Synthetic Metals 155 (2005) 461–463
Synthesis and photoluminescent properties of novel furopyrimidine derivatives Jung In Pyo a , Eun Jee Hwang a , Chan Seong Cheong a , Soo-Hyoung Lee b , Sang Woo Lee c , In Tae Kim c,∗∗ , So Ha Lee a,∗ a
Life Sciences Division, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Republic of Korea b Optoelectronic Materials Research Center, Korea Institute of Science and Technology, Seoul 130-650, Republic of Korea c Department of Chemistry, Kwangwoon University, 447-1 Wolgye-Dong, Nowon-Ku, Seoul 139-701, Republic of Korea Received 1 April 2005; received in revised form 1 June 2005; accepted 2 June 2005 Available online 10 November 2005
Abstract The novel furopyrimidine derivatives were synthesized and their photoluminescent properties were measured by UV–vis spectroscopy and luminescent spectroscopy. The compounds showed strong emitting properties in the range of 384 and 478 nm. © 2005 Published by Elsevier B.V. Keywords: Furopyrimidine; Photoluminescent; Organic light-emitting diode; Fluorescent dye
1. Introduction Organic light-emitting diodes (OLED) have undergone dramatic improvement since pioneering work of Tang and VanSlyke [1]. Through development of good material and device fabrication, various colors of high brightness have been developed for use in single or multicolor application [2,3]. For multicolor applications, it is necessary to have a set of red [4], green [5], and blue [6] emitting materials with excellent luminous efficiency, proper chromaticity, and the photochemical stability of emitters. Though many emitting materials have been reported, they have some problem in terms of color purity, luminous efficiency and a long-term thermal stability. Synthesis and photochromic properties of diarylethenes containing furopyrimidine bridges was published and the observed fluorescence of them was assigned to emission from –* state [7]. Many researches have not been progressed about N-substituted furopyrimidine derivatives, which showed big bathochromic shift by the substituents of amine. In this letter, we will report on synthesis and photoluminescent properties of novel furopyrimidine derivatives, which are possible to apply ∗ ∗∗
Corresponding author. Tel.: +82 2 958 6832; fax: +82 2 958 5189. Corresponding author. E-mail address:
[email protected] (S.H. Lee).
0379-6779/$ – see front matter © 2005 Published by Elsevier B.V. doi:10.1016/j.synthmet.2005.06.017
as violet to blue emitting material of OLEDs or fluorescent dye. 2. Synthesis Furoin reacts with malonitrile in the presence of diethyl amine to give 2-amino-4,5-di-(2-furanyl)-furan-3-carbonitrile (1) over 90% yield [8]. The nitrile 1 was stirred for 3 h with formic acid in the presence of acetic anhydride at 0 ◦ C and refluxed for 24 h to afford pyrimidine-4-one 2 in 72% yield. Compound 2 was thought to be made via the formylation to amino group and transformation of cyano group to amide group, followed by attack of the amino group to the carbonyl group as shown in Scheme 1 [9,10]. Furopyrimidines (4a–4j) were obtained in high yield from the reaction of the chloride compound 3 with some amines. Here, compound 3 was obtained via the reaction of pyrimidin-4-one 2 with phosphorus oxychloride under reflux. 3. Results and discussion The absorption spectra and photoluminescent spectra of the compounds (4a–4j) were monitored using dichloromethane on the concentration of 50 M by UV–vis spectroscopy and luminescent spectroscopy, respectively. The results are shown in
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Scheme 1. Synthesis of furopyrimidine derivatives (4a–4j).
Table 1 and the typical example of spectrum is shown in Fig. 1 for compounds 4b, 4h, and 4j. The melting points of all compounds were gained by differential scanning calorimetry (DSC) thermograms. Careful examination of DSC thermograms revealed that endothermic steps transitions appeared at over 126 ◦ C for all compounds and the thermal analysis (TGA) results indicated that furopyrimidines (4a–4j) showed good thermal stability over 250 ◦ C for all compounds. All furopyrimidine derivatives (4a–4j) displayed intenser photoluminescence (PL) in concentration of 50 M CH2 Cl2 solution than that of 4,4 -bis(2,2diphenyl-1-ethen-1-yl)biphenyl made from Idemitsu Kosan Ltd. Co., in comparison with intensity of luminescence emitted when irradiated with UV light. Furopyrimidine derivatives (4a–4g) with 2-furyl group on positions 5 and 6 of the furan ring of the compounds showed intense violet to blue luminescence in range of 407 and 431 nm, respectively. The photoluminescence (PL) spectrum of 4a showed the emission maximum at 411 nm Table 1 The λmax value for compounds 4b, 4h, and 4j Compound
4a 4b 4c 4d 4e 4f 4g 4h 4i 4j a b
λmax (nm)a UV
PL
334 348 334 338 333 335 338 337 334 339
411 414 410 408 415 412 407 384 400 478
mp (◦ C)
FWHMb (nm)
126 179 175 160 130 161 164 154 198 157
100 131 115 98 98 107 96 58 62 90
In CH2 Cl2 solution on 50 M concentration. The full widths at half maximum value.
Fig. 1. UV and PL spectra of compounds 4b, 4h, and 4j.
with a full width at half maximum (FWHM) of 100 nm, and that of 4b showed bathochromic shift by 20 nm with a full width at half maximum of 131 nm. Compound 4j substituted with methyl group of R3 showed at a PL maximum at 400 nm, while compound 4i substituted with hydrogen group of R3 emitted light near 478 nm, resulting in the difference of about 78 nm in the PL emission maxima. 4. Conclusion We have developed the first luminescent furopyrimidine derivatives with high thermal stability and these novel materials exhibited intense violet to blue luminescence. Future work will focus on the fine tuning of emitting properties through synthesis of more compounds, and measurement of their photophysical and electrophysical characteristics.
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Acknowledgements Financial support from Ministry of Science and Technology is gratefully acknowledged, and this work was partly supported by a research grant of Kwangwoon University (2004) and by the Information Technology Research Center (ITRC) Support Program. References [1] C.W. Tang, S.A. VanSlyke, Appl. Phys. Lett. 51 (1987) 913–915. [2] L.S. Hung, C.H. Chen, Sci. Eng. R Rep. 39 (2002) 143–222. [3] U. Mitschke, P.J. bauerle, J. Mater. Chem. 10 (2000) 1471–1507.
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