School of Mathematics and Natural Sciences

Chemical Chameleon



Xylene, isomer mixture - DANGER

H226, H304, H312+H332, H315, H319, H335, H373
P210, P260, P280, P301+P310, P305+P351+P338, P370+P378

1,3,3-Trimethylindolino-6'-nitrobenzopyrylospirane (Spiropyrane)

Not a dangerous substance according to GHS

10 mg spiropyrane are solved in about 10 mL xylene (or toluene) in a test tube with screw cap. The solution is then distributed to three testtubes with screw caps. Testtube no. 1 is kept at room temperature, no. 2 is heated in a waterbath to roughly 60 °C. No. 3 is cooled in a beaker to about 0 °C using an ice-water micture.

Testtube no. 1 is irradiated with violet light (λ = 400 nm) or UV-Light (λ = 365 nm) from an LED flashlight. Within 1-2 seconds the solution changes its color to blue. The coloration fades within 20-30 s after the flashlight has been switched off.

The irradiation is repeated with the heated sample in testtube no. 2. The coloration is one again immediate; but it fades within less than 5 s after swtching the flashlight off.

The cooled down sample in testtube no. 3 also changes its color immediately while being irradiated. But after switching the flashlight off, the color stays behind for a longer timespan of about two minutes. If the blue solution is irradiated with green light (λ = 530 nm) from an LED flashlight directly after being irradiated with violet or UV-light, then the color of the solution fades within about 10 s.

Instead of using a spiropyrane solution in xylene (or toluene), the experiments for creation and destruction of the blue substance (merocyanine, an isomer of spiropyrane), an "Intelligent Foil" can be used. The flashlight is placed directly onto the foil for irradiation and for warming and cooling the foil it can be submerged in warm or cold water.

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