Hydrogen-Bonding-Induced Enhancement of Fermi Resonances

• Published in: The journal of physical chemistry. B Vol. 117; no. 49; pp. 15843 - 15855-15843-15855
• Main Authors: Greve, Christian, Nibbering, Erik TJ, Fidder, Henk
• Format: Journal Article
• Language: English
• Published: 02-02-2013
• Subjects: Aniline; Frequency shift; Hydrogen bonding; Hydrogen bonds; Oscillators; Polarization; Quantitative analysis; Stretching
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp4084103

Hydrogen bonding of the amino group of aniline-d sub(5) results in a huge enhancement of the NH sub(2) bending overtone absorption strength, mainly attributed to the Fermi resonance effect. A quantitative analysis is presented, using a hybrid mode representation and encompassing experimental data on aniline with 0, 1, or 2 hydrogen bonds to dimethylsulfoxide (DMSO). Changes in enthalpy, hydrogen-bonding-induced frequency shifts, and the transition dipole moment increase of the local N-H stretching oscillator all demonstrate that the hydrogen bond is strongest in the single hydrogen-bonded complex. Linear IR overtone spectra show that the oscillator strength decreases upon hydrogen bonding for the N-H stretching overtones, which is opposite to the effect on the fundamental N-H stretching transitions. Polarization resolved 2D-IR spectra provide detailed information on the N-H stretching overtone manifold and support the relative orientations of the various IR transitions.