The NICS (Nucleus-Independent Chemical Shift) as a probe of the relative stability of β-chalcogenovinylaldehydes stabilized through intramolecular chalcogen-chalcogen interactions

Density functional calculations, at the B3LYP/6-311+G(3df,2p) level, have been carried out for the complete series of β-chalcogenovinylaldehydes, CH(X)-CHCH-YH (X, Y=O, S, Se, Te), to estimate the strength of H-X⋯Y or X⋯Y-H intramolecular chalcogen-chalcogen interactions, through the use of appropriate homodesmotic reactions. For the same set of compounds the value of the nucleus-independent chemical shift (NICS), on points 1 Å above the corresponding ring critical point, has been obtained at the B3LYP/6-311+G(3df,2p) level. For non-stabilizing chalcogen-chalcogen interactions the NICS value is positive, while the opposite is found when the interaction is stabilizing. In general, there is a good linear correlation between both magnitudes and therefore, we can conclude that NICS value is a reliable probe of the strength of intramolecular chalcogen-chalcogen interactions in this set of compounds.