The vibrational spectrum of a molecule is considered to be a unique physical property and is characteristic of the molecule. As such, the infrared spectrum can be used as a fingerprint for identification by the comparison of the spectrum from an “unknown” with previously recorded reference spectra. This is the basis of computer-based spectral searching. In the absence of a suitable reference database, it is possible to effect a basic interpretation of the spectrum from first principles, leading to characterization, and possibly even identification of an unknown sample. This first principles approach is based on the fact that structural features of the molecule, whether they are the backbone of the molecule or the functional groups attached to the molecule, produce characteristic and reproducible absorptions in the spectrum. This information can indicate whether there is backbone to the structure and, if so, whether the backbone consists of linear or branched chains. Next it is possible to determine if there is unsaturation and/or aromatic rings in the structure. Finally, it is possible to deduce whether specific functional groups are present. If detected, one is also able to determine local orientation of the group and its local environment and/or location in the structure. The origins of the sample, its prehistory, and the manner in which the sample is handled all have impact on the final result. Basic rules of interpretation exist and, if followed, a simple, first-pass interpretation leading to material characterization is possible. This article addresses these issues in a simple, logical fashion. Practical examples are included to help guide the reader through the basic concepts of infrared spectral interpretation.

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Interpretation of Infrared Spectra, A Practical Approach

Synth. React. Inorg. Met-Org. Chem

We report data from infrared absorption (FTIR) and X-ray photoelectron spectroscopies that correlate the molecular conformation of oligo(ethylene glycol) (OEG)-terminated self-assembled alkanethiolate monolayers (SAMs) with the ability of these films to resist protein adsorption. We studied three different SAMs of alkanethiolates on both evaporated Au and Ag surfaces. The SAMs were formed from substituted 1-undecanethiols with either a hydroxyl-terminated hexa(ethylene glycol) (EG6-OH) or a methoxy-terminated tri(ethylene glycol) (EG3-OMe) end group, or a substituted 1-tridecanethiol chain with a methoxy-terminated tri(ethylene glycol) end group and a −CH2OCH3 side chain at the C-12 atom (EG[3,1]-OMe). The infrared data of EG6-OH-terminated SAMs on both Au and Ag surfaces reveal the presence of a crystalline helical OEG phase, coexisting with amorphous OEG moieties; the EG[3,1]-OMe-terminated alkanethiolates on Au and Ag show a lower absolute coverage and greater disorder than the two other compounds. The...

Molecular Conformation in Oligo(ethylene glycol)-Terminated Self-Assembled Monolayers on Gold and Silver Surfaces Determines Their Ability To Resist Protein Adsorption

Effects of short-time vibratory ball milling on the shape of FT-IR spectra of wood and cellulose

Infrared spectra of soluble polyaniline

This book should be of interest to senior undergraduates, postgraduates and research workers in physics, physical sciences, physical chemistry.

Lionel J. Bellamy

Papers

The infra-red spectra of complex molecules