Experiment on Photocromism and Piezochromism
Experiment B10- Photocromism and Piezochromism
Reece Harms 4320288
Introduction
This experiment investigates an oxidative coupling reaction in an to synthesise triphenylimidazole dimer from 2,4,5-triphenyl-1H-imidazole. The resulting compound was investigated for both photochromic and piezochromic properties by way of formation of a stable radical, utilizing visual observations and UV-Vis as a means of distinction. Both the oxidative coupling reaction and the dimers interaction with light are depicted in the reactions in figure 1.
Figure 1: Oxidative Coupling reaction of 2,4,5-triphenyl-1H-imidazol
Experimental
Ethanol (100ml), potassium hydroxide (8.065g, 2.568mmol) and water (5ml) were added in order to 2,4,5-triphenyl-1H-imidazol (0.9402g, 3.17mmol). The mixture was stirred until clear before it was cooled to 5 ºC. A solution of potassium ferricyanide (3.0021 g, 9.085mmol), water (250ml) and ethanol (100ml) was prepared and added dropwise into the mixture ensuring the temperature did not rise above 10 ºC. A grey precipitate was isolated from the yellow mixture through vacuum filtration and washed with water (50ml x 5) and 50% aqueous ethanol. The mixture was dried under vaccuum suction and the melting point was determined. Yield: 0.85g, 90.8% m.p-199.8-200.3ºC. A portion of the dimer (0.0305 g, 0.0514mmol) was quantitatively dissolved in 25ml of toluene. The solution was left for 60min until colorless. The UV-Vis spectra was recorded for the colorless sample. The solution was irradiated using a lamp resulting in a purple solution and the UV-Vis spectrum was retaken. UV (): 524.92nm ε colourless (45.2M-1cm-1) coloured (760M-1cm-1) 1H NMR (300MHz, CDCl3) δ 7.26 (30H, m) 13C NMR DEPT (75MHz, CDCl3) δ 166.5, 149.0, 138.11, 137.9, 134.4, 134.4, 132.7, 132.01-126.13, 112.38.
Results and Discussion
The triphenylimidazole dimer that was synthesized displayed a melting range of 199.8-200.3 ºC which is higher than the literature value of
Reece Harms 4320288
Introduction
This experiment investigates an oxidative coupling reaction in an to synthesise triphenylimidazole dimer from 2,4,5-triphenyl-1H-imidazole. The resulting compound was investigated for both photochromic and piezochromic properties by way of formation of a stable radical, utilizing visual observations and UV-Vis as a means of distinction. Both the oxidative coupling reaction and the dimers interaction with light are depicted in the reactions in figure 1.
Figure 1: Oxidative Coupling reaction of 2,4,5-triphenyl-1H-imidazol
Experimental
Ethanol (100ml), potassium hydroxide (8.065g, 2.568mmol) and water (5ml) were added in order to 2,4,5-triphenyl-1H-imidazol (0.9402g, 3.17mmol). The mixture was stirred until clear before it was cooled to 5 ºC. A solution of potassium ferricyanide (3.0021 g, 9.085mmol), water (250ml) and ethanol (100ml) was prepared and added dropwise into the mixture ensuring the temperature did not rise above 10 ºC. A grey precipitate was isolated from the yellow mixture through vacuum filtration and washed with water (50ml x 5) and 50% aqueous ethanol. The mixture was dried under vaccuum suction and the melting point was determined. Yield: 0.85g, 90.8% m.p-199.8-200.3ºC. A portion of the dimer (0.0305 g, 0.0514mmol) was quantitatively dissolved in 25ml of toluene. The solution was left for 60min until colorless. The UV-Vis spectra was recorded for the colorless sample. The solution was irradiated using a lamp resulting in a purple solution and the UV-Vis spectrum was retaken. UV (): 524.92nm ε colourless (45.2M-1cm-1) coloured (760M-1cm-1) 1H NMR (300MHz, CDCl3) δ 7.26 (30H, m) 13C NMR DEPT (75MHz, CDCl3) δ 166.5, 149.0, 138.11, 137.9, 134.4, 134.4, 132.7, 132.01-126.13, 112.38.
Results and Discussion
The triphenylimidazole dimer that was synthesized displayed a melting range of 199.8-200.3 ºC which is higher than the literature value of
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