Transition metal complexes vibrational modes

Fourier-transform infrared (FTIR) spectroscopy Spectroscopy based on excitation of vibrational modes of chemical bonds in a molecule. The energy of the infrared radiation absorbed is expressed in inverse centimeters (cm ), which represents a frequency unit. For transition-metal complexes, the ligands -C N and -C=0 have characteristic absorption bands at unusually high frequencies, so that they are easily distinguished from other bonds. The position of these bonds depends on the distribution of electron density between the metal and the ligand an increase of charge density at the metal results in a shift of the bands to lower frequencies. 

Freedman TB, Cao XL, Young DA et al (2002) Density functional theory calculations of vibrational circular dichroism in transition metal complexes Identification of solution conformations and mode of chloride ion association for (+)-tris(ethylenediaminato)cobalt (III). J Phys Chem A 106 3560-3565... 

Transition metal complexes containing terminal hydrido Kgands exhibit stretching (vmh) and deformational (8mh) vibrations at 2200-1600 and 800-600 cm respectively. The 8mh vibrations are not characteristic but mixed with other modes.Their region is more difficult to access due to the overlap with vibrations of other Kgands and solvents commonly used in inorganic/organometallic chemistry. Therefore 8mh wiK not be discussed here. 

Urdahl et al. (62) reported the first vibrational relaxation measurement of a transition metal complex, W(CO)e, in seC02. The authors determined the lifetime of the Tiu asymmetrical CO stretching mode of W(CO)e at 1990 cm as a function of density at 33°C and 50°C. At the lowest densities, the vibrational... 

A general discussion of the infrared spectra of transition metal complexes has been published (23). Although correlations of CO bending modes (24) and of band intensities (25,26) have appeared and vibrations of other ligands are often noted, the number of CO stretching modes and their exact frequencies are the data most frequently cited for metal carbonyl com-... 

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