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Photophysical and Redox Properties of Dinuclear Ru(II) Complexes Prepared from the Photosensitizing Unit [Ru(bpy)<sub>2</sub>(dppz-NH<sub>2</sub>)]<sup>2+</sup> (dppz-NH<sub>2</sub>: 7-amino-dipyrido[3,2-a:2',3'-c] phenazine)
Photophysical and Redox Properties of Dinuclear Ru(II) Complexes Prepared from the Photosensitizing Unit [Ru(bpy)2(dppz-NH2)]2+ (dppz-NH2: 7-amino-dipyrido[3,2-a:2',3'-c] phenazine)
Bulletin of the Korean Chemical Society. 2014. Feb, 35(2): 663-665
Copyright © 2014, Korea Chemical Society
  • Received : November 04, 2013
  • Accepted : December 11, 2013
  • Published : February 20, 2014
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Chang-Shik Choi

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Experimental Section
Materials . Ru(bpy) 3 Cl 2 6H 2 O was supplied from Aldrich Chemical Co. and was recrystallized twice from methanol. [Ru(bpy) 2 (dppz)] 2+ was synthesized according to the reported method. 5 Other chemicals were obtained commercially and were used as received. Solvents used for the spectral measurements were the fluorometric grade supplied from Kanto Chemical Co. For column chromatography, active and neutral aluminum oxides with 70-230 mesh ASTM, or Sephadex LH-20 (Pharmacia) were used. In addition, for the preparative thin layer chromatography, the silica or aluminum oxide (Merck) was used.
Measurements . Absorption spectra were measured with a Shimadzu UV-2500 spectrophotometer at 25 °C, and emission spectra with a Shimadzu RF-5300 spectro-fluorometer at 25 °C.
Emission intensities of the sample solutions (1.00 × 10 −6 mol dm −3 , λ em = 440 nm) were normalized by their absorbance at 440 nm, and were reported relative to that of 1.00 × 10 −6 mol dm −3 Ru(bpy) 3 Cl 2 in aqueous solution (ϕ = 0.04). The time-resolved emission decay was measured by exciting the samples in acetonitrile with a nitrogen laser pulse (337 nm) filtering off as a coumarin chromophore (447 nm). The emission was then dispersed with a Hamamatsu Photonics C-28 disperser and monitored on a Hamamatsu Photonics M-25 streak camera. All samples were deoxygenated by the freeze-thaw cycle system before a life-time measurement. Cyclic voltammetry was carried out at 25 °C in acetonitrile containing 1.00 × 10 −1 mol dm −3 tetrabutylammonium perchlorate as a supporting electrolyte using a Nikko Keisoku NPG FZ-2501-A potentiogalvanostat (sweep rate 50-200 mVs −1 ). Each sample (5.00 × 10 −4 mol dm −3 ) was deoxygenated by N 2 bubbling before measurement. Average of anodic and corresponding cathodic peaks was reported as the redox potential ( vs SCE). Glassy carbon and platinum electrodes were used as working and counter electrodes, respectively, and a Ag/Ag + type RE-5 electrode (BAS Inc., 0.248 V vs SCE) as a reference electrode. Ferrocene (0.41 V vs SCE) was used for calibration, and observed potentials were reported as those vs SCE.
Syntheses . Photosensitizing unit, [Ru(bpy) 2 (dppz-NH 2 )] 2+ was prepared as reported previously. 5
[Ru2AP]4+ . To a DMA (6 mL) and dehydrated pyridine (3 mL) solution of [Ru(bpy) 2 (dppz-NH 2 )] 2+ (60 mg, 0.06 mmol), terephthaloyl chloride (5 mg, 0.02 mmol) was added and reacted by refluxing for 25 h under N 2 atmosphere: orange powder (38 mg, yield 75%), 1 H-NMR (acetone- d 6 , 500 MHz) δ 7.43 (t, J = 6.5 Hz, 4H), 7.66 (t, J = 6.5 Hz, 4H), 8.03-8.20 (22H), 8.26-8.29 (4H), 8.33-8.35 (2H), 8.51 (d, J = 5.2 Hz, 2H), 8.53 (d, J = 5.2 Hz, 2H), 8.84-8.89 (8H), 9.00 (s, 2H), 9.62-9.66 (4H), 9.98 (s, 2H); Anal. Calcd for C 84 H 68 N 18 F 24 - O 8 P 4 Ru 2 including 6 mol water: C, 45.05; H, 3.06; N, 11.26%. Found: C, 44.67; H, 2.95; N, 11.46%.
[Ru2AE]4+ . To a DMA (5 mL) and dehydrated pyridine (2 mL) solution of [Ru(bpy) 2 (dppz-NH 2 )] 2+ (65 mg, 0.07 mmol), fumaryl chloride (diluted 0.1 mL, 0.03 mmol) was added and reacted by refluxing for 25 h under N 2 atmosphere: orange powder (42 mg, yield: 67%); 1 H-NMR (acetone-d 6 , 500 MHz) δ 7.42-7.45 (4H), 7.64-7.67 (4H), 8.02-8.20 (20H), 8.26-8.29 (4H), 8.32-8.34 (2H), 8.49-8.53 (4H), 8.84- 8.89 (8H), 8.98 (s, 2H), 9.61-9.64 (4H), 9.98 (s, 2H); Anal. Calcd for C 80 H 60 N 18 F 24 O 5 P 4 Ru 2 including 3 mol water: C, 45.00; H, 2.83; N, 11.81%. Found: C, 45.17; H, 3.03; N, 11.66%.
Acknowledgements
This work was supported by Far East University.
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