1a) or it can donate electrons back to the original donor carbonyl carbon atom forming “reciprocal” n→π* interactions (Fig. The acceptor carbonyl oxygen, therefore, can donate electrons to another nearby carbonyl carbon either to form a sequential chain of O We anticipated that due to n→π* interaction both donor and acceptor C═O bonds will be polarized, which will make the acceptor carbonyl oxygen atom a better electron donor and the donor carbonyl carbon atom a better electron acceptor. Direct spectroscopic evidence for n→π* interaction was recently reported by using gas-phase infrared spectroscopy 30. ♼═O ( θ) of ~109° and the pyramidality (Δ, Θ) of the acceptor carbon atom towards the donor oxygen atom 9, 14, 17, 25, 29.♼═O distance (d) of less than 3.22 Å, bond angle ∠O.♼═O n→π* interaction is characterized by a short O.♼═O interactions between the side-chain and backbone carbonyl groups of Asp, Asn, Glu, and Gln were also observed in the high-resolution crystal structures of proteins 26, 27.♼═O n→π* interactions not only influence geometries of important small molecules 12, 13, 14, 15 but also play crucial roles in determining the three dimensional structures of polyesters 16, peptides 17, peptoids 18, 19, 20, 21 and proteins 22, 23, 24, 25.
♼ ═ O ~ 109°) have attracted a great deal of attention in recent years 6, 7, 8, 9, 10, 11.♼═O) n→π* interactions where one of the lone pairs ( n) on the oxygen atom of a carbonyl group is delocalized over the antibonding π* orbital of a nearby carbonyl C═O bond ( π* C═O) along the Bürgi-Dunitz trajectory 5 ( ∠O.Intermolecular noncovalent interactions of varying magnitude are also responsible for the existence of different states of matter 4. Nature effectively uses combinations of weak noncovalent interactions in the functional forms of various biologically important molecules such as nucleic acids and proteins 1, 2, 3.
0 kommentar(er)
