Focusing on biochemical and pharmaceutical inhibitor systems the interaction of cyclic peptides with model peptides have been investigated by ATR-FTIR-spectroscopy. Information about the participation of special functional groups e.g. COOH, COO−, NH3+ or peptide backbone was gathered by observing cyclohexapeptides (c(X1LX2LX3)) which are interacting with covalently coated Si-ATR-crystals (l-arginine, tripeptide I (aNS), tripeptide II (SNa)). To determine the interaction, further studies about the band sequence (1800–1500cm−1) for non-adsorbed cyclohexapeptides and for the interaction with the silicon surface (SiOH) were necessary. The spectra of the interacting cyclohexapeptides with the SiOH-groups were treated like reference spectra for the evaluation of the peptide–peptide interaction. Based on these spectra, we can conclude that there is peptide–peptide interaction with the coating and not with the residual OH-groups.Determination of interaction mechanisms was done by spectra which represent adsorbed molecules only. The amount of adsorbed molecules was considerably less than a monolayer. Therefore the intensities of the spectra are about 10−4 absorbance units. The spectra contain information about both changes of the coating and of the cyclohexapeptide.

Uniaxially oriented films of cyclic siloxanes were prepared by vapour deposition on semiconductor and metal substrates. An alkyloligothiophene diffused into this layer adopts its orientation. The orientation of the layer and the diffusant has been characterised by FTIR-ATR spectroscopy. The diffusion process was monitored by ATR and SPR spectroscopy as well as by spectral interferometry. Diffusion coefficients vary by five orders of magnitude depending on the order of the siloxane film.

With the focus on microelectronic and sensor devices the diffusion process of gases in ultrathin films coating the surface of semiconductor crystals has been studied with the method of time resolved FTIR-ATR spectroscopy. A formula to calculate attenuated total reflectivities for all film thicknesses is presented. Based on this formula a least-squares program was developed. The reflectivity measured by time resolved ATR spectroscopy for diffusion processes in thin films characteristically depend on their thickness. Therefore in addition to diffusion coefficients film thicknesses in a range of 10 nm up to the penetration depth can be calculated from the reflectivities as well. Measurements of diffusing gases in some polymers with different chemical and structural characteristics will be discussed in this paper.

Oligomers with a dimethylsiloxane backbone coated as thin films on different substrate surfaces were thermally as well as photochemically cross-linked. The structure and the degree of cross-linking were examined spectroscopically. Diffusion of different gases in the thin polymer films was measured by time resolved infrared ATR-spectroscopy. The process of diffusion is almost immediately followed by a swelling of the polymer proportional to gas concentration. Therefore diffusion may also be measured by spectral interferometry, giving a very sensitive device for optical sensing of hydrocarbons. Furthermore, diffusion in polymers may be measured very accurately by spatially resolved UV/Vis-spectroscopy. Diffusion coefficients may also be determined indirectly from the equilibrium of monomers and excimers indicated by the fluorescence intensities. This method allows the in situ observation of the cross-linking process.

The characteristic differences shown by optical spectra of oligothiophenes (OTs) in films on silica surfaces and in solution are explained by the Molecular Exciton Model. Thus unsubstituted OTs in monolayers are arranged in a side-by-side manner, whereas substitution with terminal alkyl groups destroys this alignment, thereby reducing the π-overlap of adjacent molecules. With the orientation of the transition moments within the molecular framework known from stretched sheet experiments polarized UV/Vis and IR spectra reveal that the long molecular axis of the unsubstituted OTs in monolayers on silica is directed perpendicularly to the surface, while alkyl substituted oligomers do not show any anisotropy. This influence of the alkyl groups and the reduced order in multilayers of unsubstituted OTs both suggest a decisive role of the interaction between surface and π-electron-system for the molecular arrangement in thin films.

Thin films of oligothiophenes αnTs are prepared by vapour deposition on fused silica and crystalline sapphire substrates, and characterized with respect to molecular orientation by polarized fluorescence, UV-Vis and IR absorption spectroscopy. Isolated αnTs are adsorbed in the submonolayer region with their long molecular axes parallel to the surface plane. In the monolayer region, the αnTs organize with their long axes perpendicular to the surface plane forming aggregates of the pin cushion type with a mean tilt angle of θ = 15 ± 3° relative to the normal of the macroscopic surface. Terminal alkylation of αnT or multilayer coverage results in a loss of orientation with respect to the surface. Heating the substrate during film deposition either reduces or enhances the molecular order depending on temperature and molecular chain length.

Mid-IR spectra of lead phthalocyanine (PbPc) thin films show a pronounced dependence on the sublimation rate and substrate temperature during film preparation under ultrahigh vacuum conditions. Below 400 K thin PbPc films can be prepared in a quasi-monoclinic form, whereas high amounts of a quasi-triclinic form are produced at higher substrate temperatures. These structures were identified from an analysis of the spectral changes between the two modifications. For this purpose, simplified normal coordinate model calculations were performed for the porphin ring system PbPc with C4v and C2v symmetry respectively.

A new method of an on-line coupling of TLC and FTIR spectroscopy is introduced. By the combination of a computer controlled x—y-stage with a “diffuse reflectance unit” and an FTIR spectrometer using commercially available GC-IR software it is possible to obtain chromatograms of a TLC separation. The chromatograms can be generated both frequency dependent as spectral windows of a certain range and frequency independent as Gram-Schmidt trace. During the measurement the series of interferograms are saved on a hard disk, so that the desired TLC-FTIR spectra can be immediately computed after the end of the measurement. If necessary, a stationary measurement can be performed at the position of maximum substance concentration with high resolution and coaddition of interferograms. The quality of the TLC-FTIR spectra is sufficient for identification of unknown substances and discrimination of closely related substances. There are different ways to present the huge amount of received data: as a 3-dimensional stacked plot of the measured spectra, as horizontal sections through that stacked plot, as a contour plot, with which a rapid check of peak purity is possible, or as frequency dependent chromatograms at any wavelength of interest.

Adsorption states of 2-propanol on TiO2 surfaces form an important preliminary stage of photocatalytic reactions. Several adsorption states are discussed. The different adsorption states are characterized by the shape of their vibrational spectrum. DRIFT spectra were registrated with different degrees of coverage with an evacuable cell, which allows for manipulation under vacuum condition. Force constant calculations are an important aid for the clarification of the structure of adsorption states. An OH⋯O hydrogen bond as well as a coordinative TiO bond take part in a non- dissociative chemisorbed state.

Es wird eine Methode zur Durchführung von on-line DC-IR Messungen vorgestellt. Durch die Kombination eines computergesteuerten Meßtisches mit einer Diffusen-Reflexions-Einheit und eines FTIR-Spektrometers können mit gängiger GC-IR-Software Chromatogramme eines dünnschichtchromatographischen Trennlaufs aufgenommen werden. Die Chromatogramme können frequenzabhängig als spektrale Fenster und frequenzunabhängig als Gram-Schmidt-Spur berechnet werden. Speichert man die während einer Messung anfallenden Interferogramme auf einer Festplatte ab, können die DC-IR-Spektren der Komponenten sofort aus dem Interferogrammfile berechnet werden. Falls erforderlich, kann sich daran eine stationäre Messung mit hoher Auflösung und Spektrenakkumulation an der Stelle des Peakmaximums anschließen. Die Qualität der erhaltenen DC-IR- Spektren reicht aus, um auch strukturell sehr ähnliche Substanzen identifizieren und diskriminieren zu können. Als übersichtliche Darstellung der anfallenden Daten dient die Abbildung der DC-IR-Spektren in Abhängigkeit von der Plattenposition als Kontur-Plot, womit auch eine rasche Prüfung auf Peakreinheit vorgenommen werden kann.

Quadrupolar and dipolar relaxation times have been determined for pyrrole, 3,4-bis(trifluoromethyl)-pyrrole and their H-bonded complexes with pyridine. Correlation times, activation energies and quadrupole coupling constants are compared. Correlation times of imido-, α- and β-protons of pyrrole are used as probes for a qualitative discussion of the anisotropic reorientation of pyrrole and the pyrrole—pyridine complex.

Polarized infrared spectra of melittin incorporated into macroscopically oriented lipid membranes are reported. From the linear dichroism of the amide I and amide II vibrational bands, the spatial orientation of the melittin helices was determined as being preferentially parallel to the membrane normal, under our experimental condition of low water content and an ordered lipid phase. Considering the various models for the orientation of melittin in lipid membranes proposed in the literature, we conclude that our data are in accord with an arrangement whereby the hydrophobic part of the polypeptide either spans the bilayer in the form of two bent helix segments, or is folded back within one monolayer in the form of a wedge.

We reported the vibronic and cation spectra of 3,4-difluoroanisole. The band origins of the S1 ← S0 electronic transition of the cis and trans rotamers appear at 35,505 ± 2 and 35,711 ± 2 cm−1 and the adiabatic ionization energies are determined to be 67,780 ± 5 and 68,125 ± 5 cm−1, respectively. Most of the observed active vibrations in the electronically excited S1 and cationic ground D0 states mainly involve in-plane ring deformation and substituent-sensitive bending vibrations. Analysis of the obtained vibronic and cation spectra suggests that the molecular geometry, symmetry, and vibrational coordinates of the cation in the D0 state are like those of the neutral species in the S1 state for these two isomeric species.

The infrared spectra of 3,3,3-trifluoropropene and hexafluoropropene were studied in the vapour phase and in solution between 4000 and 40 cm-1 . Raman spectra of the compounds as vapours and liquids were recorded and polarization data obtained. The spectra of both molecules are interpreted in terms of Cs symmetry. Complete vibrational assignments, including the torsional mode, are presented, based upon infrared and Raman vapour contours, Raman polarization measurements and the results of a normal coordinate analysis