Multiwfn forum

saeed_E

Member

Registered: 2019-12-21

Posts: 80

Blue-shift instead of expected red-shift in XB-bonded complexes

Dear Tian,

In some cases of XB-bonded complexes such as R-F...Y or R-Cl...Y (R: highly electron-withdrawing group, Y: Lewis base), after formation of complex the R-F (R-Cl) distance is contracted instead of an expected elongation! In other words, while we expect a red-shift happens for the R-F stretching frequency, a blue-shift is observed instead; that is, R-F distance in R-F...Y complex is shorter than the respective value in the isolated R-F.

Could you please let me know your valuable rationalization regarding such an unexpected contraction happened in R-F distance?

Sincerely,
Saeed

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,468

Website

Re: Blue-shift instead of expected red-shift in XB-bonded complexes

I don't have a clear answer. Please try to google something like "blue-shift halogen-bond" to see if there are existing relevant studies.

saeed_E

Member

Registered: 2019-12-21

Posts: 80

Re: Blue-shift instead of expected red-shift in XB-bonded complexes

Dear Tian,
Thank you very much for your valuable guidance.

Sincerely,
Saeed