Simulation of infrared spectra

This structure encoding method has been applied both for the classification of a data set comprising 31 corticosteroids, for which affinity data were available in the literature, binding to the corticosteroid-binding globulin (CBG) receptor, and for the simulation of infrared spectra [28, 29). 

Tools TeleSpec - Online Service for the Simulation of Infrared Spectra [75]... 

Another code for representation of the 3D structure of a molecule with a fixed number of variables irrespective of the number of atoms in the molecule (3D MoRSE code) has been proposed by Soltzberg and Wilkins. This molecular description is based on methods used in the interpretation of electron diffraction data. The approach has been used successfully for both the simulation of infrared spectra... 

A slight modification of the general form of an RDF leads to a molecular descriptor, the radial distribution function (RDF) code, which includes atom properties that address characteristic atom features in the molecular environment. Fields of application for RDF codes are the simulation of infrared spectra and deriving molecular structure information from infrared spectra [40,41]. 

Weigel, U.-M. and Herges, R., Simulation of Infrared Spectra Using Artificial Neural Networks Based on Semiempirical and Empirical Data, Anal. Chim. Acta, 331, 63, 1996. 

Dubois, J.E., et al., Simulation of Infrared Spectra An Infrared Spectral Simulation Program (SIRS) which Uses DARC Topological Substructures, J. Chem. Inf. Comput. ScL, 30, 290, 1990. 

The simulation of infrared spectra with CPG networks has already been described. The more interesting topic lies at hand The input of a query infrared spectrum into a reverse-trained Kohonen network provides a structure descriptor. The question now is whether it is possible to obtain a 3D structure from this descriptor. 

Selzer, P., et al.. Rapid Access to Infrared Reference Spectra of Arbitrary Organic Componnds Scope and Limitations of an Approach to the Simulation of Infrared Spectra by Nenral Networks, Chem.-Eur. J., 6, 920, 2000. 

One of the advantages of the simulation of infrared and Raman spectra is the ability to separate the contribution that different conformers make to the overall spectrum. Mathieu and Grand [54] used a quasi-harmonic method using ab initio... 

Diffuse-reflection spectroscopy is a widely used experimental technique which, different from the previously mentioned techniques, is not only based on reflection and refraction but additionally on diffraction. The exact description, e.g. assuming Mie scattering, and quantitative simulation of the spectra is at least difficult (Grosse, 1990). The most comprehensive overview on all related aspects was given by Kortiim (1969). Experimental examples refer mostly to the visible spectral range, more recent reviews deal with near infrared (Osborne and Feam, 1986), infrared (Korte, 1990b), and far infrared spectroscopy (Ferraro and Rein, 1985). 

Yamaguchi Y, Frisch M, Gaw J, Schaefer HF III, Binkley JS (1986) Analytic evaluation and basis set dependence of intensities of infrared spectra. J Chem Phys 84 2262-2278 Yokoyama I, Miwa Y, Machida K (1992) Simulation of vibrational spectra of acetic acid by an extended molecular mechanics method and half band width parameters. Bull Chem Soc Japan 65 746-760 Yost EC, Tejedor-Tejedor MI, Anderson MA (1990) In situ CIR-FTIR characterization of sahcylate complexes at the goethite/aqueous solution interface. Env Sci Tech 24 822-828... 

These spectra serve to illustrate the sensitivity of rotational fine structure to the transition moment orientations and rotational constants. In practice, individual rotational lines cannot be resolved in most infrared vibration-rotation spectra, because the rotational constants are too small. In spectra such as that in Fig. 6.14, the bunched groups of Q-branch lines frequently materialize as single intense bands, while the more sparse P and R branches form weak continua. Rotational structures are frequently analyzed by comparing them with computer-generated spectra derived from assumed rotational constants and selection rules. By weighting the rotational line intensities with appropriate Boltzmann factors (cf. Eq. 3.28) and assigning each rotational line a frequency width commensurate with the known instrument resolution, realistic simulations of experimental spectra are possible if the rotational constants and selection rules are properly adjusted. 

Infrared spectra are strongly dependent on the 3D structure of a compound, as reflected by the success of attempts to simulate infrared spectra from 3D structure representations (see Section 10.2.5). Infrared spectra should therefore be taken as representations of a chemical compound for modeling properties that are suspected to be dependent on the 3D structure of a compound NMR spectra also depend on... 

Fig. 7.12 Experimental and calculated infrared spectra for liquid water. The black dots are the experimental values. The thick curve is the classical profile produced by the molecular dynamics simulation. The thin curve is obtained by applying quantum corrections. (Figure redrawn from Guilbt B 1991. A Molecular Dynamics Study of the Infrared Spectrum of Water. Journal of Chemical Physics 95 1543-1551.)...

Vibrational spectroscopy has played a very important role in the development of potential functions for molecular mechanics studies of proteins. Force constants which appear in the energy expressions are heavily parameterized from infrared and Raman studies of small model compounds. One approach to the interpretation of vibrational spectra for biopolymers has been a harmonic analysis whereby spectra are fit by geometry and/or force constant changes. There are a number of reasons for developing other approaches. The consistent force field (CFF) type potentials used in computer simulations are meant to model the motions of the atoms over a large ranee of conformations and, implicitly temperatures, without reparameterization. It is also desirable to develop a formalism for interpreting vibrational spectra which takes into account the variation in the conformations of the chromophore and surroundings which occur due to thermal motions. 

A formally antiaromatic 1,4-dihydropyrazinothiadiazole has been prepared and characterized by single crystal X-ray spectroscopy. The antiaromatic character of which has been supported computationally using NICS measurements <20070L1073>. CHIH-DFT computational studies on acenaphtho[l,2-f]-l,2,5-thiadiazole 1,1-dioxide led to simulations of its infrared (IR) and ultraviolate (LJV) spectra, the dipole moment and polarizability <2007JMT373>. 4,6-Dinitrobenzothiadiazole was determined to have an electrophilic reactivity of —8.40 which corresponds to a pK z° of 7.86 for Meisenheimer complexation with water and is close to the demarcation boundary (E = —8.5) between super-and normal-electrophiles and between reactive dienophiles and inert partners in Diels-Alder adduct formation <20070BC1744>. 

Brewer and Field Spec spectrophotometers and pyranometers) and LOWTRAN 7 code (6) results. In this way, this model can be also a useful tool for a wide range of applications in Visible and Infrared spectra, mainly for data validation and for the simulation of the radiation changes due to changes in the atmospheric chemical composition. 

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