Dimers of 1,8a-Dihydro-1,8-Naphthyridine Derivatives as Models of Chiral Self-Recognition

Abstract

A theoretical study of the dimer formation of chiral 1,8a-dihydro-1,8-naphthyridine derivatives has been carried out by means of DFT calculations. In the cases treated, the heterochiral dimers (RS or SR) are always more stable than the homochiral ones (RR or SS). Two possible proton transfer processes have been studied, the concerted and the non-concerted ones. The non-concerted TS corresponds to a true TS while the concerted one presents two imaginary frequencies. The geometrical characteristics of the hydrogen bonds in all the structures calculated have been correlated using the Steiner-Limbach model.

A theoretical structural analysis of the factors that affect 1JNH, 1hJNH and 2hJNN in N–H···N hydrogen‐bonded complexes

“…Finally, b is an adjustable parameter that in general has a value of 0.4 approximately. [38,39] Eqn 5 can be rewritten as Eqn. 6 that depends on the sum and difference of the NH distances.…”

Thermodynamic and kinetic effects of Lewis acid complexation on a Schiff base present in two tautomeric forms

“…As can be seen, those cases where the hydrogen atom is located approximately at the same distances of the two heavy atoms ( r 1 − r 2 = 0) correspond to the smallest values of the “ r 1 + r 2 ” parameter. This situation is associated to a shrinking of the system or complexes due to the compression in the region of the hydrogen transfer 45, 47, 48…”

“…This situation is associated to a shrinking of the system or complexes due to the compression in the region of the hydrogen transfer. [45,47,48] The topological analysis of the electron density shows the presence of bond critical points (BCP) in the intermolecular hydrogen bond for the tautomers A and B, as well as in those elongated bonds between the heavy atom and the hydrogen in the TS structure ( Fig. 7).…”

“…A careful examination of the interatomic distances in the hydrogen bond interaction between the heavy atoms and the hydrogen shows that a shortening of the hydrogen bond interaction is associated with a lengthening of the covalent bond. This observation calls for the potential establishment of a Steiner–Limbach relationship43–46 (originally developed for intermolecular complexes)47, 48 in these intramolecular hydrogen bonds. Using an exponential relationship as proposed by Pauling, one can calculate the valence of the hydrogen atom in each of the two interactions where the hydrogen is involved, the covalent bond and the hydrogen bond.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 16, 2005) and the discipline

“…In many cases hydrogen bonds play an important role. Picazo et al [103] conducted DFT calculations on the formation of the dimer of chiral 1,8a-dihydro-1,8-naphthyridine derivatives. Two possible proton transfer processes have been studied, the concerted and the non-concerted ones.…”