I have an azo dye, which I suspect it may form intramolecular hydrogen bond after photoisomerization. The intramolecular hydrogen bond may have faciliated the proton transfer.
After photoisomerization, the cis form geometry in TDDFT resulted in blue-shift wavelength absorption. But in spectrometer, I got red-shift wavelength instead, around 450 nm. So I simulate the proton transferred geometry of my cis-azo dye in TDDFT, the wavelength is around 450 nm, close enough to spectrometry result.
In conclusion, in TDDFT after isomerization, there will be blue-shift, unless hydrogen transfer is there. Since I found red-shift in spectroscopy, I want to highligh that proton transfer is actually there, perhaps proven by TDDFT.
Is it reasonable that I run "opt=redundant", to scan hydrogen transfer vs. total energy, to prove the proton transfer activation energy is below ~20 Kcal/mol, saying the proton transfer is ground state/thermally achievable?
Attached data is one of my proton transfer energy profile. Thanks
The attached figure shows that the proton transfer is barrierless. Thus the process is extremely efficient. You can also do the same calculation in the ground state to show that there exist a barrier which makes the proton transfer process slow.
Thanks, the proton transfer proceeds after photoisomerization (trans -> trans* ->-> cis), so it's ground state proton transfer. Cis form approached atoms for hydrogen transfer to occur... ideally
Mr. Chen,
You could try with ADMP and BOMD, however within a large time scale.
My proposed hypothesis is that, after photoisomerization (trans->cis) the proton transfer state is stable enough for typical absorbance measurement. Slightly different from ESIPT, which proton transfer is transient. Thanks for the paper. Now im trying to prove ground state hydrogen transfer is there.
Ground state proton transfer can be proved by varying the solvent polarity and hydrogen bonding donating capability. The relative concentration of the two forms may vary with solvent.
Thanks, I know there are some equations related to wavenumber shifting and solvent polartiy.
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