Synthesis, photoluminescence properties and theoretical insights on 1,3-diphenyl-5-(9-anthryl)-2-pyrazoline and -1 H -pyrazoleby Baoli Dong, Mingliang Wang, Chunxiang Xu



Chemistry (miscellaneous) / Biophysics


scence ical insights on y

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FT es ift olin es yra en to metal ions (10–12). Ma et al. reported that the introduction of anthracene and 365 nm for pyrazoline and pyrazole. 1,3-diphenyl-5Research article

Accepted: 8 June 2012 Published online in Wiley Online Librarycondensed rings into the 5-position of pyrazoline ring could increase the melting point of the compounds and be beneficial to their optoelectronic application (13). In the current study, we prepared 1,3-diphenyl-5-(9-anthryl)-2-pyrazoline (P1) with an anthracene ring in the 5-position. We oxidized this pyrazoline to 1,3-diphenyl-5-(9-anthryl)-1H-pyrazole (P2) using two very simple oxidation methods. Interestingly, the optical properties of the two compounds changed from nearly no fluorescence to bright emission in solution. Through density functional theory (DFT) calculations, we investigated the factors that led to a significant difference in the optical properties of the 1,3,5-triaryl-2-pyrazoline and its corresponding pyrazole. (9-anthryl)-2-pyrazoline and 1,3-diphenyl-5-(9-anthryl)-1H-pyrazole were synthesized according to the method shown in Fig. 1.

Synthesis of 1, 3-diphenyl-5-(9-anthryl)-2-pyrazoline

A mixture of acetophenone (10 mmol), 9-anthrylaldehyde (10 mmol) and 3mol/L aqueous sodium hydroxide (6 mL) in ethanol (30 mL) was stirred at room temperature for 3 h. The resulting solid was filtered, dried and * Correspondence to: Mingliang Wang, School of Chemistry and Chemical

Engineering, Southeast University, Nanjing 211189, PR China.

E-mail: aIntroduction 1,3,5-Triaryl-2-pyrazoline derivatives have attracted much interest due to their favorable photophysical properties including high hole-transport efficiency and excellent blue emission (1–4). They have been widely used as whitening and brightening reagents for synthetic fibers as fluorescence probes in biological research and clinical diagnosis such as novel hole-transport materials for increasing the efficiency of an organic light-emitting diode (OLED) device (5–9). In their oxidized forms, pyrazoles, are also important nitrogen-containing heterocyclic compounds and have received much attention due to their applications as ultraviolet stabilizers and analytical reagents in the complexation of transition melting point apparatus and uncorrected. Elemental analyses were performed using a CE instruments EA-1100 (CE Instruments, Ltd., Wigan,

UK). ESI-mass spectra were recorded on a Micromass Quatrro II triple quadrupole mass spectrometer (Waters Corporation, Milford, MA, USA).

Infrared spectra were obtained with a Bruker Tensor 27 FT-IR spectrometer (Bruker Optik Asia Pacific Ltd. Honk Kong, China) 1H and 13C NMR spectra were recorded at 297 K on a Bruker Avance 300 MHz NMR spectrometer (Bruker, China) using CDCl3 as solvent and TMS as internal standard.

UV–vis spectra were recorded on a Shimadzu UV-3600 spectrometer (Shimadzu Scientific Instruments, Colombia, MD, USA). Fluorescence spectra were obtained on aHoriba FluoroMax 4 spectrofluorometer (Horiba

Instruments Co. Ltd., Shanghai, China). Fluorescence quantum yields were determined using a solution of quinine sulfate in 0.05 N H2SO4 as a standard (Φf = 0.55). Excitation wavelengths were set at 350 nm forSynthesis, photolumine properties and theoret 1,3-diphenyl-5-(9-anthr and -1H-pyrazole

Baoli Dong,a Mingliang Wanga* and

ABSTRACT: 1,3-Diphenyl-5-(9-anthryl)-2-pyrazoline and 1,3-d were synthesized and characterized using 1H NMR, 13C NMR, properties were characterized by UV–vis absorption and fluor fluorescence spectra of the two compounds showed a red sh fluorescent quantum yields (Φf = 0.90 in toluene) while pyraz fluorescence divergence of the two similar compounds was inv calculations. The energetically lowest-lying state S1 in the p electron-transfer states that resulted in the fluorescence qu pyrazole corresponded to an optically allowed state that led 2012 John Wiley & Sons, Ltd.

Keywords: pyrazoline; pyrazole; fluorescence; DFTReceived: 13 March 2012, Revised: 30 May 2012, ( DOI 10.1002/bio.2404Experimental

All materials were commercially available and used without further purification. Melting points were recorded on electrothermal digital

Luminescence 2012 Copyright © 2012 Johnhunxiang Xub enyl-5-(9-anthryl)-1H-pyrazole with an anthryl chromophore -IR, mass spectrometry and elemental analysis. Their optical cence spectroscopy. It was observed that the absorption and with respect to that of anthracene. Pyrazole exhibited high e showed nearly no fluorescence in solution. The significant tigated theoretically through density functional theory (DFT) zoline exhibited both characteristics of locally excited and ching of anthryl chromophore whereas the S1 state in the high fluorescence quantum yields in solutions. Copyright ©l)-2-pyrazolineSchool of Chemistry and Chemical Engineering, Southeast University,

Nanjing 211189, PR China b State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, PR China

Wiley & Sons, Ltd. crude product was isolated and recrystallized from ethyl acetate as follows:

Yield: 80%; light yellow;mp: 238–239 C. FT-IR (KBr, cm-1): 3054, 1592, 1492, zoline and pyrazole (P1 and P2).

B. Dong et al.1391, 1326, 1119, 882, 752, 681, 669. 1H NMR (CDCl3): d / ppm, 8.55 (d, J=15.6 Hz, 2H), 8.31 (d, J=9.3 Hz, 1H), 8.04-8.14 (m, 3H), 7.70-7.82 (m, 2H), 7.44-7.76 (m,7H), 7.27 (s, 1H), 6.99 (s, 3H), 6.63-6.67 (m, 1H), 4.01-4.06 (m, 1H), 3.54-3.64 (m, 1H). 13C NMR (CDCl3): d / ppm 147.18, 132.80, 129.92, 128.81, 126.93, 125.96, 124.88, 123.25, 119.51, 113.77, 61.12, 42.47. ESI-MS: 399.17 (M+H)+. Anal. calcd. for C29H22N2: C 87.41; H 5.56; N 7.03. Found: C 87.50; H 5.62; N 6.88.

Synthesis of 1,3-diphenyl-5-(9-anthryl)-1H-pyrazole

A mixture of P1 (1 g) and activated carbon (0.1 g) in 30 mL HoAc was placed in a 100-mL three-necked flask under an oxygen atmosphere and stirred at 118C for 4 h. The reaction mixture was then filtered and the obtained clear solution was poured into ice water slowly. The crudecrystallized from ethyl acetate/acetic acid (1:1 v/v) mixed solution resulting in yellow crystals of 3-(9-anthryl)-1-phenylprop-2-en-1-one.