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Author: Subject: Solvatochromism related questions
alexleyenda
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[*] posted on 3-11-2015 at 00:50
Solvatochromism related questions


Hi,
I have a few questions about a lab about solvatochromism, I have searched hours for the answers before asking!

1- First, we prepared the solutions by adding a bit of a dye diluted in acetone in test tubes, drying the acetone, then adding the new solvent. We dried the acetone before adding the solvant for almost every solvents like methanol. propanol. DCM. DMF, DMSO... but to prepare the solutions of the dye with acetonitrile and ethyl acetate, we were asked not to dry the acetone before adding the new solvent... why ??? I guess it has to do with solubility but.. ? PS: the dye is 1-docosyl-4-(4-hydroxystyryl)pyridinium bromide.

2- What should be the excited state structure of the dye and how does it explain its negative solvatochromism? It is not in the litterature (or I haven't found it), but the best explanation I have found yet is that the bromide anion make a charge transfert to the pyridinium part so that the excited state is neutral overall, so less polar, a bit like in the case of l-ethyl-4-(methoxycarbonyl)pyridinium iodide.

If anyone know something about solvatochromism and can help, it would be appreciated!




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