Crystal structures and optical properties of novel fluorene–bithiophene and trithiophene-based diols

Two novel compounds, 2,5-bis(9-hydroxyfluoren-9-yl)-[2,2′] bithiophene (BHFBT) and 2,5-bis(9-hydroxyfluoren-9-yl)-[2,2′:5′,2″] trithiophene (BHFTT) consisting of thiophene rings and two fluorenyl groups have been synthesized and characterized. The crystal structures were determined by single crystal X-ray diffraction method. The compound BHFBT maintained guest-free crystal structure, but BHFTT only obtained crystal structure with inclusion of guest molecules. The two fluorenyl groups were situated at opposite sides for BHFBT while at the same side for BHFTT. Consequently, the two C–OH bonds directed to the same side to each other for BHFBT but directed to opposite sides for BHFTT. Red shift of their optical absorption and emission spectra has also been observed with the increasing number of thiophene rings.