of the naphthalenyl units in the orthorhombic crystalline (Cryortho) and helical columnar LC (Colhel) structures. This packing mode was used to rationalize the excimer emission from the PL data. As temperature increased to 100 degrees C, the PL intensity gradually decreased. Interestingly, it dropped abruptly at 100 degrees C in the LC temperature range. Dielectric relaxation spectroscopic analysis indicated that molecular reorientation allowing full rotational motion was initially activated at 100 degrees C. The sudden variation in the rotational rigidity was associated with triazolyl hydrogen-bonding, which affected the emission intensity.