Not a blog about the science or practice of travel through books, but perhaps rather about science, practice and travel through books.

Luminescent compounds

Colorful chemistry is great, but luminescent chemistry is even better. This week we synthesized two luminescent compounds: Alq3 with q = 8-quinolinolate and Eu(tta)3(phen) with tta=theonyltrifluoracetone, phen = 1,10-phenantroline.

Europium complex in solution

We tested the compounds under UV-light, where Alq3 emitted green light and Eu(tta)3(phen) red, due to fluorescence. The compounds would produce the same light in an electric field (electroluminescence), which is the basic principle behind OLED-displays, but unfortunately this requires a more complex setup.

Alq3 emits green light when radiated with UV-light. This is a typical main group luminescent compound, where the luminescence comes from π-π*-transitions in the conjugated system (the other common transition is n-π*. As the transitions take place in molecular orbitals, there is a large gap between the many vibrational states and the emission peak is broad. Also, it’s only slightly shifted from the absorption peak.

Eu(tta)3(phen) emits red light when radiated with UV-light. Eu is a rare-earth metal and the luminescence come from ff-transitions on the metal. This gives very sharp emission-peaks (because the transitions take place in atomic orbitals), which is good. Also, the absorption peak is shifted a large difference from the absorption peak. This ensures the compound is really white when no stimuli is added, while Alq3 is slightly yellowish.

A fun fact is that an Europium (Eu) compound is used in the Euro banknotes for anti-counterfeiting.

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