Discrimination of hydrogen-bonded complexes with axial chirality

Abstract

Articles you may be interested inStructure and tunneling dynamics in a model system of peptide co-solvents: Rotational spectroscopy of the 2,2,2-trifluoroethanolwater complex Hydrogen-bonded OH stretching modes of methanol clusters: A combined IR and Raman isotopomer studyThe chiral self-discrimination of twelve molecules showing axial chirality has been studied. They included peroxides, hydrazines, carboxylic acids, amides, and allenes. The homo and heterochiral dimers of the selected compounds, that present two hydrogen bonds, have been studied by means of density functional theory ͑B3LYP/6-31ϩG**͒ and ab initio ͑MP2/6-31ϩG** and MP2/6-311ϩϩG**͒ methods. The energetic differences found for the complexes of each compound have been rationalized based on their electron density maps and the natural bond orbital analysis. In some cases, intermolecular oxygen-oxygen interactions have been found and interpreted as additional stabilizing contacts.

Chirality Recognition between Neutral Molecules in the Gas Phase

“…Therefore, HOOH, H 2 NÀNH 2 and its homologues are among the simplest representatives. [180,181] In the vibrational ground state, HOOH converts between left-and right-handed helices on a timescale of 3 ps (full oscillation period) [182] after being localized in one of the helicities. Its dimer features two equivalent hydrogen bonds and is presumably centrosymmetric, that is, it involves monomers of opposite helicity.…”

Bonding Properties Related with Chiral Discrimination in Dinuclear Metal Complexes of Group 10

“…If the chirality is not taken into account, the analysis of the metal-halogen vs. metal-nitrogen bond lengths for the analogous complexes show good correlations for every metal family (r 2 values of 0.99 and higher). It was not possible to establish any correlation with the relative energies and the M-L bond lengths, however, although this was expected based on the reasoning related to Equation (2). It is very important to note, however, that in the heterochiral complexes the M-N bond lengths have the propensity to be shorter than in their homochiral analogs.…”

“…[1] Peroxides and hydrazine present axial chirality with low racemization barriers. [2,3] The presence of different chiral molecules of hydrazine has been used to explain the experimental results of clusters in the gas phase. [4] A topic that has received only a limited experimental interest so far is chiral biodiscrimination based upon axial chirality.…”

High resolution NMR of free radicals: 13C magic angle spinning of two solid organic free radicals derived from 4,5-dihydro-1H-imidazol-3-oxide-1-oxyl and theoretical calculation of their NMR properties

“…Interactions between electronegative atoms have been described in the literature, [18][19][20] and in some cases were considered to explain the extra stability of those systems in which they are present. 21,22 However, in this case, tautomer 3b shows an O···H interaction that appears to be more stabilizing than the O···N one. The ortho-ortho' interactions observed in these molecules show small values of the electron density and positive values of the Laplacian, similar to those found in hydrogen bond interactions.…”