芘及其衍生物電子性質之理論探討

Theoretical Studies on Electronic Properties of Pyrene and Its Derivatives

王伯昌(Bo-Cheng Wang) ； 張金泉(Jian-Chuang Chang) ； 左希軍(Hsi-Chun Tso) ； 程長遠(Chang-Yuan Cheng)

《化學》 59卷4期 (2001/12) Pp. 545-556

https://doi.org/10.6623/chem.2001064

摘要

藉由ab initio (HF、DFT and MP2)及semiempirical method (AM1、PM3 and ZINDO)對芘(pyrene)中心發色團的分子結構、HOMO、LUMO、分子軌域能階及UV電子光譜(electronic spectrum)進行詳細之研究，得到AMI搭配ZINDO的理論計算結果與實驗數據相當近似，進而以AMI和ZINDO方法對芘的1、2和4單取代衍生物進行取代基及取代位置探討時，若取代甚為拉電子則LUMO呈現下降趨勢，推電子時則HOMO呈現上升趨勢，惟兩者皆具有降HOMO-LUMO能隙之功能；對電子光譜方面而言，取代基在1和4位置時，其π→π*，呈現較大的紅位移，而芘發色團上同時加入推、拉電子基時，則其π→π*電子光譜將產生更大的紅位移。惟取代基過大將造成平面結構扭曲而減小軌域重疊度，致使電子不易由基態(ground state)躍遷至激發態(excited state)，而產生少許藍位移。綜上所得，本研究再以AMI和ZINDO方法對文獻上數個藍光的芘衍生物進行計算比對，得到理論計算結果與其實驗值相當吻合，預期本理論計算研究程序將可成功探討分子材料之電子性質，並將之應用到目前相當熱門的OLED材料上。

關鍵字

芘 ； 電子光譜 ； HOMO ； LUMO ； OLED

並列摘要

Using ab initio (HF, DFT and MP2) and semiempirical methods (AM1, PM3 and ZINDO), the chromophore of pyrene molecule was studied in details. For its molecular structure, HOMO, LUMO, molecular orbital energies and UV electronic spectra, theoretical calculations using AMI in conjunction with ZINDO showed results consistent with experimental data. Further investigation on 1-, 2- and 4- monosubstituted derivatives of pyrene with the effect of the position of substitution and substituents showed: (1) the substituent is a electron-withdrawing group and the LUMO has a tendency to decrease; (2) the substituent is a electron-releasing group and the HOMO has a tendency to increase. However, both substituents are the effective in reducing the energy gap between HOMO and LUMO. In terms of electronic spectra, the transition π→π* shows a larger red-shift if the substitutions on the 芘 ring are in 1- and 4-. The red-shift is even larger if the substituents contain both electron-releasing and electron-withdrawing groups. Nevertheless, the substituents are large, a slight blue-shift would occur, because they should distort the planar structure of parent pyrene molecule, decrease the overlap of πorbitals, and hinder the electron transition from π→π*. According to the above conclusion, semiempirical AM1 and ZINDO methods generated several blue pyrene derivatives in this work, and agree very well with the experimental measurements. Presumably, the procedures of theoretical calculation employed in this study can be successfully applied to investigation on the electronic properties of other molecular materials, and further, to the design of novel materials for OLED.

並列關鍵字

pyrene ； electronic spectroscopy ； HOMO ； LUMU ； OLED