Dears,
We have prepared a reaction of 2,3-diamino-1,4-naphthoqiunone and 2,3- dichloropyrrol. The expected product is a close-ring 2,3-dichloro-1H-naphtho[2,3-d]pyrrolo[1,2-a]imidazole-1,5,10-trione. However, the crystal structure and NMR showed that the obtained product is 1-(3-amino-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-3,4-dichloro-1H-pyrrole-2,5-dione (1), which means no ring-closure as the previously reported article with 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one (2). We performed a computational study of a proposed mechanism and no difference in the case of thermochemical parameters. We noticed that the HOM-LUMO in the case of TS is different with a higher difference in the case of (2) "closed-ring product". Furthermore, a higher dipole moment is obtained with 2 in comparison of 1. We searched in the literature about a good explanation for this behavior and the relationship but no good case was obtained. Can anybody help in explaining this behavior and supply us with some good references.
* attached the mechanisms in both cases, HOMO-LUMO value is inserted in parenthesis ().
Hi Murad,
To begin with, I just have a few questions just to ensure that what you are comparing is indeed what it should be. From what type calculation did you get the HOMO-LUMO gap? Have you carried out, say, a TDDFT calculation and matched the transition spectral from the DFT with the experimental result from UV spectra for your compound? This will help you see clearly both the energy gap and the identities of the MOs with their contributions to any transition. Sometimes, we observe for some reason that the max absorption is not a LUMO-HOMO transition and so the use of HOMO-LUMO MO diagram to illustrate the change from one conformer to the other might not suffice.
Also, the basis set and functionals employed in the two cases above, how similar are they? Are they the same? A change in the level of theory used can indeed lead to a discrepancy in your result. Was the geometry optimised in both cases? Is there a comparison of the calculation with any experimental result? Answering these little but key questions should give insight to your question. Hope it helps.
David
Dear.
Thank you for your replay
As I have no uv spectra I have performed only dft at level 6-31g**/b3lyp, the basis sets are the same for all calculations
Hi,
Let's say you trust what you are getting out of the calculation, you might still wanna run the TDDFT to see what is happening with the energy gaps, that would give you some info in the MOs you are using to track the reaction.
David
- Badges
- Science topic
- Similar topics
- Psychology