A Molecular Orbital Study on the Optical Properties of Fluorescent Dyes
- PDF / 42,420 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 59 Downloads / 186 Views
A Molecular Orbital Study on the Optical Properties of Fluorescent Dyes Su-Jin Park, Dae-Yup Shin, Seung-Hoon Choi, Han-Yong Lee, Ho-Kyoon Chung and Jung-Sik Kim1, Jin-Kyu Lee1 Corporate R&D Center, Samsung SDI Co. Ltd., Suwon, Korea 1 School of Chemistry and Molecular Engineering, Seoul National University, Seoul, Korea ABSTRACT Fluorescent dyes including Nile Red (NR), fluorescein, rhodamine and 4(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) derivatives were investigated to find an application for the organic light emitting device (OLED). Relationship between the molecular structure and optical property was calculated by ab initio (HF and DFT/6-31G*) and semiempirical (AM1/PM3 and INDO/S) calculation methods for the geometry optimization and for the information of electronic transition, respectively. The absorption maximum and the oscillator strength of molecules strongly depended on the molecular dipole moment, especially for the molecules having both strong electron donor and acceptor group. Since the calculated results were comparable with several experimental results, these semiempirical molecular orbital calculation methods could be used as a powerful prediction tool for optical properties of the luminescent molecules.
INTRODUCTION Nile Red (NR), fluorescein, rhodamine and 4-(dicyanomethylene)-2-methyl-6-(pdimethylaminostyryl)-4H-pyran (DCM) are well-known fluorescent laser dyes and their luminescent characteristics have been studied for the organic light emitting device (OLED) application and the present literature abounds in experimental and theoretical approaches on optical properties of these dyes. However, systematic studies on the substituents effect of their derivatives have not been thoroughly carried out. In this work several fluorescent dyes (see Fig. 1 for structures) were selected and designed to investigate optical properties for their substituent-containing structures. The substitution patterns were chosen so as to aid the design of new and long wavelength absorbing molecules. First of all, the fluorination effect was evaluated in order to examine the influence of fluorine on these fluorescent molecules. The substitution of hydrogen atoms by fluorine atoms in organic AA7.4.1
compounds often results in profound changes in their optical properties, largely due to the highly electronegative nature and small van der Waals radius of the fluorine atom [1]. Secondly, electron push-pull effect on the fluorescent dyes was studied. Electron push and pull function in π−conjugation system of organic molecule was understood as an important key leading change of the molecular dipole moment and bathochromic shift in the luminescent property [2]. In order to evaluate the bathochromic shift induced by implementing the push-pull structure, fluorescent dyes containing strong electron withdrawing group such as dicyanomethylidene, or electron pushing group such as dialkylamine substituent, or both, were studied. For the derivatives containing dicyanomethylidene or fluorine, feasible synthes
Data Loading...
