I am working with some stilbene derivative compounds and in solution I have an stokes shits value around 40-50 nm, because the maximun emission is at 360 nm. However in solid stated the emission arise 460 nm, which means around 150 nm of stokes shift. I do not know how can be explain or if there is any example. Thank you.
Dear Cabrera
Stokes shift to increase in solid state is common phenomena. It is generally due to greater intermolecular interactions in solid state. Molecules having planar structure or which can attain planar structure in solid state give maximum stokes shift due to greater intermolecular interactions as compared to non planar molecules. Molecules having rotatable group's tends to attain planarity in solid state which increase their conjugation also, hence causing red shift. Close face to face packing in solid state can form excimers also, which produce large red shifts. Molecules having Donor-Acceptor architecture are even more prone to svere intermolecular interactions in solid state. So it all depends upon the structure of your molecule and the type of functional groups it possess.
Good luck
The absorption spectra is similar, but the emission is red-shifted. By solid I mean films, prepared from a concentrated solution, a drop was place on a quartz slice, and leave to dry in air. I did not find this kind of large red-shift for stilbene derivates when change from solution to films (or solid)....
Thank you for your answers, I have been reading a large amount of pappers about stilbene, but about this particular effect of a huge red-shift in solid state. Thank you again...
Dear Cabrera
Stokes shift to increase in solid state is common phenomena. It is generally due to greater intermolecular interactions in solid state. Molecules having planar structure or which can attain planar structure in solid state give maximum stokes shift due to greater intermolecular interactions as compared to non planar molecules. Molecules having rotatable group's tends to attain planarity in solid state which increase their conjugation also, hence causing red shift. Close face to face packing in solid state can form excimers also, which produce large red shifts. Molecules having Donor-Acceptor architecture are even more prone to svere intermolecular interactions in solid state. So it all depends upon the structure of your molecule and the type of functional groups it possess.
Good luck
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