Fluorenic core oligomers, displaying interesting photoluminescence properties, have been synthesized by an organometallic route. The crystal and molecular structure of a fluorene derivative and three homologous oligomers have been studied. The spiro-derivative of dibromofluorene shows a very strong interaction between the H and Br atoms. The thienyl-terminated oligomer with a spiro-substituent adopts a particular herringbone arrangement with overlap of only the end-thienyl residues, conformationally disordered. The crystal of the all-phenyl derivative consists of the packing of discrete molecules cofacially arranged. The molecule with linear alkyl chains on the 9-position of the fluorene core and thienyl rings as end-groups exhibits polymorphism and its crystal structure, tetragonal, is very peculiar because of the loose packing allowing a good separation among adjacent thienyl rings.
The absorption and emission properties of this series were investigated and the electroluminescence
of single-layer devices was characterized. The photoluminescence properties of the molecules are strongly dependent on their structural organization, displaying a red-shift of the emission from the amorphous phase, to the crystalline structure, to the aggregated form.
A comparison of the packing of these oligomers and oligothienylenes fully accounts for the optical properties of the reported molecules.
氟烯核寡聚物通过有机
金属方法合成,显示出有趣的光致发光特性。对一个
氟烯衍
生物及三种同系寡聚物的晶体和分子结构进行了研究。二
溴氟烯的螺旋衍
生物显示出氢原子与
溴原子之间非常强的相互作用。带有螺旋取代基的
噻吩末端寡聚物采用特定的鱼骨排列,仅有末端
噻吩残基重叠,且构象无序。全苯衍
生物的晶体由靠面排列的离散分子堆积而成。带有线性烷基链的
氟烯核心在9位上的分子,末端为
噻吩环,表现出多晶型,其晶体结构为四方形,非常奇特,因为其松散的堆积允许相邻的
噻吩环之间有良好的分离。
研究了这一系列的吸收和发射特性,并对单层器件的电致发光进行了表征。这些分子的光致发光特性强烈依赖于其结构组织,发射从无定相到晶体结构再到聚集形态表现出红移。
对这些寡聚物和寡
噻吩烯的堆积进行比较,充分说明了所报道分子的光学特性。