Fluorescent Molecular Complexes of 9-Hydroxyfluoren-9-yl Substituted Thiophene and Thienothiophenes with 1,2,4,5-Tetracyanobenzene:Crystalline Complexation of Bulky and Conformationally Mobile Molecules

Abstract

Abstract Bis(9-hydroxyfluoren-9-yl)-substituted thiophene (1), thieno-[3,2-b]thiophene (2), and thieno[2,3-b]thiophene (3) were recrystallized with 1,2,4,5- tetracyanobenzene (TCNB) from CH2Cl2 to afford crystalline complexes (1)2(TCNB), (2)(TCNB)(CH2Cl2), and (3)(TCNB)(CH2Cl2), respectively. These crystals are yellow and fluorescent in the solid state. X-ray analyses of (1)2(TCNB) and (3)(TCNB)(CH2Cl2) revealed that the fluorenyl moieties and the TCNB ring are arranged in a face-to-face manner. The coloring and fluorescent properties are ascribed to a weak charge-transfer (CT) interaction, which is brought about by lattice-controlled packing rather than intrinsic CT interactions. The nature of the fluorescence is discussed on the basis of the crystal structure and the lifetime of the emission.