Dynamic and electro-optical non-equivalency of NH bonds in amino groups of aniline, aminotoluenes and monohalogen-substituted anilines in their H-bonded 1 : 1 and 1 : 2 complexes

Hydrogen-Bonding-Induced Enhancement of Fermi Resonances: A Linear IR and Nonlinear 2D-IR Study of Aniline-d5

“…This indicates that the hydrogen bond is strongest in the single hydrogen-bonded species. This conclusion was reached by others for various aniline/solvent complexes and water/solvent complexes and is further corroborated by a thermodynamic analysis (see the SI). In terms of Gibbs free energy, both equilibria of Scheme favor the single hydrogen-bonded species at 23 °C.…”

“…The extracted N–H stretching local mode frequency downshifts 88 and 80 cm –1 upon hydrogen bonding, again confirm that the hydrogen bond is strongest for the single hydrogen-bonded complex An···DMSO. In previous investigations on double hydrogen-bonded aniline–solvent complexes, , it was tacitly assumed that the observed Fermi band/ν(NH 2 ) s energy separation was entirely due to the Fermi coupling (degenerate decoupled states). This results in too large values for the coupling between these modes and the frequency downshift caused by the hydrogen bonding.…”

“…Aniline is a representative model system for DNA nucleobases, , which, due to its characteristic amino group, can illustrate the effect of hydrogen bonding of N–H stretching oscillators on Fermi resonances with NH 2 bending overtone transitions. Moreover, as a fairly small molecule, aniline has a relatively sparse vibrational manifold in the N–H stretching region, − and therefore, the number of meaningful Fermi resonances that need to be considered is still limited. By varying the DMSO concentration in ternary mixtures of An and DMSO in tetrachloromethane (CCl 4 ), we can change the composition from only free An through predominantly single hydrogen-bonded An···DMSO to almost exclusively double hydrogen-bonded An···(DMSO) 2 complexes.…”

The Influence of Substituents in Arene Ring of Aniline on Dynamic, Energetic and Electrooptical Non-equivalency of Amino Group NH-Bonds in Complexes with Intermolecular H-Bond of 1:1 and 1:2 Composition

“…In earlier works [ 1,2] Electrooptical characteristics of amino group dp/dq (the derivative of dipole moment with respect to bond length) and dp/dq' ( Infrared spectra, dynamic and electrooptical properties of amino group NIIbonds of analogous 1: 1 complexes in CC& were reported in [3] for I, in [4] for III, VIII, in [ S ] for IV, V, IX and in [6] for VI, VII. Similar investigations for 1:l complexes of 11 with various proton acceptors and for 1: 1 complexes of 111-IX with dioxane were done in present work.…”

“…Downloaded by [University of Exeter] at 01:04 05 June 2016In the case of aniline and mono-(methyl, fluoro, chloro, bromo)-substituted anilines[2] the next general regularity for free and H-bonded molecules was observed:AMm,, = 3.425y(HNH)) + 278.0 ~0 .9 9 Hence, with increase of combined inductive influence of substituents in aniline arene ring on amino group state the type of dependence of spectraldifYerence AM'"=M,"'-M,"' for monomers and H-bonded 1 :2 complexes on valent angle y(HNH) value changes. Force constants of bonded NH-groups in H-bonded 1: 1 and 1:2 complexes of I-IX w i t h various proton acceptors aren't equivalent, Table 4.…”