Infrared complexes

Norman, M.L., J. Qian, R.E. Miller and D.R. Worsnop Infrared complex refractive indices of supercooled liquid HNO3/H2O aerosols,/. Geophys. Res. (Atmos.) 104 (1999) 30571-30584. 

Analysis of the infrared spectra requires accounting for thin film interference effects, which, upon shock compression, change the composite reflectivity. To analyze the thin film interference effects, the infrared complex refractive index spectra for ambient samples of PVN, and the inert polymethylmethacrylate (PMMA), were determined as described in the section above. The only modification to the description above is the inclusion here of the dispersive rarefaction wave that releases the pressure [102]. 

On extension in infrared complex 880 (OEM 152). + Shell with sharp filaments on IR emission peak. + Two knots (clusters ) 3 S of LI-LMC 847. 

Irregular filamentary shell and knot on infrared complex LI-LMC 880 (DEN 152). 

Extended diffuse filaments on edge of infrared complex 1015 (DEN 189). 

Shell at edge of extended infrared emission. Shell) infrared complex LI-LMC 1090. 

Network of filamentss infrared complex LI-LMC 1274. IR peak on main nebula. 

The chaimel-flow electrode has often been employed for analytical or detection purposes as it can easily be inserted in a flow cell, but it has also found use in the investigation of the kinetics of complex electrode reactions. In addition, chaimel-flow cells are immediately compatible with spectroelectrochemical methods, such as UV/VIS and ESR spectroscopy, pennitting detection of intennediates and products of electrolytic reactions. UV-VIS and infrared measurements have, for example, been made possible by constructing the cell from optically transparent materials. 

Van der Waals complexes can be observed spectroscopically by a variety of different teclmiques, including microwave, infrared and ultraviolet/visible spectroscopy. Their existence is perhaps the simplest and most direct demonstration that there are attractive forces between stable molecules. Indeed the spectroscopic properties of Van der Waals complexes provide one of the most detailed sources of infonnation available on intennolecular forces, especially in the region around the potential minimum. The measured rotational constants of Van der Waals complexes provide infonnation on intennolecular distances and orientations, and the frequencies of bending and stretching vibrations provide infonnation on how easily the complex can be distorted from its equilibrium confonnation. In favourable cases, the whole of the potential well can be mapped out from spectroscopic data. 

Infrared spectroscopy can also be carried out in molecular beams. The primary advantages of beam spectroscopy are tliat it dispenses almost entirely witli monomer absorjitions tliat overlap regions of interest, and tliat tlie complexes are... 

The earliest molecular beam infrared experiments on Van der Waals complexes used photodissociation spectroscopy a molecular beam is irradiated witli a tunable infrared laser and tire molecular beam intensity is measured as a function of... 

Most infrared spectroscopy of complexes is carried out in tire mid-infrared, which is tire region in which tire monomers usually absorb infrared radiation. Van der Waals complexes can absorb mid-infrared radiation eitlier witli or without simultaneous excitation of intennolecular bending and stretching vibrations. The mid-infrared bands tliat contain tire most infonnation about intennolecular forces are combination bands, in which tire intennolecular vibrations are excited. Such spectra map out tire vibrational and rotational energy levels associated witli monomers in excited vibrational states and, tluis, provide infonnation on interaction potentials involving excited monomers, which may be slightly different from Arose for ground-state molecules. 

For complexes such as Ar-H2, Ar-HF and Ar-lTCl, vibrational predissociation is a very slow process and does not cause appreciable broadening of the lines in the infrared spectmm. Indeed, for Ar-ITF, ITuang et al [20] showed that... 

Figure C 1.3.5. Spectra of two different infrared bands of HF dimer, corresponding to excitation of the bound (lower panel) and free (upper panel) HF monomers in the complex. Note the additional line width for the bound HF, caused by vibrational predissociation with a lifetime of about 0.8 ns. (Taken from 1211.)...

Tunable visible and ultraviolet lasers were available well before tunable infrared and far-infrared lasers. There are many complexes that contain monomers with visible and near-UV spectra. The earliest experiments to give detailed dynamical infonnation on complexes were in fact those of Smalley et al [22], who observed laser-induced fluorescence (LIF) spectra of He-l2 complexes. They excited the complex in the I2 B <—A band, and were able to produce excited-state complexes containing 5-state I2 in a wide range of vibrational states. From line w idths and dispersed fluorescence spectra, they were able to study the rates and pathways of dissociation. Such work was subsequently extended to many other systems, including the rare gas-Cl2 systems, and has given quite detailed infonnation on potential energy surfaces [231. 

Anderson D T, Schwartz R L and Todd M W and Lester M I 1998 Infrared spectroscopy and time-resolved dynamics of the ortho-Hj-OH entrance channel complex J. Chem. Phys. 109 3461-73... 

L. J. Bellamy, The Infrared Spectra of Complex Molecules, Whey, Chichester, 1975. 

Bellamy, The Infra-Red Spectra of Complex Molecules, 1954 (Methuen). Randall, Fowler, Fuson and Dangl, Infrared Determination of Organic Structures, 1942 (Van Nostrand). 

Although no chemical reaction occurs, measurements of the freezing point and infra-red spectra show that nitric acid forms i i molecular complexes with acetic acid , ether and dioxan. In contrast, the infrared spectrum of nitric acid in chloroform and carbon tetrachloride - is very similar to that of nitric acid vapour, showing that in these cases a close association with the solvent does not occur. 

Co(II), Ni(n), Cu(n), and Zn(II) complexes of Schiff bases derived from 4-aryl-2-aminothiazoles and salicylaldehyde have been prepared, and structure 276 (Scheme 170) was established by magnetic susceptibility measurements and by infrared, electronic, and mass spectra (512). 

Hydrazinothiazoles form stable complexes with Mn ", Ni. Cd Cu ", Co ", Fe ", and Fe " this property was used to detect small amounts of these salts in mixtures by paper chromatography (547, 548). Some infrared features of the complexes formed with the silver salts and with the mercuric salts have been reported (1583). 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

Experimental confirmation of the metal-nitrogen coordination of thiazole complexes was recently given by Pannell et al. (472), who studied the Cr(0), Mo(0), and W(0) pentacarbonyl complexes of thiazole (Th)M(CO)5. The infrared spectra are quite similar to those of the pyridine analogs the H-NMR resonance associated with 2- and 4-protons are sharper and possess fine structure, in contrast to the broad, featureless resonances of free thiazole ligands. This is expected since removal of electron density from nitrogen upon coordination reduces the N quad-rupole coupling constant that is responsible for the line broadening of the a protons. 

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