S5-01-01, Materials Research Laboratory, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117 543.
J Phys Chem B. 2010 Feb 11;114(5):1782-9. doi: 10.1021/jp907697f.
A series of perylenediimide-based small molecules (PDI1-PDI5) containing electron-deficient groups in the bay region were synthesized and characterized. The PDI derivatives were found to be capable of forming molecular glasses with glass transition temperatures ranging from 50 to 102 degrees C. Detailed investigations of the optical properties of the synthesized derivatives were performed and compared with those obtained from quantum chemical calculations. Optimized molecular structures of the PDI derivatives exhibited core-twisting by 16 degrees and torsional angle between the bay substituent and the perylene core in the range of 60-72 degrees. The PDI derivatives exhibited absorption maxima in the range of 2.27-2.36 eV and emission maxima in the range of 2.10-2.28 eV. The impact of the bay substituents on the emission, fluorescence quantum yield, and lifetimes in solutions and thin films was established. The red shift of emission maxima (from 2.282 to 2.095 eV) observed for various PDIs in solutions was accompanied by significant reduction in the emission quantum yield (from 0.73 to 0.44) and corresponding increase of the fluorescence lifetime (from 4.5 to 6.8 ns). This was in agreement with quantum chemical calculations indicating decrease of the radiative relaxation rate due to reduction of the oscillator strength and remarkable decrease of the torsional activation barrier. The spectral properties of the wet-casted perylenediimide films featuring different bay substituents were also studied. The variation in the emission peak (of 0.25 eV) and the considerable increase of the Stokes shift (of 0.4 eV) are explained in terms of the formation of the amorphous state. The influence of the bay substituents on the thermal and spectral properties of the films are discussed.
一系列含有缺电子基团的并五苯二酰亚胺小分子（PDI1-PDI5）被合成并进行了表征。研究发现，PDI 衍生物能够形成玻璃化转变温度在 50 至 102 摄氏度之间的分子玻璃。对合成衍生物的光学性质进行了详细研究，并与量子化学计算得到的结果进行了比较。优化后的 PDI 衍生物的分子结构表现出核心扭曲 16 度，以及桥取代基和并五苯核心之间的扭转角在 60-72 度范围内。PDI 衍生物在 2.27-2.36 eV 范围内表现出吸收最大值，在 2.10-2.28 eV 范围内表现出发射最大值。建立了桥取代基对溶液和薄膜中发射、荧光量子产率和寿命的影响。在溶液中观察到各种 PDIs 的发射最大值红移（从 2.282 到 2.095 eV），伴随着发射量子产率（从 0.73 到 0.44）的显著降低和荧光寿命（从 4.5 到 6.8 ns）的相应增加。这与量子化学计算一致，表明由于辐射弛豫率的降低和扭转活化能垒的显著降低，辐射弛豫率降低。还研究了具有不同桥取代基的湿涂并五苯二酰亚胺薄膜的光谱性质。发射峰（0.25 eV）的变化和斯托克斯位移（0.4 eV）的显著增加可以用无定形状态的形成来解释。讨论了桥取代基对薄膜的热和光谱性质的影响。
