Related Experiment Video
Updated: Mar 13, 2026

Characterizing Individual Protein Aggregates by Infrared Nanospectroscopy and Atomic Force Microscopy
Published on: September 12, 2019
Mass resolved IR spectroscopy of aniline-water aggregates
I León1, P F Arnáiz1, I Usabiaga1
1Department of Physical Chemistry, Faculty of Science and Technology, University of the Basque Country, Barrio Sarriena s/n, 48940 Leioa, Spain. josea.fernandez@ehu.es.
Abstract:
Aniline is the simplest aromatic amine and therefore it is a prototypical system to study the microhydration and excited state dynamics of aromatic amines. However, to date a discrete spectrum of singly hydrated species has not been obtained. Here we present for the first time the IR/UV spectrum of, aniline1(H2O)1, aniline1(H2O)2, and aniline2(H2O)1. The origin band of the monohydrated complex is shifted around 700 cm-1 to the blue, as a result of large changes in geometry upon electronic excitation. In addition, massive fragmentation from higher-order clusters appears where the origin band was expected to be, helping the clusters to elude their detection for a long time. The addition of a second water or aniline molecule shifts the origin band back to the vicinity of that of aniline and fragmentation of these species is one of the sources of such fragmentation. The dramatic changes in the structure of monohydrated clusters that follow electronic excitation resemble the behavior of the solvent in other aromatic amine-water systems, reinforcing the idea of aniline-water as an interesting model system to study such behavior.
Related Concept Videos
IR Frequency Region: X–H Stretching
NMR Spectroscopy Of Amines
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
According to Hooke's law, the vibrational frequency is directly proportional to...
Mass Spectrometry of Amines
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
IR Spectroscopy: Molecular Vibration Overview
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...

